OCS Study

MMS 2001-011

Deepwater Program:

Literature Review, Environmental Risks of

Chemical Products Used in Gulf of Mexico

Deepwater Oil and Gas Operations

Volume I: Technical Report

U.S. Department of the Interior

Minerals Management Service

Gulf of Mexico OCS Region

D e e p w a t e r

1000 ft. (305 m)

Isobath

S h a l l o w W a t e r

Western Planning Area Central Planning Area Eastern Planning Area

Gulf of Mexico
U.S. Department of the Interior

Minerals Management Service

Gulf of Mexico OCS Region

OCS Study

MMS 2001-011

Deepwater Program:

Literature Review, Environmental Risks of

Chemical Products Used in Gulf of Mexico

Deepwater Oil and Gas Operations

Volume I: Technical Report

Authors

Paul Boehm

David Turton

Amar Raval

Arthur D. Little, Inc.

Dan Caudle

Sound Environmental Solutions, Inc.

Deborah French

Applied Sciences Associates, Inc.

Nancy Rabalais

Louisiana Universities Marine Consortium

Robert Spies

Jay Johnson

Applied Marine Sciences, Inc.

Prepared under MMS Contract

01-98-CT-30900

by

Arthur D. Little, Inc.

Global Environment and Risk (GER) Group

Houston, Texas 77002

Published by

New Orleans

February 2001
iii

DISCLAIMER

This report was prepared under contract between the Minerals Management Service (MMS) and

Arthur D. Little, Inc. This report has been technically reviewed by the MMS and has been

approved for publication. Approval date does not signify that the contents necessarily reflect the

views and policies of the MMS, nor does mention of trade names or commercial products

constitute endorsement or recommendation for use. It is, however, exempt from review and

compliance with the MMS editorial standards.

REPORT AVAILIBILITY

Extra copies of the report may be obtained from the Public Information Office (MS 5034) at the

following address:

U.S. Department of the Interior

Minerals Management Service

Gulf of Mexico OCS Region

Public Information Office (MS 5034)

1201 Elmwood Park Boulevard

New Orleans, Louisiana 70123-2394

Telephone Number: (504) 736-2519 or

1-800-200-GULF

CITATION

Suggested citation:

Boehm, P., D. Turton, A. Raval, D. Caudle, D. French, N. Rabalais, R. Spies, and J. Johnson.

2001. Deepwater Program: Literature Review, Environmental Risks of Chemical

Products Used in Gulf of Mexico Deepwater Oil and Gas Operations; Volume I:

Technical Report. OCS Study MMS 2001-011. U.S. Department of the Interior, Minerals

Management Service, Gulf of Mexico OCS Region, New Orleans, LA. 326 pp.

COVER

The cover shows the Gulf of Mexico Region, its three planning areas, and the 1,000 ft (305 m)

isobath that separates shallow and deep water.
v

ACKNOWLEDGMENTS

We would like to thank Dr. Mary Boatman and Wallace O. Adcox of MMS who respectively

served as Contracting Officer’s Technical Representative (COTR) and Contract Officer for this

project. The Scientific Review Board members for this project: Mr. Tom Randolph of Randolph

Consulting, Dr. Andrew Glickman of Chevron, and Mr. Charlie Henry of the U.S. Coast Guard

(District 8), who also supports the National Atmospheric Administration (NOAA) as a Science

Support Coordinator (SSC), were very helpful. Three Gulf of Mexico operators provided

essential information for this work. They included; Shell (Andy Burglass, Blake Hebert),

Chevron (Sandi Fury, Stacy Staten, Ron Dupre), and BP Amoco (Bill Scaife). Five chemical

suppliers provided information and data on offshore chemicals. These were: Baker Petrolite

(Roger Quinn), Baroid Halliburton (Vic Saunier, Keith Foley) BJ Services (Carl Shaw), MI

Drilling Fluids (Alex Stewart, Steven Rabke, John Candler, Fred Weddell, Judy McLaughlin),

and Nalco Exxon Energy Chemicals (Cindy Crow and Steven Neff). Their help is greatly

appreciated. The combined efforts of these people made this project possible.

The subcontractors to Arthur D. Little, Inc. on this project included Dr. Deborah French (Applied

Science Associates, Inc.) who led the chemical spill modeling, Mr. Jay Johnson and Mr. Robert

Spies (Applied Marine Sciences, Inc.) who performed the toxicity literature review, and Dr.

Nancy Rabalais (Louisiana Universities Marine Consortium) who provided information on the

biological communities found in the deep waters of the Gulf of Mexico. A special thanks to the

assistant chief scientist for this project, Dr. Dan Caudle of Sound Environmental Solutions, Inc.

(SES).
vii

TABLE OF CONTENTS

EXECUTIVE SUMMARY......................................................................................................... xxv

1.0 INTRODUCTION............................................................................................................... 1

2.0 CHEMICALS USED IN GULF OF MEXICO OIL AND GAS OPERATIONS............... 3

2.1 INTRODUCTION......................................................................................................... 3

2.1.1 The Need for Chemicals.........................................................................................3

2.1.2 Brief Historical Perspective ...................................................................................6

2.1.3 Development of Chemical Inventory .....................................................................7

2.2 CHEMICALS USED ON WELLS AND FORMATIONS ..................................................... 8

2.2.1 Drilling Fluid Chemicals........................................................................................8

2.2.2 Cementing Chemicals ..........................................................................................14

2.2.3 Completion, Stimulation, and Workover Chemicals ...........................................19

2.3 CHEMICALS APPLIED TO PRODUCTION PROCESSING SYSTEMS............................... 27

2.3.1 Overview..............................................................................................................27

2.3.2 Production-treating Chemicals.............................................................................32

3.0 CHEMICAL USAGE........................................................................................................ 35

3.1 INTRODUCTION....................................................................................................... 35

3.2 MODEL RESULTS.................................................................................................... 36

3.2.1 Drilling Fluid Chemicals Volume Estimates .......................................................36

3.2.2 Cementing Chemicals Volume Estimates............................................................40

3.2.3 Completion, Stimulation, and Workover Chemicals Volumes Estimates............43

3.2.4 Production-treating Chemicals Volume Estimates ..............................................46

3.3 COMPARISON OF CHEMICAL USE IN SHALLOW AND DEEP WATER......................... 50

4.0 HAZARDOUS SUBSTANCES........................................................................................ 53

4.1 INTRODUCTION....................................................................................................... 53

4.2 APPROACH TO ESTIMATING QUANTITIES OF HAZARDOUS CHEMICALS USED AND

STORED OFFSHORE................................................................................................. 53

4.3 HAZARDOUS SUBSTANCES IN E&P CHEMICALS APPLIED TO WELLS ..................... 54

4.3.1 Drilling Fluid Chemicals......................................................................................54

4.3.2 Completion, Stimulation and Workover Chemicals ............................................56

4.3.3 Production-treating Chemicals Processing Systems ............................................60

5.0 OFFSHORE CHEMICAL STORAGE AND HANDLING REGULATIONS AND

PRACTICES, AND CHEMICAL SPILL HISTORY EVALUATION............................ 63

5.1 INTRODUCTION....................................................................................................... 63

5.2 CHEMICAL TRANSPORTATION AND STORAGE REGULATIONS RELATED TO

OFFSHORE E&P OPERATIONS ................................................................................ 65

5.3 CHEMICAL STORAGE AND HANDLING BY CHEMICAL CLASS.................................. 66

5.3.1 Chemicals Applied to Wells.................................................................................66

5.3.2 Chemicals Applied to Production Processing Systems........................................68

5.3.3 Factors Affecting Chemical Spills .......................................................................70
viii

5.4 GULF OF MEXICO CHEMICAL SPILL DATA AND RECORDED SPILLS........................ 72

5.4.1 Background ..........................................................................................................72

5.4.2 Historical Chemical Spill Data.............................................................................73

5.5 CHEMICAL SPILL RESPONSE................................................................................... 75

5.6 SUMMARY .............................................................................................................. 79

6.0 BIOLOGICAL COMMUNITIES POTENTIALLY AFFECTED FROM SPILLS OF

CHEMICALS USED IN DEEPWATER E&P ................................................................. 81

6.1 INTRODUCTION....................................................................................................... 81

6.2 DEEP-SEA BENTHOS AND DEMERSAL FAUNA......................................................... 82

6.3 PHYSICAL ENVIRONMENTAL SETTING.................................................................... 82

6.4 BIOLOGICAL PROCESSES ........................................................................................ 84

6.5 CHEMOSYNTHETIC COMMUNITIES.......................................................................... 87

6.6 BIOGENICALLY-STRUCTURED AND LIVE-BOTTOM HABITATS................................ 92

6.7 HARD-BOTTOM NORTHWESTERN GULF OF MEXICO .............................................. 93

6.8 NORTHEAST GULF OF MEXICO HARD-BOTTOM HABITATS .................................... 95

6.9 PELAGIC, OCEANIC COMMUNITIES......................................................................... 95

6.10 PROTECTED SPECIES............................................................................................... 97

6.11 CONTINENTAL SHELF ............................................................................................. 99

6.12 COASTAL HABITATS............................................................................................. 102

6.13 SUMMARY ............................................................................................................ 102

7.0 SPILL SCENARIOS AND MODELING PARAMETERS............................................ 105

7.1 INTRODUCTION..................................................................................................... 105

7.2 SELECTION OF CHEMICALS FOR PROFILING.......................................................... 105

7.3 CHEMMAP MODEL DESCRIPTION...................................................................... 108

7.3.1 CHEMMAP Chemical Database........................................................................109

7.3.2 Chemical Fates Model........................................................................................110

7.4 ENVIRONMENTAL DATA....................................................................................... 112

7.4.1 Geographical Data..............................................................................................113

7.4.2 Wind Data ..........................................................................................................113

7.4.3 Currents..............................................................................................................117

7.5 SCENARIO SPECIFICATION.................................................................................... 119

7.6 STOCHASTIC MODELING OF TRAJECTORY AND FATES.......................................... 121

7.7 CHEMICAL SPILL SCENARIOS ............................................................................... 124

7.8 SPILL MODELING ASSUMPTIONS .......................................................................... 131

7.9 SUMMARY ............................................................................................................ 135
ix

8.0 PROFILES OF SELECTED CHEMICALS AND THEIR ASSOCIATED RISK

CHARACTERIZATION ................................................................................................ 137

8.1 INTRODUCTION..................................................................................................... 137

8.2 PROFILE EXPLANATION........................................................................................ 138

8.2.1 Summary ............................................................................................................138

8.2.2 Model Profile .....................................................................................................139

8.2.3 Uncertainties ......................................................................................................147

8.3 TWENTY-ONE PROFILES THAT CHARACTERIZE THE QUALITATIVE POTENTIAL

FOR RISK OF CHEMICALS USED IN THE GULF OF MEXICO .................................... 147

9.0 REFERENCES................................................................................................................ 313
xi

LIST OF FIGURES

Figure 1. The Gulf of Mexico Region, its Three Planning Areas, and the 1,000 ft.

(305 m) Isobath that Separates Shallow and Deep Water....................................... 2

Figure 2. Chemical Use by Stage of Oil & Gas E&P (GOM)................................................ 5

Figure 3. Mud Circulating System on a Drilling Rig. (Source: MI Drilling Fluids)........... 10

Figure 4. Well Profile Showing Cementing Intervals for a Typical Deepwater Well

(Source: MI Drilling Fluids). ............................................................................... 16

Figure 5. Completed Producing Zones; (a) Perforations, (b) Gravel-Pack. ......................... 21

Figure 6. Simplified Typical Oilfield Process Diagram for an Offshore Platform.

(Source: Hudgins and Petrotech Consultants, Inc. 1991)..................................... 30

Figure 7. Number of Wells Drilled by One Operator in 1998. (Source: Operator Data) .... 37

Figure 8. Total Number of Wells Drilled in the Gulf of Mexico in 1998.

(Source: MMS Fast Facts Database 1998)........................................................... 37

Figure 9. Schematic of Flowline and Umbilical Subsea Architecture in the Gulf

of Mexico. ............................................................................................................. 71

Figure 10. Detailed Schematic of Subsea Manifold and Template Base. .............................. 71

Figure 11. Location of live-bottom, chemosynthetic and biogenically-structured

communities of the northern Gulf of Mexico........................................................ 88

Figure 12. Location of live-bottom and chemosynthetic communities of the

northwestern Gulf of Mexico. ............................................................................... 89

Figure 13. Location of live-bottom, chemosynthetic and biogenically-structured

communities of the northeastern Gulf of Mexico. ................................................ 90

Figure 14. Cyclones are the most common place to find sperm whales, as indicated

by the stars placed on this diagram of the Gulf's eddies, made from an

August 21, 1997, regional altimetry map. (Data courtesy of Robert Leben,

Colorado Center for Astrodynamics Research, in Biggs and Wormuth 1998)..... 99

Figure 15. Gridded map of habitats in eastern portion of the study area.............................. 114

Figure 16. Gridded map of habitats in western portion of the study area. ........................... 114

Figure 17. Gridded map of bathymetry used in the modeling for the shelf spill site. .......... 115

Figure 18. Gridded map of bathymetry in the area of the shelf spill site. ............................ 115

Figure 19. Gridded map of bathymetry used in the modeling for the shelf spill site. .......... 116

Figure 20. Gridded map of bathymetry in the area of the deepwater spill site..................... 116

Figure 21. Peak exposure concentration (ppb) of hydrochloric acid dissolved in water

at each location: averaged over all simulations (Scenario 1). ............................ 154

Figure 22. Peak exposure concentration (ppb) of hydrochloric acid dissolved in the

water at each location: worst case of all simulations (Scenario 1)..................... 154

Figure 23. Peak exposure concentration (ppb) of glutaraldehyde (surface release)

dissolved in the water at each location: averaged over all simulations

(Scenario 11). ...................................................................................................... 169
xii

Figure 24. Peak exposure concentration (ppb) of glutaraldehyde (surface release)

dissolved in the water at each location: worst case of all simulations

(Scenario 11). ...................................................................................................... 169

Figure 25. Peak exposure concentration (ppb) of glutaraldehyde (bottom release)

dissolved in the water at each location: averaged over all simulations

(Scenario 12). ...................................................................................................... 170

Figure 26. Peak exposure concentration (ppb) of glutaraldehyde (bottom release)

dissolved in the water at each location: worst case of all simulations

(Scenario 12). ...................................................................................................... 170

Figure 27. Peak exposure concentration (ppb) of miscible organic solution

(amides/imidazolines and guaternary ammonium chloride) as particulate

in the water at each location: averaged over all simulations (Scenario 14a). .... 176

Figure 28. Peak exposure concentration (ppb) of miscible organic solution

(amides/imidazolines and guaternary ammonium chloride) as particulate

in the water at each location: worst case of all simulations (Scenario 14a)....... 176

Figure 29. Peak exposure concentration (ppb) of THPS dissolved in the water at each

location: averaged over all simulations (Scenario 13). ...................................... 182

Figure 30. Peak exposure concentration (ppb) of THPS dissolved in the water at each

location: worst case of all simulations (Scenario 13)......................................... 182

Figure 31. Peak exposure concentration (ppb) of zinc bromide dissolved in the water

at each location: averaged over all simulations (Scenario 4). ............................ 188

Figure 32. Peak exposure concentration (ppb) of zinc bromide dissolved in the water

at each location: worst case of all simulations (Scenario 4). ............................. 188

Figure 33. Peak exposure concentration (ppb) of sodium hydroxide as dissolved in

the water at each location: mean case of all simulations (Scenario 2)............... 202

Figure 34. Peak exposure concentration (ppb) of sodium hydroxide dissolved in the

water at each location: worst case of all simulations (Scenario 2)..................... 202

Figure 35. Peak exposure concentration (ppb) of potassium chloride dissolved in water

at each location: averaged over all simulations (Scenario 3). ............................ 208

Figure 36. Peak exposure concentration (ppb) of potassium chloride dissolved in the

water at each location: worst case of all simulations (Scenario 3)..................... 208

Figure 37. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets at each location: averaged over all

simulations (Scenario 15t)................................................................................... 217

Figure 38. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets in the water at each location: worst

case of all simulations (Scenario 15t). ................................................................ 217

Figure 39. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: averaged over all

simulations (Scenario 15t)................................................................................... 218

Figure 40. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: worst case of all

simulations (Scenario 15t)................................................................................... 218
xiii

Figure 41. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location:

averaged over all simulations (Scenario 15t). ..................................................... 219

Figure 42. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location:

worst case of all simulations (Scenario 15t)........................................................ 219

Figure 43. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets at each location: averaged over all

simulations (Scenario 15t)................................................................................... 229

Figure 44. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets in the water at each location: worst

case of all simulations (Scenario 15t). ................................................................ 229

Figure 45. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: averaged over all

simulations (Scenario 15t)................................................................................... 230

Figure 46. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: worst case of all

simulations (Scenario 15t)................................................................................... 230

Figure 47. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location:

averaged over all simulations (Scenario 15t). ..................................................... 231

Figure 48. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location:

worst case of all simulations (Scenario 15t)........................................................ 231

Figure 49. Peak exposure concentration (ppb) of lignite as particulate in the water at

each location: averaged over all simulations (Scenario 8)................................. 239

Figure 50. Peak exposure concentration (ppb) of lignite as particulate in the water at

each location: worst case of all simulations (Scenario 8). ................................. 239

Figure 51. Peak exposure concentration (ppb) of lignite dissolved in the water at each

location: averaged over all simulations (Scenario 8). ........................................ 240

Figure 52. Peak exposure concentration (ppb) of lignite dissolved in the water at each

location: worst case of all simulations (Scenario 8)........................................... 240

Figure 53. Peak exposure mass per unit area (g/m2

) of lignite in the sediment averaged

over all simulations (Scenario 8)......................................................................... 241

Figure 54. Peak exposure mass per unit area (g/m2

) of lignite in the sediment at each

location: worst case of all simulations (Scenario 8)........................................... 241

Figure 55. Peak exposure mass per unit area (g/m2

) of methyl alcohol as slicks on the

water surface at each location: worst case of all simulations (Scenario 9). ....... 250

Figure 56. Peak exposure concentration (ppb) of methyl alcohol as slicks and pure

liquid droplets in the water at each location: worst case of all simulations

(Scenario 9). ........................................................................................................ 250

Figure 57. Peak exposure concentration (ppb) of methyl alcohol dissolved in the water

at each location: averaged over all simulations (Scenario 9). ............................ 251
xiv

Figure 58. Peak exposure concentration (ppb) of methyl alcohol dissolved in the water

at each location: worst case of all simulations (Scenario 9). ............................. 251

Figure 59. Peak exposure concentration (ppb) of methyl alcohol adsorbed to suspended

sediment in the water at each location: averaged over all simulations

(Scenario 9). ........................................................................................................ 252

Figure 60. Peak exposure concentration (ppb) of methyl alcohol adsorbed to suspended

sediment in the water at each location: worst case of all simulations

(Scenario 9). ........................................................................................................ 252

Figure 61. Peak exposure concentration (ppb) of ethylene glycol dissolved in the water at

each location: averaged over all simulations (Scenario 10)............................... 259

Figure 62. Peak exposure concentration (ppb) of ethylene glycol dissolved in the

water at each location: worst case of all simulations (Scenario 10)................... 259

Figure 63. Peak exposure mass per unit area (g/m2

) of ethylene glycol in the sediment

at each location: averaged over all simulations (Scenario 10). .......................... 260

Figure 64. Peak exposure mass per unit area (g/m2

) of ethylene glycol in the sediment

at each location: worst case of all simulations (Scenario 10). ........................... 260

Figure 65. Peak exposure concentration (ppb) of sodium bisulfite (modeled as sodium

sulfite) dissolved in the water at each location: averaged over all simulations

(Scenario 5). ........................................................................................................ 269

Figure 66. Peak exposure concentration (ppb) of sodium bisulfite (modeled as sodium

sulfite) dissolved in the water at each location: worst case of all simulations

(Scenario 5). ........................................................................................................ 269

Figure 67. Peak exposure concentration (ppb) of barite as particulate in the water at

each location: averaged over all simulations (Scenario 6)................................. 278

Figure 68. Peak exposure concentration (ppb) of barite as particulate in the water at

each location: worst case of all simulations (Scenario 6). ................................. 278

Figure 69. Peak exposure mass per unit area (g/m2

) of barite in the sediment at each

location: averaged over all simulations (Scenario 6). ........................................ 279

Figure 70. Peak exposure mass per unit area (g/m2

) of barite in the sediment at each

location: worst case of all simulations (Scenario 6)........................................... 279

Figure 71. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 12:00 hours on 1 January 1992: 12 hours after

the spill. ............................................................................................................... 280

Figure 72. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 2 January 1992: 24 hours

after the spill........................................................................................................ 280

Figure 73. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 3 January 1992: 2 days

after the spill........................................................................................................ 281

Figure 74. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 5 January 1992: 4 days

after the spill........................................................................................................ 281
xv

Figure 75. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 7 January 1992: 6 days

after the spill........................................................................................................ 282

Figure 76. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 9 January 1992: 8 days

after the spill........................................................................................................ 282

Figure 77. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 11 January 1992: 10 days

after the spill........................................................................................................ 283

Figure 78. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 15 January 1992: 14 days

after the spill........................................................................................................ 283

Figure 79. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 21 January 1992: 20 days

after the spill........................................................................................................ 284

Figure 80. Particulate concentration of barite following a hypothetical surface release

in the offshore Gulf of Mexico at 00:00 hours on 29 January 1992: 28 days

after the spill........................................................................................................ 284

Figure 81. Peak exposure concentration (ppb) of barite as particulate in the water at

each location: averaged over all simulations (Scenario 17)............................... 285

Figure 82. Peak exposure concentration (ppb) of barite as particulate in the water at

each location: worst case of all simulations (Scenario 17). ............................... 285

Figure 83. Peak exposure concentration (ppb) of DESCO/ lignosulfonate as particulate

in the water at each location: worst case of all simulations (Scenario 7)........... 293

Figure 84. Peak exposure concentration (ppb) of DESCO/ lignosulfonate dissolved

in the water at each location: averaged over all simulations (Scenario 7). ........ 293

Figure 85. Peak exposure concentration (ppb) of DESCO/ lignosulfonate dissolved

in the water at each location: worst case of all simulations (Scenario 7)........... 294

Figure 86. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) as pure liquid droplets in the water at each location:

averaged over all simulations (Scenario 16t). ..................................................... 306

Figure 87. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) as pure liquid droplets in the water at each location: worst

case of all simulations (Scenario 16t). ................................................................ 306

Figure 88. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) dissolved in the water at each location: averaged over all

simulations (Scenario 16t)................................................................................... 307

Figure 89. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) dissolved in the water at each location: worst case of all

simulations (Scenario 16t)................................................................................... 307

Figure 90. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) adsorbed to suspended sediment in the water at each location:

over all simulations (Scenario 16t)...................................................................... 308
xvi

Figure 91. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) adsorbed to suspended sediment in the water at each

location: worst case of all simulations (Scenario 16t)........................................ 308

Figure 92. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled

as naphthalene) in the sediment at each location: worst case of all

simulations (Scenario 16t)................................................................................... 309
xvii

LIST OF TABLES

Table 1 Drilling Fluid Chemicals: Codes, Functional Categories, Descriptions, and

Material Types Used ................................................................................................... 12

Table 2 Cementing Chemicals: Codes, Functional Categories, Descriptions, and

Material Types Used ................................................................................................... 17

Table 3 Completion, Stimulation, and Workover Chemicals: Codes, Functional

Categories, Descriptions, and Material Types Used ................................................... 24

Table 4 Production-treating Chemicals: Codes, Functional Categories, Descriptions,

and Material Types Used............................................................................................. 32

Table 5 Volume Estimates for Drilling Fluid Chemicals Used in the Gulf of Mexico............ 38

Table 6 Storage Volumes of Drilling Fluid Chemicals Used in the Gulf of Mexico............... 40

Table 7 Volume Estimates for Cementing Chemicals Used in the Gulf of Mexico ................ 42

Table 8 Volume Estimates for Completion, Stimulation, and Workover Chemicals

Used in the Gulf of Mexico......................................................................................... 44

Table 9 Volume Estimates for Production-treating Chemicals Used in the Gulf of

Mexico......................................................................................................................... 48

Table 10 Storage Volumes of Production-treating Chemicals Used in the Gulf of

Mexico......................................................................................................................... 49

Table 11 Total Estimated Quantities of Hazardous Substances Found in Drilling Fluid

Chemicals in the GOM in 1998................................................................................... 55

Table 12 Total Estimated Storage Volumes of Hazardous Substances Found in Drilling

Fluid Chemicals in the GOM in 1998 ......................................................................... 55

Table 13 Total Estimated Quantities of Hazardous Substances found in Completion,

Stimulation, and Workover Chemicals in the GOM in 1998...................................... 57

Table 14 Total Estimated Storage Volumes of Hazardous Substances Found in

Completion, Stimulation, and Workover Chemicals in the GOM in 1998................. 59

Table 15 Total Estimated Quantities of for Hazardous Substances Found in Productiontreating Chemicals in the GOM in 1998 ..................................................................... 61

Table 16 Total Estimated Storage Volumes of Hazardous Substances Found in Productiontreating Chemicals in the GOM in 1998 ..................................................................... 62

Table 17 Gulf of Mexico Chemical (Liquids) Spill Data (1990-1998)...................................... 73

Table 18 Gulf of Mexico Chemical (Solids) Spill Data (1990-1998)........................................ 74

Table 19 Emergency Response Contact Information for Chemical Spills in the Gulf of

Mexico......................................................................................................................... 78

Table 20 List of Twenty-one Chemicals Selected for Detailed Chemical Profiles.................. 106

Table 21 Chemical Database: Physical – Chemical Properties............................................... 110

Table 22 Scenario Specification Data Required by the Model ................................................ 119

Table 23 Model Habitat Grid Dimensions ............................................................................... 121

Table 24 Stochastic Model Inputs............................................................................................ 124

Table 25 Spill Model Assumptions.......................................................................................... 131
xviii

Table 26 Chemical Properties Assumed For Model Runs ....................................................... 133

Table 27 Chemical Risk Characterization Summary ............................................................... 137

Table 28 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 1. Dissolved concentration of hydrochloric acid and hydrofluoric acid

(modeled as hydrochloric acid) in all subtidal habitats............................................. 153

Table 29 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01-hours (0.01 ppb-hours): Scenario 1. Dissolved concentration of

hydrochloric acid and hydrofluoric acid (modeled as hydrochloric acid) in all

subtidal habitats......................................................................................................... 153

Table 30 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 11. Dissolved concentration of glutaraldehyde (surface release) in all

subtidal habitats......................................................................................................... 167

Table 31 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 11. Dissolved concentration

of glutaraldehyde (surface release) in all subtidal habitats. ...................................... 167

Table 32 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 12. Dissolved concentration of glutaraldehyde (bottom release) in

all subtidal habitats.................................................................................................... 168

Table 33 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 12. Dissolved concentration

of glutaraldehyde (bottom release) in all subtidal habitats. ...................................... 168

Table 34 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 14a. Particulate concentration of miscible organic solution

(amides/imidazolines and quaternary ammonium chloride) in all subtidal

habitats. ..................................................................................................................... 175

Table 35 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 14a. Particulate concentration

of miscible organic solution(amides/imidazolines and quaternary ammonium

chloride) in all subtidal habitats. ............................................................................... 175

Table 36 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 13. Dissolved concentration of THPS in all subtidal habitats.................... 181

Table 37 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 13. Dissolved concentration

of THPS in all subtidal habitats. ............................................................................... 181

Table 38 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 4. Dissolved concentration of zinc bromide in all subtidal habitats........... 187
xix

Table 39 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 mg/m3

-hours (0.01 ppb-hours): Scenario 4. Dissolved concentration

of zinc bromide in all subtidal habitats. .................................................................... 187

Table 40 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 2. Dissolved concentration of sodium hydroxide in all subtidal

habitats. ..................................................................................................................... 201

Table 41 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01-hours (0.01 ppb-hours): Scenario 2. Dissolved concentration of

sodium hydroxide in all subtidal habitats.................................................................. 201

Table 42 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 3. Dissolved concentration of potassium chloride in all subtidal

habitats. ..................................................................................................................... 207

Table 43 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 mg/m3-hours (0.01 ppb-hours): Scenario 3. Dissolved concentration

of potassium chloride in all subtidal habitats............................................................ 207

Table 44 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 15t. Concentration of amides/imidazolines in naphtha (modeled as

naphthalene) as droplets in all subtidal habitats........................................................ 213

Table 45 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 15t. Dissolved concentration of amides/imidazolines in naphtha

(modeled as naphthalene) in all subtidal habitats...................................................... 213

Table 46 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 15t. Concentration of amides/imidazolines in naphtha (modeled as

naphthalene) adsorbed to suspended sediments in all subtidal habitats.................... 213

Table 47 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 15t. Particulate concentration

of amides/imidazolines in naphtha (modeled as naphthalene) in all subtidal

habitats. ..................................................................................................................... 214

Table 48 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 15t. Dissolved concentration

of amides/imidazolines in naphtha (modeled as naphthalene) in all subtidal

habitats. ..................................................................................................................... 215

Table 49 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 15t. Concentration of

amides/imidazolines in naphtha (modeled as naphthalene) adsorbed to

suspended sediments in all subtidal habitats............................................................. 216
xx

Table 50 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 15t. Concentration of amides/imidazolines in naphtha (modeled as

naphthalene) as droplets in all subtidal habitats........................................................ 225

Table 51 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 15t. Dissolved concentration of amides/imidazolines in naphtha

(modeled as naphthalene) in all subtidal habitats...................................................... 225

Table 52 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 15t. Concentration of amides/imidazolines in naphtha (modeled as

naphthalene) adsorbed to suspended sediments in all subtidal habitats.................... 225

Table 53 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 15t. Particulate concentration

of amides/imidazolines in naphtha (modeled as naphthalene) in all subtidal

habitats. ..................................................................................................................... 226

Table 54 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 15t. Dissolved concentration

of amides/imidazolines in naphtha (modeled as naphthalene) in all subtidal

habitats. ..................................................................................................................... 227

Table 55 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 15t. Concentration of

amides/imidazolines in naphtha (modeled as naphthalene) adsorbed to

suspended sediments in all subtidal habitats............................................................. 228

Table 56 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 8. Particulate concentration of lignite in all subtidal habitats. ................... 236

Table 57 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 8. Dissolved concentration of lignite in all subtidal habitats. .................... 236

Table 58 Areas (m2

) and distMarch 8, 2001ance (m) from the spill site exposed above the

indicated

threshold levels under average and worst case environmental conditions:

Scenario 8. Mass loading of lignite onto sediments in all subtidal habitats.............. 236

Table 59 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 8. Particulate concentration

of lignite in all subtidal habitats. ............................................................................... 237

Table 60 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 8. Dissolved concentration

of lignite in all subtidal habitats. ............................................................................... 237

Table 61 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.0001 (g/m2

)-hours: Scenario 8. Mass loading of lignite onto sediments in

all subtidal habitats.................................................................................................... 238
xxi

Table 62 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 9. Mass per unit area (g/m2

) of methyl alcohol as slicks in all subtidal

habitats.. .................................................................................................................... 247

Table 63 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 9. Concentration of methyl alcohol slicks and pure liquid droplets

in all subtidal habitats. Note that these concentrations occur only instantaneously

after the spill, as dissolution would be immediate. ................................................... 247

Table 64 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 9. Dissolved concentration of methyl alcohol in all subtidal habitats........ 247

Table 65 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 9. Concentration of methyl alcohol adsorbed to suspended sediments

in all subtidal habitats................................................................................................ 248

Table 66 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 9. Dissolved concentration

of methyl alcohol in all subtidal habitats. ................................................................. 248

Table 67 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 9. Concentration of methyl

alcohol adsorbed to suspended sediments in all subtidal habitats............................. 249

Table 68 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 10. Dissolved concentration of ethylene glycol in all subtidal habitats..... 257

Table 69 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 10. Mass loading of ethylene glycol onto sediments in all subtidal

habitats. ..................................................................................................................... 257

Table 70 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 10. Dissolved concentration

of ethylene glycol in all subtidal habitats.................................................................. 258

Table 71 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.0001 (g/m2

)-hours: Scenario 10. Mass loading of ethylene glycol onto

sediments in all subtidal habitats............................................................................... 258

Table 72 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 5. Dissolved concentration of sodium bisulfite (modeled as sodium

sulfite) in all subtidal habitats. .................................................................................. 268

Table 73 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 mg/m3-hours (0.01 ppb-hours): Scenario 5. Dissolved concentration

of sodium bisulfite (modeled as sodium sulfite) in all subtidal habitats................... 268
xxii

Table 74 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 6. Particulate concentration of barite in all subtidal habitats. .................... 275

Table 75 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 6. Mass loading of barite onto sediments in all subtidal habitats............... 275

Table 76 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 6. Particulate concentration

of barite in all subtidal habitats. ................................................................................ 276

Table 77 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 6. Particulate concentration

of barite in all subtidal habitats. ................................................................................ 276

Table 78 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 17. Particulate concentration of barite in all subtidal habitats. .................. 277

Table 79 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 17. Particulate concentration of barite in all subtidal habitats. .................. 277

Table 80 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 7. Particulate concentration of DESCO/ lignosulfonate in all subtidal

habitats.. .................................................................................................................... 291

Table 81 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 7. Dissolved concentration of DESCO/lignosulfonate in all subtidal

habitats. ..................................................................................................................... 291

Table 82 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 7. Dissolved concentration

of DESCO/lignosulfonate in all subtidal habitats. .................................................... 292

Table 83 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 16t. Concentration of alkylbenzene sulfonic acids in naphtha

(modeled as naphthalene) as droplets in all subtidal habitats. .................................. 300

Table 84 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 16t. Dissolved concentration of alkylbenzene sulfonic acids in

naphtha (modeled as naphthalene) in all subtidal habitats........................................ 300

Table 85 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 16t. Concentration of alkylbenzene sulfonic acids in naphtha (modeled

as naphthalene) adsorbed to suspended sediments in all subtidal habitats. .............. 301
xxiii

Table 86 Areas (m2

) and distance (m) from the spill site exposed above the indicated

threshold levels under average and worst case environmental conditions:

Scenario 16t. Mass loading of alkylbenzene sulfonic acids in naphtha (modeled

as naphthalene) onto sediments in all subtidal habitats............................................. 301

Table 87 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 16t. Concentration of

alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) as droplets

in all subtidal habitats................................................................................................ 302

Table 88 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3)-hours (0.01 ppb-hours): Scenario 16t. Dissolved concentration

of alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) in all

subtidal habitats......................................................................................................... 303

Table 89 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.01 (mg/m3

)-hours (0.01 ppb-hours): Scenario 16t. Concentration of

alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) adsorbed to

suspended sediments in all subtidal habitats............................................................. 304

Table 90 Areas (m2

) impacted at each dosage level of exposure above a threshold of

H=0.0001 (g/m2

)-hours: Scenario 16t. Mass loading of alkylbenzene sulfonic

acids in naphtha (modeled as naphthalene) onto sediments in all subtidal

habitats. ..................................................................................................................... 305
xxv

EXECUTIVE SUMMARY

Chemicals have been used in offshore Gulf of Mexico (GOM) oil and natural gas

exploration and production (E&P) since development of the offshore resources over a half a

century ago. From 1947 to 1985, E&P activities focused on the shallow waters of the continental

shelf. Since the mid-1980s, however, the pace of exploration and development in the deep waters

of the GOM has accelerated rapidly. By the end of 1999, approximately 1,200 wells had been

drilled in water depths exceeding 1,000 ft. (305 m) (Minerals Management Service, May 2000).

Moreover, production from these deepwater wells have now surpassed production in shallow

water, despite the fact that only 4% of all producing fields in the GOM are in deep water.

The United States Minerals Management Service (MMS) is mandated to manage the

development of GOM oil and natural gas resources, while also ensuring safe operations and

protection of the human and natural environment. As a part of this overall management

responsibility, the MMS must consider possible impacts from chemicals used in oil and gas

development to both the natural and human socio-economic environments. To accomplish this,

an understanding of the types and quantities of chemical products used offshore, especially in

deep water, as well as their potential impact is needed. This report identifies the types of

chemicals used in the GOM via an extensive inventory. It presents their properties, toxicity,

usage patterns, and storage and handling practices. Through the use of spill modeling, the

potential for environmental risk for a select group of chemicals is evaluated. In addition, this

report includes an overview of relevant legislation.

Chemicals perform critical functions during drilling; cementing; well completion,

stimulation, and workover processes; and producing processes. Without these essential

formulations, the safe, cost-effective extraction of oil and gas resources would not be feasible. In

offshore operations, chemicals fall naturally into four major classes:

1. Drilling fluid chemicals

2. Cementing chemicals

3. Completion, stimulation, and workover chemicals

4. Production-treating chemicals

This document presents the inventory of chemicals typically used in ongoing oil and gas

E&P activities in the GOM. The compiled data and inventories are based primarily on

information received from three major energy companies operating in both the shallow and deep

waters of the GOM; annual reports provided in World Oil magazine (June 1999, August 1999,

and November 1999) on available chemicals; MSDS sheets from chemical suppliers; and a

review of Hudgins’ (1991) report on chemical usage in the North Sea, that explains the need,

use, and function of chemicals used offshore.
xxvi

Twenty-one chemicals were selected for detailed characterization based on volumes used

and stored offshore, toxicity, and fate in the environment. A standard chemical profile was

developed to present the data collected on each chemical and their impact on the marine

environment. The chemicals profiled are:

Acids

Hydrochloric Acid

Hydrofluoric Acid

Chemical Stabilizer

Sodium Hydroxide

Potassium Chloride

Oxygen Scavenger

Sodium Bisulfite

Antifoam/Defoaming Agents

Silicones

Corrosion Inhibitor

Amides/Imidazolines

Amines & Amine Salts

Insoluble Solids

Barite

Biocides

Glutaraldehyde

Quaternary Compounds

Tetrakishhydroxymethyl

Phosphonium Sulfate

(THPS)

Fluid-Loss Agents

Lignite

Thinners & Dispersants

Lignosulphonate

Reactive Salt – Solid

Zinc Bromide

Calcium Bromide

Ammonium Chloride

Gas Hydrate Prevention

Methanol

Ethylene Glycol

Triethylene Glycol

Solvents/Carriers

Heavy Aromatic

Naphtha

Models were developed for offshore E&P operations to estimate the volume of chemical

transported, stored, and expected to be used at any one time in the GOM. For this report we

utilized a small, but representative subset of chemical usage data from 1998 obtained from three

operators and their chemical suppliers. Once unitized, these data were extrapolated to total GOM

usage volume estimates for 1998 for each chemical. Given future information on the number of

wells, types of wells, well depth, water depth and production data, these models can be used to

extrapolate from the unitized data the total volumes of a chemical(s) used in the GOM in any

year or, if needed, on a project-specific basis for any number of wells to be drilled or quantity of

fluid produced.

Definite differences are apparent in chemical use in deep and shallow waters in the

GOM. For individual locations, these include:

• Higher amounts of drilling fluid chemicals needed in individual wells in deep water, some of

which are probably due to the nature of the formations and reservoirs being accessed

• Higher amounts of some production-treating chemicals (e.g., hydrate inhibitors) needed in

deepwater production, which may be due to the deepwater environment

• Higher amounts of other production-treating chemicals (e.g., defoamers) needed in

deepwater production, which may be due to the nature of the produced fluids

It is not clear how comparisons of the total volumes of chemical used in the future will

change. However we do know that, with the increasing use of subsea completions in deep water,

there will be an increase in the use of umbilicals to supply chemicals to them. The use of

umbilicals will result in the storage of larger volumes offshore, which will be transported on the
xxvii

sea floor. There is nothing fundamentally different about chemical treating in deep water. The

same chemicals are used to complete the same functions in both shallow and deep water. As with

any area within the GOM, the nature of the geologic formation, the reservoir, and the local

environment are the primary factors that will affect chemical use.

As part of this study, the types and volumes of hazardous substances used, handled, and

stored in offshore E&P operations were identified. Hazardous chemicals were defined as those

substances listed in the U.S. Code of Federal Regulations (CFR) – Chapter 40, Protection of the

Environment, Part 116, that designates hazardous substances per the Clean Water Act. Only

eight hazardous substances were found to be stored in amounts exceeding reportable quantities:

sodium hydroxide, potassium hydroxide, zinc bromide, hydrofluoric acid, diethylamine, toluene,

xylene and naphthalene.

Over the past decade, the number of liquid chemical spills in the Gulf of Mexico (GOM)

has steadily increased. In 1998, the percentage of spill incidents across the Gulf region accounted

for almost 27% of all incidents in U.S. water bodies. Of the four chemical classes, a

disproportionately large ratio (i.e., eight of 17, or 47%) of spills related to completion,

stimulation, and workover chemicals were reported. Completion, stimulation, and workover

chemicals are likely to be directly applied from supply boats instead of being transferred to the

platform or rig and then used. While the number of chemical spills in the Gulf are certainly

related to the ongoing E&P activities in the region, the increase in number of spills reported

since 1990 may not be directly correlated to an increase in operations. A portion of the increase

in spill reports can be attributed to the improvement in reporting and management practices by

offshore operators and chemical supply companies over the last decade.

Jurisdiction for regulations for the transportation, storage, and use of chemicals is divided

between the federal government and individual states. Onshore and in state waters, the state has

primary jurisdiction, followed by the federal government. In outer continental shelf (OCS)

waters in the GOM, the U. S. Congress specifically delegated jurisdiction to the federal

government. In the Continental Shelf Lands Act (43 U.S.C. 1333), the authority of enforcement

for “the subsoil and seabed of the outer continental shelf” and “all devices permanently or

temporarily attached to the seabed” are areas of “exclusive federal jurisdiction.” Federal agencies

that issue regulations that apply to chemicals used offshore include:

• U.S. Department of Transportation (DOT, Title 49, Part 172 of the Code of Federal

Regulations)

• Occupational Safety and Health Administration (OSHA, Title 29)

• U.S. Environmental Protection Agency (EPA, Title 40)

As chemicals move through the supply chain from the manufacturing to the formulation

stage, packaging containers, record keeping, and handling policies are adopted to meet all

potential domestic and international regulatory requirements. Frequently, chemicals are stored

offshore in the containers in which they were transported. Therefore, the same safety and

containment standards that were used for transportation are met or exceeded for storage.
xxviii

Exploration for oil and gas is increasingly extending into the deeper waters of the Gulf of

Mexico. Biological communities potentially at risk from the use of chemicals, therefore, extend

past the break of the continental shelf (generally accepted as the upper limit of the deep sea).

This fact puts deep-sea benthic pelagic biological communities and oceanic pelagic communities

potentially at risk. Certain aspects of deepwater development may possibly pose novel threats of

impact, either because of the technology, the chemical compounds, the differing environment, or

the different biological communities and ecological processes (Carney 1998).

The major types of benthic communities within the continental shelf zone are those

associated with soft-bottom habitats that vary in sedimentary composition. Many biogenically

structured communities, such as coral reefs or “live” bottoms, occur throughout the Gulf of

Mexico. Within the deep sea, the benthic communities are dominated by soft-bottom dwelling

organisms, with an added importance of microhabitat structuring. Hydrocarbon seeps with their

chemosynthetic, or otherwise specialized biological communities, are places where gas and oil

flow naturally out of the sea floor and are quite common on the continental slope of the northern

Gulf of Mexico. Much less is known of the deep sea and oceanic communities.

Our knowledge base for the effects of chemicals or habitat perturbation is the most

meager for the deep sea. It is expected, however, that ecological processes in the deep sea are

fundamentally similar to those of the continental shelf. Biological communities at risk from

chemical spills associated with deepwater E&P are most likely those which are deeper than the

continental shelf break. Biologically sensitive communities in coastal and continental shelf

depths may be affected from spills during transit of materials either via ship or pipeline.

Spill modeling was performed to estimate concentrations resulting from worst-case

chemical spill scenarios that were developed from the assembled inventory data. The results

were used to evaluate the potential impacts of spills of selected chemicals on the marine

environment. The modeling was performed using Applied Science Associates’ (ASA) chemical

spill model CHEMMAP. A total of 17 spill scenarios was developed, modeled, and reviewed.

Sixteen spill scenarios were modeled using shallow water data and one spill scenario was

modeled in deep water. The shallow water current data were obtained from measurements made

by Texas A&M University as part of the LATEX program. For each of the chemicals modeled,

habitat areas exposed to peak concentrations or mass loadings within range intervals were

tabulated. These peak exposure concentrations were compared against acute toxicity data to

estimate the potential impact to the environment. The results of the modeling effort are discussed

in conjunction with the detailed chemical profiles in Section 8.0.

Detailed chemical profiles were developed for selected chemicals used in deepwater E&P

operations. Each profile is a description of the subject chemical and contains a summary,

background information (i.e., fate in the environment, fate in the process system, other

components, CAS number, chemical formula, and important synonyms and trade names),

chemical and physical properties, health and safety properties, use and handling properties,

environmental concentrations and toxicological effects, spill modeling results, aquatic toxicity

levels, risk characterization, references, and spill modeling results in the form of tables and

figures.
xxix

The process we have used to estimate the ecological risks associated with spills of oilfield

chemicals is subject to several inherent sources of uncertainty. No toxicity data were found for

the Gulf marine species actually potentially affected by the chemicals. Many of the species for

which data were found are test species used in compliance testing for waste stream discharges.

All comparisons of toxicity data were to average or worst-case peak modeled concentrations.

Because these modeled peak concentrations would generally last only a short time, comparison

to toxicity results from standard 96-hour tests probably provides an exaggerated estimate of

acute impacts. Conversely, overall impacts may be underestimated because we have included no

consideration of long-term or chronic exposures to spilled chemicals.

Summary

This report includes a general inventory of chemicals employed during exploration and

production operations in the Gulf of Mexico, a brief history of their use, the drivers, triggers, and

regulatory guidelines for their use, and a discussion of their spill history and potential for

spillage. While a majority of the chemicals utilized in E&P operations are not, or do not, contain

hazardous materials, as specified by U.S. Code of Federal Regulations (CFR) – Chapter 40,

Protection of the Environment, Part 116, those that are, or do, have been identified. In addition,

utilizing data collected from operators in the Gulf, models were developed and usage and storage

estimates were made for chemicals/functional groups of chemicals. These models can be used to

estimate total volume usage at any time in the future or to estimate the chemical usage for a

particular project.

As part of the risk characterization, the results of the modeling effort were integrated with

the toxicity data collected for the chemical profiles. The results of this analysis indicate that a

potential for impact exists for both zinc bromide and ammonium chloride. The modeled impacts

for zinc bromide were predicted based on a 45,000 gallon release to the environment. While a

spill of ammonium chloride was not modeled, a review of the chemical’s structure and properties

indicate that it would behave similarly to potassium chloride. Utilizing the modeled exposure

concentrations for potassium chloride as a surrogate for ammonium chloride, a comparison with

marine toxicity thresholds was conducted that indicates a positive potential for environmental

impact. Since the analysis was conducted by proxy, this predication must be qualified as only an

indicator of potential risk and the need for a more focused study on the effects of ammonium

chloride on the marine environment.
1

1.0 INTRODUCTION

Chemicals have been used in offshore Gulf of Mexico (GOM) oil and natural gas

exploration and production (E&P) since development of the offshore resources over a half a

century ago. From 1947 to 1985, E&P activities focused on the shallow waters of the continental

shelf. Since the mid-1980s, however, the pace of exploration and development in the deep waters

(Figure 1) of the GOM has accelerated rapidly. By the end of 1999, approximately 1,200 wells

had been drilled in water depths exceeding 1,000 ft. (305 m) (Minerals Management Service,

May 2000). Moreover, production from these deepwater wells have now surpassed production in

shallow water, despite the fact that only 4% of all producing fields in the GOM are in deep

water. Today these deepwater fields provide over half the Gulf’s daily oil production, with an

additional 50-60 deepwater wells projected to be developed by 2007 (U.S. Department of the

Interior 2000). The variety and volume of chemicals used offshore to aid in the extraction of oil

and gas continues to grow. In addition, many technological changes have enabled expansion into

even deeper waters (e.g., underwater robotics, remotely operated vehicles, and navigational

technologies). These advances will likely continue to impact deepwater chemical usage.

The unique deepwater physical/environmental conditions (e.g., increased pressure, low

seawater temperature at depth, and higher formation temperature) and the unique biological

habitats in these areas (e.g., benthic communities), combined with increased exploration of

resources, have raised concerns about chemical usage and their impact in deep water as well as

throughout the GOM. The United States Minerals Management Service (MMS) is mandated to

manage the development of GOM oil and natural gas resources, while also ensuring safe

operations and protection of the human and natural environment. As a part of this overall

management responsibility, the MMS must consider possible impacts from chemicals used in oil

and gas development to both the natural and human socio-economic environments.

To accomplish this, an understanding of the types and quantities of chemical products

used offshore, especially in deep water, as well as their potential impact is needed. This report

identifies the types of chemicals used in the GOM via an extensive inventory. It presents their

properties, toxicity, usage patterns, and storage and handling practices. Through the use of spill

modeling, the potential for environmental risk for a select group of chemicals is evaluated. In

addition, this report includes an overview of relevant legislation. Specifically, objectives of this

project included:

• Establishing a baseline inventory of the chemical products, compounds, and mixtures in

current use by operators in the GOM, with emphasis on deep waters (over 1,000 ft. or 305 m)

• Estimating the amount of such chemicals expected to be used as exploration in the GOM

increases, with emphasis on deep waters

• Locating and collecting technical information on chemical volumes in typical GOM

operations

• Developing conceptual models using a range of chemical spill scenarios and predicted

impacts as a result of these spills

• Developing an inventory of types and amounts of hazardous substances stored, handled,

transferred to, and used on offshore oil and gas facilities in all water depths
2

 (Not to Scale)

Figure 1. The Gulf of Mexico Region, its Three Planning Areas, and the 1,000 ft. (305 m) Isobath that Separa

Water.

D e e p w a t e r

1000 ft. (305 m)

Isobath

S h a l l o w W a t e r

Western Planning Area Central Planning Area Eastern Planning Area

Gulf of Mexico

2
3

2.0 CHEMICALS USED IN GULF OF MEXICO OIL AND GAS OPERATIONS

2.1 Introduction

This section summarizes current information on chemical usage in the GOM in both deep

and shallow water areas. It includes information on the types, variety, and volume of chemicals

used in the GOM and the factors that determine their use.

2.1.1 The Need for Chemicals

Chemicals perform critical functions during drilling; cementing; well completion,

stimulation, and workover processes; and producing processes. For drilling chemicals, these

functions include such applications as lifting cuttings, applying back-pressure to the formation,

and stabilizing the wellbore. For production-treating chemicals, the functions include such tasks

as aiding phase separations, controlling corrosion, and controlling water-formed scale deposition.

Without these essential formulations, the safe, cost-effective extraction of oil and gas resources

would not be feasible. Technical problems encountered during the exploration and development

of new reserves in deepwater areas of the GOM, such as higher bottom hole pressures and

temperatures, subsea completions, and heat loss in production risers, have impacted chemical

usage.

In offshore operations, chemicals fall naturally into four major classes:

1. Drilling fluid chemicals

2. Cementing chemicals

3. Completion, stimulation, and workover chemicals

4. Production-treating chemicals

Drilling, cementing, completion, stimulation, and workover chemicals are applied

directly to the wells, whereas production-treating chemicals are applied to the produced streams.

It is convenient to subdivide chemicals into these four classes since each group is manufactured,

distributed, and supplied by a distinct group of companies and therefore information on these

chemicals is typically provided in this natural grouping. In addition, different departments within

operating oil companies typically manage the use of each chemical class; and, historically, this

chemical division has been mirrored by the suppliers that offered each class of chemical

independently.

Chemicals in each class are predominantly used during different stages of an oil or gas

well’s life span and serve a unique technical or economic function. The development and use of

chemicals is influenced by several factors:

• Solving or addressing operating problems (such as lifting cuttings during drilling, stabilizing

wellbores, increasing permeability of formations, and breaking emulsions, among many

others)
4

• Reducing overall costs

• Improving worker safety

• Complying with environmental regulations

To help understand chemical use in offshore E&P operations, it is useful to consider the

life cycle of a typical oil or gas field. Such a field will progress through the following five

distinct stages; exploration, development, active production, re-development, and harvest. A

brief description of each stage is provided below.

• Exploration – The search for oil and gas using seismic data, exploratory drilling for strata

identification and confirmation of hydrocarbons.

• Development – the setting of platforms, drilling of production and injection wells,

installation of gathering lines and separation equipment. The last part of this phase may

overlap with the active production stage.

• Active production – The period when the recoverable reserves in the reservoir are brought to

the surface, treated and sold.

• Re-development – When the original reserves are nearing depletion, the wells and equipment

in place are used to recover minor reserves that may have been encountered while drilling the

original wells. During this phase wells are re-completed in new zones where reserves might

exist.

• Harvest mode - At some point a field or wells in it can no longer produce sufficient revenue

to justify additional capital investment. In this case production continues as long as no new

capital investment is not required. At the end of harvest mode properties are abandoned or

sold.

Figure 2 represents the distribution of chemical usage (approximate) throughout the life

cycle of a field. This data illustrates the differences in chemical usage between the chemical

classes during each life cycle stage. For example, most of the drilling fluid chemicals are used in

the development phase that will last roughly 10% or less of the total life of the field. During that

period, large quantities of drilling fluid chemicals are used, but the time period is relatively short.

Conversely, the greatest percentage of production-treating chemicals are used during the active

production phase of the field. The shallow water region in the GOM contains many fields in

different phases of their life cycle. The majority of shallow water operations are in the active

production phase or later, while the deep-water region is largely in the exploration and

development phases.
5

LEGENDDF = Drilling Fluid ChemicalsC = Cementing ChemicalsCSW = Completion, Stimulation, aPT (O) = Production-treating ChemPT (W) = Production-treating Chem

Figure 2. Chemical Use by Stage of Oil & Gas E&P (GOM).

0

0.10.20.30.40.50.60.70.80.9

1

DF C CSW PT(O) PT(W) DF C CSW PT(O) PT(W) DF C CSW PT(O) PT(W) DF C CSW PT(O) PT(W) D

% Chemical Usage Over the Life Cycle (by Chemical Class)

EXPLORATION DEVELOPMENT ACTIVE PRODUCTION RE-DEVELOPMENT 

1-2 yrs. 3-5 yrs. 20-30 yrs. 8-10 yrs. 

2% 2% 2% 0% 0% 1% 1%

90% 90%

75%

80%

70%

15%

0% 0%

3% 3%

8%

12%

20%

5

STAGE DURATION (APPROXIMATE)

5
6

Chemical use is an operational art as much as an engineering science. The task of

selecting and managing chemicals requires the expertise of many individuals within the chain of

companies/services required to take an offshore E&P project through its functional life.

Therefore, when referring to the compiled GOM chemical inventory presented in this report, it is

important to note that the specific types of chemicals discussed and the volumes of the chemicals

are approximations and that this inventory serves as a guide to the probable chemicals and the

volumes that might be used and stored for a particular offshore operation in the GOM.

2.1.2 Brief Historical Perspective

The first chemical treatment technologies were developed over 90 years ago to separate

water from oil prior to refining operations. Since then, the use and application of chemicals has

continued to evolve and impact every facet of the E&P process.

Since the development of rotary drilling techniques, drilling fluid chemicals have been

employed to solve a wide range of well control problems and to promote efficient drilling rates.

There has been a steady improvement in drilling fluid chemicals and their application, starting

with early attempts to improve cuttings removal and control well flow. Drilling fluid density

assists in the application of back-pressure on an oil-bearing formation and also helps to control

the flow of oil. Before the use of drilling fluid chemicals, pictures of drilling rigs taken during

the first half of the twentieth century regularly showed “gushers” or plumes of oil being sprayed

high into the air and spreading crude oil over a wide area. At the time, environmental impacts

were unknown and unregulated.

The development and use of production-treating chemicals dates back to at least 1913,

when W. S. Barnickel received a chemical patent to break emulsions. In the early days of oil

refining, engineers identified the need to separate water from crude oil so that the water would

not cause corrosion during the refining process, leading to damaged equipment and the potential

loss of life (Hilliard 1987). In 1908, F. G. Cottrell patented a dehydration apparatus using an

electric field to dehydrate oil. Later Cottrell and Barnickel founded Petrolite Corporation (now

part of Baker Petrolite), which became, and currently is, a major supplier of oilfield chemicals

and process equipment.

During the first 20 to 30 years of E&P in the GOM, oil companies (operators) developed

chemical technology within their companies to satisfy their technology needs. As illustrated in

the 1958 edition of the API Green Book (NACE 1958) oil companies were supporting the

development of chemical formulations through their internal research efforts.

In contrast, today most of the oilfield chemical research and development is conducted by

suppliers rather than by the oil companies and is driven by market demands. In the early 1970s,

in parallel with the shift in development from oil companies to suppliers, regulations on the

discharge of waste by the Environmental Protection Agency (EPA) were developed. The

National Pollutant Discharge Elimination System (NPDES) added environmental protection as

an objective of chemical-treating technology. Oil companies demanded chemical formulations

from their suppliers that would provide the same functionality as those they were using, but

would not cause them to exceed NPDES limits or impact other regulations. Since many

chemicals used in offshore oil and gas operations are ultimately discharged as part of a waste
7

stream, this resulted in many new chemical formulations. Regulations and market demands

continue to influence the chemical development strategies of chemical suppliers in the Gulf.

(Drilling fluid chemicals, for example, will not sell on the market unless the resulting mud has a

96-hr LC50 of at least 100,000 mg/L to Mysid shrimp. Most muds on the market have 96-hr

LC50s of 500,000 mg/L or more.)

Current research in chemical formulation development is now more likely to examine

product improvements such as ways to improve efficiency of treatment or to decrease the impact

of the product on the environment. Harless’s work on biocides is an example of improving

efficiency. His paper, Mechanisms and Field Performance of 9, 10-Anthraquinone as a Biogenic

Sulfide Inhibitor, discussed using 9,10 anthraquinone in combination with glutaraldehyde to

control bacterial growth more completely (Harless 2000). Salma compared several commercial

biocides to a new proprietary compound in Acrolein: A Cost Effective Solution for Iron Sulfide

and Hydrogen Sulfide in Produced Waters to determine impacts on non-target species at

effective control levels (Salma 2000). One of the newer alternative biocides,

Tetrakishydroxymethyl phosphonium sulfate (THPS) decreases environmental impact when

discharged because it reacts with oxygen and rapidly degrades to a much less toxic form.

Examples of product development driven by environmental concerns can also be seen in

the area of corrosion inhibitor development. In the early 1990s, Haslegrave et al. (1992)

examined chemical structural relationships to toxicity of corrosion inhibitors and found ways of

decreasing toxicity while retaining function for some inhibitors. More recently, Brenzinski and

Halliburton Energy Services (1999) identified formic acid and potassium iodide as intensifiers

used in acid corrosion inhibitors. These examples typify the trend in technical development and

have resulted in inhibitors that are more effective, longer lasting and with lower potential to

impact the environment.

2.1.3 Development of Chemical Inventory

In the following sections we provide the inventory of chemicals typically used in ongoing oil and gas E&P activities in the GOM. While thousands of chemicals are sold for use in

the offshore oil and gas industry, no definitive information source exists and much of the

available information is considered proprietary. Therefore, the scientific literature on these

chemicals is scarce and does not typically include formulations or compositions. These sections,

therefore, present compiled data and inventories based primarily on data received from three

major energy companies operating in both the shallow and deep waters of the GOM; annual

reports provided in World Oil magazine (June 1999, August 1999, and November 1999) on

available chemicals; MSDS sheets; and a review of Hudgins and Petrotech Consultants, Inc.’s

(1991) report on chemical usage in the North Sea, which explains the need, use, and function of

the chemicals used offshore.

For each of the four chemical classes: drilling; cementing; completion, stimulation, and

workover; and production-treating, two tables and a searchable MS Access database that

includes information on chemical products; chemical handling (i.e., storage and transportation).

and physical and chemical properties for selected chemicals and/or products have been

developed. The first table, presented within the body of the report, describes each of the

functional categories within the class; the type of material (i.e., generic chemicals) used; and the
8

code for each category. The second table of the inventory, presented in Appendix A, is the

“product database” and lists actual products within each class; a description of these products;

their functions; and suppliers. Codes for each of the functional categories link the two tables and

the searchable MS Access database. The following discussions present an inventory of chemicals

used in the GOM aggregated into functional categories for each class of chemical along with a

description of the function and examples of the type of chemicals in each category.

2.2 Chemicals Used on Wells and Formations

2.2.1 Drilling Fluid Chemicals

2.2.1.1 Overview

Chemicals applied as part of the well drilling process are referred to as drilling fluid

chemicals or muds. These chemicals are required to overcome technical issues in the drilling

process, improve the efficiency and safety of well drilling, and protect associated equipment. To

perform these tasks, a variety of chemicals may be mixed together to develop the site-specific

properties required by the drilling fluid chemicals or muds. These properties may include:

• Controlled and relatively high viscosity

• Controlled and relatively high density

• Lubricity

• Low tendency to filter or lose components because of flow into the formation

• Stability to high temperature and high shear forces

To provide these qualities, nearly all drilling fluid chemicals are very stable dispersions

of solids in a continuous liquid carrier or emulsions of one liquid in another. In these instances,

each liquid phase will contain dispersed solids. Therefore, components are added to drilling fluid

chemicals to stabilize and promote emulsions and dispersions.

Defined by the nature of the continuous phase liquid carrier, these drilling fluid chemicals

can be divided into three categories; water-based, oil-based, and synthetic-based. Water-based

drilling fluid chemicals are used on all wells. Even if deeper portions are drilled with oil-based or

synthetic-based fluids, the upper portion of all wells is still drilled with water-based fluids.

Drilling fluid chemicals are added to muds and can generally be categorized as either

necessary for the drilling of the well or necessary to protect the equipment or formation. The

various properties of drilling fluid chemicals provide the functionality that allow the drilling

fluid chemical to:

• Carry cuttings from the well hole bottom to the surface for disposal (viscosity)

• Control pressure on the formation (density)

• Lubricate and cool the drill bit and string (lubrication)

• Suspend drill cuttings in the fluid when circulation is interrupted (thixotrophy)

• Support the drill string weight (density)
9

• Transmit hydraulic horsepower to the bit

• Control loss of drilling fluid chemicals to the formation both by flow into cracks and by

filtration of the liquid portion into the formation (plugging agents)

• Stabilize the hole wall and protect the formation (filter cake)

• Protect the mud components from bacteria (bactericide)

• Protect the drilling equipment from the corrosivity of the drilling fluid chemical (corrosion

inhibitor)

Drilling fluid chemicals used in the GOM have been divided into the following 18

functional categories (World Oil, March 1999).

• Alkalinity, pH control additives • Lost circulation materials

• Bactericides • Lubricants

• Calcium reducers • Pipe-freeing agents

• Corrosion inhibitors • Shale control inhibitors

• Defoamers • Surface-active agents

• Emulsifiers • Temperature stability agents

• Filtrate reducers • Thinners, dispersants

• Flocculants • Viscosifiers

• Foaming agents • Weighting materials

These functional categories are described in the drilling fluid chemical inventory (Section

2.2.1.2).

Drivers for Drilling Chemical Use

The amount of drilling chemicals used is determined by a complex combination of the

number of wells drilled, depth of the wells, and the type of drilling mud used.

The true vertical depth of a well is theoretically determined by the depth of the target

formation. However, the actual depth drilled is affected by well deviation and sidetracks. The

type of drilling fluid chemicals used is determined by:

• Properties of the formations penetrated

• Formation pressures encountered

• Temperatures of the formations encountered

• Environmental regulations

These properties drive the use of particular drilling fluid chemicals. For example, drilling

through clay formations triggers the need for drilling fluid chemical additives that will prevent

clay swelling, while drilling through salt requires a drilling fluid chemical that will not dissolve

it; i.e., salt-saturated, water-based muds or non water-based muds. Water-based muds become
10

increasingly unstable at high temperatures; thus, high temperatures trigger the use of non waterbased muds. Conventional oil based muds are often not used because of the possibility of an

emergency disconnect of the marine riser releasing hundreds of barrels of whole mud to the

water-column.

Application

Figure 3 shows the mud circulating system on a drilling rig. Mud components are added

in the mixing hopper and are mixed in the mud pit. Drilling fluid chemicals are transported to

and stored at the well site, and drilling fluids are prepared on site from the various functional

components. The time required to drill an exploratory well is typically 70-90 days (Minerals

Management Service 2000). A supply of drilling fluid chemicals sufficient to complete the well

being drilled is stored on the rig.

Figure 3. Mud Circulating System on a Drilling Rig. (Source: MI Drilling Fluids)

During the drilling phase, water-based drilling fluid chemicals are in continuous demand

because these fluids are dynamic materials that are constantly changing in their chemical and

physical characteristics as they are used. The properties of the drilling fluid in the system change

as clay solids from the formation being drilled mix with drilling fluids and are thereby added to

the process system. Since the clay from the formation reacts in the same manner as the clay used
11

to make the mud, the ratio of clay to other components changes and additional chemicals are

needed to restore the mud’s properties. Drilling fluids are also modified as they become

associated with cuttings removed from the process system. The properties of the drilling fluid in

the system are monitored several times a day. Additives such as barite, caustic, lignite, and

lignosulfonate are used to maintain the functionality of the fluid. Thus, the addition of chemicals

to the mud system is on-going throughout the drilling process.

Characterization

Almost all water-based drilling fluid chemicals used in large amounts are fine solids.

They are designed to be dispersed or dissolved in water; both processes are enhanced if the solids

are in a very fine, powdered form. Chemical characteristics of the drilling fluid chemicals range

from chemically inert and insoluble in water to soluble and highly reactive. Therefore, solids can

be generally classified into five groups according to their solubility and chemical reactivity with

seawater constituents as follows:

• Water insoluble, non-reactive (e.g., barite, bentonite clay)

• Partially water-soluble, non-reactive (e.g., lignite)

• Water-soluble, non-reactive (e.g., potassium chloride)

• Water-soluble, mildly reactive (e.g., calcium chloride)

• Water-soluble, vigorously reactive (e.g., sodium hydroxide)

SBF and OBF drilling formulations are essentially water-based drilling fluids dispersed

in an organic carrier or emulsified in an organic carrier. Similar solids are used in these

formulations, however some of the inert solids such as weighting agents and viscosifiers used in

these are treated with amines and other organic additives to make them more oleophillic. In

addition to the universal constituents found in all drilling fluids non-water-based fluids also

contain emulsifiers.

Fate in the Process System

All drilling fluid chemicals eventually become drilling wastes. Drilling fluid chemicals

become part of the drilling waste stream in two ways. First, they cling to drill cuttings as the

cuttings are discharged. Second, they become excess material either made during drilling

operations or at the end of the well.

Water-based drilling waste and associated drilling fluid chemicals are discharged where

permitted. Drilling wastes, from wells drilled in Coastal Areas or in the Territorial Seas, are

collected in cuttings boxes and hauled ashore for disposal in landfills. Oil-based fluids are

prohibited from discharge in the Gulf of Mexico. Synthetic-based fluids are prohibited, however

cuttings can be discharged in the Central and Western Planning Areas (Figure 1). In the Outer

Continental Shelf (OCS), such discharges are allowed if the waste meets discharge limits. The

discharge limits include a toxicity limit, a limit on cadmium and mercury in barite, and a sheen

test. Water-based drilling fluid components are designed to comply with these limits.
12

Fate in the Marine Environment

Permitted discharges are limited by several factors, including the rate of discharge, the

formulation of the mud and cuttings, and the state of the material (i.e., free dispersion of solids in

a liquid). Accidental discharges (“spills”) may be sudden and consist of a single component

product that might be a solid contained in paper sacks or a steel container.

Some drilling fluid chemicals are chemically inert (e.g., barite, clay, etc.) and will

become part of the sediment and disperse along the bottom. Others strongly react with the

environment (i.e., caustic materials such as caustic soda, caustic potash, acids, etc.) and produce

reaction products (sodium chloride, potassium chloride), some of which are natural constituents

of seawater. Most organic materials (e.g., lignite, lignosulfonate, polymers, etc.) will eventually

be degraded in the environment by bacterial action.

2.2.1.2 Drilling Fluid Chemicals Inventory

Drilling fluids are typically formulated to meet the site’s unique requirements off-shore

and then transported to the site. Additional drilling fluid components and base fluid may than be

added to maintain the needed properties. Drilling fluid chemical components can be divided into

18 functional categories. Each operation will employ a unique formulation of these components

that incorporates an appropriate subset of the functional categories.

Table 1 summarizes the 18 functional categories of drilling fluid chemicals used in

offshore operation in the Gulf of Mexico. Each drilling fluid category is defined and examples of

chemicals are included in each category.

Table 1

Drilling Fluid Chemicals: Codes, Functional Categories, Descriptions, and Material Types Used

Code Functional Categories Description Material Types Used

A Alkalinity, pH control

additives

Controls the alkalinity or acidity

of a fluid. These factors are

important in controlling mud

properties.

Lime (CaO), caustic soda (NaOH), soda ash

(Na2CO3), bicarbonate of soda (NaHCO3),

other common acids and bases

B Bactericides Prevents bacterial degradation of

organic additives.

Aldehydes and others

CA Calcium reducers Used to counteract the effects of

calcium from seawater, cement

contamination, anhydrites, and

gypsum from the formation on

mud properties.

Soda ash (Na2CO3), bicarbonate of soda

(NaHCO3), caustic soda (NaOH). and certain

polyphosphates

CO Corrosion inhibitors Controls corrosion acids and acid

gases.

Amine- and phosphate-based products and

other specially formulated chemicals

D Defoamers Used to reduce foaming action

that affects mud properties.

Alcohol-based materials, silicone-based

materials, aluminum stearate, alkyl

phosphates
13

Table 1

Drilling Fluid Chemicals: Codes, Functional Categories, Descriptions, and Material Types Used

(continued)

Code Functional Categories Description Material Types Used

E Emulsifiers Used to create a heterogeneous

mixture of two insoluble liquids.

They may be anionic (-), nonionic (no charge), or cationic (+).

Detergents, soaps, organic acids, and waterbased surfactants are used in water-based

muds

FR Filtrate reducers Used to decrease fluid (as

opposed to whole mud) loss

through the filter cake on the

walls of the wellbore.

Bentonite clays, lignite, CMC (sodium

carboxymethylcellulose), polyacrylate, and

pregelatinized starch

FL Flocculants Used to increase viscosity,

increase effectiveness of clay

viscosifiers, or clarify or de-water

low solids fluids.

Inorganic salts, hydrated lime, gypsum

(calcium sulfate penta hydrate), soda ash

(Na2CO3), bicarbonate of soda (NaHCO3),

sodium tetraphosphate, and acrylamide-based

polymers

FO Foaming agents Used to create foam in water to

permit air or gas drilling through

water-bearing formations.

See inventory for product examples (e.g.,

amplifoam, airfoam B)

LO Lost circulation materials Used to plug leaks in the

wellbore and prevent the loss of

whole drilling fluid to the

formation.

Nut shells, natural fibrous materials, inorganic

solids

LU Lubricants Used to reduce torque and drag

on the drill string.

Oils, synthetic liquids, graphite, surfactants,

glycols, and glycerin

P Pipe-freeing agents Spotted at a particular point in a

well to prevent the drill pipe from

sticking to the formation.

Detergents, soaps, oils, surfactants, and other

chemicals

SH Shale control inhibitors Used to control shale hydration

and subsequent wellbore

enlargement, heaving and caving

of water-sensitive shales.

Soluble calcium and potassium salts, other

inorganic salts, and organic compounds

SU Surface-active agents Used to modify the interfacial

tension between contacting

surfaces. They may act as

emulsifiers, de-emulsifiers,

wetting agents, flocculants, or

deflocculants.

See inventory for product examples (e.g.,

avabiowet, anco rope)

TE Temperature stability

agents

Used to increase the stability of

dispersions, emulsions, and

rheological properties at high

temperatures.

Acrylic polymers, sulfonated polymers,

copolymers, lignite, lignosulfonate, and

tannin-based additives
14

Table 1

Drilling Fluid Chemicals: Codes, Functional Categories, Descriptions, and Material Types Used

(continued)

Code Functional Categories Description Material Types Used

TH Thinners, dispersants Used as a deflocculant to reduce

the attraction (flocculation) of

clay particles which causes high

viscosity and gel strength. That

is, they balance the effect of

viscosifiers and control mud

viscosity and gel strength.

Tannins, various polyphosphates, lignite,

lignosulfonates

V Viscosifiers Used to increase viscosity in

muds.

Bentonite, attapulgite clays, CMC, and other

polymers

W Weighting materials Used to increase the density of

the mud and thereby enable it to

control formation pressures.

Barite (barium sulfate), lead compounds, iron

oxides, calcium carbonate, and similar

products

2.2.2 Cementing Chemicals

2.2.2.1 Overview

Cements ensure structural integrity in wells and are essential to the drilling and

completion of wells. During the drilling process, the internal walls of the hole are maintained by

drilling fluid chemicals. When more stability is needed to keep the hole from collapsing or

becoming unstable, steel casing is placed in the hole. Cement is then used to bind the steel casing

to the formation and to seal off unwanted flow between the wellbore and the formation.

Cement formulations are placed in wells as a liquid slurry of dry particulate solids in

water. The solids chemically react with the water to form a dense, contiguous solid mass,

impermeable to liquids To position the cements in the well, they are preceded by volumes of

spacer fluid and followed by displacer fluids. Similar to drilling fluid chemicals in form, they

have many of the same properties as drilling fluid chemicals. A cement formulation must:

• Not react until it is put in place

• Not filter out onto the formation

• Be temperature stable

• Remain dispersed until it reacts

• Have the correct density

• Bond to the steel and the formation
15

Cementing chemicals that are used in the GOM to achieve the properties discussed above

can be divided into one of 15 functional categories (World Oil, March 1999).

• Basic cements • Silica to reduce or prevent high

temperature strength retrogression

• Accelerators and salts • Retarders

• Extenders and density-reducing additives • Anti-gas migration agents

• Free-water control and solids suspending

agents

• Anti-foam and defoaming agents

• Dispersants • Density-increasing or weighting agents

• Bond improving and expanding additives • Additives and mixtures to reduce or

prevent lost circulation

• Fluid loss control additives • Spacers and chemical washes or preflushes

• Specialty cement blends

These functional categories are described in Section 2.2.2.2.

Drivers for Cement Chemical Use

The use of cement chemicals depends on the same factors as those affecting drilling fluid

chemical use, therefore, the total volume of cement used is determined by the number of wells

completed, the depth of the wells, and the type of cement used.

However, the type of cement used and the additives chosen to formulate it may not be

affected in the same way by formation pressure, temperature, and geology. Pressures and

temperatures affect setting rate of the cement, triggering the need for chemicals to adjust setting

rates. For very deep wells, the weight of the cement can fracture the formation, which triggers

the need for chemicals to lighten the weight of the cement.

Application

The components of cementing chemical formulations are transported to the drilling rig

and are mixed and applied on site under the supervision of the cement supplier. The cement

formulations are designed by the supplier to meet the needs of the particular job. As wells are

drilled, a section of open hole without casing is created (see Figure 4). There is a limit to the

length of hole that can be supported without casing. When that limit is reached, drilling stops and

new casing is installed. The new casing is bonded to the bottom of the previous casing and to the

formation below it with cement. A deep well may require several strings of successively smaller

diameter casing and each string will result in a new cementing job.
16

Figure 4. Well Profile Showing Cementing Intervals for a Typical Deepwater Well

(Source: MI Drilling Fluids).

Characterization

Like drilling fluid chemicals, cementing chemicals are almost all solids, supplied in

powdered or fine particle form. Many cementing chemicals are identical in both form and

composition to drilling fluid chemicals and can similarly be classified according to solubility and

reactivity in water.

Fate in the Process System

The majority of cementing chemical formulations become integrated as a part of the well,

forming a solid barrier between the outside of the well casing and the inside of the formation

face. It is difficult to calculate the exact amount of cement needed because the geometry of the

hole not known precisely. Extra cement is therefore applied to the well to ensure that voids are

completely filled. When setting the surface casing, this extra cement may be pushed up around

the casing and out into the marine environment. For deeper casing, the excess is removed and

becomes part of the drilling waste. Discharges of cements are included in NPDES permits as a

miscellaneous discharge.

Fate in the Marine Environment

When cement itself is discharged, it will react with water just as it does in use and form

solids that become part of the sediment. These solids will exist in seawater as small particulates

due to dilution by seawater before the reaction is complete. If excess cement is left in the well

until it cures and then drilled out, the cement is incorporated in and disposed of with the cuttings.

30 in. shoe @ + 730 ft

20 in. shoe @ + 1,900 ft

13-3/8 in. shoe @ 6,400 ft

7-3/4 in. liner top @ 13,820 ft

9-7/8 in. shoe @ 13,956 ft

7-3/4 in. liner shoe @ 15,627 ft

8-1/2 in. hole to 15,785 ft

6 in. hole to 16,300 ft

CEMENT
17

2.2.2.2 Cementing Chemicals Inventory

The properties of the type of cement needed are based on the characteristics of the well

being cased and the geologic formation. Once these properties are determined, cement

components are transported to the offshore site and a slurry is formulated to meet the unique

requirements of that site. Cement chemicals used in the GOM have been divided into 15

functional categories. For any given operation, the cementing components stored on site will

include a subset of these functional categories.

Some of the functional components contribute to the properties of the cement slurry

itself; that is, they give it the properties it needs to function properly. Other categories act to:

• Protect the cement slurry (e.g., fluid loss control additives, anti-foam and defoaming agents,

additives to prevent lost circulation)

• Place the slurry in the proper place (e.g., spacers and chemical washes or pre-flushes)

• Control slurry stability (e.g., dispersants, anti-gas migrating agents)

Table 2 lists, defines, and provides examples of each of the cement chemical categories

currently used in offshore Gulf operations.

Table 2

Cementing Chemicals: Codes, Functional Categories, Descriptions, and Material Types Used

Code Functional Categories Description Materials Types Used

BC Basic cements Basic materials Portland cements, blast furnace

slag, calcium aluminate

AS Accelerators and salts Increases rate of setting Sodium chloride, calcium chloride,

sodium silicate, calcium sulfate

hemihydrate

ED Extenders and density-reducing

additives

Increases volume of mix and

reduces density

Bentonite, attapulgite, flyash,

natural pozzolan, diatomaceous

earth, perlite, fumed silica, glass

microspheres

FWS Free-water control and solids

suspending agents

Improves uniformity of the mix Polymers, sodium silicates,

biopolymers, bentonite,

attapulgite, fumed silica

DIS Dispersants Disperses fine solids and

prevents settling

Polynaphthalene sulfonate, citric

acid and citrate salts, proprietary

additives

BIE Bond improving and expanding

additives

Improves bond to formation and

casing

Styrene/butadiene copolymer,

fumed silica, fumed silica/flyash

blend, calcium sulfate

hemihydrate, metal oxide,

aluminum powder, proprietary

materials
18

Table 2

Cementing Chemicals: Codes, Functional Categories, Descriptions, and Material Types Used

(continued)

Code Functional Categories Description Materials Types Used

FCA Fluid loss control additives Reduces loss of liquids from

mix to formation

Proprietary materials,

styrene/butadiene copolymer,

acrylic latex

SHT Silica to reduce or prevent high

temperature strength

retrogression

Improves strength in high

temperature environments

Sand, silica flour, microfine silica

RET Retarders Slows rate of setting Lignosulfonate, modified

lignosulfonate, organic acid,

carboxymethyl hydroxyethyl

cellulose, borax/borate salt, nonborax/borate salt, proprietary

synthesized polymer or copolymer,

citric acid or citrate salt

AGM Anti-gas migration agents Controls gas flow through mix Polymeric blends (non-latex),

styrene/butadiene copolymer,

acrylic, fumed silica, fumed

silica/polymer blends, calcium

sulfate hemihydrate, proprietary

polymeric blends, aluminum

powder

ADA Anti-foam and defoaming agents Reduces foaming in the cement

mix

High molecular weight alcohols,

polyalcohols, silicones

DIW Density increasing or weighting

agents

Increases density of the mix Sand, silica flour, microfine silica,

ilmenite, hematite, barite,

manganese oxides, calcium

carbonate

LCA Additives and mixtures to

reduce or prevent lost circulation

Reduces loss of cement to the

formation

Cements, foamed cement, nonaqueous slurries, sodium silicate

solutions, sand, mica, cellophane

flake, gilsonite, ground coal,

walnut plugs, perlite, polymer

fibers, wood chips, polyester,

ground thermoplastic or rubber,

proprietary materials

SCW Spacers and chemical washes or

pre-flushes

Helps in the placement of

cement mix

Liquid materials either emulsified

or with additives

SCB Specialty cement blends Special purpose products Blends of cement with flyash, clay,

pozzolan, silica
19

2.2.3 Completion, Stimulation, and Workover Chemicals

2.2.3.1 Overview

Completion chemicals are used to clean wells after drilling, to control them while they

are being perforated, and to make them operational when essential equipment such as packers

and tubing are added. After the last casing is set at the end of the drilling phase, perforations

must be placed in the casing so that the producing formation is open to the wellbore. While

creating the perforations, it is important to hold back-pressure on the formation and to avoid

destabilizing or contaminating the formation.

To accomplish these objectives, clean brines, free of solids, are used. To maintain backpressure, high-density salts may be used to prepare the brines. Once the perforations are created,

the same brine may be left in the well while the tubing is set and the packers are placed. The

packers isolate the annulus between the casing and tubing from the interior of the tubing. The

brine is left in the annulus so that, if a packer fails, the brine will be available to help control

flow from the well. The same types of brines used as completion fluids may also be used as

spacers and displacement fluids in other completion, stimulation, and workover procedures.

Stimulation procedures include fracturing or acidizing to achieve a desired production

rate. These procedures act to increase permeability that allows increased flow from the well. To

achieve these objectives, stimulation fluids must dissolve part of the formation or contaminants

in it or they must provide hydraulic pressure that can fracture the formation. Acid solutions and

gel brines are used to accomplish these objectives. These procedures are performed on both old

and new wells as the need arises.

Formations that are unconsolidated need to be gravel-packed to prevent the formation

from flowing into the wellbore. Formations with low permeability perform better if fractures are

created in them around the wellbore. Occasionally, residual drilling fluids may remain in the

formation around a new well and decrease flow from the well. These fluids can be dissolved with

acid. In older wells, water-formed scales can form around a wellbore and block the formation.

These materials can also be dissolved by acid. Acidizing and gravel-packing are often performed

together.

There are 27 functional categories of completion and acidizing fluids used in the GOM.

• Water-based completion fluid • Anti-sludge agent

• Water-based polymers • Foamers

• Friction reducers • Scale inhibitors

• Fluid loss • Iron (Fe) control

• Diverting agents • Oxygen scavenger

• Polymer plugs • Mutual solvents

• Acid inhibitors • Corrosion inhibitors

• Acid retarders • Paraffin control

• Emulsifiers • Miscellaneous products
20

• Clay stabilizers • Acid systems

• Surfactants • Retarded acid plus

• Non-emulsifiers • Mud acid plus surfactants

• Fines suspender • Mud acid plus alcohol

• Regarded HF

For fracturing chemicals, there are 24 functional categories of additives and two

categories of proppants (granular particles) used in the GOM.

• Water-based polymers • Defoamers

• Friction reducers • Oil gelling additives

• Fluid loss additives (FLAs) • Biocides

• Breakers • Acid-based gel systems

• Emulsifiers • Water-based systems

• Clay stabilizers • Crosslinked gel systems

• Surfactants • Alcohol/water systems

• Non-emulsifiers • Oil-based systems

• pH control additives • Polymer plugs

• Crosslinkers • Continuous mix gel concentrates

• Foamers • Resin-coated proppants

• Gel stabilizers • Intermediate-to-high strength ceramic

proppants

Drivers for Completion, Stimulation, and Workover Chemicals

Completions, stimulations, and workovers are not limited to new wells. While new wells

do require completion and stimulation, old wells are also recompleted to produce from new

zones. Old wells may undergo workover and stimulation to increase production rates. The

amount of these chemicals used is driven by:

• The number of wells needing treatment

• The depth and length of the interval being treated

• The type of procedure used

New wells need stimulation to remove mud residue blocking the formation or to increase

porosity near the wellbore. Active, producing wells are stimulated to remove water-formed

scales or clay fines that have migrated to the wellbore and blocked the formation around the

perforations. Workovers are done to install new equipment or to remove obstructions such as

sand in the wellbore. The need for these procedures depends on reservoir or formation-specific

problems.
21

Application

Completions and stimulations are normal procedures used to equip a new well and put it

into service. Stimulation and workover procedures are also conducted on formation intervals in

existing wells to enhance production. Figure 5 shows a set of perforations in a casing and a

gravel-packed formation. Completion fluids are used in the well when the perforations are made.

Slurries of gravel in water are used to place gravel-packs and some types of gravel-packs include

acid stimulations. Completion, stimulation, and workover chemicals are all applied as water

solutions and are mixed (if needed) and pumped by the supplier’s personnel. The final chemical

formulation required for each procedure may be brought to the site as either a pre-mixed

formulation or as component parts to be mixed on site. Typically, completion, stimulation, and

workover chemicals are not stored on site for extended periods, but rather are transported to the

site in the required amounts prior to the job.

 (a) (b)

Figure 5. Completed Producing Zones; (a) Perforations, (b) Gravel-Pack.

Fracturing is used to create and maintain conductive tracks in the formation. Once

formed, these cracks are kept open with granular particles (proppants) and provide a relatively

porous structure that holds back the formation and allows flow though the crack. Cracks are

created with hydraulic pressure, and fracturing (frac) fluids/chemicals are designed to transmit

such pressure efficiently. The process includes several stages, including:

• Prepad – designed to penetrate the formation, help initiate fractures, and cool the formation

• Pad – viscous fracturing fluid without proppants to generate the fractures

• Proppant stages – carries proppant into the fractures

• Flush – used to displace the working solutions through the tubing and place it where it is

needed
22

Acidizing is used to remove formation damage near the wellbore, to increase formation

permeability, to remove scale and other debris, and to change the formation wetability

characteristics. Formation damage may result from:

• Clay and fines (i.e., from residual drilling fluids or loose formation material)

• Perforation plugging (i.e., from compaction perforating waste)

• Emulsions (i.e., caused by chemicals added during other procedures that stabilize oil water

emulsions)

• Relative permeability (i.e., caused by chemicals used in other processes which change the

wetability of the formation)

• Asphaltenes and paraffin (i.e., organic materials that may precipitate from crude oil)

Characterization

Completion, stimulation, and workover chemicals include water-soluble materials and

insoluble materials such as proppants. The formulations used are water solutions of acids, salts,

or both. Acids are delivered to the site by the supplier in bulk tanks as ready-made solutions

while proppants and salts are delivered as solids (sacks stacked on pallets) and are mixed on site.

Acidizing chemical categories can be divided into several subcategories:

• Basic functional components (i.e., acid and process control chemicals; e.g., acid systems,

diverting agents, acid retarders)

• Process aids (i.e., chemicals that solve problems resulting from the acid reaction products;

e.g., friction reducers, fines suspenders, iron control, mutual solvents)

• Protectors (i.e., chemicals used to protect the fluid, formation, or equipment; e.g., acid

inhibitors, oxygen scavengers, corrosion inhibitors)

These materials are divided among a large number of classes according to their solubility

and chemical reactivity in seawater. These include:

• Inorganic acids, highly reactive with seawater constituents (hydrochloric, hydrofluoric acids)

• Water-soluble inorganic salts, unreactive and reactive (sodium chloride, potassium chloride,

calcium chloride, zinc bromide)

• Water-soluble organic polymers (xanthan gum, guar gum)

• Soluble inorganic solids (rock salt)

• Organic acids (acetic acid, benzoic acid)

• Low molecular weight organic polymers (polyacrylamides, alkyl ammonium compounds)

• Surfactants
23

Fate in the Process System

Completion, stimulation, and workover chemicals end up in one of three places:

• Discharged or disposed of as waste

• Remaining in the well as packer fluid or part of the well

• Injected into the formation

Clear completion fluids are used during perforations of the casing, placement of tubing,

and setting of packers. Fluid remaining in the tubing after completion of the job is either

disposed or recycled. In nearshore areas, the fluid must be hauled to shore, while in the OCS it

can be discharged in accordance with NPDES permit limits.

Fracturing, acidizing, and gravel-packing processes also involve the use of completion,

stimulation, and workover chemicals. These processes are used to improve the ability of the well

to give up produced fluids by increasing permeability and/or porosity. After the fluids have

performed their desired function, they are produced back and disposed of in the same manner as

completion fluids. In existing fields, the returns may be combined with the produced water,

processed through the treating system, and discharged. In the coastal region, they are injected

underground.

Fate in the Marine Environment

Many components of completion, stimulation, and workover chemicals are either acids or

salt solutions. The acids rapidly react with the seawater environment and become part of the

natural constituents of seawater. Some salts, such as those containing calcium, zinc, and other

reactive ions, also react with the constituents of seawater and become solids. These solids will

initially be suspended in the water column and eventually become part of the sediment. Some

components of this class of chemical are solid materials used as proppants or as gravel-pack.

These materials are inert solids and will end up in the sediment.

Inorganic acids discharged to the marine environment will react with the carbonate

equilibrium system. The reaction produces salts such as sodium chloride and sodium fluoride and

carbon dioxide. The salts are natural constituents of seawater; the carbon dioxide goes into the

atmosphere. The organic completion, stimulation, and workover chemicals will initially spread

through the water column as dissolved material and will eventually biologically degrade.

2.2.3.2 Completion, Stimulation, and Workover Chemicals Inventory

Once the need for completion, stimulation, and workover chemicals is specified, the fluid

components are either pre-formulated and transported to the offshore site or transported as

components and prepared on-site. World Oil published separate articles on acidizing and

fracturing in 1999. This report has adopted the division of fracturing chemicals into 22 functional

categories, proppants in two categories, and acidizing chemicals into 28 functional categories.

Table 3 summarizes the functional inventory of completion, stimulation, and workover

chemicals likely to be found in the GOM. It also lists and defines each of the completion,

stimulation, and workover chemical categories and shows examples of chemicals included in

each category.
24

Table 3

Completion, Stimulation, and Workover Chemicals: Codes, Functional Categories,

Descriptions, and Material Types Used

Code Functional Categories Description Material Types Used

A-WBC Water-based completion fluid Brine solutions and surfactants

for cleaning wells

See inventory for example products

(e.g., MudClean OB, Wellwash-1000)

A-WBP Water-based polymers Used for adjusting viscosity Xanthate, modified natural polymers

A-FR Friction reducers Used for decreasing resistance

to flow

Anionic polyacrylamides, cationic

polyacrylamides

A-FL Fluid loss Used for reducing loss of fluid

to the formation

Graded silica flour, oil soluble resins,

benzoic acid

A-DA Diverting agents Used to divert acid from high

permeable formations to lower

permeability formations

Graded rock salt, flake benzoic acid,

graded oil soluble resin, oil soluble

graded naphthalene

A-PP Polymer plugs Used similarly to diverting

agents

Guar or hydroxypropylguar,

hydorxyethylcellulose, crosslinked

hydroxypropylguar

A-AI Acid inhibitors Used to keep acid from

corroding steel

Propargyl alcohol, ethyl octynol,

acetaldehyde, crotonaldehyde,

quaternary ammonium salts

A-AR Acid retarders Used to slow the reaction of acid

with the material being

removed. Needed to spread the

action of the acid deeper into the

formation.

Oil wetting surfactants

A-E Emulsifiers Used to create emulsified acid

mixtures

See inventory for example products

(e.g., Nowferr 5, Claymaster 5C)

A-CS Clay stabilizers Used to protect integrity of

formation clays

Alkyl quaternary ammonium

compounds, ammonium chloride,

potassium chloride

A-S Surfactants Used to clean surfaces being

acidized

See inventory for example products

(e.g., SuperFlow III, FC-100)

A-NE Non-emulsifiers Wetting agents that do not

promote emulsification

See inventory for example products

(e.g., AquaFlow, LoSurt 259)

A-FS Fines suspender Used to disperse fine solids in

acidizing fluids

See inventory for example products

(e.g., ST 100, SSO-21M)

A-ESA Anti-sludge agent Used to prevent the formation of

emulsions

Dodecylbenzene sulfonic acid

A-F Foamers Used to develop light weight

mixtures

See inventory for example products

(e.g., FAW-18W, F100)

A-SI Scale inhibitors Used to prevent the formation of

inorganic scales

See inventory for example products

(e.g., L35, Corexit-7647)

A-IC Iron (Fe) control Used to complex iron three and

prevent re-precipitation in the

formation

Organic acids, EDTA
25

Table 3

Completion, Stimulation, and Workover Chemicals: Codes, Functional Categories,

Descriptions, and Material Types Used (continued)

Code Functional Categories Description Material Types Used

A-OS Oxygen scavenger Used to remove oxygen from

acidizing fluids and control

oxygen corrosion

Bisulfites

A-MS Mutual solvents Used to control the formation of

water in oil emulsions

Ethylene glycol monobutyl ether

(EGMBE)

A-CI Corrosion inhibitors Used to control corrosion due to

oxygen, carbon dioxide and

hydrogen sulfide

Ammonium bisulfite, aldehydes

A-PC Paraffin control Used to control solid paraffin

deposition

See inventory for example products

(e.g., P800, Paratrol 30)

A-MP Miscellaneous products Special products from all areas

not otherwise categorized

See inventory for example products

(e.g., Ammonium Biofluoride, HCl)

A-AS Acid systems Basic acid types used Hydrochloric acid, hydrofluoric acid,

organic acids with various additives

A-RAS Retarded acid plus Mixtures of mineral acids and

organic acids and other specialty

acid mixes with slower reaction

rates

Mixtures of inorganic and organic

acids or inorganic acids and gelling

agents

A-MAP Mud acid plus surfactants Special acid formulations for

removing residual drilling fluids

and clay

See inventory for example products

(e.g., Available, Special Custom

Blend)

A-MAA Mud acid plus alcohol Gas well acidizing, low surface

tension, fluid clean up

See inventory for example products

(e.g., Gas Well Mud Acid, Custom

Formulated)

A-RHF Retarded HF Generates mud acid (HF) in the

formation

See inventory for example products

(e.g., Fluorbonic Acid, Clay Acid)

F-WBP Water-based polymers Natural and manufactured

polymers for increasing

viscosity in fracturing fluids

Guar gum, hydroxypropyl guar,

hydroxyethyl cellulose

F-FR Friction reducers Used to reduce resistance to

flow

Anionic polyacrylamides, cationic

polyacrylamides

F-FLA Fluid loss additives (FLAs) Insoluble solids used to stop loss

of fluids to the formation

Graded silica flour, oil soluble resins,

benzoic acid

F-B Breakers Used to reduce viscosity in

polymer solutions

See inventory for example products

(e.g., Enzyme G, AP breaker)

F-E Emulsifiers Used to stabilize emulsions of

multiphase fluids

See inventory for example products

(e.g., PS-3, SEM-5)

F-CS Clay stabilizers Used to reduce clay swelling

and resulting damage to

formations

Alkyl quaternary ammonium

compounds, ammonium chloride,

potassium chloride

F-S Surfactants Used as wetting agents and

cleaners

See inventory for example products

(e.g., WS-70, InFlo 150)
26

Table 3

Completion, Stimulation, and Workover Chemicals: Codes, Functional Categories,

Descriptions, and Material Types Used (continued)

Code Functional Categories Description Material Types Used

F-NE Non-emulsifiers Wetting agents that do not

promote emulsification

See inventory for example products

(e.g., AquaFlow, LOSURF 300)

F-PCA pH control additives Used to adjust the pH of fluids Caustic soda, sodium carbonate,

ammonium hydroxide, organic acids,

sodium acetate, sulfamic acid

F-C Crosslinkers Metal compounds used to

enhance polymer performance

by crosslinking of polymers.

See inventory for example products

(e.g., Delay, Sodium Borate)

F-F Foamers Used to create low density foam

fluids

See inventory for example products

(e.g., S-400, WF-1)

F-GS Gel stabilizers Used to give stability to

polymers in high temperatures

Methanol. See inventory for other

example products

F-D Defoamers Used to control foam in fluids See inventory for example products

(e.g., Defoamer, AFA-3)

F-OGA Oil gelling additives Gelling agents for oil-based

fluids

See inventory for example products

(e.g., OG-14 Gellant, J601)

F-BC Biocides Used to control bacterial

degradation of polymers

Aldehydes

F-ABG Acid-based gel systems Specialty gel system used in

fracturing operations.

Preformulated mixture

See inventory for example products

(e.g., XLA-3)

F-WBG Water-based systems Specialty gel system used in

fracturing operations.

Preformulated mixture

See inventory for example products

(e.g., AquaFrac, Gelled Water)

F-CGS Crosslinked gel systems Specialty gel system used in

fracturing operations.

Preformulated mixture

See inventory for example products

(e.g., Saturn I, Vicking D)

F-AWS Alcohol/water systems Specialty gel system used in

fracturing operations.

Preformulated mixture

See inventory for example products

(e.g., Binary Foam, Crosslinked)

F-OBS Oil-based systems Specialty gel system used in

fracturing operations.

Preformulated mixture

See inventory for example products

(e.g., Sandoil, Super Rheo Gel)

F-PP Polymer plugs Used to stop loss of fluid to

formation fractures

Guar, hydroxypropylguar,

hydoxyethylcellulose

F-CMG Continuous mix gel

concentrates

Specialty gel system used in

fracturing operations.

Preformulated mixture

See inventory for example products

(e.g., LGC-1, XLFC-3)

F-RCP Resin-coated proppants Proppants for holding formation

cracks open

See inventory for example products

(e.g., SUPER-WEL-Frac)

F-IHC Intermediate-to-high-strength

ceramic proppants

Proppants for holding formation

cracks open

See inventory for example products

(e.g., MIGHTY-PAC, Z-PROP)
27

2.3 Chemicals Applied to Production Processing Systems

2.3.1 Overview

While drilling fluid chemicals, cementing chemicals and completion, stimulation, and

workover chemicals are applied to wells, production-treating chemicals are applied to production

processing systems. Chemicals applied to wells are used in large amounts over a short period of

time (e.g., tons of drilling chemical are used for each well and a well is drilled in 70 to 90 days).

Production-treating chemicals are used in moderate amounts over most of the life of a field (e.g.,

one to 10 gal. is used daily for years at a time). For drilling fluid, cementing, completion,

stimulation, and workover chemicals, a single formulation is used on each well and that

formulation is made on site from components transported to the offshore site. Production-treating

formulations, on the other hand, are prepared at supplier facilities and transported as formulated

products to the offshore site.

Wells drilled into hydrocarbon-bearing reservoirs produce a mixture of gas, liquid

hydrocarbons, water, and dispersed solids. The exact composition of the produced stream

depends on such factors as:

• Type of production (i.e., oil, gas, or both)

• Properties of the oil produced (e.g., paraffinic crude, asphaltic crude, condensate)

• Age of the field (i.e., the life cycle stage of the reservoir)

• Source of energy driving the reservoir (e.g., water-driven, gas-driven)

• Lifting method (e.g., free flowing, gas lift, submersible pump)

As the material is removed from the formation, it may be necessary to use chemicals to

perform or facilitate the performance of one or more of the following production operations:

• Protecting downhole and surface equipment from corrosion

• Protecting downhole and surface equipment from mineral scale deposits

• Protecting gathering lines and process equipment from gas hydrates

• Separating the phases

− Cleaning and stabilizing the gas and oil for sales

− Cleaning produced water for disposal

• Processing water for waterflooding

• Protecting against foaming in gas liquid separations

• Removing oxygen

• Preventing or removing paraffin (solid hydrocarbon) deposits

Chemicals are an essential part of several of these operations. Published studies in the

1980s culminate with a definitive explanation of the use of chemical production and exploration

operations (Hudgins and Petrotech Consultants, Inc. 1991). There are 14 functional categories of

production-treating chemicals in use in the GOM. In each of these functional categories,

generally several generic classes of chemicals possess the required properties.
28

• Biocides • Surfactants

• Corrosion inhibitors • Paraffin treating chemicals

• Scale inhibitors • Solvents and additives

• Emulsion breakers • Oxygen scavenger

• Reverse breakers • Hydration inhibition chemicals

• Antifoam • Dehydration chemicals

• Coagulants, flocculants • Sweetening chemicals

Drivers for Production-treating Chemical Use

Activities that must be performed during production operations that trigger the use of

chemicals can be subdivided into:

• Separating of phases (to clean oil or gas for sale, to clean water for disposal, to prevent

foaming in oil/gas separation)

• Preventing of corrosion

• Preventing of solid deposition (water-formed scales, paraffin or asphaltenes, gas hydrates)

• Controlling of bacterial growth

The scope of these activities depends on several factors, including:

• Type of production (oil or gas)

• Type of oil produced (paraffinic or asphaltic)

• Viscosity and gravity of the oil produced

• Composition and salinity of the water being produced

• Presence and level of hydrogen sulfide and carbon dioxide in the gas produced

• Relative rates of oil and water production

For example, asphaltic oils require more emulsion breaker for separation and, for all oils,

the higher the density the more emulsion breaker required. The higher the carbon dioxide and

hydrogen sulfide content of the produced fluids, the more corrosion inhibitor required.

The stage in the field’s life cycle has an effect on the level of chemical treatment. For

example, exploration and development stages use little production-treating chemicals. As the

field enters the long period of active production (e.g., five years), chemical treating becomes

increasingly important. Early in the life of a field, little water is produced and emulsion problems

are minimal, especially if the produced oil is hot. In these early stages, even when produced

water is corrosive, corrosion inhibitor is typically not required as the produced stream is likely to

oil external. As the field ages, water production will increase and oil production will decrease. If

the reservoir is waterflooded, the produced stream will begin to cool. All these changes directly

increase the need for emulsion breakers, water clarifiers, and corrosion inhibitors. Waterflooding

can also increase the need for scale inhibitors.
29

One large supplier interviewed for this study summarized his company’s experience in

the GOM with the following general comments concerning production chemical use.

a) Defoamers are used almost exclusively in new deepwater production.

b) Asphaltene inhibitor usage is limited to new deepwater production.

c) About 95% to 100% of platforms that discharge water use water clarifiers.

d) Demulsifiers are used on 70% to 80% of oil platforms.

e) Subsea wells have not proven to be corrosive and most are not treated with corrosion

inhibitors.

f) H2S scavengers are used predominantly in the Mobile Bay and Texas Gulf areas.

g) From 80% to 85% of paraffin inhibition is used for preventing deposition in pipelines or

subsea flowlines. Surface flowlines present minimal problems.

h) From 70% to 90% of corrosion inhibitor is for flowlines and pipelines rather than downhole

tubulars.

Application

Applications of production-treating chemicals are made in one of three ways (Hudgins

and Petrotech Consultants, Inc. 1991):

• Continuous injection at low rates at appropriate points in the process piping or downhole in

producing wells

• Batch applications of high concentrations to wells or process equipment

• Squeeze treatments

Squeeze treatments use discrete volumes of high concentrations injected into the

formation surrounding a wellbore so that the chemical can adsorb or precipitate in the formation

and re-dissolve over a period of time. This procedure allows the placement of a volume of

chemical that can provide a relatively continuous treatment concentration as it desorbs and enters

the produced stream. This type of application procedure is necessary when continuous treatment

of produced streams is needed at the bottom of a well where continuous injection is impractical.

Figure 6 shows a generic treating system. Chemicals are injected upstream of the vessels where

their function is needed. For example, emulsion breaker is added upstream of separators; watertreating chemical is added upstream of water-treating processes.
30

Figure 6. Simplified Typical Oilfield Process Diagram for an Offshore Platform. (Source:

Hudgins and Petrotech Consultants, Inc. 1991)

Production-treating chemicals are shipped offshore on a regular basis to the platform.

Continuous applications are administered using small pumps that inject chemicals at low rates

into a flowline at an appropriate point. Chemicals are pumped directly from the tank they were

shipped in or from a permanent bulk tank. Application rates are determined by on-site testing and

usually conducted by a supplier’s representative. The supplier representative is also frequently

responsible for monitoring the chemical’s performance. Platform operators provide daily checks

on the functioning of the injection system and the status of the chemical reservoirs. Batch

treatment and squeeze treatments are usually performed by a supplier’s specialist who typically

visits the platform to supervise and administer the chemicals required.

Characterization

Production-treating chemicals are normally supplied as liquid solutions and are either

pure chemical (e.g. methanol, glycols) or complex mixtures. In general, complex mixtures

consist of:

• A solvent carrier

• One or more active ingredients

• Secondary ingredients, or “helpers”

The solvent may be water-soluble or oil-soluble, depending on the phase it is meant to

treat. The solvent aids in rapid dispersion of the active ingredient(s) into the production stream.

Gas

Oil

Water

High Pressure 

Separator

Intermediate

Separator

Face

Water

Knock

Out Bulk Oil 

Treater

Oil 

Shipping 

Tank

Water 

Skimmer

CPI 

Unit Flotation 

Unit

Platform Gas 

Users

Glycol 

Regenerator

Glycol 

Unit

SIMPLIFIED FLOW DIAGRAM

Test 

Separators

WELLS High Pressure

IntermediateLow PressureTest

WELL 

MANIFOLDS

THREE STAGE COMPRESSOR 

PACKAGE

Oil Sales

Gas Sales

Gas

Oil

Water

High Pressure 

Separator

Intermediate

Separator

Face

Water

Knock

Out Bulk Oil 

Treater

Oil 

Shipping 

Tank

Water 

Skimmer

CPI 

Unit Flotation 

Unit

Platform Gas 

Users

Glycol 

Regenerator

Glycol 

Unit

SIMPLIFIED FLOW DIAGRAM

Test 

Separators

WELLS High Pressure

IntermediateLow PressureTest

WELL 

MANIFOLDS

THREE STAGE COMPRESSOR 

PACKAGE

Oil Sales

Gas Sales
31

Active ingredients provide the primary function(s). Sometimes there may be only one

active ingredient (e.g. sodium bisulfite). In other formulations, two or more active ingredients

may be combined to produce the desired effect (e.g. quaternary ammonium compound and

amides/imidazolines are both active in some water-based corrosion inhibitors). The secondary

ingredients or helpers are used to solve stability or applications problems. For example, mutual

solvents may be added to a product stream so that the active ingredient will stay in solution at

lower temperatures. Another example of a secondary ingredient function is the use of wetting

agents and surfactants in corrosion inhibitors, which enable the active ingredient to reach the

surface of the steel it is meant to protect. Ethoxylated nonylphenol, a corrosion inhibitor

component performs this function and is further addressed in Sections 7.0 and 8.0.

Production-treating chemicals are frequently proprietary products. To be most effective

formulations are tailored to the needs of a particular site. Therefore, the same basic formulation

may actually be supplied in several variations and sold under different product names. Gulf of

Mexico chemical suppliers agreed to provide, on condition of anonymity, detailed information

on three products used in the spill model scenarios. Compositions for these chemicals are shown

in Section 7.0 as Product A, a water-soluble/dispersible corrosion inhibitor, Product B, an oilsoluble corrosion inhibitor, and Product C, an oil-soluble emulsion breaker.

Fate in the Process System

A production-treating chemical’s fate depends on which phase it was designed to treat

and its physical state and properties. Possible fates include:

• Leaving the production-treating system as waste in produced water (water clarifiers or

flocculants)

• Being lost to the formation (biocides in waterflood water)

• Leaving the production-treating system as part of vessel bottom waste (emulsion breaker in

oil adsorbed to solids)

• Being consumed in chemical reactions within the system (oxygen scavenger)

• Leaving the production-treating system as part of the sales oil and gas (organic solvents and

emulsion breakers)

Fate in the Marine Environment

In the marine environment, the fate of production-treating chemical components include:

• Biological degradation of organic materials

• Chemical reaction

• Dilution to background concentrations

Organic components range from simple molecules, like methanol, to very complex ones,

like amides/imidazolines. Simple chemicals, such as methanol and ethylene glycol, are used in

the highest volumes. These chemicals typically partition between the gas, hydrocarbon liquid,

and water phases. While more than half of these chemicals partition into the water phase and are
32

disposed of with the water, making them one of the highest volume discharges of productiontreating chemicals, these chemicals can also be recovered from the gas stream and recycled. The

more complex organic molecules are usually highly surface active and are used in very low

concentrations. The water-insoluble molecules tend to adsorb on solids or disperse as droplets.

These phases tend to increase surface-to-volume ratios and, therefore, also increase potential

biological degradation rates.

Inorganic components such as oxygen scavengers and water-treating agents used to

create flocs are subject to chemical reaction. Residual sodium bisulfite, an oxygen scavenger,

reacts with oxygen in the sea to form sodium ions and sulfate ions. Both these ions are natural

constituents of seawater. Aluminum ions in water clarifiers will complex with seawater

constituents to form solids and are eventually removed to the sediment.

2.3.2 Production-treating Chemicals

Production-treating chemicals can be classified into 14 functional categories. Table 4 lists

these categories, describes the function of each, and shows some of the generic types of chemical

used in each. An inventory of products identified for this project is provided in Appendix A.

Table 4

Production-treating Chemicals: Codes, Functional Categories, Descriptions, and Material Types

Used

Code Functional Category Description Material Types Used

P-B Biocides Chemicals used to control the

growth of bacteria that can

generate hydrogen sulfide and

cause corrosion and bacteria that

produce slime and biomass.

Quaternary amine salt and amine

acetate, aldehydes, THPS, sodium

hypochlorite, other

P-CI Corrosion inhibitors Used to prevent or minimize

internal corrosion in offshore

production systems.

Amides/Imidazolines, amines and

amines salts, quaternary

ammonium salts, nitrogen

heterocyclics

P-SI Scale inhibitors Used to prevent water-formed

scales (calcium carbonate, barium

sulfate, and strontium sulfate).

Phosphate esters, phosphonates,

and polymers

P-EB Emulsion breakers Used to de-stabilize water in oil

emulsions to make oil saleable.

Oxyalkylated resins, polyglycol

esters, alkyl aryl sulfonates

P-RB Reverse breakers Used to de-stabilize oil in water

dispersions and facilitate gravity

separation. Used to reduce the

interface tension, allowing the oil

droplets to coalesce into large

drops.

Polyamines, polyamine quaternary

compounds

P-A Antifoam Used to de-stabilize foam in the

separation of gas and liquids in

separators. Used to reduce

foaming of water during deoxygenation for waterfloods.

Silicones, polyglycol esters
33

Table 4

Production-treating Chemicals: Codes, Functional Categories, Descriptions, and Material Types

Used (continued)

Code Functional Category Description Material Types Used

P-CF Coagulants, flocculants Used to make small solids

agglomerate so that they can be

separated by filtration or flotation.

Applied to the removal of solids

from injection water and to

improve oil removal for overboard

discharge.

Aluminum sulfate, other metal

compounds, polymeric amides

P-S Surfactants Used to remove small amounts of

oil or grease from the platform

and/or equipment.

Alkyl aryl sulfonates, ethoxylated

alkyl phenols

P-TC Paraffin treating chemicals Used to prevent solid organic

deposits from depositing on the

walls of the piping and equipment.

Also includes solvents for

removing such deposits.

Hydrocarbon polymers, solvents

P-SA Solvents and additives Used as carriers in the various

chemical formulations.

Hydrocarbon solvents are used for

those chemicals meant to reach the

oil phase. Alcohols and glycols are

used as mutual solvents in both

water-soluble and oil-soluble

formulations.

Naphtha, light aromatic naphtha,

heavy aromatic naphtha, kerosene,

ethylene glycol, other low

molecular weight glycols,

methanol, isopropanol

P-OS Oxygen scavenger Used to remove oxygen from

waterflood water.

Sodium bisulfite, ammonium

bisulfite

P-HIC Hydrate inhibition chemicals Used to control the formation of

gas hydrates in gathering piping

systems.

Methanol, ethylene glycol

P-DC Dehydration chemicals Used to remove water vapor from

natural gas.

Triethylene glycol

P-SC Sweetening chemicals Used to remove carbon dioxide

and hydrogen sulfide from natural

gas.

Proprietary products; the most

common systems are

monoethanolamine (MEA) or

diethanolamine (DEA)
35

3.0 CHEMICAL USAGE

3.1 Introduction

Models were developed for offshore E&P operations to estimate the volume of chemical

transported, stored, and expected to be used at any one time in the Gulf of Mexico (GOM). Since

MMS anticipates more extensive and frequent use of these chemicals to enhance throughput of

the oil and gas in deep water, these models are likely to contribute to a realistic evaluation of

potential environmental impacts.

These models were developed as follows:

1. Data was provided by three major operators in the GOM and their chemical suppliers (total

of eight).

2. The data was unitized to yield average volumes or concentrations for each operational unit

(well or production amount).

3. The unitized data were multiplied by the corresponding number of wells or fluid production

data to extrapolate total volume estimates for the entire GOM.

For this report we used a small, but representative subset of chemical usage data from

1998 obtained from three operators and their chemical suppliers. Once unitized, these data were

extrapolated to total GOM usage volume estimates for 1998 for each chemical class and

functional category. Given future information on the number of wells, types of wells, well depth,

water depth and production data these models can be used to extrapolate (i.e., from the unitized

data) the total volumes of a chemical(s) used in the GOM in any year or, if needed, on a projectspecific basis for any number of wells to be drilled or quantity of fluid produced. Economic

factors are incorporated into the projected number of wells and operations and thus into the

model.

Separate models were developed for drilling fluid chemicals, cementing chemicals,

completion stimulation and workover chemicals, and production-treating chemicals to account

for the variability in the factors that affect chemical use in each of these categories. For example,

the volume of cementing chemicals used is primarily a function of the number of wells drilled

and the depth of the well, whereas the volume of production-treating chemicals is a function of

the produced stream type, the operation that needs to be performed (e.g. emulsion breaking), and

the length of time for the operation.

Specifics regarding the underlying data, model assumptions, and limitations, along with

estimated volumes, are described in each of the following subsections.
36

3.2 Model Results

3.2.1 Drilling Fluid Chemicals Volume Estimates

The amount of drilling fluid chemicals applied to a well is primarily a function of well

depth, though this relationship is neither simple nor linear. Factors such as the uniformity of the

well diameter, a fluctuating application rate, and the occasional necessity of sidetracks and other

drilling-related problems all factor into the final usage volume.

Drilling Fluid Chemicals: Subcategories

To generate drilling fluid volumes using the model, fluid use per unit well is needed.

Since this is a function of the changing geometry of the bore hole and the depth of the well,

information collected on drilling fluid chemicals was divided into five categories of well depth

intervals. These intervals were determined from an analysis of drilling operation data received

from an operator and discussions with chemical suppliers and other operators.

Location Well Depth Water Depth

Shelf (shallow water) < 5,000 ft. < 1,000 ft.

Shelf (shallow water) 5,000 – 10,000 ft. < 1,000 ft.

Shelf (shallow water) > 10,000 ft. < 1,000 ft.

Deep water > 10,000 ft. < 4,000 ft. *

Deep water > 10,000 ft. > 4,000 ft. *

* This is a differentiation in water depth, not well depth. Nearly all wells in deep water are

drilled to depths of 10,000 ft. or greater, but differences in drilling technology used in

waters greater than 4,000 ft. require separate categories.

Drilling Fluid Chemicals: Data Sources

The base data for the model are derived from chemical usage data for 58 wells drilled in

the GOM during 1998. A chart depicting the distribution of these wells across the selected

intervals is shown in Figure 7. The types and amount of drilling fluid chemicals for these wells

were supplied by three chemical suppliers who provided (i.e., by functional group) the quantity

of drilling fluid chemicals used for each operation.

Using these data, the per operation (average) quantities of chemical for each category

were calculated. These per operation volumes are shown in Table 5. The list of chemicals in

Table 5 is not a mud formulation; rather, it is a list of all drilling fluid components and additives

applied to the wells listed above for all types of drilling mud formulations.
37

Figure 7. Number of Wells Drilled by One Operator in 1998. (Source: Operator Data)

Drilling Fluid Chemical: Volume Estimates

To estimate or extrapolate the total volume of drilling fluid chemicals used in the GOM

we multiplied the total volumes of drilling fluid chemicals in 1998, using information obtained

from MMS’s Fast Fact database by the number of wells drilled in the GOM for each depth

interval. These data include all wells spudded in 1998, regardless of whether or not they were

completed in 1998. The distribution of these wells by depth interval is in Figure 8. Given

production data for future years or projects, an individual could extrapolate the total volume of

chemical usage for any year or proposed activity. Volume and storage estimates of drilling fluid

chemicals are found in Tables 5 and 6, respectively.

Figure 8. Total Number of Wells Drilled in the Gulf of Mexico in 1998. (Source: MMS Fast

Facts Database 1998)

0

5

10

15

20

25

30

35

Number of Wells 2 17 33 4 2

SW < 5,000 SW 5,000-

10,000

SW > 

10,000 DW < 4,000 DW >4,000

0

50

100

150

200

250

300

350

Number of Wells 41 178 341 34 9

SW < 5,000 SW 5,000-

10,000

SW > 

10,000 DW < 4,000 DW >4,000
38

Table 5

Volume Estimates for Drilling Fluid Chemicals Used in the Gulf of Mexico

Shallow Water Wells by Well Depth Deep-water Well

Functional Categories Wells 0-5,000 ft. Wells 5,000 - 10,000 ft. Wells > 10,000 ft. Shallow Water

Wells Total(s)

Water Depth < 4,000 ft. Wate

Wells by Depth Total wells = 41 Total wells = 178 Total wells = 340 559 Total wells = 34 Total w

Average

Used (1)

Total Average

Used (1)

Total Average

Used (1)

Total Total(s) Average Used (1) Total Avera

Used 

Weighting materials, lbs.Barite, iron oxides, calcium carbonates, etc

61,200 2,510,000 282,000 50,200,000 803,000 273,000,000 326,000,000 10,100,000 344,000,000 3,100

Viscosifiers - Clays, lbs. 12,800 525,000 64,700 11,500,000 100,000 34,00,000 46,000,000 301,000 10,200,000 304,0Viscosifiers - Polymers, lbs. 338 13,800 1,630 291,000 696 237,000 541,000 2,500 85,000 12,6Thinners, dispersants, and Temperaturestability agents(2), lbs.Tannins & modified tannins (DESCO),lignosulfonate, lignite, polyphosphates

3,270 134,000 12,800 2,290,000 18,900 6,430,000 8,850,000 145,000 4,920,000 5,00

Filtrate reducers (solid), lbs.Clays, lignite, polymers, etc

4,830 198,000 5,990 1,070,000 18,900 6,430,000 7,700,000 148,000 5,040,000 55,6

Filtrate reducers (liquid), gal.Clays, lignite, polymers, etc

- - - - - - - - - 345 

Alkalinity, pH control additives, &Calcium reducers(2), lbs.Lime, carbonate salts and certainpolyphosphates

4,500 184,000 9,900 1,760,000 33,100 11,200,000 13,200,000 124,000 4,222,000 43,7

Lost circulation materials, lbs.Insoluble particulate matter

5,740 235,000 22,300 3,970,000 21,900 7,460,000 11,700,000 93,200 3,170,000 246,0

Lubricants, gal.Oils, synthetic liquids, graphite surfactants,glycols & glycerin

- - 625 111,000 212 71,900 183,000 - - - 

38
39

Table 5

Volume Estimates for Drilling Fluid Chemicals Used in the Gulf of Mexico (continued)

Shallow Water Wells by Well Depth Deep-water Well

Functional Categories Wells 0-5,000 ft. Wells 5,000 - 10,000 ft. Wells > 10,000 ft. Shallow Water

Wells Total(s)

Water Depth < 4,000 ft. Wate

Wells by Depth Total wells = 41 Total wells = 178 Total wells = 340 559 Total wells = 34 Total w

Average

Used (1)

Total Average

Used (1)

Total Average

Used (1)

Total Total(s) Average Used (1) Total Avera

Used 

Shale control inhibitors (liq), gal. - - 3,700 658,000 1,630 554,000 1,210,000 22,400 763,000 - Shale control inhibitors (solid), lbs.Inorganic salts & organics

- - 8,520 1,520,000 15,100 5,140,000 6,660,000 281,000 9,550,000 494,0

Emulsifiers & Surface active agents2, gal. - - 16 2,880 433 147,000 150,000 50 1,700 - Minor Additives:Bactericides, gal. - - - - 3 850 850 - - - Defoamers, gal. 10 410 24 4,190 37 12,400 17,000 3,480 118,000 448 Scale Inhibitors, gal. - - - - 2 584 584 - - - 

Total Solids (lbs.) 420,000,000 

Total Liquids (gal.) 1,560,000 

Notes:(1) These quantities were calculated using MMS data on number of wells drilled, and data on chemicals used by one company and its 

wells. Wells were subdivided into categories for projection purposes and data from each category was used to project data for well

(2) These classes of materials are combined because they use similar or identical types of chemicals.

39
40

Table 6

Storage Volumes of Drilling Fluid Chemicals Used in the Gulf of Mexico

Notes:

(1) Median is the number in the middle of the set of numbers. The number zero in the median column indicates that

chemicals were not used for a majority of the wells in the study as provided by the GOM operator.

(2) This value represents the total volume needed to drill the well and was assumed to be the amount stored on-site

and a conservative estimate eof the spill volume. However, the known storage capacity for barite and cement is

30,000 cubic ft. or 8.4 million lbs. on the Diamond Offshore rig Ocean Confidence.

3.2.2 Cementing Chemicals Volume Estimates

Similar to drilling fluids, the amount of cementing chemicals applied per well is primarily

a function of well depth. Unlike drilling fluid chemicals, cements are used in discrete units each

time a section of casing is added. Such factors as sidetracks do not add to the volume used as

they do for drilling fluid chemicals.

Functional Categories Average Maximum Median (1)

Weighting materials, lbs

Barite, iron oxides, calcium carbonates, etc.

Viscosifiers

Clays, lbs 103,000 403,000 50,000

Polymers, lbs 1,490 15,000 288

Thinners, dispersants, and Temperature 

stability agents, lbs.

Tannins & modified tannins (DESCO), 

lignosulfonate, lignite, polyphosphates 

Flitrate reducers (solid), lbs 24,100 166,000 5,350

Flitrate reducers (liquid), gals 12 690 0

Clays, lignite, polymers, etc.

Alkalinity, pH control additives, & Calcium 

reducers, lbs

Lime, carbonate salts and certain polyphosphates

Lost circulation materials, lbs

Insoluble particulate matter

Lubricants, gal

Oils, synthetic liquids, graphite surfactants, 

glycols & glycerin

Shale control inhibitors (liq), gal 3,880 49,500 0

Shale control inhibitors (solid), lbs 47,200 510,000 0

Inorganic salts & organics

Emulsifiers & Surface active agents, gal 247 7,260 0

Minor Additives:

Bactericides, gal 1 80 0

Defoamers, gal 283 11,000 0

Scale Inhibitors, gal 1 55 0

33,900 412,000 13,900

305 3,850 0

24,500 196,000 6,880

31,500 286,000 11,900

1,340,000

Volumes Stored Offshore

15,600,000 (2) 296,000
41

Cementing Chemicals: Subcategories

Based on an analysis of the cementing operation data received from the operator and

discussions with chemical suppliers and operators, cementing chemical usage can also be further

sub-divided by well and water depth. The four categories that correspond to the depth intervals

defined for drilling fluid chemicals. The water-depth related drilling issues that necessitated the

two additional deepwater categories do not affect cementing chemicals.

Location Well Depth Water Depth

Shelf < 5,000 ft. < 1,000 ft.

Shelf 5,000 – 10,000 ft. < 1,000 ft.

Shelf > 10,000 ft. < 1,000 ft.

Deep water > 10,000 ft. > 1,000 ft.

Cementing Chemicals: Data Sources

Data on the volume of cementing chemicals were provided by one operator. These data

were not extensive enough to be representative of the entire GOM; therefore, the information

was augmented with data from two of the operator’s chemical suppliers. Based on historical use

patterns for these chemicals, the suppliers provided the average quantities of each functional

chemical class used to complete a cementing job in each of the well depth intervals. Along with

these data, cementing chemical formulations were provided, and these formulations were

recommended as representative of all wells cemented in each well depth interval. These data

provided the volumes of chemical per well for each of the depth categories.

Cementing Chemicals: Volume Estimates

The number of wells cemented in 1998 in the GOM was assumed to be the same as the

number of wells drilled. Multiplying the average cementing compositions for each category by

the number of wells drilled in each category yields an estimate of the total cementing chemicals

used in the GOM for 1998. By replacing the number of wells with future projections, new

volumes can be generated. The 1998 volume estimates are shown in Table 7.

Typical volumes used and stored at a specific site can also be found in Table 7. In this

case, the single well formulations represent typical amounts stored. Using this table it can be

determined that the maximum quantity likely to be found offshore at any one site is 430,000 lbs.

(basic cements) for a well drilled to a depth > 10,000 ft. 
42

Table 7

Volume Estimates for Cementing Chemicals Used in the Gulf of Mexico

(1) Amounts are averages used on typical wells. Every well does not contain all products. Amounts are calculated from nominal cemen

suppliers and checked against market share data and typical jobs performed by an operator.

(2) Data on number of wells drilled from MMS Fast Facts downloaded on September 19, 1999 (1998 data).(3) Terminology from World Oil 1999 Cementing Supplement.(4) Weights for liquid products calculated assuming density of 10 lbs./gal.

5,000-10,000 ft.

Wells Drilled in 1998(2) Total Wells = 41 Total Wells = 178 Total Wells = 340 To

Functional Categories/Components (3) Average Used(1) (lbs) Total Weight, lbs Average Used(1) (lbs) Total Weight, lbs Average Used(1) (lbs) Total Weight, lbs Average Use

Basic Cements 181,700 7,450,000 278,000 49,500,000 430,000 146,000,000 203,000,000 430,0

Accelerators & salts(4) 985 40,400 985 175,000 1,410 479,000 695,000 1,41

Extenders & density- reducing additives 4,575 188,000 4,580 814,000 8,500 2,890,000 3,890,000 8,50

Free water control and solids suspending agents 0 0 160 28,500 230 78,200 107,000 230 

Dispersants 114 4,660 569 101,000 963 327,000 433,000 963 

Bond improving and expanding additives 643 26,400 643 115,000 643 219,000 360,000 643 

Fluid-loss control additives 610 25,000 913 162,000 1,050 356,000 544,000 1,05

Silica to reduce or prevent high temperature strength 

retrogression 0 0 0 0 41,400 14,100,000 14,100,000 41,40

Retarder 0 0 255 45,400 588 200,000 245,000 588 

Anti-gas migration agents 275 11,300 275 49,000 275 93,600 154,000 275 

Anti-foam and defoaming agents 270 11,100 385 68,500 633 215,000 295,000 633 

Density increasing or weighting agents 0 0 0 0 12,500 4,250,000 4,250,000 12,50

Additives and mixtures to reduce or prevent lost circulation 29 1,200 29 5,190 29 9,910 16,300 29 

Spacers and chemical washes/pre-flushes 110 4,510 160 28,500 200 68,000 101,000 200 

Shallow Wells 

0-5,000 ft. >10,000 ft. 

Shallow Wells Total (lbs)

42
43

3.2.3 Completion, Stimulation, and Workover Chemicals Volumes Estimates

The type and volume of completion, stimulation, and workover chemicals which are

likely to be used and stored at an offshore location depends on the operation needed, the length

of the treatment interval, and the type of formation being treated. For example, solid formations

may require fracturing which uses acids and proppants, while unconsolidated formations may

require gravel-packing.

Completion, Stimulation, and Workover Chemicals: Subcategories

The number of jobs performed in each treatment class is equal to the number of new

wells drilled and a small percentage of existing older wells which were recompleted, stimulated,

or worked over. Using data from chemical suppliers on the number of jobs performed and their

market share, the number of completion, stimulation, and workover jobs completed in 1998 was

estimated. This number was compared to an operator’s estimate of the fraction of their wells

recompleted, stimulated, or worked over in 1998 as a check of these estimates. This process

yielded the following estimates:

Treatment Number of Jobs in Shallow

Water

Number of Jobs in Deep Water

Completions 920 43

Fracturing 321 15

Acid Gravel-Packs 599 28

Acidizing 150 0

Completion, Stimulation, and Workover Chemical: Data Sources

The data provided by the operator on completion, stimulation, and workover chemical

use were not extensive enough to be representative of the entire GOM. Therefore, data on each

of the subclasses were augmented by information obtained from a chemical supplier. The lack of

actual completion, stimulation and workover applications data on specific wells means that some

fine detail is lost. The available data on specific fracturing and acid jobs were consistent with the

information gathered from the chemical supplier.

For completion fluids, the supplier calculated the average well volume they treated in the

GOM, the total volume of fluids they sold, and their market share. These data were used to

determine average quantities of completion, stimulation, and workover chemicals used on all

wells in the GOM in 1998. For the other subclasses, the supplier furnished the number of jobs,

the average quantities of each functional category used, and the market share for each subclass.

Completion, Stimulation, and Workover Chemicals: Volume Estimates

Multiplying the number of jobs by the per operation or average volume of chemical used

for each class of job yields an estimate for the quantities of all functional categories of

completion, stimulation, and workover chemicals used throughout the GOM for 1998. These

volume estimates are shown in Table 8. The per operation/average volumes represent typical

volumes stored at offshore sites.
44

Table 8

Volume Estimates for Completion, Stimulation, and Workover Chemicals Used in the Gulf of

Mexico

Shallow Water Deepwater Total OCS

Total Amount for 1998 Total Amount for 1998 Total Amount for 1998

Wells Total = 920 43

Completion Fluid Chemicals & Packer Fluid Chemical Jobs

Water-based Completion Fluid

 Sodium Chloride, bbls 121 111,000 5,190 116,000

 Sodium Bromide, bbls 0.53 490 23 513

 Calcium Chloride, bbls 236 217,000 10,100 227,000

 Calcium Bromide, bbls 26 23,700 1,110 24,800

 Zinc Bromide, bbls 18 16,200 755 16,900

 Potassium Chloride, bbls 21 19,300 900 20,200

Water-based Completion Fluid Additives:

Water-based Polymers

 HEC, lbs 90 82,900 3,870 86,700

 Xanthum Gum, lbs 13 11,800 553 12,400

 Starches, lbs 36 33,000 1,540 34,500

Corrosion Inhibitors, gal 28 25,800 1,210 27,000

Oxygen Scavengers, gal 2 1,840 86 1,930

Biocides, gal 0 358 17 374

Fluid Loss Additives

 Calcium Carbonate, lbs 167 153,000 7,160 160,000

 Sodium Chloride, lbs 101 92,600 4,330 97,000

 Mineral Fiber, lbs 5 4,920 230 5,150

Defoamers, gal 3 2,530 118 2,640

Surfactants

Terpenes, gal 3 3,040 142 3,190

Surfactants, gal 17 16,100 751 16,800

Degreasers, gal 3 2,530 118 2,650

Floculants, gal 7 6,460 302 6,770

Frac Gravel Pacs Total Wells = 321 Total Wells = 15

Proppant, lbs 80,000 2,570,000 1,200,000 26,900,000

Water-based Completion Fluids 25,000 8,030,000 375,000 8,400,000

Water-based Polymers, lbs 625 201,000 9,380 210,000

Surfactant, gal 50 16,000 750 16,800

Clay stabilizes (KCl), lbs 7,296 2,340,000 109,000 24,500,000

Crosslinkesr, gal 100 32,100 1,500 33,600

Breakers, gal 250 80,300 3,750 84,000

Breakers ( Catalyst), gal 50 16,000 750 16,800

Functional Categories/ Components:

Single Well 

Amount
45

Table 8

Volume Estimates for Completion, Stimulation and Workover Chemicals Used in the Gulf of

Mexico (continued)

Shallow Water Deepwater Total OCS

Total Amount for 1998 Total Amount for 1998 Total Amount for 1998

Wells Total = 920 43

Acid Gravel Pacs Total Wells = 599 Total Wells = 28

Sand, lbs 9,000 5,390,000 252,000 5,640,000

Acid Systems

MCA, gal (Total vol) 1,120 670,000 31,300 701,000

 HCL, lbs 977 585,000 27,400 613,000

HCl:HF, gal (Total vol) 2,240 1,340,000 62,800 1,410,000

 HCl, lbs 2,710 1,620,000 75,900 1,700,000

 HF, lbs 301 180,000 8,430 189,000

Surfactants, gal 17 9,980 467 10,400

Acid inhibitors, gal 10 6,040 282 6,320

Iron (Fe) control, gal 168 101,000 4,710 105,000

MSA (acetic acid), gal 34 20,100 941 21,100

5% NH4Cl Overflush, gal 3,120 1,870,000 87,400 1,960,000

 Ammonium Chloride, lbs 1,320 791,000 37,000 828,000

Mutual solvent, , gal 111 66,600 3,110 69,700

Anti-sludge agent, gal 10 5,990 280 6,270

Acidizing Producing Wells Total Wells = 150 Total Wells = 0

MCA, gal (Total vol) 1,120 168,000 0 168,000

 HCL, lbs 977 147,000 0 147,000

HCl:HF, gal (Total vol) 2,240 336,000 0 336,000

 HCl, lbs 2,710 407,000 0 407,000

 HF, lbs 301 45,200 0 45,200

Surfactants, gal 17 2,500 0 2,500

Acid inhibitors, gal 10 1,510 0 1,510

Iron (Fe) control, gal 168 25,200 0 25,200

MSA (acetic acid), gal 34 5,040 0 5,040

Anti-sludge agent, gal 10 1,500 0 1,500

5% NH4Cl Overflush, gal 3,120 468,000 0 468,000

 Ammonium Chloride, lbs 1,320 198,000 0 198,000

Mutual solvent, , gal 111 167,000 0 167,000

Functional Categories/ Components:

Single Well 

Amount
46

3.2.4 Production-treating Chemicals Volume Estimates

The quantity of production-treating chemicals needed at a particular site depends

primarily on the volume rate of the produced streams. The variety and representative quantities

used at any particular location can depend on many variables, such as:

• Type of production (i.e., oil or gas)

• Type of oil produced (i.e., paraffinic or asphaltic)

• Viscosity and gravity of the oil produced

• Composition and salinity of the water being produced

• Presence and level of hydrogen sulfide and carbon dioxide in the gas produced

• Relative rates of oil and water production

Production-treating Chemicals: Subcategories

Based on an analysis of the on-going operations in the GOM, data received from the

operator and discussions with chemical suppliers and operators, no single set of chemical use

concentrations could represent the entire GOM. Operations in the GOM were categorized based

on water depth, type of production, type of gathering system, and the presence of hydrogen

sulfide in gas production. Under this approach, seven nominal models were defined for the

different types of production. However, data were only collected for six, since data for deepwater

gas production from wellheads above the surface was not available.

• Shallow water oil production

• Shallow water gas production

• Shallow water gas production with H2S

• Deepwater oil with wellheads above the surface

• Deepwater oil with subsea wellheads

• Deepwater gas with wellheads above the surface

• Deepwater gas with subsea wellheads

Production-treating Chemicals: Data Sources

One of the larger operators in the GOM provided a 1998 dataset for each of the categories

listed above which included the following information:

• Functional categories of production-treating chemicals used

• Specific chemical products used

• Treatment rates in gallons per day

• Monthly use volumes

• Production rates for gas, oil, and water on all their production in each of these types
47

With these data, it was possible to determine average concentrations used for each

functional category of production-treating chemical in each of the production types. Although

each chemical may not be used at all locations, it was assumed that the production chemicals

were used at all locations in each subcategory.

Production-treating Chemicals: Volume Estimates

The production rates for gas, oil, and water for the GOM were taken from the MMS Fast

Facts database. For both total GOM and for deep water, production data for the following were

acquired:

• crude oil

• liquids from gas production (condensate liquids)

• gas production from gas wells

• gas resulting from oil production,

• water production

Using production ratios reported by the operator, these values were allocated to each of

the operational subcategories. Multiplying these production rates by the unitized values for each

functional category yields total volume estimates of production-treating chemical throughout the

GOM. Table 9 shows these total volume estimates for 1998 as an example of model application.

Comparing the total volume estimates shown in Table 9, the variability in production-treating

chemical by production category is evident. For example, corrosion inhibitor use is much higher

in gas production with hydrogen sulfide than for other types.

In Table 10 the maximum and average volumes for production-treating chemicals used in

offshore fields are shown. These volumes are typical of the volumes of production-treating

chemicals that might be stored offshore. In addition to these values, five umbilicals were

identified and their holding capacity and number of storage sites are also presented.
48

Table 9

Volume Estimates for Production-treating Chemicals Used in the Gulf of Mexico

Notes:(1) Both DVA gas and subsea gas are included since there was no separate data on DVA gas.(2) Production data (1998) was taken from the MMS Fast Facts Database and allocated to fit the pattern of industry data submitted to A(3) Concentrations are averages of industry data submitted for each category of production-treating chemicals.(4) All sites used glycol except one, which used TEG. One used ethylene glycol and regenerated it.

Annual Production Rates(2) 

Gas, mcf 

Oil, bbls 

Water, bbls 

Functional Category(3)

Conc. 

(ppmv)

Annual Total 

(gal)

Conc. 

(ppmv)

Annual Total 

(gal)

Conc. 

(ppmv)

Annual Total 

(gal)

Conc. 

(ppmv)

Annual Total 

(gal)

Conc. 

(ppmv)

Annual Total 

(gal) Conc. (

Emulsion Breakers 16.5 495,000 12.7 59,200 105.5 130,000 0 0 161.7 23,400 0 

Reverse Breakers 26.1 518,000 40.5 119,000 79.4 97,500 19.6 15,700 0 0 0 

Scale Inhibitor 15.7 312,000 16.5 48,600 595.2 732,000 0 0 0 0 0 

Corrosion Inhibitor 7.4 146,000 54.9 162,000 1763.7 2,170,000 0 0 1231.5 23,600 0 

Biocide 1.6 32,300 11.5 34,000 0 0 7.8 6,300 0 0 0 

Paraffin Treating Chemicals 15.7 160,000 7.9 13,600 0 0 18.7 80,100 0 0 0 

Antifoam 4.3 44,200 0 0 0 0 40.7 175,000 0 0 44

Oxygen Scavenger 0.15 2,930 5.82 17,100 105.8 130,000 0 0 0 0 0 

Acid 0 0 0.97 2,860 37.0 45,500 0 0 0 0 0 

Hydration Inhibition ChemicalsGlycols(4) 0 0 3.489E-04 949,000 3.489E-04 734 1.38E-03 330,000 8.275E-04 185,000 0 

 Hydration Inhibition ChemicalsMethanol 0 0 2.443E-04 665,000 2.443E-04 514 2.625E-04 62,700 2.096E-02 4,680,000 1.765

Totals - 1,710,000 - 2,070,000 - 3,300,000 - 669,000 - 4,910,000 - 

Total Shelf 7,080,000

To

Deepw

Deepwater Gas(1) Shelf Oil Shelf Gas Shelf Gas with H2S Deepwater DVA Oil Dee

223,000,000

2,980,000

239,000,000102,000,000

19,100,000 457,000

1,740,000,000

243,000,000471,000,000

2,720,000,000

41,100,00070,100,000

2,100,000

142,000

29,300,000

48
49

Table 10

Storage Volumes of Production-treating Chemicals Used in the Gulf of Mexico

Notes:(1) All sites using glycol except one, which used TEG. One used ethylene glycol and regenerated it.(2) No shelf sites used glycol, however one deepwater site used a shelf platform to store ethylene glycol, which was supplied to the de(3) All sites reported are for deepwater use. Shelf sites all stored small quantities. Storage at shelf sites were all for deepwater and the 

them by an umbilical.

Functional Category

Number of 

Sites

Maximum 

(gal) Average (gal)

Number of 

Sites Maximum (ga

Emullsion Breakers 30 670 313 1 700 

Reverse Breakers 34 780 288 1 280 

Scale Inhibitor 14 500 312 - - 

Corrosion Inhibitor 20 2,940 528 2 500 

Biocide 20 500 184 2 110 

Paraffin Treating Chemicals 3 550 378 1 5,500 

Antifoam 3 550 268 7 2,000 

Oxygen Scavenger 3 500 252 - - 

Acid 2 200 200 - - 

Storage(2) 1 63,000 63,000 3 550 

Umbilicals 1 106,000 106,000 1 132 Storage(3) 4 96,600 49,700 3 7,440 Umbilicals 4 7,270 3,210 0 0 

 Hydration Inhibition 

Chemicals-Glycols(1)

 Hydration Inhibition 

Chemicals-Methanol

Shallow Water Production Deepwater Prod

Volumes Stored Offshore

49
50

3.3 Comparison of Chemical Use in Shallow and Deep Water

Comparing shallow and deep water, 559 wells in shallow water used 420,000,000 lbs. of

solid chemicals and 1,560,000 gal. of liquid chemicals in 1998, compared to 419,000,000 lbs. of

solid chemicals and 890,000 gal. of liquid chemicals for 43 wells in deep water. This means that

the average deepwater well uses approximately 14 times more solid drilling fluid chemicals than

the average shallow water well. Most of this is weighting agent (barite). While wells in deep

water use more drilling fluid chemicals in most functional categories, the largest increases are in

filtrate reducers, shale control inhibitors, and defoamers. Table 6 shows the maximum, average,

and median volumes for drilling fluid chemicals used in all 56 wells in the database supplied by

the operator. It includes data from wells in both shallow and deep water. Generally, less chemical

is stored on a rig than is needed to drill the entire well. Quantities of drilling fluid chemical used

per well in deep water are greater than quantities for similar depth wells in shallow water. The

differences may reflect drilling problems caused by the water depth or differences in the

formations being drilled. Note that median values of zero show that less than half the wells used

that chemical and stored it on the rig.

Based on the data and model estimates, 559 wells used 228,000,000 lbs. of cementing

chemicals in shallow water and 43 wells used 21,400,000 lbs. of cementing chemicals in deep

water. On an average well basis, deepwater wells used 22% more chemicals per well than

shallow water wells. As is expected, this reflects the fact that all wells in deep water are drilled to

great depths, while a range of depths are drilled in shallow water.

Environmental conditions, formation/reservoir factors, deepwater production

characteristics all account for differences between shallow water and deepwater use of

production-treating chemicals. The data indicate that deepwater gas production requires more

hydrate inhibitors per unit of production than shelf gas production. However, it cannot be

determined if these differences will continue as the field ages and water production increases at

these deepwater locations. Additionally, although the data indicates that defoamer is used almost

exclusively in deep water, this may be due to the nature of the produced fluids and the

environment through which they are produced, rather than the increase in water depth.

In summary, while the nature of the geologic formation, the reservoir, and the local

environment will not alter the basic chemical treating principles governing chemical use, they

will affect the type and amount of chemical employed. Definite differences are apparent in

chemical use in deep and shallow waters in the GOM. For individual locations, these include:

• Higher amounts of drilling fluid chemicals needed in individual wells in deep water, some of

which are probably due to the nature of the formations and reservoirs being accessed

• Higher amounts of some production-treating chemicals (e.g., hydrate inhibitors) needed in

deepwater production, which may be due to the deepwater environment

• Higher amounts of other production-treating chemicals (e.g., defoamers) needed in

deepwater production, which may be due to the nature of the produced fluids
51

It is not clear how comparisons of the total volumes of chemical used in the future will

change. The life cycle of a field will likely affect the quantity of chemical used in that field over

time. For example, while we know that deepwater wells use more drilling fluid chemical, we do

not know the expected ratio of new shallow wells to new deep wells. Similarly, while we know

that production-treating chemical use will increase as the deepwater wells age, we are unsure of

the magnitude of this increase.

With the increasing use of subsea completions in deep water, there will be an increase in

the use of umbilicals to supply chemicals to them. This will impact the use and storage of

production-treating chemicals. Some of these subsea wells are very remote from platforms or

other storage and supply points. Five umbilicals were identified in the data that form the basis for

the production-treating chemical projections in this report; one of them was 62 miles long.

Several of the umbilicals were supplied from platforms in shallow water. It is apparent that the

use of umbilicals will result in the storage of larger volumes offshore, and these will be

transported on the sea floor. Umbilicals will also impact storage on platforms that may not be in

deep water.
53

4.0 HAZARDOUS SUBSTANCES

4.1 Introduction

As part of this study, the types and volumes of hazardous substances found in chemicals

used, handled, and stored in offshore E&P operations were identified. The results may be used to

both assess potential impacts of the chemicals identified, and understand future usage trends in

deep waters as compared to shallow waters.

For the purposes of this report, hazardous chemicals are defined as those substances listed

in the U.S. Code of Federal Regulations (CFR) – Chapter 40, Protection of the Environment, Part

116, that designates hazardous substances per the Clean Water Act. Reportable quantities for

these substances are listed in Part 117 of this act.

4.2 Approach to Estimating Quantities of Hazardous Chemicals Used and

Stored Offshore

The data set of chemical usage assembled (described in Section 3.0) to develop the

inventories, and build the estimation models were also used to identify and predict the volume of

hazardous substances used and stored in the Gulf of Mexico (GOM). Material safety data sheets

(MSDSs) were collected for all products appearing in the base data set. These sheets list

hazardous components and information about component concentrations. The data listed on

MSDSs were used to preliminarily identify the presence of hazardous substances and to modify

the prediction models to estimate volumes of hazardous chemicals used. The hazardous

substances identified from the MSDSs were compared to the designations of hazardous

substances found in 40 CFR, Part 116, to ensure that those chemicals listed as hazardous on the

MSDSs were also identified as hazardous in the regulation.

To generate the volume of hazardous substances used in offshore operations, the volumes

of each chemical in the base data set, and the percentage of hazardous substance reported on the

MSDSs, were multiplied to calculate volumes of hazardous substances in each chemical.

Hazardous substance concentrations reported in the MSDSs are given as ranges, such as 1% to

5% or 30% to 60%. In the calculation of hazardous substance volumes in each chemical and/or

product, the concentration was assumed to be the upper limit of reported ranges. These

calculated volumes of hazardous substances were substituted for the volumes of the chemicals in

the models to create an estimation model for hazardous substances. The resulting models were

used to estimate the total amount of hazardous substances used in 1998 from the base data

sample. Estimations for any number of wells or amount of production can be obtained by

entering the proper well numbers or production data as described in detail in Section 3.0.

These estimates are limited by the following assumptions:

• Only data that were actually used in the base data submitted by the participating operating

companies would be included in determining typical quantities.

• If the MSDSs showed a range of concentration for a hazardous substance, the upper limit

would be used in predictions so the resulting amount would be conservatively high.
54

4.3 Hazardous Substances in E&P Chemicals Applied to Wells

Hazardous substance volume estimates for 1998 and typical volumes stored are shown

below for each class of chemicals used offshore.

Calculated amounts stored at selected sites can be compared to reportable quantities in

the tables. No hazardous materials listed in 40 CFR, Part 116, were identified in the literature

review of cementing chemicals; therefore, no data is presented here for this chemical class.

4.3.1 Drilling Fluid Chemicals

Table 11 shows five drilling chemical products contained three of the 296 hazardous

substances listed in 40 CFR, Part 116. Table 12 shows the maximum, average, and median

quantities of these substances stored offshore. These quantities were calculated from data

provided by the participating operating company that supplied drilling fluid chemical usage data

for 58 wells drilled in the Gulf of Mexico in 1998. The hazardous substances identified are:

• Sodium hydroxide (functional categories: alkalinity, pH control additives, filtrate reducers,

emulsifiers and surface active agents)

• Potassium hydroxide (functional categories: alkalinity, pH control additives, defoamers)

• Acetic acid (functional category: alkalinity, pH control additives)
55

Table 11

Total Estimated Quantities of Hazardous Substances Found in Drilling Fluid Chemicals in the GOM 

Notes:(1) Total number of shallow water wells from Table 5 in Section 3.0(2) Total number of deepwater wells from Table 5 in Section 3.0

Table 12

Total Estimated Storage Volumes of Hazardous Substances Found in Drilling Fluid Chemicals in the G

Number of 

wells (1)

Total Quantity 

(lbs)

Sodium Hydroxide Flitrate reducers (FR) ChemTrol-X 1310732 559 2,250 

Potassium Hydroxide, 

Sodium Hydroxide

Alkalinity, pH additives (A) Caustic Soda, Caustic 

Potash

1310583 1310732 559 6,800,000 

Acetic Acid Alkalinity, pH additives (A) Acetic Acid 64197 559 25,800 

Sodium Hydroxide

Emulsifiers & Surface 

Active Agents (E) Mil-Clean 1310732 559 0 

Potassium Hydroxide Defoamers (D) W.O. Deafom 1310583 559 35 

 Functional Category 

(code) Product

Hazardous Substances in 

Product CAS No.

Shallow Water 

Maximum 

Sodium Hydroxide Filtrate reducers (FR) 1310732 1% 1000 (454) 12,800 

Potassium Hydroxide, 

Sodium Hydroxide Alkalinity, pH additives (A)

1310583 1310732 100% 1000 (454) 116,000 

Acetic Acid Alkalinity, pH additives (A) 64197 56% 5000 (2270) 2,400 

Sodium Hydroxide

Emulsifiers & Surface 

Active Agents (E) 1310732 4% 1000 (454) 2 

Potassium Hydroxide Defoamers (D) 1310583 1% 1000 (454) 107 

Hazardous Substances 

in Product CAS No.

Storage 

Hazardous Substance 

Concentration in 

Product (%)

Reportable 

Quantity 

lbs (kg)

 Functional Category 

(code)

55
56

Since the alkalinity functional category is used in every drilling fluid formulation, all

drilling fluid formulations contain some hazardous substances. Only two hazardous substances,

sodium hydroxide (filtrate reducers and alkalinity and pH additives) and potassium hydroxide

(alkalinity and pH additives), were stored in amounts greater than reportable quantities (see

Table 12).

4.3.2 Completion, Stimulation and Workover Chemicals

Table 13 shows nine completion, stimulation, and workover chemical products

containing hazardous substances. The products are used in six functional categories. These nine

products contain 10 of the 296 hazardous substances listed in 40 CFR, Part 116. Table 14 shows

the average quantities stored offshore for each of these chemicals.

Hazardous substances identified in completion, stimulation, and workover chemicals

include:

• Acetaldehyde • Acetic acid

• Ammonium bisulfite • Ammonium chloride

• Crotonaldehyde • Dodecylbenzene sulfonic acid

• Hydrochloric acid • Hydrofluoric acid

• Potassium hydroxide • Zinc bromide

The average amount of each functional category of completion, stimulation, and

workover chemicals used per job is assumed to be the average amount stored offshore at any

single site.
57

Table 13

Total Estimated Quantities of Hazardous Substances found in Completion, Stimulation, and Workover Chemica

Shallow Water 

CSW Class Hazardous

Substances in

Product

Functional

Category (code)

Product CAS No. Number of

Wells (1)

Total Quantity

(lbs.)

N

Completion Fluids &

Packer Fluids Jobs

Zinc Bromide Water-base

Completion Fluid

(A-WBC)

Zinc Bromide 7699458 920 7,280,000 

Ammonium

Bisulfite

Oxygen

Scavenger

(A-OS)

Anhib II Inhibitor 10192300 920 5,340 

Fracing /Gravel-Packs Potassium

Hydroxide

Crosslinker

(F-C)

CL-31 Crosslinker 1310583 920 603,000 

Acid Gravel-Packs Hydrochloric

Acid

Acid Systems

(A-AS)

MCA Acid 7647010 599 585,000 

Hydrochloric

Acid

Acid Systems

(A-AS)

HCl:HF Acid 7647010 599 1,620,000 

Hydrofluoric Acid Acid Systems

(A-AS)

HCl:HF Acid 7464393 599 180,000 

Crotonaldehyde Acid Inhibitor

(A-AI)

SCA-130 4170303 599 2,620 

Acetaldehyde Acid Inhibitor

(A-AI)

SCA-130 75070 599 2,620 

Acetic Acid Acid Systems

(A-AS)

MSA Acid 64197 599 20,400 

Dodecylbenzene

Sulfonic Acid

Anti-Sludge

Agent (A-ESA)

AS 5 27176870 599 41,200 

Ammonium

Chloride

Water-base

Completion Fluid

(A-WBC)

Clayfix 12125029 599 791,000 

57
58

Table 13

Total Estimated Quantities of Hazardous Substances found in Completion, Stimulation, and Workover Chemica

(continued)

Shallow Water 

CSW Class Hazardous

Substances in

Product

Functional

Category (code)

Product CAS No. Number of

Wells (1)

Total Quantity

(lbs.)

N

Acidizing Producing

Wells

Hydrochloric

Acid

Acid Systems

(A-AS)

MCA Acid 7647010 150 147,000 

Hydrochloric

Acid

Acid Systems

(A-AS)

HCl:HF Acid 7647010 150 407,000 

Hydrofluoric Acid Acid Systems

(A-AS)

HCl:HF Acid 7464393 150 45,100 

Crotonaldehyde Acid Inhibitor

(A-AI)

SCA-130 4170303 150 657 

Acetaldehyde Acid Inhibitor

(A-AI)

SCA-130 75070 150 657 

Acetic Acid Acid Systems

(A-AS)

MSA Acid 64197 150 5,100 

Dodecylbenzene

Sulfonic Acid

Anti-Sludge

Agent (A-ESA)

AS 5 27176870 150 10,300 

Ammonium

Chloride

Water-based

Completion Fluid

(F-WBC)

Clayfix 12125029 150 198,000 

Notes:(1) Total number of shallow water wells from Table 8 in Section 3.0(2) Total number of deepwater wells from Table 8 in Section 3.0

58
59

Table 14

Total Estimated Storage Volumes of Hazardous Substances Found in Completion, Stimulation, and Workover C

in 1998

CSW Class Hazardous

Substances in

Product

Functional Category

(code)

Product CAS No.

Hazardous

Substance

Concentration in

Product (%)

Completion Fluids &

Packer Fluids Jobs

Zinc Bromide Water-based Completion

Fluid (A-WBC)

Zinc Bromide 7699458 54% 

Ammonium Bisulfite Oxygen Scavengers (A-OS) Anhib II Inhibitor 10192300 30% 

Fracing /Gravel-Packs Potassium Hydroxide Crosslinker (F-C) CL-31 Crosslinker 1310583 60% 

Acid Gravel-Packs Hydrochloric Acid Acid Systems (A-OS) MCA Acid 7647010 30% 

Hydrochloric Acid Acid Systems (A-OS) HCl:HF Acid 7647010 18% 

Hydrofluoric Acid Acid Systems (A-OS) HCl:HF Acid 7464393 6% 

Crotonaldehyde Acid Inhibitor (A-AI) SCA-130 4170303 5% 

Acetaldehyde Acid Inhibitor (A-AI) SCA-130 75070 5% 

Acetic Acid Acid Systems (A-AS) MSA Acid 64197 10% 

Dodecylbenzene Sulfonic

Acid

Anti-Sludge Agent

(A-ESA)

AS 5 27176870 80% 

Ammonium Chloride Water-based Completion

Fluid (A-WBC)

Clayfix 12125029 100% 

Acidizing Producing

Wells

Hydrochloric Acid Acid Systems (A-OS) MCA Acid 7647010 30% 

Hydrochloric Acid Acid Systems (A-OS) HCl:HF Acid 7647010 18% 

Hydrofluoric Acid Acid Systems (A-OS) HCl:HF Acid 7464393 6% 

Crotonaldehyde Acid Inhibitor (A-AI) SCA-130 4170303 5% 

Acetaldehyde Acid Inhibitor (A-AI) SCA-130 75070 5% 

Acetic Acid Acid Systems (A-OS) MSA Acid 64197 10% 

Dodecylbenzene Sulfonic

Acid

Anti-Sludge Agent

(A-ESA)

AS 5 27176870 80% 

Ammonium Chloride Water-based Completion

Fluid (A-WBC)

Clayfix 12125029 100% 

59
60

Only two hazardous substances, zinc bromide (water-based completion fluid) and

hydrofluoric acid (acid systems), were stored in amounts greater than reportable quantities and

these quantities are shown in Table 14.

4.3.3 Production-treating Chemicals Processing Systems

Table 15 shows six functional categories of production-treating chemicals contained 14

of the 296 hazardous substances listed in 40 CFR, Part 116. Table 16 shows quantities stored at a

number of offshore sites. An operating company provided data for production-treating chemicals

used at 59 production-treating facilities, 49 in shallow water and 10 in deepwater. These data

were used to make estimates of the quantities used in 1998. Hazardous substances identified

include:

• Acetic acid • Aluminum sulfate

• Ammonium bisulfite • Ammonium chloride

• Diethylamine • Ethylbenzene

• Hydrochloric acid • Naphthalene

• Phosphoric acid • Potassium hydroxide

• Sodium bisulfite • Sulfuric acid

• Toluene • Xylene

Only four hazardous substances, diethylamine (corrosion inhibitors), toluene (paraffin

inhibitors), xylene (demulsifiers and corrosion inhibitors), and naphthalene (demulsifiers and

corrosion inhibitors) were stored in amounts greater than reportable quantities (see Table 16). Of

these four hazardous substances, three are aromatic solvents (i.e., toluene, xylene, naphthalene).
61

Table 15

Total Estimated Quantities of for Hazardous Substances Found in Production-treating Chemicals in the 

Shallow Water Deep 

Acetic Acid Emulsion Breakers (P-EB) 64197 322,000 Acetic Acid Reverse Breakers (P-RB) 64197 400 

Aluminum Sulfate Reverse Breakers (P-RB) 10043013 9,900 

Ammonium Bisulfite Corrosion Inhibitors (P-CI) 10192300 5,400 Ammonium Bisulfite Oxygen Scavenger (P-OS) 10192300 132,000 

Ammonium Chloride Scale Inhibitors (P-SI) 12125029 500 Ammonium Chloride Reverse Breakers (P-RB) 12125029 500 

Diethylamine Corrosion Inhibitor (P-CI) 124403 600 

Ethylbenzene Corrosion Inhibitor (P-CI) 100414 12,300 Ethylbenzene Emulsion Breakers (P-EB) 100414 101,000 

Hydrochloric Acid Reverse Breakers (P-RB) 7647010 600 Hydrochloric Acid Emulsion Breakers (P-EB) 7647010 5,600 Hydrochloric Acid Scale Inhibitors (P-SI) 7647010 19,300 

Naphthalene Corrosion Inhibitors (P-CI) 91203 18,300 Naphthalene Emulsion Breakers (P-EB) 91203 231,000 11,Naphthalene Reverse Breakers (P-RB) 91203 3,400 

Phosphoric Acid Reverse Breakers (P-RB) 7664382 1,400 

Potassium Hydroxide Emulsion Breakers (P-EB) 1310583 3,100 Potassium Hydroxide Reverse Breakers (P-RB) 1310583 12,700 

Sodium Bisulfite Oxygen Scavenger (P-OS) 7631905 9,000 

Sulfuric Acid Reverse Breakers (P-RB) 7664939 800 

Toluene Paraffin Treating Chemicals (P-TC) 108883 420,000 

Xylene Corrosion Inhibitors (P-CI) 1330207 3,100 Xylene Emulsion Breakers (P-EB) 1330207 143,000 

Totals 1,460,000 11,

Hazardous Substances in Product

Total Estimated Quantities 

Functional Category CAS No.

61
62

Table 16

Total Estimated Storage Volumes of Hazardous Substances Found in Production-treating Chemicals in th

 Hazardous Substances in Product Functional Category (code) CAS No.

Hazardous Substance 

Concentration in 

Product 

(% - Range)

Repo

Qua

lbs 

Acetic Acid Emulsion Breakers (P-EB) 64197 47% 5,000 Acetic Acid Reverse Breakers (P-RB) 64197 5% 5,000 

Aluminum Sulfate Reverse Breakers (P-RB) 10043013 10% 5,000 

Ammonium Bisulfite Corrosion Inhibitors (P-CI) 10192300 40% 5,000 Ammonium Bisulfite Oxygen Scavenger (P-OS) 10192300 60% 5,000 

Ammonium Chloride Scale Inhibitors (P-SI) 12125029 4% 5,000 Ammonium Chloride Reverse Breakers (P-RB) 12125029 5% 5,000 

Diethylamine Corrosion Inhibitors (P-CI) 109897 10% 100 

Ethylbenzene Corrosion Inhibitors (P-CI) 100414 20% 1,000 Ethylbenzene Emulsion Breakers (P-EB) 100414 5%-10% 1,000 

Hydrochloric Acid Emulsion Breakers (P-EB) 7647010 5% 5,000 Hydrochloric Acid Reverse Breakers (P-RB) 7647010 20% 5,000 Hydrochloric Acid Scale Inhibitors (P-SI) 7647010 20% 5,000 

Naphthalene Emulsion Breakers (P-EB) 91203 3%-10% 100 Naphthalene Reverse Breakers (P-RB) 91203 5% 100 Naphthalene Corrosion Inhibitors (P-CI) 91203 5%-10% 100 

Phosphoric Acid Reverse Breakers (P-RB) 7664382 70% 5,000 

Potassium Hydroxide Emulsion Breakers (P-EB) 1310583 5% 1,000 Potassium Hydroxide Reverse Breakers (P-RB) 1310583 5%-7% 1,000 

Sodium Bisulfite Oxygen Scavenger (P-OS) 7631905 37% 5,000 

Sulfuric Acid Reverse Breakers (P-RB) 7664939 1% 1,000 

Toluene

Paraffin Treating Chemicals 

(P-TC) 108883 30%-100% 1,000 

Xylene Corrosion Inhibitors (P-CI) 1330207 5% 100 Xylene Emulsion Breakers (P-EB) 1330207 3%-10% 100 

62
63

5.0 OFFSHORE CHEMICAL STORAGE AND HANDLING REGULATIONS AND

PRACTICES, AND CHEMICAL SPILL HISTORY EVALUATION

5.1 Introduction

In general, factors that determine the overall risk from chemicals spilled into the marine

environment include the toxicity of the chemical spilled, the volume of the spill, and the number

of spills that will occur. Ultimately, the magnitude of these factors will be determined by the

quality of the external environment (i.e., presence of a sensitive marine habitat, metocean

conditions, and general weather conditions).

This section discusses regulations impacting chemical transportation and storage,

offshore chemical storage and handling practices, possible failure modes (e.g., transfers,

collisions, mechanical failures), and state of the art practices related to chemical spill response in

the Gulf of Mexico (GOM).

Over the past decade, the reported number of liquid chemical spills in the GOM has

steadily increased. In 1998, the percentage of spill incidents across the Gulf region accounted for

almost 27% of all incidents in U.S. water bodies (Table 17). The information provided in this

section presents the offshore chemical storage and handling data and summarizes chemical spill

information publicly available for the GOM. Based on this data, a qualitative analysis of spill

potential is presented for both shallow and deep water. Since none of the data obtained

distinguishes between activities and/or events that caused these chemical spills it is not possible

to determine which were a result of E&P related activities.

Agencies such as the U.S. Department of Transportation (DOT), the Occupational Safety

and Health Administration (OSHA), and the Environmental Protection Agency (EPA) have

jurisdiction over various aspects of chemical transportation, storage, and use offshore.

Regulations promulgated by these agencies impact container types and transport methods,

transportation safety, control of the types of chemicals allowed offshore, and other issues. These

regulations provide safety controls that limit the potential of a chemical spill offshore. For

example, vessel wall thickness for shipping containers is controlled so that the containers can

withstand rough handling without rupturing. Chemical use, storage, and transport offshore are

regulated and the combination of the various regulations exerts considerable control over

protection of workers, the public, and the environment.

Storage and handling practices include factors such as different types of storage

containers used, shipping practices, how transfers are made, and how the chemicals are used with

regard to particular E&P activities. Other factors include offshore transport/support vessel traffic

density, and current/future application practices (e.g., the use of umbilicals) in chemical delivery

to drill rigs, production-treatment systems (including producing wells), and other treatment

points.
64

The National Response Center (NRC), a division of the United States Coast Guard

(USCG), is the sole federal point of contact for reporting oil and chemical spills above reportable

quantities as per the CERCLA listed chemicals table (40 CFR Part 302.4: Designation of

Hazardous Substances). The primary function of the NRC is to serve as the sole national point of

contact for reporting all oil, chemical, radiological, biological, and etiological discharges into the

environment anywhere in the United States and its territories. In addition to gathering and

distributing spill data for Federal On-Scene Coordinators and serving as the communications and

operations center for the National Response Team (NRT), the NRC maintains agreements with a

variety of federal entities to make additional notifications regarding incidents meeting

established trigger criteria. The NRC is staffed by USCG personnel who maintain a 24 hour per

day, 365 day per year telephone watch. NRC watch standers enter telephonic reports of

pollution incidents into the EPA’s Incident Reporting Information System (IRIS) and

immediately relay each report to the predesignated Federal On-Scene Coordinator (FOSC). The

NRC also provides emergency response support to the FOSCs. This includes extensive reference

materials, state of the art telecommunications and operation of automated chemical identification

and chemical dispersion information systems.

In addition to the NRC, offshore operators are also required to report spills (i.e., chemical

and oil) to the state EPA’s (i.e., Alabama, Florida, Louisiana, Mississippi, or Texas) within

whose boundary the spill occurs. The MMS, has access to both databases (i.e., the NRC’s and

IRIS’s) and thus is able to retrieve information regarding chemical spills reported within the

GOM.

The USCG is currently developing regulations that address the implications of hazardous

substance releases in the marine and freshwater environments. These regulations are required

under the 1990 Oil Pollution Act (OPA-90) and are currently undergoing a public review

process. The proposed regulations define the response plans that need to be prepared for all

marine transportation-related facilities and tank vessels carrying hazardous substances. These

response plans are to include an impact analysis for a worst case discharge and will pre-identify

the areas where impact to human health and the environment could occur. The plans will also

identify worst case planning volumes, endpoints, and distances to endpoints. The proposed

regulations state that dispersion modeling will be necessary to assess the potential risks and

develop response strategies. The proposed rules state that dispersion modeling capabilities will

need to be available within 2 hours of a spill, along with air and water sampling resources, and

readiness of various response equipment. This regulation would be the first of its kind (Applied

Science Associates 2000).

Information on regulatory guidelines for the transportation and storage of chemicals, and

storage and handling information, was obtained from three operating companies which agreed to

provide data for this study, five of their eight chemical suppliers, and other industry sources.

Historical spill data was obtained from publicly available reports published by the USCG since

1990 (USCG 1990-1999). Where available, specific chemical spill volumes are cited in Tables

17 and 18. Importantly, the information on chemical spills does not provide specific locations

within the GOM nor is the particular activity and/or cause identified. This fact makes it very

difficult to quantitatively or qualitatively determine the number of chemical spills with the GOM

either in shallow or deep waters that resulted from E&P activities.
65

5.2 Chemical Transportation and Storage Regulations Related to Offshore E&P

Operations

Jurisdiction for regulations for the transportation, storage, and use of chemicals is divided

between the federal government and individual states. Onshore and in state waters, the state has

primary jurisdiction, followed by the federal government. In outer continental shelf (OCS)

waters in the GOM, the U. S. Congress specifically delegated jurisdiction to the federal

government. In the Continental Shelf Lands Act (43 U.S.C. 1333 Public Lands: Interior), the

authority of enforcement for “the subsoil and seabed of the outer continental shelf” and “all

devices permanently or temporarily attached to the seabed” are areas of “exclusive federal

jurisdiction.” By this act, the U.S. Congress has indicated that it expects the USCG to be the

principal federal agency on matters of worker health and safety, as well as continuing the present

role it exercises for safety of vessels, diving, artificial islands, fixed drill rigs, and similar

structures (Memorandum of Understanding Between the Occupational Safety and Health

Administration and the USCG, 1982).

Regulations on offshore chemical transportation, worker safety, hazardous substances,

and waste handling and disposal impact the storage and handling of chemicals offshore. These

regulations often intertwine with one another, affecting the implementation of both. For example,

OSHA regulates the methods and containers in which chemicals are stored, and DOT regulates

the containers used for transport of chemicals offshore. Since the containers used in transport are

often also used for storage, containers are designed to comply with both DOT and OSHA

requirements. While a detailed explanation of these regulations is beyond the scope of this study,

a brief outline of the primary regulations and requirements is provided to demonstrate the effects

of regulations on offshore chemical storage and handling.

Federal agencies that issue regulations that apply to chemicals used offshore include:

• U.S. Department of Transportation (49 CFR, Part 172: Hazardous Materials Table, Special

Provisions, Hazardous Materials Communications, Emergency Response Information, and

Training Requirements)

• Occupational Safety and Health Administration (OSHA) (29 CFR, Chapter 17: Occupational

Safety and Health Standards)

• U.S. Environmental Protection Agency (EPA) (40 CFR: Protection of the Environment)

The DOT regulations (49 CFR) control transportation. Part 172 addresses hazardous

materials for all overland and marine transportation of chemicals from source to shore base.

These codes cover packaging standards, labels and markings on containers, labeling exceptions,

and emergency response. Each type of packaging has its own standards for materials of

construction, wall thickness, labeling, and other elements.

Once transported offshore, chemicals stored and used are subject to Federal OSHA

regulations. These laws may be enforced by State OSHA or the USCG on behalf of Federal

OSHA, depending on the boundary for state waters. OSHA also mandates that chemical

suppliers provide Material Safety Data Sheets (MSDSs) for their products. MSDSs summarize

several regulatory requirements and are frequently used by industrial consumers as guides for
66

their employees in complying with regulations, even when the chemicals are not hazardous and

they are not required to do so. The larger chemical suppliers of offshore oilfield chemicals are

engaged in international business/trade and ship products into and out of the United States. For

this reason, many have adopted the international (United Nations) MSDS format to comply with

international laws. MSDSs for chemicals/products selected for detailed analysis (Section 8.0) are

presented in Appendix B.

Chemicals may fall under several EPA regulations that implement legislative acts passed

by the U.S. Congress, including:

• Comprehensive Environmental Response, Compensation and Liability Act (CERCLA),

which not only encompasses all media but includes those materials formally regulated by the

Federal Water Pollution Act (FWPA)

• Resource Conservation and Recovery Act (RCRA)

• Toxic Substances Control Act (TSCA)

The USCG applies regulations to transportation of chemical products on boats from a

shore base to offshore rigs and/or platforms. These regulations address much of the same details

as mandated by OSHA (29 CFR, Chapter 17) and DOT (49 CFR, Part 172) regulations, but have

there own specific rules and reporting requirements. In addition, they also require information on

hazards and health impacts.

As chemicals move through the supply chain from the manufacturing to the formulation

stage, packaging containers, record keeping, and handling policies are adopted to meet all

potential domestic and international regulatory requirements. Frequently, chemicals are stored

offshore in the containers in which they were transported. Therefore, the same safety and

containment standards that were used for transportation are met or exceeded for storage.

Chemical supply companies and operating companies typically provide specific training

to their employees regarding chemical transportation, storage, handling and use. The complexity

of regulations affecting these issues and the number of agencies involved, often make it difficult

for most workers, chemical suppliers, and consumers to maintain a complete understanding of

offshore chemical storage and handling. Chemical supply companies therefore, address this by

maintaining specialists who develop policies and procedures that ensure all regulatory

requirements are met.

5.3 Chemical Storage and Handling by Chemical Class

5.3.1 Chemicals Applied to Wells

A supply of chemical components is normally kept on site (offshore) to provide the

necessary chemicals for drilling, cementing, and completion, stimulation, and workover. For

exploratory wells, a quantity of each drilling fluid component sufficient to drill the well may be

brought to the drilling rig. For development drilling, in which the drill rig remains in one place

and drills a number of wells from the same surface site, supply boats regularly deliver drilling

components to the site to maintain the supply at a level sufficient to drill the well underway.
67

5.3.1.1 Drilling Fluid Chemicals

Drilling fluid chemicals are used during the exploration and development stages.

Normally, these stages comprise approximately 10% or less of the life of an oil or natural gas

field. The majority of these chemicals are inorganic materials that are unreactive in the marine

environment, such as barite and clays.

Once on site, chemical storage becomes the responsibility of the operating company.

Waste resulting from the use of the chemical is treated and disposed of by the operating

company. A chemical supplier may agree, as part of their service, to take back empty containers

and excess chemicals and dispose of them, but responsibility remains with the customer.

Solid drilling fluid components are customarily shipped in sacks, which are stacked on

pallets. On a drilling rig, they are stored on pallets, in the sacks, and within a storage area

provided specifically for drilling chemicals. A typical sack of weighting agents and viscosifiers

weighs approximately 100 lbs. For all other solids, a sack typically weighs 50 lbs. The number of

sacks per pallet depends on the sack size and bulk density of the material. Some low-density

materials are shipped in larger sacks and a pallet may contain as few as 30 sacks. Some

conventional sacks of lower density material such as lignite may be shipped on pallets containing

70 sacks. High-density materials such as barite may be shipped on pallets of 40-60 sacks.

On some types of drill rigs, bulk tanks are used to store high volume materials such as

barite and clay. These bulk tanks are refilled from cargo tanks on supply boats. The transfer from

supply boat to bulk tank is made using an air blower that suspends the fine solids of barite or

clay in air and carries them into the bulk tank. Almost all water-based drilling fluid components

are solids. Those that are not solids are usually minor components and are shipped in buckets or

drums.

Single well amounts shown in Table 5, Section 3.0, illustrate those typical for each

category of well.

5.3.1.2 Cementing Chemicals

Cementing chemicals are used primarily during the exploration and development stages.

Normally, these stages comprise 10% or less of the life of an oil or natural gas field. The

majority of these chemicals are basic cements that react with seawater to form natural

constituents found in marine sediments.

Cementing chemicals are transported to drill rigs by the chemical supplier as needed for

each cementing job. Solid cement components are customarily shipped in sacks and stacked on

pallets. Since the casing in each well is installed in several separate stages, the amount of cement

chemicals stored and used for each job is less than the total for the entire well. On drilling rigs,

solid cementing chemical components are typically stored in sacks and placed on pallets.

Individual sacks of cements typically weigh 94 lbs.
68

The number of sites storing and using cementing chemicals at any one time is a subset of

the number of drilling rigs operating. Only a few rigs are engaged in cementing at any one time;

therefore, the number of sites storing cement is much fewer than the number of rigs operating at

the time.

Single well amounts shown in Table 7, Section 3.0, illustrate those typical for each

category of well.

5.3.1.3 Completion, Stimulation, and Workover Chemicals

Completion, stimulation, and workover chemicals are used primarily during the

development and active production stages. Normally, these stages comprise 50% to 60% or more

of the life of an oil or natural gas field. The majority of these chemicals are acid formulations,

brine solutions, and solid proppants.

Completion, stimulation, and workover chemicals are delivered to well sites on an asneeded basis. Acid solutions are supplied in bulk tanks as ready mixed products. Additives are

typically supplied in 5 gal. buckets or 55 gal. drums. Salt solutions may be prepared on site by

adding solid salts and additives to water.

Storage offshore is temporary, since these chemicals are shipped for each job and stored

until the job is completed. Chemicals are mixed and used under the supervision of the chemical

supplier. The empty containers are frequently reusable vessels and are returned to the supplier.

Sacks and smaller containers are disposed of as waste.

The number of sites storing completion, stimulation, and workover chemicals at any one

time is related to the number of wells being completed, stimulated, or repaired. The number of

wells being completed in any one year will be related to the number of drilling rigs working in

that year although the actual completions may be done using workover rigs rather than drilling

rigs. Therefore, the total number of sites storing completion, stimulation, and workover

chemicals is less than the number of working drilling rigs.

Single well amounts of completion, stimulation, and workover chemicals are shown in

Table 8, Section 3.0, and illustrate typical amounts for each category of well.

5.3.2 Chemicals Applied to Production Processing Systems

Production-treating chemicals are primarily applied during the development, active

production, and re-development stages. Normally, these stages comprise 60% to 70% or more of

the life of an oil or natural gas field. The majority of these chemicals are not concentrated in any

one functional category.

Production-treating chemicals used offshore are delivered by the chemical supplier to the

customer’s shore base. They are shipped on the customer’s boat to the offshore platform. An

amount sufficient to meet chemical requirements for an interval longer than the re-supply time is

usually maintained on the platform. Re-supply times are determined by factors such as boat
69

schedules and may potentially be impacted by weather delays. Data on typical volumes for each

category of production-treating chemicals stored on platforms was gathered from the operating

companies participating in this study. There are thousands of sites, in both shallow and deep

waters in the GOM that store and use production-treating chemicals.

Production-treating chemicals are stored in one of two ways on platforms:

• In the shipping containers

• In bulk tanks that serve as the reservoir feeding the injection pumps

If bulk tanks are used, chemicals are transferred from the shipping containers to the bulk

containers once they reach the platform. If chemicals are stored in the shipping containers, they

are pumped directly from the container or transferred to pump reservoirs as needed.

Typical shipping container sizes were gathered from two major GOM production-treating

chemical suppliers and include containers with volumes of 500 gal., 385 gal., 200 gal., 55 gal.,

and 5 gal.

One supplier provided data on the percentage of the product shipped in specific

containers for 35 of its major chemical products. An evaluation of the information indicates that

55 gal., 200 gal., and 385 gal. containers were the most common container sizes used, with the

200 gal. container being used for at least a portion of most products. For all but three of the 35

products, the shipping container was the final storage container. For these three, a permanent onsite storage tank was used.

The second chemical supplier reported that several central facilities that it supplies use

550 gal. stainless steel transporters as permanent storage. In addition, a second tank is also kept

in reserve. Smaller structures use 275 gal. stainless steel transporters or 220 gal. polypropylene

(poly) tanks as permanent storage. Poly tanks may be dictated by the ability of the platform crane

to pick them up. Usually, chemicals are shipped in similar tanks, but can also be supplied in

smaller transporters as reported above. For deepwater structures, the supplier reported that 500 to

1,000 gal. permanent storage tanks are designed into some facilities and piping is provided to

connect transport tanks to the built in storage tanks. Most offshore platforms normally receive a

weekly boat run for chemical re-supply.

Alternative Chemical Delivery Systems

In conventional shallow water systems, production-treating chemicals are delivered to a

platform and are added to the system on the platform. In deep water, there is an increasing use of

subsea completions, and the use of umbilicals. Umbilicals are used to carry the produced stream

to the platform as well as to deliver production-treating chemicals to production wells. This

technology is becoming more prevalent as a result of its efficiency in treating very deep subsea

flowlines. These wells might be several miles (i.e., over 60 miles) from the platform or structure

receiving the production.
70

Methanol and various types of glycols (e.g., ethylene glycol) are the primary types of

production-treating chemicals transported in umbilicals to support deepwater operations. Their

primary functions are to inhibit hydrate formation that results from the interaction of gas and

water as a result of the physical conditions of the deepwater environment. Very deep water

always has low temperature, and considerable heat loss will occur in long flowlines. If the

temperature goes below the hydration point, solids can form and block the flowline.

The volume estimation models described in Section 3.0 were developed using 1998 data

to provide estimates of the quantity of chemicals stored and used offshore. The models contain

information on chemical storage that aids in estimating the size of individual shipments that are a

factor in determining the risk of accidental discharges.

5.3.3 Factors Affecting Chemical Spills

The shallow water region of the GOM has a long history of development. There are many

small fields with multiple platforms that require a significant amount of support as part of normal

operations. However, most shallow water trips by transport/support vessels are relatively short

and metocean conditions are typically milder than the deepwater region. Conversely, the

deepwater region of the GOM has a relatively short history of development (i.e., since the midto late-1980s). Deepwater fields are and will continue to be located much further from shore, and

trips by transport/support vessels are and will be of longer duration. In addition, metocean

conditions may be more extreme than in shallow water. These factors will require careful

monitoring since little is known about spill potential and risk in deep water.

New technological advancements, specifically for deepwater applications, such as the use

of umbilicals to supply production-treating chemicals to subsea producing wells, are an example

of a new tool that increases the probability and adds a new potential source for accidental

chemical spills. These umbilical lines are typically long and have a relatively high volume

compared to topside storage vessels. Importantly, umbilicals have been in use for a relatively

short period of time (i.e., 3-5 years), limiting any measurable performance and/or safety data.

Most of the umbilicals used for chemical transport purposes are flexible and may be constructed

of carbon steel with zinc coating. They usually range between three- to less than one-inch in

diameter. For example, a production well system operating in the Mississippi Canyon region of

the Gulf ties back to a platform at West Delta 143, which is over 63 miles away. To supply that

system with needed production-treating chemicals, the operator has laid a three-inch umbilical

line. Figures 9 and 10 show examples of umbilicals used in deepwater operations.
71

Source: www.offshore-technology.com/projects/mensa/mensa5.html

Figure 9. Schematic of Flowline and Umbilical Subsea Architecture in the Gulf of Mexico.

Source: www.offshore-technology.com/projects/mensa/mensa4.html

Figure 10. Detailed Schematic of Subsea Manifold and Template Base.
72

5.4 Gulf of Mexico Chemical Spill Data and Recorded Spills

5.4.1 Background

With the passage of the Federal Water Pollution Control Act (FWPC) (i.e., the Clean

Water Act) in 1972, the USCG was provided with statutory authority to regulate oil pollution

prevention and response activities in the United States waterways. The FWPC requires that any

discharge of an oil and or hazardous substance in a harmful quantity be reported to the

appropriate agency of the United States. Most importantly, it provided for the development of a

National Contingency Plan (NCP) which would “provide for efficient, coordinated and effective

action to minimize damage from oil and hazardous substances discharges, including

containment, dispersal, and removal of oil and hazardous substances.” The President of the

United States delegated the authority and responsibility of establishing this plan to the Council

on Environmental Quality.

In August of 1973, the President, in executive order No. 11735, delegated the authority

and responsibility of establishing this plan to the Council on Environmental Quality. As a result,

the National Oil and Hazardous Substances Pollution Contingency Plan was developed and

implemented later that year. This plan established the NRC, which became operational in August

of 1974 at USCG Headquarters in Washington, D.C. for the reporting of, and coordination of

response to, pollution by oil and hazardous substances.

Since 1973, the USCG has been maintaining the Marine Safety Management System

(MSMS) at USCG Head Quarters in Washington, DC. The MSMS data represents discharges

reported to the USCG by responsible parties, other government agencies (e.g., MMS), or as

discovered and reported by USCG personnel. The current MSMS database is a combination of

three databases:

1. The Pollution Incident Reporting System (PIRS) with data from 1973 to 1985

2. The Marine Safety Information System (MSIS) with data from 1985 to 1991

3. The Modified MSIS System (MIN-MOD) with data from 1991 to present

In the event of a chemical spill offshore, proper protocol is to contact the NRC at 1-800-

424-8802. Spill information, including material involved, mode of transportation, injuries,

damage, fatalities, and other incident details is collected and the information entered directly into

the U.S. EPA’s Incident Reporting Information System (IRIS).

As discussed, CERCLA requires that all releases of hazardous substances (including

radionuclides) exceeding reportable quantities be reported by the responsible party to the NRC.

40 CFR, Part 302 Designation, reportable quantities, and notification, promulgates reportable

quantities and reporting criteria. SARA Title III requires that all extremely hazardous chemicals

that exceed reportable quantities be reported to the NRC as well as to State Emergency Response

Commissions (SERC) and Local Emergency Planning Committees (LEPC). See Table 19 which

lists those organizations/agencies to be contacted following a chemical spill. Links to internet

resources are also provided as are sites of general interest related to this subject.
73

5.4.2 Historical Chemical Spill Data

Currently, there is limited information on chemical spill events in the Gulf of Mexico and

more specifically, there is little to no information available on chemical spills that resulted from

E&P activities in the GOM. What chemical spill information found is presented in this section

and when possible, a distinction is made regarding the activity and/or cause of the documented

spill.

Statistical information on chemical spills in the GOM was obtained from the USCG and

the MMS. While data on historical spills were requested from operators and suppliers, no

information could be obtained from these sources. Since 1990, the USCG has maintained records

of reported chemical spills that are collated and presented as national summaries within an

annual report. These summaries are available on the USCG’s website, see Table 19.

The data sets for chemical spills are subsets of pollution incidents in and around U.S.

waters and have been available since 1990. Chemical spill data are divided by the following

types of categories and presented in individual tables by:

• Chemical spill sizes (from 1 to 100 gal. to > 1,000,000 gal.)

• Water body (the Gulf of Mexico is one of nine listed)

• Location

• Major source overview

Waterbody category data for the GOM was combined from the available annual chemical

spill summaries (i.e., 1990-1998). Table 17 shows the total quantity of liquid (i.e., in gallons)

chemicals spilled, and Table 18 shows the total quantity of solid (i.e., in pounds) chemicals

spilled. The data does not distinguish between the activity that caused the chemical spills or

whether the spill was from fixed structures and/or transport vessels.

Table 17

Gulf of Mexico Chemical (Liquids) Spill Data (1990-1998)

(1) This information was obtained from the National Response Center Database. The data

provided by the USCG for 1998 was supplemented with this information.

Year

Number of

Spills

% of Spill 

Incidents 

(U.S. 

Waters)

Spill Volume 

(gal)

% of Spill 

Volume 

(U.S. 

Waters)

Average 

Spill Size 

(gal)

Median 

Spill Size 

(gal)

Maximum

Spill Size 

(gal)

1990 4 2.90% 1,217 1.20% 304 108 1,000

1991 11 6.90% 5,189 1.70% 472 8 5,000

1992 8 5.30% 162 0.00% 20 5 70

1993 11 8.30% 597 0.30% 54 2 550

1994 8 5.80% 6,055 0.10% 757 1 5,922

1995 7 4.70% 1,133 0.40% 162 1 1,000

1996 13 10.70% 3,501 5.60% 269 1 3,276

1997 27 22.90% 390,842 77.60% 14,476 1 381,565

1998 32 26.70% 65,577 18.40% 2,049 1 63,000(1)
74

Table 17 indicates that the number of liquid chemical spills (i.e., excluding oil) has

steadily increased in the GOM from 1990-1998. The percentage of spill incidents for the Gulf

region has also increased and accounted for almost 27% of all incidents in U.S. water bodies by

1998.

Analyzing the chemical spill data provided, it is important to recognize that a few large

single events accounted for the majority of the volume of chemicals spilled. For example, in

1997 and 1998, the average size of the average liquid chemical spills appeared to increase from

previous years in the GOM. However, this was a result of high volume single-event spills that

accounted for the majority of the liquid chemicals discharged into U.S. waters. For example, one

liquid chemical spill in the GOM in 1997 accounted for 381,565 gal. (not an E&P related spill)

of the total 390,842 gal., leaving a total of 9,277 gal. from the remaining 26 spill incidents.

Likewise, one liquid chemical spill (zinc bromide) in 1998 accounted for 63,000 gal. of the total

65,677 gal., leaving a total of 2,577 gal. from the remaining 31 spill incidents.

The 1997 liquid chemical spill of ethylene dichloride (not used in E&P operations) was a

result of a collision between two vessels near the sea buoy entrance to the lower Mississippi

River. The 1998 chemical spill of zinc bromide was a result of a valve being left in the wrong

position on an offshore platform. The zinc bromide chemical spill was the largest E&P spill

found in the survey, and a 45,000 gal. spill of zinc bromide was selected for spill modeling and

detailed chemical profiling (Profile 7) in Section 8.0.

Table 18

Gulf of Mexico Chemical (Solids) Spill Data (1990-1998)

Table 18 data do not indicate any clear patterns regarding spills of solid chemicals in the

GOM. When spilled, the average quantity is usually large, and this is most likely due to how

these solid chemicals are transported (i.e., sacks, containers on pallets). There is no information

available regarding sources and or causes for any of these chemical spills.

Year

Number of 

Spills

% of Spill 

Incidents 

(U.S. 

Waters) Spill Size (lbs)

% of Spill 

Volume 

(U.S. 

Waters)

Average 

Spill Size 

(lbs)

Median 

Spill Size 

(lbs)

Maximum 

Spill Size 

(lbs)

1990 6 14.60% 604,082 69.80% 100,680 33,684 446,000

1991 4 8.00% 9,787 1.80% 2,447 27 9,730

1992 1 3.00% 3,000 0.50% 3,000 3,000 3,000

1993 7 35.00% 13,729 52.10% 1,961 1,800 4,178

1994 1 2.70% 27,000 1.50% 27,000 27,000 27,000

1995 0 0.00% 0 0.00% 0 0 0

1996 3 12.50% 29,802 22.20% 9,934 14,742 14,960

1997 0 0.00% 0 0.00% 0 0 0

1998 1 3.10% 10,822 1.30% 10,822 10,822 10,822
75

As part of this study, the MMS provided chemical spill data from February 1997 to

February 2000, for a total of 17 recorded spills in federal waters of the GOM. An evaluation of

the data set indicates that of the four chemical classes, a disproportionately large ratio (i.e., eight

of 17, or 47%) of spills related to completion, stimulation, and workover chemicals were

reported. Within this chemical class, zinc bromide was the primary chemical spilled (i.e., total of

six spills), with spill volumes ranging from 168 gal. to 7,140 gal. Geographically, five of 17

spills occurred in the Garden Banks region and three spills occurred in the Mississippi Canyon

area of the Gulf. The 12 other spills were spread throughout the Gulf with no more than two

spills within one area or block.

Completion, stimulation, and workover chemicals are likely to be directly applied from

supply boats instead of being transferred to the platform or rig and then used. Such a handling

system may afford more opportunity for spills to occur, and as a result some chemical suppliers

have developed containment systems and “slop tanks” that address some of the problems

associated with such operations. Completion, stimulation, and workover chemicals are probably

stored at over 300-400 offshore sites in the GOM at any one time. Another eight spills were

reported for production-treating chemicals that are stored at over 2,000 sites in the GOM (i.e.,

not drilling sites).

5.5 Chemical Spill Response

Currently, there are no federal or state regulations and/or protocols for responding to

chemical spills related to E&P activities in the Gulf of Mexico and/or other U.S. waters. As

discussed, the USCG is in the process of developing regulations that will address the

implications of hazardous substance releases in the marine and freshwater environments.

Today, the responsible party transporting/storing/using chemical(s) at the time a spill

incident occurs (i.e., during transport, release from an offshore drill and/or production rig) follow

individual protocols that normally result in one or all of the following organizations being

contacted immediately; the National Response Center (NRC), the U.S. Coast Guard (USCG),

and the state’s environmental regulatory agency. Chemical spill response may be divided into

three distinct stages.

First Responder Level

The responsible party will normally secure the area or terminate the action that caused the

chemical spill while ensuring safety to workers on the particular offshore structure. The

responsible party will then communicate with the USCG to ensure human safety has been

addressed and they will team together to determine if any additional measures are required. At

this level, awareness is at the lowest level and trained individuals should only recognize that

there is a problem, provide some assessment if it can be done safely, and ensure that the proper

authorities are notified.
76

Second Responder Level

The team of the USCG and responsible party now work to get more information

regarding the chemical spill with emphasis on the safety of personnel and the general public.

Immediate actions to reduce the risk (i.e., source control) to those immediately at threat are

taken. Next, the USCG’s team will often call on specialists pre-identified to provide technical

support, such as the National Oceanic Atmospheric Administration (NOAA) Scientific Support

Coordinators (SSCs) and the EPA’s Emergency Response Team (ERT). The SSCs are divided

into nine districts and serve on the Federal On-Scene Coordinators (FOSC) staff as the lead of a

scientific team and provide expertise in environmental chemistry, oil slick tracking, pollutant

transport modeling, natural resources at risk, environmental trade-offs of countermeasures and

cleanup, information management, contingency planning and liaison to the scientific community

and the natural resources trustees. The ERT group is a specialty group of trained scientists and

engineers who’s capabilities include multimedia sampling and analysis, hazard assessment,

cleanup techniques, and technical support.

The USCG’s team will then obtain the following technical information specific to the

chemical substance; density of the substance spilled in seawater (i.e., to determine if the

substance will float or sink) and packaging/container details (if any), solubility in seawater (i.e.,

slight, high, insoluble), fate and transport characteristics of the chemical substance (i.e.,

persistence in the marine environment), chemical toxicity, geological conditions of the receiving

environment (i.e., sandy, silty, rocky). During this phase, the USCG’s team (i.e., USCG, the

responsible party, SSCs or ERT) will consult with various experts from the chemical

manufacturers company, the USCG, and might also contact CHEMTREC whose extensive

database of 24-hr. contacts contains experts including chemical manufacturers, shippers, carriers,

emergency response contractors and other organizations that have information and resources.

As information is gathered, the USCG’s team will evaluate the need for a hazardous

materials response often coordinating this strategy with various spill response organizations.

Since there are no protocols and/or regulations such as the Oil Pollution Act of 1990 (OPA-90)

that require all those who transport petroleum and petroleum products in U.S. coastal waters to

ensure by contract the resources necessary to respond to “worst case discharge” to the

“maximum extent practicable,” all chemical spills are treated on a case-by-case basis and

evaluated using the criteria as described here.

Within shallow water, the determination whether there is a response action is often based

on whether or not the chemical substance can be recovered and whether the recovery effort is

economical based both on the value of the chemical substance and the cost of the recovery

mission. In addition, much more is known about the shallow water environment (i.e., biological

communities, geology, etc.) as compared to the deep waters of the GOM.

Third Responder Level

By the third stage, significantly more resources are available and a Unified or Joint

approach is taken to respond to the spill incident. The USCG’s team, with the consultation of

chemical experts and spill response specialists, have determined an action plan that includes an

environmental assessment, mitigation, and cleanup plan determination and implementation. At

this point, the company responding to the chemical spill, which may include the USCG,

government organizations (i.e., the Marine Preservation Association (MPA) which funds the
77

Marine Spill Response Corporation (MSRC)), and/or commercial spill response companies, will

initiate the spill response with the assistance and guidance from the USCG as well as the

responsible party. The technical specialist (i.e., SSCs or ERT) will provide input either on-scene

or through various communication means to the Unified Command (i.e., lead person responding

for the responsible party, federal government, and effected states).

Often, in developing the chemical spill cleanup strategy, the USCG and responsible

parties will refer to the CAMEO database. CAMEO ® is a system of software applications used

widely to plan for and respond to chemical emergencies. It is one of the tools developed by

EPA’s Chemical Emergency Preparedness and Prevention Office (CEPPO) and NOAA’s Office

of Response and Restoration to assist front-line chemical emergency planners and responders.

CAMEO can be used to access, store, and evaluate information critical for developing

emergency plans. In addition, CAMEO supports regulatory compliance by helping users meet

the chemical inventory reporting requirements of the Emergency Planning and Community

Right-to-Know Act (EPCRA, also known as SARA Title III). The CAMEO system integrates a

chemical database and a method to manage the data, an air dispersion model, and a mapping

capability. All modules work interactively to share and display critical information in a timely

fashion. CAMEO initially was developed because NOAA recognized the need to assist first

responders with easily accessible and accurate response information. Since 1988, EPA and

NOAA have collaborated to augment CAMEO to assist both emergency responders and

planners. CAMEO has been enhanced to provide emergency planners with a tool to enter local

information and develop incident scenarios to better prepare for chemical emergencies. The

Bureau of Census and the USCG have worked with EPA and NOAA to continue to enhance the

system.

To support information presented in this section, multiple government and private

organizations specializing in hazardous materials response were contacted to determine state ofthe-art response to chemical spills, particularly in the GOM regions. Each of the spill response

companies specialize in responding to oil spills, and have little or no experience in responding to

chemical spills. Most companies and/or organizations indicated that they were waiting for the

USCG to issue regulations with respect to chemical substances before developing protocols

related specifically to chemical spill response. As discussed, the USCG has been in the process

of evaluating the need for and developing regulations for responding to chemical spills and has

initiated the development of regulations.

Table 19 contains a compilation of chemical spill response contact information for the

Gulf of Mexico.
78

Table 19

 Emergency Response Contact Information for Chemical Spills in the Gulf of Mexico

Organization/Agency Contact Information

Internet URL Reference Phone Number

National/Federal Contacts

National Response Center (NRC) http://www.nrc.uscg.mil/index.htm 1-800-424-8802 (24 Hours)

United States Coast Guard (USCG) http://www.uscg.mil/ 1-800 424-8802 (24 Hours) – same

as the NRC

USCG Department of Marine Safety

and Environmental Protection

http://www.uscg.mil/hq/gm/gmhome.htm---

U.S. EPA’s Incident Reporting

Information System (IRIS)

http://www.epa.gov/ngispgm3/iris/ 1-513-569-7254 or e-mail:

RIH.IRIS@epamail.epa.gov

National Oceanic and Atmospheric

Administration (NOAA) – Office of

Response and Restoration /

Scientific Support Coordinators

(SSCs)

http://response.restoration.noaa.gov/ 1-504-589-4414; NOAA’s District 8

office located in New Orleans,

Louisiana. This district office covers

the coastal and offshore zones of

Texas, Louisiana, Mississippi,

Alabama, and part of Florida

State/Local Contacts

State Emergency Response

Commissions (SERC)

http://www.epa.gov/tri/sercs.htm ---

Local Emergency Planning

Committees (LEPC)

http://www.epa.gov/tri/lepcs.htm ---

Alabama Waters (Alabama

Department of Environmental

Management)

http://www.adem.state.al.us/ ---

Florida Waters (The Florida

Department of Environmental

Protection)

http://www.dep.state.fl.us/ ---

Florida State Emergency Response

Commission

--- 1-800-320-0519 (24 Hours)

Florida Marine Patrol (FMP) --- 1-800-342-5367 (24 Hours, In State)

Louisiana Waters (Louisiana

Department of Environmental

Quality)

http://www.deq.state.la.us/ 1-225-342-1234 (24 Hours)

Mississippi Waters (Mississippi

Department of Environmental

Quality)

http://www.deq.state.ms.us/newweb/

homepages.nsf

---

Mississippi Emergency Management

Agency (MEMA)

--- 1-800-222-MEMA (6362) or 1-601-

352-9100

Texas Waters - (The Texas Natural

Resource Conservation Commission

– TNRCC)

http://www.tnrcc.state.tx.us/ 1-800-832-8224 (24 Hours)

Texas General Land Office (TGLO) http://www.glo.state.tx.us/ 1-512-475-1575
79

Table 19

 Emergency Response Contact Information for Chemical Spills in the Gulf of Mexico (continued)

Organization/Agency Contact Information

Internet URL Reference Phone Number

Industry/Other Contacts

CHEMTREC http://www.chemtrec.org/ 1-800-262-8200

GOM spill summaries (oil and

chemicals) from the USCG

http://www.uscg.mil/hq/gm/nmc/response/stats/ac.htm---

5.6 Summary

The information provided in this section summarizes the majority of chemical spill

information available for the GOM. The type and extent (i.e., 1990-1998) of these data allow for

purely qualitative judgments on the sources and/or causes of chemical spills. In addition, given

the quality of the data collected and evaluated there is no definitive way to determine whether

these chemical spills occurred in shallow or deep water (i.e., since geographic locations within

the Gulf and/or water depths are not included in the data set) or to determine the activities and/or

events that caused these chemical spills.

While the number of chemical spills in the Gulf may be related to the ongoing and

increasing E&P activities in the region, the increase in number of spills reported since 1990 may

not be directly correlated to an increase in E&P operations. A percentage of the overall increase

in reported spills can likely be attributed to the improvement in reporting and management

practices by offshore operators and chemical supply companies over the last decade.

Of the four chemical classes, the application of completion, stimulation, and workover

chemicals from supply boats poses the greatest potential for accidental spills to the marine

environment. This risk is largely the result of the method in which these chemicals are handled

and transferred. In order to address this potential risk, some supply companies have developed

containment systems and “slop tanks” that address some of the problems associated with such

operations.
81

6.0 BIOLOGICAL COMMUNITIES POTENTIALLY AFFECTED FROM SPILLS OF

CHEMICALS USED IN DEEPWATER E&P

6.1 Introduction

This section of the report is an overview of the biological communities potentially

affected by spills of chemicals used in deepwater E&P. An emphasis is afforded the deep sea

because the focus of chemicals selected for this study are those new or specific to deepwater oil

and gas activities.

Exploration for oil and gas is increasingly extending into the deeper waters of the Gulf of

Mexico. Biological communities potentially at risk from the use of chemicals, therefore, extend

past the break of the continental shelf (generally accepted as the upper limit of the deep sea). The

Law of the Sea sets this break at 1,000 ft. (305 m); however, for the Gulf of Mexico, the depth of

656 ft., or 200 m, more closely coincides with the shelf break and is used in the Deepwater Oil

and Gas Royalty Relief Act and for resources estimation. This fact puts deep-sea benthic pelagic

biological communities and oceanic pelagic communities potentially at risk. Certain aspects of

deepwater development may possibly pose novel threats of impact, either because of the

technology, the chemical compounds, the differing environment, or the different biological

communities and ecological processes (Carney 1998).

Many wastes and/or accidental discharges from drilling activities will migrate towards

the bottom. Due to multiple wells and horizontal drilling, there is an expected greater volume of

cuttings to be discharged from deepwater operations than from shallow water operations.

However, there is a predicted lower density of structures for deepwater operations. Production

activities are likely to be similar with a shift in the location of subsea hardware. Processing and

separation will likely be similar. The shore infrastructure already exists.

While E&P occurs in deepwater, the infrastructure that supports these activities resides

mainly in the coastal zone; transportation and transport facilities (e.g., pipelines) span the

distance from the activities in deep water to the coastal facilities. Transportation of fluids will

probably tie in to existing shallow pipeline systems, so that the environmental risks will be

similar. Differences emerge in the types of chemicals carried and the deepwater extension of

pipelines. Thus, a broad range of biological communities can potentially be exposed to spilled

chemicals used in deepwater activities.

The major types of benthic communities within the continental shelf zone are those

associated with soft-bottom habitats that vary in sedimentary composition. Many biogenically

structured communities, such as coral reefs or “live” bottoms, occur throughout the Gulf of

Mexico. These ecosystems are usually more taxonomically diverse than the surrounding softbottom communities and are likely to differ in their sensitivities and responses to environmental

perturbations. Within the deep sea, the benthic communities are dominated by soft-bottom

dwelling organisms, with an added importance of microhabitat structuring. Hydrocarbon seeps

with their chemosynthetic, or otherwise specialized biological communities, are places where gas

and oil flow naturally out of the sea floor and are quite common on the continental slope of the

northern Gulf of Mexico. Much less is known of the deep-sea and oceanic communities.
82

Several habitats within the coastal and oceanic portion of the Gulf of Mexico have been

afforded special status as National Marine Sanctuaries and National Estuarine Research

Reserves.

6.2 Deep-sea Benthos and Demersal Fauna

The deep sea is the largest habitat on Earth. It is predominantly dark and cold; the food

supply is low; and colossal pressures are exerted on its inhabitants by the great depth of the

overlying waters. It is mostly inaccessible to human exploration and experimentation. It is not

surprising that knowledge of deep-sea life is limited, especially more so for dynamics of

populations and biological processes.

Oil and gas development in deepwater environments pose different technical and

environmental considerations than in shallow waters. Production sites are generally farther from

shore, reducing the potential of oil spills from blowouts reaching shore, although a notable

exception is the Ixtoc spill of 1979-1980. Dispersion of contaminants released from the rig or

platform are likely to be greater due to the larger volumes of receiving water. However,

geohazards related to seabed slumping may be more likely, and accidental spills may be more

difficult to control. In addition, any effects on the benthic environment may be longer lasting

because of the expected slower recovery rates of deeper benthos (Boesch and Rosenberg 1981,

Rabalais and Boesch 1987).

6.3 Physical Environmental Setting

Carney (in draft) provides a good summary of the importance of pressure, density, light,

oxygen, and currents in the deepwater environment for oil and gas activity impacts.

• Pressure increases uniformly with depth at 1 atmosphere (atm) per 10 m. This affects the

solution chemistry of discharges and spills, as well as the ecological differences in calcium

carbonate dissolution (important to meiofaunal organisms such as foraminiferans) above and

below the calcite compensation depth (CCD), at which depth the dissolution of sinking tests

equals the rate at which the material accumulates (i.e., shallow water models for fates and

effects of carbonate containing discharges must be re-evaluated). Clathrates in the upper part

of the stability envelope (approx. 500 m) may constitute a special habitat.

• Density (temperature and salinity) changes nonuniformly to 1,000 m where it becomes

uniform and high in cold, deep bottom-water. Limited stratification in deep water will allow

discharge plumes to easily propagate.

• Light decreases exponentially with depth, is present in low intensity below 200 m, and is

generally thought to be absent deeper than 1,000 m. Bioluminescence is important for

deepwater animals. Animals adapted to low light might be especially impacted by increased

turbidity from deep plumes of low transmission water. Below sensible sunlight, turbidity may

impact biological light interactions.

• Oxygen minimum (3 mg/l) lies between 200 m and 750 m in the Gulf of Mexico, mostly at

400 m. Below 750 m, oxygen is again high and relatively constant. Spills of compounds with

labile carbon may alter the local balance of oxygen consumption and replacement, especially

in the OMZ, and result in local deep anoxia.
83

• The benthic boundary layer (BBL) varies in thickness from 5 to 100 m and is a steady-state

feature of fluxed and resuspended particles important to deep pelagic fauna (i.e., aspects of

deep activities should not just focus on the seabed, but include the overlying water in the

BBL). BBL conditions redistribute the detritus pulse into a complex patchwork on the

bottom, suggesting a mechanism for environmental heterogeneity.

Currents

The deep bottom is characterized as a habitat with low energy, low tidal, geostrophic, and

thermohaline currents with episodes of high current velocity. (Nowlin 1998) indicated that Loop

Current speeds may exceed 150 cm/s at the surface with velocities as high as 5 cm/s still

persistent at 1,000 m. These speeds are restricted to the southeastern and northeastern Gulf of

Mexico and may intrude to the continental edge of the Florida panhandle. Cyclonic and

anticyclonic eddies (40-150 km) are ubiquitous on the northern slope region (LATEX-C and

GULFCET programs).

Eddie Juggernaut, in the northwestern Gulf, currently has speeds up to 150 cm/s at the

surface (N. Walker, personal communication). Eddies in the western Gulf showed velocity

spikes to 30-40 cm/s at 500 m (Nowlin 1998). Loop Current rings off south Texas influence

currents in the 200-700 m depth range, with the 200-m currents exceeding 30 cm/s during 40%

of the record and 50 cm/s during 19% of the record. Hurricane Andrew effects in the surface

waters exceeded 150 cm/s (also at 20 m off Terrebonne Bay, N. Rabalais personal observation),

but speeds decreased rapidly with depth so that at 100 m currents did not exceed 50 cm/s, and at

490 m about 5 cm/s was reached. Hurricane Allen (south Texas, mooring 9) produced currents of

90 cm/s at 200 m, 15 cm/s at 700 m, and 15 cm/s just above the bottom at the 730 m water depth.

Geology

Geologically the northern-to-western Gulf of Mexico continental slope is perhaps the

most complex continental slope environment in the ocean. It is technically difficult for deepwater

E&P, and results in a myriad of habitats for biological communities, including hard substrate,

chemosynthetic communities associated with a spectrum of hydrocarbon venting and seepage

areas, and variable sediment, slope and stability types.

Zonation

The continental shelf occupies 5.8% of the earth’s surface. The continental slope (200-

3,000 m) and rise, (3,000-4,000 m) occupy 10.7%, and the deep-sea basin and trenches make up

the remainder with 54.3% (earth surface above sea level 29.2%). The continental slope occupies

an especially important place at the boundary between the continental blocks and the deep-sea.

Terrestrial sediments predominate to its landward side, and the pelagic oceanic sediments lie

offshore. The gradient can be greater than 1 in 40, as opposed to the less than 1 in 1,000 found

on the shelf and abyss, and the relief can be (especially locally where submarine canyons

intrude) as much as 2,000 m (not the Gulf of Mexico). The gradients, topographically and

hydrographically (in terms of the meeting of shelf and oceanic water masses) are strong ones,

and the area is one of dynamic tensions with advantageous implications in terms of niche space

for resident fauna. The only other part of the ocean that is as rich in topographic features is the

boundary between the tectonic plates (the great mid-ocean ridges).
84

6.4 Biological Processes

Our knowledge base for the effects of chemicals or habitat perturbation is the most

meager for the deep sea. It is expected, however, that ecological processes in the deep sea are

fundamentally similar to those of the continental shelf, slope, or rise. The dichotomy between

deepwater and shelf environments is mostly artificial since the people working on the various

areas do not overlap in their studies. There are, however, additional environmental and physical

parameters at work in the deep sea that make populations and communities there unique. What is

not known are the sensitivities of individuals and communities to contaminants; the rates and

mechanisms for population control, biological interactions, recruitment and rates; or potential for

recovery from impact.

Carney (in draft) states that management perspectives for deep water need to address the

same issues as for shallow water.

Maximum protection should be allocated to the most important and sensitive

components. For non-fisheries, management is habitat rather than species directed, because it is

easier to delineate habitats than to assess ecological importance. Resource values in shallow

water are often driven by a fishery or aesthetic component; for deepwater, fisheries are less

important, but still fuel an aspect of the economy (see below). With regard to aesthetics, the deep

sea is not readily accessible, but there remains a public perception of high diversity; new species

remaining to be discovered, exotic morphologies, etc. In shallow water, uniqueness of habitat has

basically been defined and region- or habitat-specific management strategies can be developed.

The information base for the deep sea, however, is inadequate to do this. For the vast majority of

deep-sea species, even the most abundant, we do not know the basic information of feeding type,

reproduction, life span, predators, and population biology.

MMS needs to know if the deep benthos - with its dependence upon detrital influx, its

poorly understood diversity, and its vertical zonation - is especially more sensitive to impact than

the shelf benthos. Management, in absence of adequate information, must turn to published

generalities about deep-sea adaptation to make the “first cut” on relevance (Carney in draft).

These generalities may be based on actual evidence, prevailing paradigms, and fashions of

science. Today’s knowledge of the deep sea has replaced some of the prevailing paradigms, so

generalities must be approached cautiously.

The deep-sea benthos is mostly a soft-bottom benthic fauna with additional physiological

constraints imposed by no light, cold temperatures, and high pressure. Alteration of the soft

bottom will affect two generalities of deep species animal sediment adaptations:

1. The predominance of soft-bottom dwelling organisms and the importance of habitat

structuring.

2. Domination of deposit feeders (Carney in draft). The shallow-water strategy of recognizing

special habitats on the basis of gross substrate (hard versus soft) will be insufficient in the

deep environment where important habitat variation may occur within the vast soft bottom.
85

Other generalities are not necessarily accepted:

1. More restrictive reproductive patterns; rather, deep fauna show as much adaptive variation as

encountered in shallow water

2. Larger fauna are more the unusual and a size shift to smaller appears to be an adaptation to

low food levels (avoid disruption of food supply)

3. Dark adaptation is not supported by the presence of well-developed eyes in some animals or

forms of bioluminescence (avoid increasing turbidity)

Bathymetric Zonation – There is a progressive change of fauna with depth, with the

causal mechanisms remaining largely speculative (reviewed by Carney et al. 1983). The deep sea

cannot be treated as a uniform environment. The faunal zones most identifiable in the deep sea

are upper slope (200 to 1,000 m), an abyssal plain fauna (> 3,000 m), and a lower slope fauna

(1,000 to 3,000 m) that overlaps the others. Unfortunately, research directions in the deep sea are

not in zonation, an aspect that needs better understanding to develop management strategies

across vast areas. Current DNA techniques (Etter and Rex 1990) show that the prevailing idea of

widening vertical ranges with increasing depth is correct. Co-variance of factors with depth

complicates separating causality from correlation. Physiologically relevant factors, such as

increasing pressure with depth (Seibenaller and Somero 1989), are important. Biological factors,

such as detrital influx rate gradient (Rowe and Pariente 1992) and their effects on feeding mode

(Rex 1981) and biotic interactions, subsequently contribute to differences in community

structure. Therefore, management decisions should not presuppose any particular mechanism.

Biomass Pattern – The unit per area (weight, carbon, nitrogen, counts) decreases

exponentially with depth (variability with surface productivity, width of the continental shelf,

and latitude). With regard to potential impacts, the community subject to the impact may

decrease in size with depth. Conflicts with biomass exploiting activities, such as fishing, should

decrease, and any impact studies will be plagued by small sample sizes. Dramatic biomass

differences between the shelf break at 200 m and the slope bottom at 3,000 m suggest that these

environments are different and require depth-specific management strategies. In areas where

food biomass is rare, the disruption of natural patterns of detritus input may be the primary agent

of environmental impact.

Diversity Pattern – The deep sea is species rich and, for some areas, there is a welldefined species maximum on the lower continental slope (approx. 2,000 to 3,000 m). With

regard to impacts, they may be rightly or unjustly compared with more “charismatic” high

diversity habitats such as coral reefs and tropical forests. Since the explanation of high diversity

remains elusive, one possible interpretation is that we do not know how deep-sea ecosystems

function and are unable to predict impacts. Some of the diversity explanations suggest a high

dependence on subtle environmental variables (more than in shallow water) with an implication

for greater sensitivity to perturbation. While it is always hoped that some index of diversity

might be a precise indicator of ecosystem health, this simply has never been established (Carney,

in draft).
86

The time-stability hypothesis (Sanders 1979) states that species somehow accommodate

to each other and partition resources rather than compete in environments that are vast, old, and

stable. Such accommodation implies a fine and easily upset balance among species for a narrow

range of resources.

Cropper control is direct cropping by animals on species lower on the food chain that

were about to exclude competitively weaker species (Dayton and Hessler 1972). This idea

emphasizes the importance of predator-prey relationships, the importance of keystone species,

and the potential disruption of larger communities if a keystone species were subject to impact.

Grain matching explanation (Jumars and Ekman 1983) states that the deep-sea bottom is

finely divided into many habitats, many of which are biogenic, and that these fine-scale

differences (centimeters and smaller) indicate that the system is not as homogeneous as most

methods and scales of human observation would suggest. Biogenic structures should be more

persistent in the deep sea and are likely to be a very important agent of habitat heterogeneity.

Impacts that physically alter this finely structured sediment-water interface may have major

impacts.

Contemporaneous disequilibrium proposed by Grassle and Maciolek (1992) produces a

very dynamic picture of deep-sea diversity with a broad sea floor populated by species

emigrating from many small and temporally varying centers of high competitive success so that

large areas never come to a low diversity equilibrium. Thus, some areas of the sea floor (source

areas) may be more important than others in diversity maintenance. In order to protect these

areas, management must be able to identify them, a feat not yet accomplishable.

Current deep-sea ecology does not identify conclusively those processes maintaining

diversity. Of two views, a homogeneous environment with complex competition or a

heterogenous environment with normal competition, the second is more tractable. If the deep

benthos is a habitat-rich system on a very small scale, then processes causing this variety need to

be known and protected; these include biogenic structure, flow interactions at the sediment water

interface, and redistribution of detritus.

The process of influx of organic detritus and the biogenic structuring of the benthos are

processes of considerable management relevance because both processes are far more important

in the deep sea than on the continental shelf. The influence of detritus influx is most readily seen

in biomass or population density data. Biogenic structuring is much less understood. Potential

impacts of deep-sea nodule mining that introduced a layer of older sediment, thus diluting the

labile carbon supply, was seen as the main mechanism for impact with those operations (Jumars

1981). Burial under layers of mined sediments was expected to cause asphyxiation of the fauna,

but the experimental design to test differences between 1 and 4 cm burial was not adequate to

detect differences (Smith et al. 1988). Similar impacts might be expected with drilling activities

in the deep Gulf of Mexico.
87

For the purposes of defining management scenarios, the deep-sea benthos should be

divided into depth categories at 1,000 m, based on physical and chemical parameters, and set at

the statistical lower limit of the permanent thermocline (Carney in draft). The 200 to 1,000 m

range, or upper continental slope, is where sunlight effectively vanishes, where temperature and

salinity become stable, and where oxygen drops to a minimum value. The interaction of physical

processes and potentially impacting activities must be different in this physical transition zone

than deeper, where uniformity of physical characteristics begin.

Until recently it was agreed that deep-sea animals exhibited natural histories (primarily

reproductive strategies) that would make them especially sensitive to environmental impact. This

generality is under attack. A generality that remains valid for relevant management purposes is

that most deep-sea animals are deposit feeders. This fact, coupled with low levels of detritus

influx, suggests that the spill of any chemical spill that caused the alteration of food availability

would be potentially significant.

The high species diversity in a seemingly monotonous environment challenges core ideas

about diversification. Ideas that the deep-sea floor is vastly more complex have the greatest

management utility. Biogenic structures and small variations in sediment fabric may be more

important sources of heterogeneity than in the shallow environment. If true, then human

activities might be designed so as to minimize disruption.

6.5 Chemosynthetic Communities

Chemosynthetic seep communities occur along the northern Gulf slope between 95° and

88° W, between approximately 300 and 2,200 m, and coincide with the oil and gas rich areas of

the Gulf (biased by the geography of sampling) (CS in Figures 11-13). The presence of perennial

oil slicks, which form over many seeps and can be detected by satellite remote sensing, indicate

that seeps are present across the entire continental slope of the northwestern Gulf. Seep

communities are known to occur in some areas of acoustic wipeout, of authegenic carbonates

and of observable seepage.

One deepwater seep site in Alaminos Canyon (2,200 m) has a thriving chemosynthetic

community (Brooks et al. 1990). To the east, the Mississippi Fan and Mississippi Canyon areas

appear to have more limited seepage and a hiatus of chemosynthetic seep communities. The

easternmost occurrence of hydrocarbon fauna is in the Viosca Knoll area (88° W) (Figures 11

and 13). The existence of chemosynthetic fauna at the far eastern edge of the Gulf (Hecker

1985), unrelated to hydrocarbons, raises the possibility that such systems are even more

widespread than presently known (no sampling south of 26° N). The Florida Escarpment limits

the eastward occurrence of known seep communities; however, there are tube worms and

mytilids at the base of the Florida Escarpment at 3,600 m in areas of connate fluid seepage from

the highly porous Florida carbonate platform (Paull et al. 1984). It is reasonable to assume that

there are other exotic communities (e.g., specialized for brine seeps) which may be present.
88

Figure 11. Location of live-bottom, chemosynthetic and biogenically-structured communities of the northern Gu

indicate CS-chemosynthetic community, FMG-Florida Middle Grounds, MS-marine sanctuary, MSBNEHB-northeastern Gulf hard-bottom, NERR-National Estuarine Research Reserve, SBB-shelf breaTexas reef, PT-pinnacle trend. Bathymetric contours are in meters.

88
89

Figure 12. Location of live-bottom and chemosynthetic communities of the northwestern Gulf of Mexico. Symbo

chemosynthetic community, MS-marine sanctuary, MSB-mid-shelf bank, SBB-shelf break bank, STXBathymetric contours are in meters.

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Figure 13. Location of live-bottom, chemosynthetic and biogenically-structured communities of the northeaster

Symbols indicate CS-chemosynthetic community, FMG-Florida Middle Grounds, NEHB-northeasterNERR-National Estuarine Research Reserve, PT-pinnacle trend. Bathymetric contours are in meter

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There is general agreement that the seep communities are an invaluable resource and may

have a broad ecological role. Notice to Leasees NTL-98-11 protects them from development.

Hydrocarbon seeps are places where gas and oil flow naturally out of the sea floor, and are quite

common on the continental slope of the northern Gulf of Mexico (MacDonald and Joye 1997).

The autotrophic component of the seep community is chemoautotrophic bacteria that use

the chemical energy contained in compounds like methane and hydrogen sulfide that are

produced by the seepage. Other organisms, such as vestimentiferan tube worms and mussels

(seep mytilids), epibenthic vesicomyid clams, and infaunal lucinid and thyasirid clams form a

symbiotic partnership with bacteria. These faunal groups display distinctive characteristics in

terms of how they aggregate, the size of aggregations, the geologic and chemical properties of

the habitats in which they occur, and, to some degree, the heterotrophic fauna that occur with

them. A variety of other animals, including fishes, crustaceans, and mollusks, are attracted to the

resulting food supply. The result is diverse assemblages comprised of chemosynthetic fauna,

specialized for the seep environment, and predators and browsers that commonly occur across

the continental slope, but attain unusually high abundances at seeps.

Gas hydrates are ice-like minerals that form at the low temperatures and high pressures in

the deep sea (Sassen 1997). Hydrates contain gases, such as hydrocarbons, that are trapped inside

symmetrical cages of water molecules to form hydrate crystals. In the Gulf of Mexico gas

hydrates outcrop on the sea floor as mounds in water depths as shallow as 425 m to depths

greater than 2,000 m. Oil is usually plentiful in the sediments surrounding hydrates. The hydrate

mounds on the sea floor are covered with white and orange bacterial mats as well as various

filter-feeding bivalves and other specialized organisms. Mounds are sometimes surrounded by

rings of chemosynthetic organisms such as tube worms and mussels. The dense hesionid

polychaete populations found on the surface of an exposed hydrate at a depth of 550 m in 1997

indicates undiscovered microhabitats remain.

MacDonald et al. (1996) in their Executive Summary stated “...the seep communities are

a unique and important component of the slope ecosystem of the Gulf of Mexico. Although

susceptible to mechanical damage by offshore drilling or production activities, the ecosystems

are prevalent enough that localized disturbances should not effect [sic] the viability of these

communities.” MacDonald further stated that hydrocarbon and brine seepage has persisted in

spatially discrete areas for thousands of years. Commonality, however, is not suitable for

relaxing criteria for acceptable impact, without knowledge of the ability of undamaged or

damaged fauna to ultimately repopulate any impacted areas. The potential to repopulate can be

inferred from faunal and genetic similarity studies. The underlying supposition is that sitespecific seepage may be intermittent and that existing communities reflect numerous

repopulation events. Preliminary results indicate communities sampled above 1,000 m are quite

monotonous, but that the fauna of deeper communities are quite distinct. The genetic closeness

of the < 1,000 m sites will be determined by molecular studies in a project currently underway.
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Cold seep vestimentiferan worms can be extremely old invertebrates, with some

individuals exceeding 250 years (Bergquist et al. 2000). They must have a hard substrate upon

which to attach. The hard substrate results from a succession of geochemical and sedimentary

changes facilitated by the Beggiatoa bacterial mats. This is in stark contrast to hot vents where

related species grow at exceptionally fast rates. Fisher (2000) notes that physically damaged

communities would likely never recover.

Seep mussels grow at site-specific rates that approximate those of shallow water

heterotrophic species (if methane levels are high). Large individuals may be as old as 50 years

(where methane conditions are suboptimal). Fisher states that mytilids might even increase with

an increase of hard substrate from oil activities. These results could be interpreted in two ways

with regards to potential impacts: (1) a population of old animals exists because the population

has survived natural environmental perturbation and is robust, or (2) the community has not

experienced perturbation and would be fragile in the face of disturbance. Good estimates of

recruitment and mortality are needed to better define the stability and resilience of the

community. On the other hand, seep communities appear to be persistent through time, and

regionally may be resilient, with communities being obliterated and reestablished on a 500 yearand-less time frame. Rigorously determined recruitment and mortality rates for major species are

needed. Presently formed conjectures about resilience and stability must be tested by well

designed experiments.

An abundant heterotrophic fauna exploits both the food source and habitat of the upper

slope seeps. This fauna is numerically dominated by gastropods, but there are also galatheid

crabs, decapod crabs and shrimp, giant isopods, sea-stars, sea urchins, and several fish (listed by

species in MacDonald et al. 1996 Ex Summ). It is expected that some are truly endemic to

chemosynthetic communities, some are colonizers from surrounding benthos, and others are

temporary vagrants. Foodweb tracing indicates that mobile megafauna from the surrounding mud

bottoms do exploit the seeps as a food source. There is low endemism in the Gulf seep sites,

especially the upper slope, and a high degree of colonization by fauna from the surrounding sea

floor, in marked difference from the hydrothermal vent systems.

Faunal composition of chemosynthetic and heterotrophic fauna at sites above 1,000 m is

remarkably uniform. Faunal similarity above 1,000 m would indicate similarity in response to

impacts. Poorly studied deeper sites are known to be different. The differences in fauna with

increasing depth suggest that rules of “no impact” should persist until more is known of them.

6.6 Biogenically-Structured and Live-Bottom Habitats

“Live-bottom” habitats are “...those areas which contain biological assemblages

consisting of such sessile invertebrates as sea fans, sea whips, hydroids, anemones, ascidians,

sponges, bryozoans, or corals living upon or attached to naturally occurring hard or rocky

formations with rough, broken, or smooth topography; or areas whose lithotope favors the

accumulation of turtles, fishes, and other fauna” (Yourk 1999). The definition used by MMS also

includes seagrass communities. Although no seagrass beds exist in the deeper offshore waters

covered by this section of the report, they do occur in the coastal zone where onshore logistic

facilities and transport activities occur.
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The organisms on or associated with hard-bottom outcrops in the northern Gulf of

Mexico are controlled by: (1) proximity to the Mississippi River discharge, (2) size, relief, and

texture or rugosity of the outcrop, (3) temperature, and (4) depth and/or light availability

(Gittings et al. 1992). Colonial invertebrates, such as scleractinians and gorgonians that form the

live-bottom habitats grow slowly, require relatively stable environmental conditions, and are

very sensitive to temperature, water quality, and sedimentation. Live-bottom community

development progressively improves towards the east away from the Mississippi River plume.

Complexity of live-bottom communities (abundance and diversity) increase with vertical relief

and surface area. Community development is less extensive on isolated low-relief features

compared to similar sized areas that are part of a larger complex of such features. Live-bottom

habitats are dominated by suspension feeders, and sedimentation rates definitively influence

community structure. Only the coralline algae are depth limited (within depths less than 78 m)

and are limited by light transmission within their depth range. The discharge of the Mississippi

River influences the east-west and depth location of coralline algae in the northeastern Gulf.

The faunal composition of the live-bottom communities near the head of the DeSoto

Canyon are more complex than those farther to the west, but represent essentially the same

faunal assemblage (Shipp and Hopkins 1978). The live-bottom faunal assemblage east of the

DeSoto Canyon are more similar to those found on the southwest Florida shelf hard-bottoms.

The near-shore live-bottom communities in the northern Gulf are subjected to relatively high

seasonal temperature variations and resemble the warm, temperate Carolinian Province

communities (Schroeder et al. 1989). The offshore live-bottom communities in the northern Gulf

have clear tropical affinities, but are less diverse than similar communities in the southern Gulf

and in the Caribbean.

Given the importance of sedimentation or physical damage to the community structure

and the viability of organisms forming the live-bottom communities, any deepwater exploration

or production activities that would approximate these environmental forcing factors should be

avoided. Lease stipulations of MMS that regulate drilling activities near live-bottom features and

the EPA NPDES permitting process should afford protection to these areas. These mechanisms

generally work, although the effects of drilling operations were observed by Shinn et al. (1993)

near a pinnacle site. Given below are general locations and descriptions of live-bottom habitats

that are in areas where deepwater activities may occur.

6.7 Hard-Bottom Northwestern Gulf of Mexico

A variety of hard substrate south Texas shelf reefs (STXR in Figures 11 and 12) are dead

coral-coralline algal reefs between 60 and 90 m isobaths. The reefs vary in relief from 1 to 22 m.

They are not associated with salt diapirs, but rather were reefs growing on a carbonate shelf

during the Late Pleistocene and Early Holocene. A nepheloid layer prevents the continuous

encrustation of live-bottom organisms except from the surface of the banks. Cover organisms

consist of tubicolous polychaetes, algae, sponges, soft corals, and ascidians.
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The north Texas and Louisiana reefs and banks located on the continental shelf and slope

are associated with salt diapirs or structures caused by salt tectonics (Rezak et al. 1985, Rezak

1988). On the outer continental shelf of Louisiana (Shelf Break Banks, SBB in Figures 11 and

12) are a series of rock outcroppings on which live-bottom communities flourish. The geologic

formations resulted from the movement of Pleistocene rocks to the seabed surface from salt

dome forcing and related faulting. During low sea level stand-in Pleistocene glacial periods, the

rocks were eroded by wind and water so that the central salt dome collapsed, the less resistant

rock beds eroded away, and the hard rock pinnacles remained. The pinnacles vary in size and

depth. Consolidated silts, clays and sands cover the rock pinnacles to depths of less than 0.3 m.

MMS views the banks as areas of greater biological importance, diversity, and interest than the

surrounding sea floor areas (Dempre and Bull 1999). There are 28 named topographic features

that rise from the surrounding mud/clay bottom; all are protected by MMS lease stipulations.

The mid-shelf banks (MSB in Figures 11 and 12) rise from depths of 80 m or less and

have a relief of 4 to 50 m (Rezak et al. 1985). These are outcrops of relatively bare, bedded

Tertiary limestones, sandstones, claystones, and siltstones. Stetson, Claypile, Coffee Lump,

Sonnier, Fishnet, and 32 Fathom Banks are typical of this category. Sonnier Bank in Vermilion

Block 305 is in 70 m water depth, rises to within 23 m of the water surface, and is composed of

eight pinnacles. Cover on Sonier Bank is highly variable but averages 70% and is dominated by

sponges, fire coral, brown algae, and tube-forming polychaetes. The lack of live corals indicates

that the water temperature falls below 20° C during winter. There is a high density and diversity

of fish.

The shelf-edge carbonate banks and reefs are located on complex diapiric structures.

They are carbonate caps that have grown over outcrops of a variety of Tertiary and Cretaceous

bedrock and salt dome caprock. The relief varies from 35 to 150 m. The East and West Flower

Garden Banks are thriving coral reefs. The two Flower Garden banks harbor the most diverse

and thoroughly developed offshore hard-bottom epibenthic communities of the region.

East and West Flower Garden Banks, National Marine Sanctuaries

The East and West Flower Garden Banks are located 175 km SSE of Galveston, Texas

and are designated as a National Marine Sanctuary by NOAA (MS in Figures 11 and 12). Coral

cover averages 47.3% for both banks and has probably not changed significantly in over 25 years

(Gittings 1998, 1999). No significant temporal trends in accretionary growth are evident, and the

recent data suggest that corals have been growing at or above mean rates for the last decade or

two. Neither coral community characteristics nor growth data hint at a significant upward or

downward trend in environmental quality at the Flower Gardens. On the whole, the reef

communities have so far remained largely unaltered by human activities, despite numerous

isolated insults of anchoring, towing and fishing activities. Recovery from coral bleaching

incidents and mortality of long-spined sea urchins in 1983-84 indicate that the Flower Garden

Banks are resilient to short-term temporal change.
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6.8 Northeast Gulf of Mexico Hard-Bottom Habitats

Within five OCS areas between Cape San Blas, Florida and the Chandeleur Islands,

Louisiana, there is an approximately 5% incidence of hard-bottom on the areas mapped

(Continental Shelf Associates 1992). These are indicated in Figures 11 and 13 by the NEHB

symbols and the rectangle outlining the area of the Pinnacle Trend (PT).

To the east of DeSoto Canyon, which separates the Florida carbonate platform from the

mud and clay sediment regimes off Mississippi and Alabama, are live-bottom communities

associated with rock outcrops and areas of extensive, but very low-relief hard-bottom that are

periodically covered by sand. To the west of DeSoto Canyon, the outer edges of the continental

shelf and, on the upper slope, there are a number of trends of reef-like and pinnacle hard-bottom

areas. The organisms that live on these hard substrates represent new colonization rather than a

continuation of original reef communities.

A region of topographic relief, known as the “pinnacle trend,” is located at the outer edge

of the Mississippi-Alabama shelf between the Mississippi River and DeSoto Canyon

(Continental Shelf Associates 1992) (PT in Figures 11 and 13). The pinnacles are a series of

topographic irregularities with variable biotal cover that provide structural habitat for a variety of

pelagic fish. The pinnacle trend region contains a variety of features from low-relief rocky areas

to major pinnacles, as well as ridges, scarps, and relict patch reefs. Additional hard-bottom

features are located nearby on the continental shelf outside the actual pinnacle trend area.

Inshore, or slightly behind the shelf break at the head of the DeSoto Canyon, areas of

rock outcrop composed of a granulated sandstone are seen. These outcrops lie in bands or trends

that roughly parallel existing bathymetric contours. They were formed by consolidation of

riverine deposits transported to the shelf edge during a period of lower sea level (Benson et al.

1997).

Less well-defined hard-bottom outcrops occur on areas of the inner Mississippi/Alabama

continental shelf where sandstones and mudstones protrude through the surficial sediments

(Schroeder et al. 1989). These areas are rare and poorly developed on the Mississippi-Alabama

shelf due to the high rates of sedimentation. Hard-bottom habitat in these inner shelf areas

include reef-like outcrops with vertical relief of < 2 m, moderately sloping ridges of rock rubble

and shell hash, and surficial rock and shell rubble with little or no vertical relief (Thompson et al.

1999).

6.9 Pelagic, Oceanic Communities

As with the infauna, the population densities and biodiversity of deepwater fish and

macroinvertebrates is poorly understood, and the potential oil industry impact is unknown.

Elsewhere in the world, as in the U.S., as traditional near-shore fisheries collapse or become

more regulated, fishers switch to different target species, including the exploitation of lower

trophic-level fishes in the upper ocean and deep demersal populations. If such a switch occurs in

the Gulf of Mexico, there is a potential for conflicts of fisheries with deepwater activities

(Carney 1998).
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Multimillion-dollar fishing efforts currently in deep water include (1) upper-ocean

trolling for billfish, (2) mixed-depth long-lining for yellowfin tuna and shark, and (3) deepbottom trawling for royal red shrimp. There is a potential for equipment incompatibilities with

deepwater infrastructure, potentially environmentally hazardous exposures, and possibly a

human safety hazard. It was speculated that platforms that act as fish-attracting devices (FADs)

could impact management of highly migratory fish such as yellowfin and bluefin tunas and

broadbill swordfish that are thought to use the slope edge for spawning and feeding grounds, if in

fact FADs do attract these animals or they disrupt spawning and feeding.

Carney (in draft) states that biomass harvesting (i.e., fishing) is unlikely to be a serious

conflicting use of the deep-sea floor. To be commercially attractive species, they must be

abundant, widespread, often schooling, generally large-sized, and capable of relatively rapid

growth. Merrett and Haedrich (1997) made a strong case against large scale deep-sea fisheries

based on the patterns of biomass decline and trophic structure of the deep sea. Fish show the

same biomass decline, with high biomass species being rare and of considerable age. Fish in the

deep sea are the top predators and the populations are not adapted to being prey. Harvesting

deep-sea fish biomass would remove animals that have spent many years growing to

reproductive size, resulting in decades for populations to recover from even minimal fishing

pressure.

A. S. Bull (in Carney 1998) cites the potential for deepwater oil spills to affect larval and

juvenile stages of species that might aggregate in deepwater areas; examples include gag

grouper, yellowedge grouper, yellowfin and bluefin tunas, oceanic sharks, broadbill swordfish,

and marlin. While there exists no direct evidence that an oil spill has affected a stock as a result

of mortality of eggs and larvae (Spies 1987), there is concern that a large spill occurring during a

critical recruitment period could seriously diminish recruitment to the stock for the year (Boesch

et al. 1987). Still, effects on the stock, other than catastrophic effects, would be difficult to detect

and attribute to toxicity because of the great and largely unexplained year-to-year variability in

recruitment.

In near-shore environments, contaminants resulting from petroleum activities are more

likely to reach the seabed and be incorporated into bottom sediments or bioaccumulate in

platform-fouling communities. Juveniles of many economically important species live in inshore

environments and events there may affect those species, even though offshore adult populations

are not directly or immediately affected. Uncertainties similar to those discussed above for larval

mortality on adult stocks pertain to near-shore areas as well. Most studies of demersal or pelagic

organisms associated with offshore drilling and production platforms fail to demonstrate an

effect of chemical contaminants. The failure to detect evidence of exposure or sublethal impacts

on fishes and most larger invertebrates is a joint consequence of their mobility over the relevant

scales of environmental change and their negligible exposure to hydrocarbons and other

contaminants (Peterson et al. 1996).
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6.10 Protected Species

Certain species or environments are deemed worthy of protection by our society, not

primarily because they furnish economic benefits, but because of their aesthetic, cultural, or

social values. Included are species that may be rare or near extinction, as well as air-breathing,

higher vertebrates such as birds, mammals, and turtles.

Any animal exposed to spilled oil or chemicals might suffer deleterious effects as a result

of physical fouling. Such an impact, if confined to a few animals within a population, would

have few long-term consequences, but could have a significant effect on a discrete, concentrated

stock of animals. Birds and marine mammals that surface in an oil or contaminant spill could

inhale vapors, possibly enough to cause residual damage to the respiratory system and to serve as

a route of entry for systemic accumulation of contaminants. Oil may impair feeding in young

turtles or baleen whales. The probability that such effects could affect birds, mammals, and

turtles was rated medium (in a scale of low to high) by (Boesch et al. 1987). Similar probabilities

would likely extend to chemicals associated with deepwater activity, given similar levels of

toxicity.

The rich and abundant marine fauna of the Gulf of Mexico includes several species that

are “quite sensitive and rare” (Darnell and Schmidly 1988). Whales may never have been

common in the Gulf of Mexico (except see below on sperm whales), but massive overexploitation in the early twentieth century all but extirpated many from the world’s oceans, and

Gulf populations may very well have been affected. Marine turtles were once fairly common

along the coastlines of the Gulf of Mexico but are now rare, although conservation efforts are

resulting in increased numbers.

Endangered mammals include the blue whale, fin whale, sei whale, right whale, great

sperm whale, and West Indian manatee. All five sea turtles are threatened or endangered:

Kemp’s ridley (E), loggerhead (T), leatherback (E), hawksbill (E), and green (T). Of the sea

turtles, the leatherback is the more oceanic member of the group in the Gulf as opposed to the

others that prefer shallower waters for feeding and migratory routes. A. S. Bull (in Carney 1998)

states that the slope edge is a critical nursery ground for juvenile marine turtles, with the

potential for interaction or threats for this endangered group of animals during their early life

stages with deepwater activities.

More recent work on surveys of marine mammals and turtles indicate that there are viable

populations in the Gulf of Mexico and that deepwater operations have the potential to affect

them. The GulfCet programs sponsored by MMS, the National Marine Fisheries Service, and the

U.S. Fish & Wildlife Service documented the seasonal and geographic distribution of cetaceans

and sea turtles in the deeper areas of the Gulf (100 m to 2,000 m, north of 26° N) and

characterized their habitat in areas potentially affected by oil and gas activities (Evans and Davis

1998). Six years of data collection in the northern and western Gulf were completed in 1997.

GulfCet continues with the "Northeast Gulf of Mexico (NEGOM): Chemical Oceanography and

Hydrography" program.
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Based on visual surveys, the overall minimum number of cetaceans in the GulfCet I study

area was 19,128. A total of 487 acoustic contacts were recorded and of that number, 124 contacts

were of 12 identified species. Sperm whales were the most commonly recorded species,

accounting for 56% identified contacts. At least 17 cetacean species were identified during eight

GulfCet I aerial surveys (each of these species also was sighted during ship surveys).

The GulfCet II field program censused the region's 18 common species of dolphins and

whales in continental margin areas of present oil and gas development and in areas further

offshore to depths of 2,000 m, where oil and gas exploration will likely intensify in the near

future. The sperm whale, an endangered species, was a special focus of the GulfCet II field

program (Biggs and Wormuth 1998).

A combination of hydrographic measurements, determinations of chlorophyll biomass

and zooplankton abundance, acoustic determination of Deep Scattering Layers (masses of fish,

squid, and shrimp), and sea-surface altimetry data from satellites identified cyclones as the

preferred habitat of the sperm whales. The cyclones, sea-surface lows about 100 to 150 km wide

that spin counterclockwise, are areas of upwelling of cool, nutrient-rich water with higher than

average stocks of phytoplankton and zooplankton. The cyclones spin off the anticyclones (eddies

from the Loop Current) that spin clockwise, and are areas of downwelling and not highly

productive. The cyclones and anticyclones usually occur in pairs, with the sperm whales

preferring the periphery of the cyclones.

During an October 1996 NEGOM cruise, there were 41 sperm whales and 10 whale

groups (acoustic survey) off the Mississippi Delta and inside or at the perimeter of a cyclone.

The whales were uncommon in the deepwater canyon to the east of the cyclone and even rarer in

the anticyclone. The presence of young calves supports the hypothesis that the sperms whales

reproduce successfully in the Gulf. The pattern was repeated in May, June and August of 1997,

with sperm whales being most abundant in the cyclone or in the water flowing counterclockwise

around it (Figure 14).

Because the continental margin of the northeast Gulf of Mexico is characterized by the

temporal persistence of cyclonic eddies, the region is of considerable biological interest with

regard to marine mammals (Ortega-Ortiz 1999). During the five NEGOM cruises, a total of 334

hours of visual survey were completed for 5,418 kilometers of transect on the ship's track across

the northeastern Gulf. During this effort, 289 marine mammal sightings were registered and the

following species were identified: Atlantic spotted dolphin, Bryde's whale, bottlenose dolphin,

dwarf sperm whale, false killer whale, humpback whale, killer whale, melon headed whale,

pantropical spotted dolphin, pygmy sperm whale, Risso's dolphin, sperm whale, spinner dolphin,

and striped dolphin.
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Figure 14. Cyclones are the most common place to find sperm whales, as indicated by the

stars placed on this diagram of the Gulf's eddies, made from an August 21, 1997,

regional altimetry map. (Data courtesy of Robert Leben, Colorado Center for

Astrodynamics Research, in Biggs and Wormuth 1998).

6.11 Continental Shelf

An overview of continental shelf benthic communities of the Gulf of Mexico was

provided by Rabalais et al. (1999a). Typical soft-bottom benthic communities are composed

primarily of polychaetes, with fewer bivalves, gastropods, pericaridean crustaceans, sipunculans,

echinoderms, and miscellaneous other fauna. Sedimentary characteristics range from terrigenous

sediments delivered by major rivers, variable mixtures of sand/silt/clay, outcroppings of

Beaumont clay or its equivalents, quartz sand sheets, and carbonate sediments. There is

variability in the benthic community structure in relation to depth and depth-related factors and

sedimentary characteristics. Localized differences in fauna may result from proximity to natural

hard-bottom habitats, artificial habitats, and oil and gas production facilities. Broad-scale

differences in the benthic fauna result from the extensive and severe zone of bottom-water

hypoxia that forms along the inner to middle Louisiana continental shelf and extends periodically

onto the upper Texas coast (Rabalais et al. 1995, 1999b). A dominant feature of the TexasLouisiana shelf is the nepheloid layer created by the resuspension of muddy sediments and

subsequent flow across the bottom to the outer shelf and shelf edge where episodic deposition

may occur. The nepheloid layer is reduced in summer months.
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Most studies of the discharges onto the continental shelf from oil and gas activities

outline localized impacts, with a range of negative impacts to enhanced populations, and a range

of temporal effects, some of which may be short-lived while others are persistent.

Drilling fluid chemicals dilute rapidly in the water column and, in all but very deep or

high-energy environments, much of the drilling fluid and cuttings solids settle rapidly to the

bottom near the rig site (Neff 1987). Concentrations of barium, as a tracer for drilling effluents,

may be 10 to 20 times above background in surficial sediments near the discharge and decrease

to background within 2,000 m down current. Produced water dilutes rapidly following discharge

but significant elevations of hydrocarbons or metals can be observed up to 250 m from the

discharge (Rabalais et al. 1992). Most of the ingredients of drilling fluid chemicals have a low

toxicity to marine organisms (Neff 1987), but the fluids and cuttings that settle on the seabed can

significantly alter the benthic sedimentary regime. That, along with the sloughing of organic

material from the fouling community on submerged parts of the platform structure and the

increased bottom microrelief, may attract motile animals to the vicinity and alter the character of

the infaunal community. Contaminants from produced waters, on the other hand, may reduce the

abundance and diversity of infaunal organisms (Rabalais et al. 1992). Peterson et al. (1996)

concluded that long lasting effects of drilling activity exist in the sedimentary environment

around gas production platforms. The dual effects of toxicity and organic enrichment probably

drive readily detectable responses in benthic meiofauna and macroinfauna to 100-200 m.

The GOOMEX studies (Kennicutt et al. 1996) were intended to test and evaluate a range

of biological, biochemical and chemical methodologies to detect and assess chronic sublethal

biological impacts in the vicinity of long-duration activities associated with oil and gas E&P.

Location of the study was in a gas field in the western Gulf on the continental shelf and as

removed as possible from confounding effects of Mississippi River discharge. Sediments close to

platforms (< 500 m) were enhanced in coarse-grain materials primarily derived from discharged

muds and cuttings. Hydrocarbon and trace metal (Ag, Ba, Cd, Hg, Pb, and Zn) contaminants

were associated with these coarse-grain sediments. Contaminants were asymmetrically

distributed around each platform in response to the prevailing currents. The positive relationship

between sand content and contaminant levels is contrary to the view of contaminants being

associated with finer-grain sediments. Contaminant concentrations at most locations were below

levels thought to induce biological responses. At a few locations close to one platform, trace

metal (i.e., Cd, Hg) concentrations exceeded levels thought to induce biological effects. In

deeper water (> 80 m), sediment trace metal contaminant patterns were stable over time frames

of years. A few metals (Pb, Cd) exhibited evidence of continued accumulation in sediments over

the history of the platform at the deeper water sites (> 80 m) immediately after cessation of

drilling cf 5-10 years after the last discharge (i.e., there was persistence of contaminants in the

lower energy environments).

The meiofauna and macrofauna effects (Montagna and Harper 1996) were localized,

extending to 100 m from the platforms (less distance than in the North Sea). The pattern of

community change were increases in deposit-feeding polychaetes and nematodes that indicated

organic enrichment, while density declines of harpacticoid copepods and amphipods indicated

toxicity. Harpacticoid abundance, community diversity, genetic diversity, reproductive success,
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and survivability declined nearer the platforms with an increasing contaminant gradient at all

study sites. Changes in meiofaunal responses were most noticeable within 50 m of platforms. It

was stated that in the GOOMEX study, it was apparent that the chemical contaminants originated

from the drilling mud discharge and not from production.

Sediment chemical analyses and porewater toxicity tests with sea urchin fertilization and

embryological development assays from the GOOMEX study (Carr et al. 1996) indicated

toxicity near four of the five platforms, the majority collected within 150 m of a platform and

those with the highest concentrations of contaminants. Samples from the deepest site (> 80 m

near the Flower Gardens), which contained the highest contaminant concentrations, were the

most toxic samples of the sites. Repeatability of toxicity between seasons demonstrated the

persistence of the toxicity.

Peterson et al. (1996) drew general conclusions from the GOOMEX studies and provided

a good review of environmental fate and effects studies using benthos. For the GOOMEX

platforms, the consequences were the result of environmental forcing, organic enrichment, and

metals toxicity. The hydrocarbons occurred in concentrations that seemed too low to be

important contributors to the observed toxicological effects. PAHs were generally less than 100

ng/g which was an order of magnitude lower than what Spies (1987) suggested was needed to

induce biological response. They concluded that sediment grain pattern was unlikely to be the

primary driver of the observed biological responses. The increase in annelids closer to the

platforms occurred despite the steep gradient in sand content: total annelids would be expected

to be more abundant in finer sediments, not coarser. In contrast with annelids and oligochaetes,

amphipod abundances were depressed around all platforms, with effects confined to 50 to 100 m.

This was also consistent with literature on modest pollution and is suggestive of a toxic response.

Sea stars were reduced near the platform, but that pattern did not hold for ophiuroids.

Harpacticoid copepod abundance was depressed near the platforms, while total nematodes were

enhanced. Patterns were absent at the shallowest site (29 m) where the relatively high-energy

physical environment has led to more extensive dispersion of materials discharged. The other

sites were in 80 m and 125 m.

The disparity in results with North Sea studies (effects to 2 to 6 km) is that oil-based

drilling fluids are used in the North Sea vs. water-based in the Gulf of Mexico. They concluded

that patterns of response to sedimentary contamination were detectable at higher taxonomic

levels and that these responses were driven by intrinsic physiological and ecological

characteristics of higher taxa. Crustaceans (especially amphipods and harpacticoid copepods)

and echinoderms are sensitive to toxics whereas polychaetes, oligochaetes, and nematodes

(especially non-selective deposit feeders) are enhanced by organic enrichment (either from

hydrocarbons or biologically-produced materials falling from the platform structure). They

concluded that metals drove the toxicity effects, and that the dual effects of toxicity and organic

enrichment resulted in readily detectable responses in benthic meiofauna and macrofauna to 100-

200 m. In contrast to the emphasis on trace metals, the effects of volatile hydrocarbons from a

produced water discharge were apparent for at least one high energy, inner continental shelf

station off Louisiana (Rabalais et al. 1991, 1992).
102

6.12 Coastal Habitats

Transport of product from deep water or transport of chemicals used in drilling and

production may be the aspect of deepwater development with the greatest environmental risks,

but these will vary widely in means and geographic extent for different offshore areas (Boesch et

al. 1987). Virtually all of the oil and gas produced in the Gulf of Mexico flows through pipelines

because the extensive development and existence of onshore facilities makes this feasible. The

effects of oil spills which might occur as a result of pipeline ruptures and transshipment

accidents are dependent on the environmental characteristics of the habitats affected.

Long-term effects result from acute damage due to an oil spill on biogenically structured

habitats such as coral reefs, mangrove swamps, salt marshes, oyster reefs and seagrass beds.

Here the concern is that even though oil may not persist following an oil spill, the time required

for recovery of damaged populations of organisms that provide the physical structure of the

habitat will be many years. In some cases, where the structure-forming species actually stabilizes

the habitat, it is conceivable that permanent modification of that habitat could result from an

acute incident. The discharge of produced waters on salt marsh habitats will kill the vegetation,

but discharges into receiving waters do not affect the peripheral marsh habitat (Boesch and

Rabalais 1989). The effects of chemicals used in deepwater oil production on biogenically

structured habitats is not known.

6.13 Summary

Biological communities at risk from chemical spills associated with deepwater E&P are

most likely those which are deeper than the continental shelf break. Biologically sensitive

communities in coastal and continental shelf depths may be affected from spills during transit of

materials either via ship or pipeline.

Certain features of the deep sea and the fauna that inhabit it make them potentially more

susceptible to certain types of chemical spills. Increased turbidity from a spilled chemical such as

a drilling mud could impact animals adapted to low light (including, possibly, those with

bioluminescent capabilities) by increased turbidity from deep plumes of low transmission water

and indirectly through biological light interactions. Spills of chemicals with labile carbon may

alter the local balance of oxygen consumption and result in hypoxia or anoxia, especially in the

oxygen minimum zones. Microhabitat diversity is a key to deep-sea diversity, and any chemical

spill that alters deep habitats will likely have an impact. Chemical spills that disrupt the

accessibility of fluxed detrital material for the dominant deposit feeding-mode organisms will

affect feeding and subsequently the health of the organism(s). Chemicals that affect mortality,

population levels, biological interactions, recruitment, growth rates, through either acute or

chronic, sublethal toxicity or habitat alteration or both are likely to affect soft-bottom benthos in

the deep sea similarly to continental shelf organisms. However, basic information for most deepsea organisms (e.g., feeding type, reproduction, life span, growth rates, predators, and

community ecology) is fundamentally nonexistent.
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Chemosynthetic seep communities are considered prevalent between 300 and 1,000 m

water depth on the northern Gulf slope. Commonality, however, is not suitable for relaxing

criteria for acceptable impact without knowledge of the ability of undamaged or damaged fauna

to ultimately repopulate any impacted areas. Some organisms that inhabit the cold seep

communities may be extremely old, and damaged communities would be slow or unlikely to

recover. Hard-bottom communities with highly diverse biogenically-structured communities are

afforded protection from drilling operations, and any chemical spills that approximate these

types of effects would be expected to produce similar harm to live-bottom communities.
105

7.0 SPILL SCENARIOS AND MODELING PARAMETERS

7.1 Introduction

Spill modeling was performed to estimate concentrations resulting from worst-case

chemical spill scenarios that were developed based on the inventory data presented earlier in

Section 3.0. The results of the modeling were used to evaluate the potential impacts of spills of

selected chemicals on the marine environment, in both shallow and deep water (Section 8.0). The

modeling was performed using Applied Science Associates’ (ASA) chemical spill model

CHEMMAP (Section 7.3).

A total of 17 spill scenarios was developed, modeled, and reviewed. Sixteen spill

scenarios were modeled using shallow water data and one spill scenario was modeled in deep

water. The shallow water current data were obtained from measurements made by Texas A&M

University as part of the LATEX program (a major study of Gulf of Mexico environmental

variables). The deepwater current data were from a current meter mooring in the central-western

Gulf of Mexico in 3,000 m deep water. Most spill scenarios are for surface spills. Assuming that

surface current and wind patterns are similar in deeper water, the 16 scenarios at the shelf site are

applicable to deepwater spills at the water surface. However, while loop current eddies are

common in deep water, they are not prevalent on the shelf. Thus, the shallow water results would

not be applicable in deep water when there are eddies present at the spill site. A subsurface spill

of ethylene glycol on the shelf is hypothesized from a broken umbilical in 113 m of water, a

depth that was selected as representative of this technology.

7.2 Selection of Chemicals for Profiling

While a detailed assessment for each of the thousands of offshore chemicals or products

used was outside the scope of this project, a subset of representative chemicals used in the deep

water and shallow water were selected based on the following criteria:

• Chemicals used offshore in high volumes

• Potential impact on the environment, including:

− Toxicity

− Oxygen depletion

− Habitat modification

• Factors determining fate in the environment, including:

− Physical state - solid or liquid

− Organic or inorganic

− Chemical reactions in seawater

− Solubility

− Biological degradation

− Location of final destination (sediment, water column, or atmosphere)
106

The chemicals selected are representative of the type/range of chemicals used in offshore

Gulf of Mexico. By using this approach, an analyst in need of data on any chemical used in the

GOM can derive some information on the chemical’s behavior in the marine environment by

using one of the representative chemical or product profiles.

Twenty-one chemicals were selected for detailed characterization. A standard chemical

profile was developed to present the data collected on each chemical and their impact on the

marine environment. These profiles are presented in Section 8.0.

Table 20

List of Twenty-one Chemicals Selected for Detailed Chemical Profiles

Selected Chemical/Product (Spill

Scenario Number)

Chemical Class Chemical Profile

Number

Acids

Hydrochloric acid (1)

Hydrofluoric acid (no spill model)

CSW

CSW

1

2

Antifoam/Defoaming Agents

Silicones (no spill model) DF,PT 3

Biocides

Glutaraldehyde (11 and 12)

Quaternary Compounds (14a)

Tetrakishhydroxymethyl

phosphonium sulfate (THPS) (13)

PT,DF

PT

PT

4

5

6

Reactive Salt – Solid

Zinc Bromide (4)

Calcium Bromide (no spill model)

Ammonium Chloride (no spill

model)

CSW

CSW

CSW

7

8

9

Chemical Stabilizer

Sodium hydroxide (2)

Potassium chloride (3)

DF

DF,CSW

10

11

Corrosion Inhibitor

Amides/Imidazolines (15t)

Amines & Amine salts (15t)

PT

PT

12

13

Fluid Loss Agents

Lignite (8) DF 14

Gas Hydrate Prevention

Methanol (9)

Ethylene glycol (10)

Triethylene glycol (no spill

model)

PT

PT

PT

15

16

17

Oxygen Scavenger

Sodium bisulfite (5) PT 18
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Table 20

List of Twenty-one Chemicals Selected for Detailed Chemical Profiles (continued)

Selected Chemical/Product (Spill

Scenario Number)

Chemical Class Chemical Profile

Number

Insoluble Solids

Barite (6, 17) DF 19

Thinners & Dispersants

Lignosulphonate (7) DF,C 20

Solvents/Carriers

Heavy aromatic naphtha (15,16) PT 21

Notes: Chemical Class Definitions: DF (Drilling Fluids), C (Cementing Chemicals), CSW

(Completion, Stimulation, and Workover Chemicals), PT (Production-treating Chemicals)

The chemicals selected for spill evaluation and the selection criteria are discussed in

Section 2.0. These chemicals include:

• Hydrochloric Acid • Ethylene Glycol

• Sodium Hydroxide • Glutaraldehyde

• Potassium Chloride • Tetrakishydroxymethyl phosphonium

• Zinc Bromide sulfate (THPS)

• Sodium Bisulfite • Quaternary Ammonium Compounds

• Barite (component of product a)

• Lignosulfonate • Amides/Imidazolines (component of

• Lignite Product B)

• Methanol • Aromatic Naphtha (component of Product

C)

See Section 7.8 for spill model assumptions.

These chemicals include both single- and multi-component products. For the multicomponent products, separate fates and concentrations were determined for each component.

In Section 8.0, the results of the spill modeling are combined with chemical/physical

properties, toxicity data, and typical storage and handling information to evaluate potential

impacts of the selected chemicals and/or selected constituents. Storage and handling data

provided by operators and chemical suppliers yielded typical and worst-case spill volumes.

Worst-case spill volumes were used in the modeling analysis described below.

Mean-expected and worst-case consequences of spills were estimated using Applied

Science Associates’ (ASA) CHEMMAP in stochastic mode. The stochastic model was used to

determine the range of distances and directions contamination from spills would be likely to

travel from a particular site, given the historical current and wind speed direction data for the
108

area. A large number of model simulations were run for a given spill site, randomly varying the

spill date and time, and thus the wind and current conditions, for each run. The time histories of

multiple simulation runs were then used to generate probabilities that water surface, water

column, sediment, and shoreline areas would be exposed above thresholds of concern, as well as

areas/volumes exposed. Each simulation was evaluated to determine the maximum exposure

concentration for each location around the spill site at any time after the spill. The worst-case

(i.e., caused by worst-case environmental conditions), and the mean (expected) of all the

simulations, and the peak exposure concentrations were calculated for each location around the

spill site. These concentrations may be compared to concentrations that have been shown to have

toxic effects to determine the potential for impacts. Calculations were made to estimate volume

and total habitat area exposed above potential thresholds of concern.

Contour maps of model outputs were prepared to show the distances chemical

concentrations would extend from the spill site. The maps may be considered relative to the spill

location’s origin and representative of other potential spill sites of similar environmental (wind

and current) conditions. In this study, two spill sites were assumed: one on the continental shelf

and one in deep water (> 1,000 m). The shelf spill results are generally applicable for the

Louisiana-Texas shelf region. The deep-water results are applicable to the western Gulf of

Mexico offshore area near the site of the current data used. The mean-expected and worst-case

exposure concentrations for each location around the potential spill site may be compared to

bioassay data indicating concentrations with toxic effects and to maps of resources of concern.

7.3 CHEMMAP Model Description

The chemical spill model developed by ASA, CHEMMAP, predicts the trajectory and

fate of a spectrum of chemical products, including floating, sinking, soluble and insoluble

chemicals, and product mixtures. CHEMMAP incorporates a number of processes including:

• Simulation of the initial release and plume dynamics of a product lighter or denser than water

• Slick spreading and transport of floating materials

• Transport of dissolved and particulate materials in three dimensions (through the entire water

column)

• Evaporation and volatilization

• Dissolution and adsorption

• Sedimentation and re-suspension

• Degradation of the chemical of concern to presumably inert product(s) (biological and

chemical degradation, modeled as a constant rate)

The model uses physical-chemical properties to predict the fate of a chemical spill. These

include density, vapor pressure, water solubility, environmental degradation rates,

adsorbed/dissolved partitioning coefficient (KOC), viscosity, and surface tension.
109

CHEMMAP was developed from the fates and biological effects’ submodels in the Natural

Resource Damage Assessment Model for Coastal and Marine Environments (NRDAM/CME). The

NRDAM/CME (Version 2.4, April 1996) was published as part of the United States

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Type A

Natural Resource Damage Assessment (NRDA) Final Rule (U.S. Federal Register, May 7, 1996,

Vol. 61, No. 89, p. 20559-20614). The model is also incorporated in the U.S. Oil Pollution Act of

1990 NRDA regulations. The technical documentation for this model is in French et al. (1996a, b,

1999).

The fates model estimates the distribution of spilled substance (as mass and concentrations)

on the water surface, on shorelines, in the water column, and in the sediments. Algorithms based

on state-of-the-art published research include spreading, evaporation, transport, dispersion,

emulsification, entrainment, dissolution, volatilization, partitioning, sedimentation, and

degradation. The model is three-dimensional, using a latitude-longitude grid for environmental

data.

CHEMMAP includes the physical fates and biological effects models in the

NRDAM/CME, with several changes and additions. The biological model was not used in this

study. Most of the additions to the fates model were made to increase model resolution; allow

modification and site-specificity of input data; allow incorporation of temporally varying, threedimensional current data; and facilitate analysis of results. The stochastic modeling approach was

also added so that CHEMMAP could be run in either deterministic (single scenario) or stochastic

mode.

7.3.1 CHEMMAP Chemical Database

The CHEMMAP chemical database contains the physical-chemical properties required

by the model to simulate the transport and fate of the spilled material. The database includes a

variety of text and numeric descriptors to identify and characterize the spilled chemical or

mixture. The model is capable of simulating spills of pure chemicals, chemicals in aqueous or

hydrophobic solutions, or chemicals in emulsions (i.e., mixtures of particulate material

suspended in an aqueous base). Thus, the database also includes characteristics that define these

mixtures and solutions.

The model uses physical-chemical properties with which the user may characterize the

spilled chemical or mixture. A discussion of these properties is given in French et al. (1996a).

Table 21 lists the physical-chemical properties included in the data base. Initial data base

values were taken from French et al. (1996a). These values were updated with new information

developed as part of this study.

Several properties vary with temperature. Thus, the data base values are for a

standardized temperature of 25o C. The model corrects these parameters to the ambient

temperature for the spill incident. The algorithms for changing viscosity and vapor pressure to

ambient temperature are taken from French et al. (1996a). For pure chemical processes (i.e.,

solubility), the increase per 10 degrees Celsius is assumed to be two. For biological processes

(degradation rates), the increase in rate per increase of 10 degrees Celsius is assumed to be three.
110

Table 21

Chemical Database: Physical – Chemical Properties

Chemical type code (integer) (inorganic or organic category, from French et al., 1996a)

Molecular weight (g/mole)

Particle size as diameter, assumed spherical (m) (if solid; or suspended in bulk liquid emulsion; or droplet size for

liquid, gas, or hydrophobic solution subsurface releases; or initial plume thickness at release for dissolved

chemicals)

Density (g/cm3) at standard temperature (25o C)

Freshwater Solubility (mg/kg = mg/l = ppm) at standard temperature (25o C)

 Seawater Solubility (mg/kg = mg/l = ppm) at standard temperature (25o C)

Vapor pressure (atm.) at standard temperature (25o C)

Dissolution rate (per day) at standard temperature (25o C)

Viscosity (cp = centipoise) at standard temperature (25o C)

Surface tension at standard temperature (25o C) (dyne/cm)

Minimum thickness of a floating chemical slick, at standard temperature (25o C) (m)

Degradation rate (per day) when exposed to the atmosphere (on water surface and shorelines) at standard

temperature (25o C)

Degradation rate (per day) in the water column, at standard temperature (25o C)

Degradation rate (per day) in sediments, at standard temperature (25o C)

Octanol water partition coefficient as log10 (Kow) (dimensionless)

Sorption partition coefficient for organic carbon, as log10 (KOC); KOC = adsorbed/dissolved partition coefficient

(g/kg adsorbed per g/l dissolved)

Melting point temperature (deg. C)

Boiling point temperature (deg. C)

Density of the bulk liquid at standard temperature (25o C)

Concentration of particles in the bulk liquid (i.e., for an emulsion where liquid is aqueous) (by weight, mg/kg)

Concentration dissolved in hydrophobic solvent (13) or in suspended particles (14,15) (by weight, mg/kg)

Concentration dissolved in water (11) or aqueous phase (14,15) (by weight, mg/kg)

7.3.2 Chemical Fates Model

The chemical fates model estimates the distribution of chemical (as mass and

concentrations) on the water surface, on shorelines, in the water column, and in the sediments.

The model is three-dimensional. It separately tracks surface slicks, entrained droplets or particles

of pure chemical, chemical adsorbed to suspended particulates, and dissolved chemical.

Processes that are simulated include spreading, transport, dispersion, evaporation-volatilization,

entrainment, dissolution, partitioning, sedimentation, and degradation.

The model initializes the spilled mass at the location and depth of the release in a state

dependant upon the physical-chemical properties of the material. The state code and solubility

are the primary determining factors for the initialization algorithm.
111

If the chemical is already dissolved in water, the chemical mass is initialized in the water

column in the dissolved state. Chemical in the water column is treated as partially adsorbed to

suspended sediment particles and partially dissolved. Partitioning between these states is

assumed to be in constant proportions (based on linear equilibrium theory), using KOC from the

chemical database (Table 21).

If the chemical is an insoluble liquid or a gas, the following initialization is used. If the

density is less than or equal to that of water, and the release is at or above the water surface, the

model initializes the material in surface slicks. Otherwise, the spilled mass is initialized in the

water column at the release depth in a plume volume defined for the dissolved chemicals. Once

dissolution has occurred, chemical in the water column is treated as partially adsorbed to

suspended sediment particles and partially dissolved. Partitioning between these states is

assumed to be in constant proportions (based on linear equilibrium theory, using KOC from the

chemical database).

Soluble solids, which are spilled in a particulate form, dissolve and then are partitioned in

the water column between dissolved and particulate-using equilibrium partitioning. Insoluble

solids remain in particulate form and are transported.

If the chemical is particulate in an aqueous emulsion or dissolved in a hydrophobic

solvent, the spilled mass is initialized as particles (droplets) in the water column at the release

depth. The particle size is based on product specification data. The initial plume volume is that of

the bulk liquid volume spilled. Where the chemical of interest is both adsorbed to particles and

dissolved in the water phase of the bulk liquid, dissolved mass is also initialized in the initial

plume volume. The mass of chemical spilled is corrected from the bulk spill volume using the

appropriate density and concentration data.

Chemical mass is transported in three-dimensional space and time by surface wind drift,

other currents, vertical movement (in accordance with buoyancy), and random dispersion.

The model simulates adsorption onto suspended sediment, resulting in sedimentation of material.

Stokes Law is used to compute the vertical velocity of pure chemical particles or suspended

sediment with adsorbed chemical. If rise or settling velocity overcomes turbulent mixing, the

particles will float or settle to the bottom. Settled particles may later resuspend. However, if the

chemical is specified in the database as sticky in water, resuspension will not occur.

Wind-wave driven current (surface drift) is calculated within the fates model based on

hourly wind speed and direction data. Surface wind drift of oil has been observed in the field to

be 1-6% of wind speed in a direction 0-30 degrees to the right (in the Northern Hemisphere) of

the down-wind direction (Youssef and Spaulding 1993). It is assumed that other floating

insoluble chemicals behave similarly.

The horizontal diffusion (randomized mixing) coefficient normally ranges from 1-10

m2

/sec in coastal and marine waters. The vertical diffusion (randomized mixing) coefficient is

typically 0.0001-0.001 m2

/sec. These are reasonable values based on (Okubo 1971) and

modeling experience. The vertical diffusion coefficient of 0.0001 m2/sec keeps a shallow water

column well mixed.
112

For surface slicks, the model estimates surface spreading, slick transport, entrainment

into the water column, and evaporation to determine trajectory and fate at the surface. Spreading

is simulated using the algorithm of Fay (1971). Entrainment is modeled as for oil, using data in

Delvigne and Sweeney (1988). Surface slicks interact with shorelines, depositing and releasing

material according to whether the material is sticky and to shoreline type. The algorithms used

are those developed for oil spills, as described in French et al. (1999).

Volatilization from the water column is calculated from the chemical’s vapor pressure

using Henry’s Law, and is a strong function of temperature. Degradation is estimated assuming a

constant rate of "decay" specific to the environment where the mass exists (i.e., atmosphere,

water column or sediment).

The fates model computes, in space and time, the following:

• Water surface:

− area covered by surface slicks

− radius and thickness of surface slicks

• Water column:

− total concentration

− pure chemical droplet or particulate concentration

− dissolved concentration

− concentration adsorbed to suspended sediments

− concentration in hydrophobic droplets (state codes 13-15)

• Sediments:

− total concentration

− pure chemical droplet or particulate mass per unit area

− dissolved concentration

− concentration adsorbed to sediments

• Shorelines:

− area and length contaminated

− mass per unit area

These model output data are mapped by the user interface in an animated display. For the

stochastic model, mean-expected and worst-case exposure concentrations are plotted.

7.4 Environmental Data

The following data are used by the model. Sources of the data for this study are

described.
113

7.4.1 Geographical Data

Data for water depth, shoreline type, sediment type, and habitat type throughout the

domain were taken from several geographical databases. The model uses gridded maps to

determine location of the shoreline, habitat (or shore) type, and water depth. The geographical

data around the spill site are gridded using the shoreline location to define land and water cells.

Arc View (ESRI) Geographical Information System (GIS) software was used to create the maps.

Stochastic output is saved on this grid, allowing quantification of habitat area exposed. A depth

data grid of the same dimensions and area coverage as the habitat grid contains bathymetry from

the NOS soundings database (National Ocean Service, Hydrographic Survey Data, Version 3.2).

In anticipation that hypothetical spills might contaminate shoreline habitats, shoreline

habitat type was mapped using Arc Info (ESRI) GIS data sets available from the states of Texas

and Louisiana. Environmental Sensitivity Index (ESI) and coastline data for Texas were obtained

from the Texas General Land Office (TGLO) web site. The TGLO shoreline features were

extracted from National Wetland Inventory data and other hydrography data sets and assigned

ESI values by the University of Texas Bureau of Economic Geology. Oyster reefs in the

Galveston Bay system (except for part of Trinity Bay) were mapped by Dr. Eric Powell,

formerly of Texas A&M University, and downloaded from the TGLO web site

(http://www.glo.state.tx.us/oilspill/osdata.html).

Coastline and wetland data for Louisiana were obtained from the Louisiana Department

of Wildlife and Fisheries, Fur and Refuge Division, and the U.S. Geological Survey, Biological

Resources Division's National Wetlands Research Center. The data were published on June 1,

1997 as the 1997 Louisiana Coastal Marsh Vegetative Type Map. The data consist of polygons

coded as one of six vegetation types. Those shoreline habitats not mapped as wetland were

assumed sandy beach (by far the dominant shoreline type in areas that are not wetlands).

Figures 15 and 16 show the habitat types as gridded for input to the model. Figures 17 to

19 show the bathymetry in gridded format (as seen by the model). Figures 17 and 18 are for the

area of the shelf spill, while Figures 19 and 20 are for the area near the deepwater spill site. In

the deep water, depth data was missing for some points, which were avoided in selecting the

representative spill site.

7.4.2 Wind Data

The model uses, as input, an hourly wind time series of speed and direction. These data

are important for insoluble floating chemicals, but have little influence on dissolved

contaminants. Surface wind drift (current) for the upper 5 m of the water column is calculated

from the wind data.
114

Figure 15. Gridded map of habitats in eastern portion of the study area.

Figure 16. Gridded map of habitats in western portion of the study area.
115

Figure 17. Gridded map of bathymetry used in the modeling for the shelf spill site.

Figure 18. Gridded map of bathymetry in the area of the shelf spill site.

Shelf Spill Site Location

Lat. 27° 56’ 52.9” N

Long. 93° 15’ 1.6” W

Shelf Spill Site Location

Lat. 27° 56’ 52.9” N

Long. 93° 15’ 1.6” W
116

Figure 19. Gridded map of bathymetry used in the modeling for the shelf spill site.

Figure 20. Gridded map of bathymetry in the area of the deepwater spill site.

Shelf Spill Site Location

Lat. 27° 56’ 52.9” N

Long. 93° 15’ 1.6” W

Shelf Spill Site Location

Lat. 26° 48’ 17.8” N

Long. 93° 32’ 6.1” W
117

Data are available from NOAA buoys and land-based weather stations. Historical timeseries data from all NOAA buoys and stations are quality controlled by the National Data Buoy

Center. The data were formatted for model use at ASA.

For the deepwater spill site, winds were for the period 24 May 1990 through 23

December 1998, with a gap between 29 April and 28 October 1997. For the shelf spills, the wind

time series was chosen to be for the same time as the available current data (15 April 1992 to 4

December 1994; see below). Comparison of winds from this time to the decade long record from

the same source showed that the period from 1992-1994 was representative.

Data were predominantly from NOAA buoy 42019, located 60 nautical miles off

Freeport at 27.92o

 N, 95.35 o W. Gaps in the buoy 42019 data were filled with data from nearby

buoys. The first choice substitute was buoy 42035 (6/27/94-7/28/94) and secondarily C-Man

Station SRST2 (4/29/92-6/3/92, 10/16/92-11/20/92). Buoy 42035 is located at 29.25o N, 94.41o

W (22 nautical miles east of Galveston). C-Man Station SRST2 is located at 29.67o N, 94.05o W

(Sabine).

7.4.3 Currents

The chemical transport model is designed so that it may accept current (hydrodynamic)

data from a variety of sources. For the best spatial and temporal coverage, these data are in the

form of gridded time series data, or gridded tidal constituent data, which allow the transport

model to automatically generate current vectors for the time period of the spill. A hydrodynamic

model may be used to compute tidal, density driven, or wind-driven motion of water. The model

may be either two- or three-dimensional, with currents varying spatially in both horizontal and

vertical directions. Alternatively, constant background currents and cyclic tidal current vectors

may be manually entered into a database. The model may also use data from current meter

studies. In this study, current meter data was used.

7.4.3.1 Shelf Currents

Current meter data from the LATEX program of Texas A&M University is used for spills

in the continental shelf region (DiMarco et al. 1997). The objective in this study was to provide

the model with current velocities, which vary vertically but are spatially representative in the

horizontal. In this way, the model results may be applied to other spill sites with a similar

vertical profile of current velocities. The results are most applicable to shelf sites with similar

water depth (i.e., along the bathymetric contour running through the current meter site).

As the present analysis is of chemical spills associated with deepwater oil and gas

activities, current data for the shelf break region at about 200 m was used. The LATEX study

included a series of current meters along the 200 m isobath from near the Mississippi Delta to

south Texas reaching about 27o N (Figure 19). The meters were deployed from April 1992 to

December 1994. Mooring 10 (27° 56’ 9.6” N, 92° 44’ 42” W), which is located on the 200 m

isobath and is in an active oil and gas production area, was selected as representative for the shelf

break region. Examination of the data from this and adjacent moorings along the 200 m isobath

(DiMarco et al. 1997) showed that the currents indicate similar net transport from mooring 48 to

7. The net transport at mooring 12 and 13 is more frequently to the northeast because loop

current eddies intersected the slope and shelf.
118

At mooring 10, as for all of the moorings, there are periods in which data records are

missing. In order to fill in the missing periods, data from four nearby moorings (8, 9, 11 and 48)

were inserted into the current data file. These moorings are all on the 200 m isobath. Whenever

mooring 10 lacked observations, records of the closest mooring available with the same depth

levels (surface, mid-depth, and bottom) were substituted. The resultant current record, other than

these substitutions, is identical to original records provided by National Oceanographic Data

Center, CD-ROM Data Sets.

The current data from the three depths measured were linearly interpolated to provide a

continuous current profile in the vertical. Current was assumed zero at the sea floor, with (linear)

interpolation to the next current meter above the bottom.

7.4.3.2 Deepwater Currents

For the deepwater spill site, current meter data from mooring GG, deployed in 1987-1988

by SAIC, were used (Hamilton 1990, 1992). These data are presently maintained by Texas A&M

University, the source of the data files used in this analysis.

This mooring is in the central-western Gulf of Mexico (25o 39’ 12” N, 92o 1’ 54” W),

where the depth is 3,000 m. Loop current eddies are often in this area, slowing down and dying

in the western basin. Thus, current data from other offshore regions to the east, which may be

more extensive, may not be applicable to the central-western Gulf of Mexico. The one-year of

data at mooring GG is limited, but is the best available at this time as representative of the

region. Hamilton (1990) describes the data record for mooring GG and the fact that several

warm- and cold-core eddies passed through the region during that year of data collection.

Meters were deployed at 5 depths: 100 m, 300 m, 725 m, 1,650 m, and 2,500 m. Data

were collected from all five depths at 30-min intervals from 9 November 1987 to 30 October

1988. (Only the data from 300 m, 1,650 m and 2,500 m are described in Hamilton 1990).

In model runs, these data were assumed to apply to all years, for the corresponding

month, day and hour. For the missing period noon 30 October to noon 9 November, available

data from 1,650 m were used for other depths after multiplying by the average ratio in November

of current speed of the depth of interest to speed at 1,650 m. The ratios used were:

• 100 m : 1,650 m – 13.83

• 200 m : 1,650 m – 3.99

• 725 m : 1,650 m – 3.71

• 2,500 m : 1,650 m – 1.368

The current data from the five depths measured were linearly interpolated to provide a

continuous current profile in the vertical. Current was assumed zero at the sea floor, with (linear)

interpolation to the next current meter above the bottom.
119

7.5 Scenario Specification

The data that are required to run the CHEMMAP fates model and the assumed values

used in the model scenarios are listed in Table 22. Table 23 describes the habitat grid dimensions

used in the modeling and to tabulate results. The results are saved as average concentrations over

the area of each grid cell. Thus, the size of the habitat grid cell determines the resolution of the

model results. The habitat grid was defined such that (1) the spill site was near the center, (2) the

shoreline was included (shelf spill), and (3) the maximum possible resolution was used, given the

memory limits of the computer used to make the model runs. In addition, the chemical must be

included in the chemical database with appropriate physical-chemical properties (to be discussed

below).

Table 22

Scenario Specification Data Required by the Model

Name Description Units Value(s) Source of

Information

Spill Site for

shelf spills

Location of the spill

site

- 27o56’52. 9” N

93o

15’1. 6” W

Representative shelf

location

Spill Site for

deepwater

spills

Location of the spill

site

- 26o

48’17. 8”N

93o

32’6. 1”W

Representative deepwater location in

western G. of Mexico

Depth of

release

Depth below the water

surface of the release

M 1 (for at water

surface) or > 0 (for

sub-surface)

(See Table 25)

Start time

and date

Date and time the

release began

Date, hour,

minute

- -

Duration of

release

Time over which the

release occurred

Hours 0 (instantaneous) -

Total spill

volume or

mass

Total volume (or

weight) released (for

bulk mixture)

Bbl, gal.,

MT, kg, L,

m3

(See Table 25) (See Table 25)

Substance

released:

name, #

Chemical of concern

released (name and

identification #s)

- Name

(CAS # )

(See Table 25)

Salinity Surface water salinity ppt 32ppt (French et al. 1996a)

Water

Temperature

Surface water

temperature

Deg. C 18-29oC (French et al. 1996a)

Wind data Hourly wind speed

and direction

Kts or

m/sec, deg.

Hourly wind speed

and direction for

4/15/92-12/4/94

(shelf spills) or

5/24/90-12/23/98

(deepwater spills)

NOAA buoy 42019,

with data gaps filled

with data from

neighboring NOAA

buoy 42035 and

CMAN station SRST2

Current data

for shelf

spills

Current speed and

direction as function

of time and space

cm/sec by

x,y,z,t

LATEX current

meter data for

4/15/92-12/4/94

Current mooring 10
120

Table 22

Scenario Specification Data Required by the Model (continued)

Name Description Units Value(s) Source of

Information

Current data

for

deepwater

spills

Current speed and

direction as function

of time and space

cm/sec by

x,y,z,t

Current meter data

for 11/9/87-

10/30/88

Current mooring GG

(Hamilton 1990)

Coastline

data

Data set of shoreline

locations

Latitude,

longitude

- (GIS data)

Shoreline

type

Shoreline

classification

- (See Note 1) ESI and other

mapping; GIS data

Habitat type Habitat mapping

(shoreline and

subtidal)

- (See Note 2) Shore type and habitat

GIS data

Wind drift

speed

Speed water surface

moves downwind

relative to wind

% of wind

speed

1-6% (3.5%

average)

(Youssef and

Spaulding 1993)

Wind drift

angle

Angle to right of

downwind (in northern

hemisphere)

Deg. To

right of

downwind

0-40 (Youssef and

Spaulding 1993)

Horizontal

dispersion

coefficient

Randomized turbulent

dispersion parameter

in x & y

m2/sec 3.0 (typical value) (French et al. 1999)

Vertical

dispersion

coefficient

Randomized turbulent

dispersion parameter

in z

m2

/sec 0.0001 (typical

value)

(French et al. 1999)

Suspended

sediment

Average concentration mg/l 10 mg/l (French et al. 1996a)

Time step Calculation interval Hours 1 -

Number of

particles

# Lagrangian elements

simulating spill

# 1,000 -

Notes:

1. Shore types include: rocky, gravel, sand beach mud flat, wetland (salt marsh, mangrove), mollusk reef, coral

reef, algal bed, sea grass bed, artificial, ice edge. Environmental Sensitivity Index (ESI) data are mapped to

these categories.

2. Habitat types include the shore types listed above, plus subtidal habitats: rock bottom, gravel bottom, sand

bottom, silt-mud bottom, algal bed, sea grass bed, coral reef, mollusk reef, and subtidal areas within wetlands.
121

Table 23

Model Habitat Grid Dimensions

Attribute Shelf Spill Grid Deepwater Spill Grid

Grid W edge 95o34’15.3”W 95°33’14.7” W

Grid S edge 26°27’54.5” N 25°19’9.4” N

Cell size (o longitude) 0.00542 0.00542

Cell size (o latitude) 0.00542 0.00542

Cell size (m) west-east 533.1 533.1

Cell size (m) west-east 601.4 601.4

# cells: west-east 737 742

# cells: south-north 658 537

Water cell area (m2) 320,573 320,573

Shore cell length (m) 566 566

Shore cell width – rocky, artificial (m) 1 1

Shore cell width – beach (m) 5 5

Shore cell width – wetlands (m) 50 50

7.6 Stochastic Modeling of Trajectory and Fates

In order to determine risks to resources, multiple scenarios and conditions need to be

evaluated to develop an expectation of risk of a pollutant reaching each site of concern. There

may be specific sites of concern, or the goal may be to identify what sites are at risk.

Mean-expected and worst-case consequences of spills were estimated using CHEMMAP

applied in stochastic mode. The stochastic model was used to determine the range of distances

and directions contamination from spills are likely to travel from a particular site, given the

historical current and wind speed direction data for the area. A large number of model

simulations were run for a given spill site, randomly varying the spill date and time, and thus the

wind and current conditions, for each run. The time histories of multiple simulation runs may be

used to generate probabilities that water surface, water column, sediment and shoreline areas

would be exposed above thresholds of concern, as well as areas/volumes exposed. Each

simulation was evaluated to determine the maximum (= peak) exposure concentration (over time

after the spill) for each location around the spill site at any time after the spill. The worst case

(i.e., caused by worst case environmental conditions), and the average (i.e., mean of all

environmental conditions) over all simulations, of the peak exposure concentrations were

calculated for each location (grid cell) affected. The grid cells are 320,573 m2

 in area (for all

locations) and 113 m deep at the spill site. The peak concentrations are for one hour or more of

exposure, which is the time step used in the model runs. Of course, concentrations at the spill site

at time zero are at the maximum, i.e., at the concentration in the spill volume. The peak

concentrations calculated by the model are those at one hour after the spill, averaged over one

grid cell of volume (36 million m3) around the spill site. Concentrations continue to decrease

from these levels over time.
122

Contamination in the water column after a spill changes rapidly in space and time.

Toxicity to aquatic organisms increases with time of exposure, such that organisms may be

unaffected by brief exposures to the same concentration that is lethal at long times of exposure.

For a brief exposure, a dosage measure of concentration times exposure time is a more

appropriate index of toxicity than the peak concentration. For example, if a 96-hour LC50 is 1.0

mg/L, the dosage is 96 mg L-1 hrs. Assuming a linear time-response model, the LC50 for a 1

hour exposure would be about 96 mg/L, and for a 10-hour exposure would be about 9.6 mg/L.

Total dosages calculated by the model are:

• Water surface: Slick thickness multiplied by time present (mass per area - time) for each

dosage level (g-m-2-hrs)

• Concentrations in water: Water volume and habitat area exposed at each dosage level

(concentration-time, i.e., (mg-m-3-hrs or ppb-hrs)

• Mass loading to sediments and shorelines: Mass per unit area multiplied by time present

(mass per area - time) for each dosage level (g-m-2-hrs)

Contour maps of model outputs were prepared to show the distances chemical

concentrations would extend from the spill site. The maps may be considered relative to the spill

site and representative of other potential spill sites of similar environmental (wind and current)

conditions. The shelf spill results are generally applicable for the Louisiana-Texas shelf region,

especially along the 200 m isobath. The deepwater spill results are applicable to the slope and

offshore region of the western Gulf of Mexico to the extent that the one year of data at mooring

GG are representative. (See discussion of current data above.) The mean-expected and worstcase exposure concentrations for each location around the potential spill site may be compared to

maps of resources of concern.

The three-dimensional stochastic model in CHEMMAP quantifies, in space and over

time, for each individual model run, the following components:

• Mass or thickness (mass or volume per unit area) on water surface

• Mass or thickness (mass or volume per unit area) on shorelines

• Subsurface (water) particulate (solid or liquid droplets) concentration

• Subsurface (water) dissolved concentration

• Subsurface (water) adsorbed (to suspended sediment) concentration

• Sediment concentration

The range of possible scenarios includes various wind and current conditions, volume

spilled and other parameters. To sample this universe of possibilities, long-term wind and current

records are developed (as described above). The list of input assumptions that may be

randomized is below.

• Release date (and so wind and current patterns):

− All months of the year (quantifies risks for spills at any time of year, used in this study)

− Selected month(s) or season (quantifies risks for spills at that time of year)
123

• Spill volume:

− randomized up to a maximum possible (quantifies typical, mean risk)

− constant at maximum possible (quantifies risks for worst-case volume, used in this study)

A stochastic model case is a quantification of probabilities (statistics) based on multiple

model runs, for selected:

• Chemical or chemical mixture (with associated physical and chemical characteristics)

• Spill volume

• Location

• Thresholds of concern for:

− Surface (water or shoreline) mass or thickness

− Subsurface particulate concentration

− Dissolved chemical concentration

− Sediment concentration

For each of the components of the spill, an effects endpoint is selected which provides a

threshold above which probabilities are to be reported. These thresholds may be for mortality,

sub-lethal or chronic effects, tainting, human health impacts, or for impacts on recreational or

other human uses.

The results of multiple model runs for a stochastic case are evaluated to develop the

following statistics for each of the components listed above:

• Probability of exposure greater than a threshold (thickness or concentration)

• Time to first exceedance of the threshold

• Maximum thickness, volume or concentration at any time after the spill, at a given location

(peak exposure at each location)

− Worst-case maximum amount for all possible releases (i.e., maximum peak exposure for

all the model runs). This is calculated in two steps: (1) For each individual run (for each

spill date run), the maximum amount over all time after the spill is saved for each

location in the model grid. (2) The runs are evaluated to determine the highest amount

possible at each location. Note that these worst-case maximum amounts are not additive

over all locations. These represent maximum possible amounts that could ever reach each

site, considered individually. The spill date and time for the worst-case run is also saved.

− Mean-expected maximum amount for all possible releases (i.e., mean-peak exposure of

all model runs). This is calculated in two steps: (1) For each individual run (for each spill

date run), the maximum amount over all time after the spill is saved for each location in

the model grid. (2) The runs are evaluated to determine the mean-expected peak exposure

(mean amount for all runs) at each location. Note that these mean-expected maximum

amounts are not additive over all locations. These represent the mean of many different

runs, affecting different sites to maximum extent at different times after the spill.
124

The CHEMMAP graphical user interface produces maps of these statistics. For each

stochastic model case, maps are produced of probability of exceeding the chosen threshold, time

of first exceedance, and of peak exposure. The exposure maps are average expected and worst

possible exposure by location. These exposure maps contain contours of thickness or

concentration. Mapped geographical data of sensitive resources may be compared and/or

overlaid with model results. This will show where resources would be most at risk, and giving

indications of where protection would be most beneficial.

Table 24 lists the stochastic model inputs used in this study. Because specific toxic

endpoints are uncertain for the chemicals evaluated in this study, very low thresholds were input

to the model. This allowed the entire spill mass to be plotted, even when concentrations would

not be expected to be toxic. Thus, the probability feature was not used in evaluating the results.

The results are expressed as exposure concentrations.

Table 24

Stochastic Model Inputs

Number of stochastic runs 100

Spill dates Randomize months 1-12

Spill volume Constant at maximum spill size

Threshold: Surface slick Mass > 0.00001 g/m2

Threshold: Shoreline Mass > 0.00001 g/m2

Threshold: Dissolved Average over the water cell > 0.01 mg/m3

Threshold: Particulate Average over the water cell > 0.01 mg/m3

Threshold: Adsorbed to suspended

sediment

Average over the water cell > 0.01 mg/m3

Threshold: Total in Sediment Average over the water cell > 0.00001 g/m2 (which is 0.1

mg/m3 averaged over the top 10cm)

7.7 Chemical Spill Scenarios

Spill modeling was done for 16 shallow water scenarios, plus one deepwater scenario. All

but three of the 16 spill model scenarios were performed on single component chemicals or

mixtures of a single active ingredient in a solvent. The properties of such materials are usually

readily available and their concentrations easily determined. Production-treating chemicals,

however, presented a different issue. Many production-treating chemicals are complex mixtures

containing proprietary materials, in which both the composition and the concentration of

ingredients are not available. As a result of trade secret privileges, complete characterization of

these materials is challenging. Production-treating chemicals such as corrosion inhibitors,

emulsion breakers, and some defoamers are members of these types of materials. To overcome

this obstacle chemical suppliers agreed to provide detailed, representative compositions, for

several products so that fate and effects modeling could be completed on chemicals from each

class. For protection against potential competitors, the selected chemical products are not

identified by product name or supplier. Moreover, the actual composition is not reported in this

document, but was supplied to the MMS under separate cover. In Scenarios 14 and 16 described

below, these chemical formulations are referred to as Product A, Product B, and Product C.
125

For each spill scenario, assumptions were made on how the chemical could be spilled and

how it would enter the environment. Using information from the chemical inventory (Section

2.0) and analysis (Section 3.0), materials and volumes selected are the worst cases taken from the

range of actual use/storage volumes found in this study. The worst-case spill volumes for

Scenarios 11-16 are quite small. Preliminary test runs showed that the model need not be run for

two weeks, as for the larger spills of Scenarios 1-10. For very small spill volumes, fewer

stochastic simulations were made as well, as these scenarios produced very low concentrations.

In modeling these scenarios, it was assumed that releases were immediate. That is, if the product

is in a container that is lost or packaged in sacks when lost, the container is assumed to

immediately rupture and the material is immediately released to the environment. If the

discharge is a bottom discharge, it is assumed that the container reaches the bottom and then

immediately ruptures, releasing the material. In the Scenario 10 case, it is assumed that the

umbilical breaks at the high point of the line (i.e., a location that is closer to shore and where the

water is shallow). If an umbilical were to break at the low point, once the line is secure, the

surrounding seawater, having a greater density, will act as a plug, trapping the ethylene glycol

inside the line.

Scenarios 1-16 were at the shelf spill site. The same representative spill site (27o

56°52.9”

N, 93o

19’ 1.6” W) was used for all shelf spill scenarios (for consistency). This site was chosen

because the water depth was 114 m (370 ft.), the depth of the high umbilical release of ethylene

glycol (Scenario 10). It is also near the LATEX current meters used to generate the current data

input to the model.

Scenarios 1-13 and 17 are spills of single chemicals (pure or in aqueous solution). Thus, a

single model run was made for each. DESCO and lignosulfonate (Scenario 7) are modeled as a

class, as these products have similar properties. Multiple runs were made for Scenarios 14-16.

Table 25 lists the chemical scenarios run in the stochastic model of CHEMMAP. Section

7.8 describes the 16 (plus the deepwater barite spill) selected spill scenarios in more detail. In

Table 25, the scenarios that are spills of chemical mixtures are broken down into individual

chemical model runs, as the model evaluates results for one chemical at a time.

Spill Scenario 1 – Hydrochloric and Hydrofluoric Acids

Acids are used in stimulation and workover operations. The acid formulation selected is a

common mix used offshore. These acids are water-soluble materials and react rapidly with

seawater and enter into the buffered equilibrium system in seawater. The hydrogen ion

component becomes indistinguishable from the hydrogen ion occurring naturally in seawater.

Both chloride and fluoride ions are constituents of seawater and chloride ion is a major

constituent. Excess fluoride will precipitate as calcium fluoride or other insoluble material, some

of which may settle to the sediments.
126

Spill Scenario 2 – Sodium Hydroxide

This scenario models strong inorganic bases. These are water-soluble materials and react

rapidly with seawater and enter into the buffered equilibrium system in seawater. Sodium

hydroxide was selected to represent these materials because it is commonly used in drilling fluids

in large amounts. In the sea, the hydroxide ion component becomes indistinguishable from the

hydroxide ion occurring naturally in seawater. Sodium ion is a major constituent of seawater. If

spilled, these materials or their reaction products will remain in the water column.

Spill Scenario 3 – Potassium Chloride

This scenario models non-reactive, water-soluble salts. Water-soluble salts are used

extensively in drilling, completion, stimulation and work-over operations, as well as in

cementing operations. Although potassium chloride is no longer used often it was selected

because it has a potentially toxic impact at some concentrations. These materials will remain in

the water column. Both potassium and chloride ions appear naturally in seawater and eventually

potassium chloride will dilute to become indistinguishable from background seawater

concentrations.

Spill Scenario 4 – Zinc Bromide

The fourth scenario models water-soluble reactive salts. Zinc bromide will immediately

dissociate in seawater to the two component ions. Zinc and bromide ions react with other

constituents of seawater, forming insoluble precipitant. Most of the positive ion constituent (Zn)

will eventually end up in the sediment.

A commonly used zinc bromide/calcium bromide mixture was selected to represent this

type. Such mixtures are used as completion or packer fluids. It was chosen because there was a

relatively large volume spill of zinc bromide in the Gulf of Mexico in 1999.

Spill Scenario 5 – Sodium Bisulfite

This scenario involves a variation of water-soluble reactive salt for which the reaction in

the environment is an oxidation/reduction reaction and not a precipitation, as for previous types

discussed. This type of material is soluble in seawater, but reacts on contact with the oxygen in

seawater. Sodium bisulfite is used in production operations as an oxygen scavenger to remove

unwanted oxygen from waterflood water and produced water. On contacting seawater containing

oxygen, the bisulfite ion will react to form sulfate ion, a common constituent of seawater. Spills

of this material could cause localized oxygen depletion. This material and its reaction products

will remain in the water column.

Spill Scenario 6 – Barite

This scenario models water insoluble solids. Barite was selected to represent this

chemical type because large amounts of it are used in drilling fluids, and relatively large volumes

of it are occasionally stored offshore. The concern is that a large accidental discharge might

cause a habitat modification in the sea floor sediments. Barite is a natural constituent of

sediments at low concentration, but has the potential for short-term impacts related to habitat

modification.
127

Spill Scenario 7 – Lignosulfonate

This scenario models water-soluble organic solids or their metal salts. These materials

would be spilled as solids that will dissolve in seawater. They are known to be toxic. Two

common types of such materials are lignosulfonates and DESCO (a proprietary product made

from modified lignin). Both materials are commonly used in drilling fluids and are frequently

stored offshore during drilling operations. They are surface active, and will partition between the

water (dissolved) and sediments (suspended and on the bottom) as adsorbed material.

Lignosulfonate was used in the spill modeling because there is more data available.

Spill Scenario 8 – Lignite

This scenario models water-insoluble organic solids. The material selected for modeling,

lignite, is not soluble in fresh water, but is highly dispersible and will go into the water column

as suspended solids. Lignite is slightly water soluble in seawater at higher pHs. Because seawater

(i.e., in the Gulf of Mexico) has a pH of about 8, it will slowly dissolve as its concentration

decreases. Ultimately, it will be degraded by bacterial action and will place an oxygen demand

on the environment. Lignite was selected because large quantities are used in drilling fluids and

it is commonly stored offshore on drilling rigs.

Spill Scenario 9 – Methanol

This scenario models pure organic liquids soluble in water. This type of chemical is used

in very large volumes and is a chemical type where there is a significant difference in shallow

water and deepwater usage. Methanol was selected for this profile. Being highly water soluble, it

will remain in the water column and ultimately will biologically degrade in the environment. The

spill scenario for this chemical type is a spill at the surface. Potential impacts include both

oxygen demand and toxicity.

Spill Scenario 10 – Ethylene Glycol

This scenario also models pure organic liquids soluble in water. Ethylene glycol was

selected for profiling because it is sometimes recovered and reused. Both it and methanol are

delivered to deepwater subsea wells by umbilicals. The spill scenario for this type is a spill from

a broken umbilical. The spill from the umbilical is assumed to be at the shallow water end of the

umbilical since that would result in the highest immediate release. These materials, being highly

water-soluble will remain in the water column and will ultimately biologically degrade in the

environment. Potential impacts include both oxygen demand and toxicity.

Spill Scenarios 11 and 12 – Glutaraldehyde

This scenario models water-miscible organic mixtures consisting of a water-soluble

active ingredient and a solvent system containing an alcohol and possibly a glycol. This type of

chemical includes biocides, reverse breakers, and scale inhibitors. These materials will remain in

the water column and most of them will degrade biologically. The most common biocide used in

produced water, glutaraldehyde was selected for modeling. Scenario 11 represents surface spills

and Scenario 12 represents bottom discharges.
128

Spill Scenario 13 – Tetrakis (hydroxymethyl) Phosphonium Sulfate (THPS)

This scenario models water-miscible organic mixtures consisting of a water-soluble

active ingredient that degrades chemically in the environment. The solvent is water. The active

ingredient is an organic phosphonium compound. Tetrakis (hydroxymethyl) phosphonium sulfate

(THPS) was selected to represent this class because it also represents recent chemical

developments that attempt to improve environmental compatibility. Although it may not offer

significant advances in environmental protection over older conventional chemicals, it illustrates

one direction of change in the technology of oilfield chemical treating. THPS degrades in the

presence of oxygen to tetrakis (hydroxymethyl phosphonium oxide (THPO), which has a much

lower toxicity. The rate of degradation is dependent on several factors. The half life of the

conversion of THPS to THPO is reported to be six hours and the total degradation THPS to final

products has been estimated by the supplier to be 25 days (Albright and Wilson 1997). The

ultimate degradation products are sulfate ion, phosphate ion and carbon dioxide, all of which are

natural constituents of seawater.

Spill Scenario 14 – Quaternary Ammonium Compounds

This scenario models organic materials that may be either water-soluble or oil soluble

and are applied in water solutions. Quaternary ammonium compounds represent this type of

chemical. These chemicals are used in corrosion inhibitors and biocides. The chemical

formulation used in Scenario 14 is referred to as Product A, is a water-soluble corrosion

inhibitor, containing the following components:

• Water 22%

• Methanol 42%

• Acetic acid 3%

• Ethoxylated nonylphenol 3%

• Amides/Imidazolines 15%

• Quaternary ammonium chloride 15%

When spilled, the solution will dilute into the water column and the active ingredient will

disperse as dissolved material or as a fine dispersion of liquid droplets. Model runs were made for

the methanol, acetic acid, nonylphenol (representing the ethoxylated nonylphenol mixture), and

amides/imidazolines plus quaternary ammonium chloride. Data on the properties of

amide/imidazoline and quaternary ammonium chloride are limited. However, these active

ingredients are as (particulate) emulsions in the aqueous solvent, and have similar properties, and

so would have a similar fate. The total spill volume for these two compounds is 165 gal. (30%).

Their fate is modeled as if the particulate is insoluble and does not degrade.

It should be noted that, after the model runs were made, the corrosion inhibitor mixture

was corrected slightly to include 4.2% isopropanol (isopropyl alcohol) and 11.2% quaternary

ammonium chloride instead of 15% quaternary ammonium chloride. Thus, the model runs were

made with slightly more chemical mass spilled than the corrected composition would indicate.

This means that the model results are slightly conservative (slightly high) in concentrations

predicted.
129

Spill Scenarios 15 and 16

Scenarios 15 and 16 model water-insoluble organic solvents that are used in many

production-treating chemical formulations. These solvents contain aromatic constituents that

may be the component of highest concern in a production-treating chemical formulation. These

solvents are constituents of production-treating chemicals B and C.

Scenarios 15 and 16 involve hydrophobic active ingredients (amides/imidazolines, amines,

amine salts, and alkylbenzene sulfonic acids) in a naphtha solvent (653 aromatic solvent). The

active ingredients, at least initially, will move in the environment along with and similarly to the

naphtha solvent. However, naphtha is volatile (and also degrades), while the active ingredients are

not volatile. Thus, the active ingredients will be left behind in the water as the naphtha volatilizes

or degrades. Scenarios were run for the two products, Product B as Scenario 15 and Product C as

Scenario 16.

1. The scenarios (15t and 16t) are modeled as spills of naphtha mixture. Naphtha is a mixture of

low molecular weight aromatics and other hydrocarbons (Whiticar et al. 1992) with physical

properties similar to naphthalene (Mackay et al. 1992). Thus, the properties of naphthalene are

used in the model simulations for naphtha plus hydrophobic active ingredient(s). To calculate

the concentration of one component of the mixture, the results may be multiplied by the

fractional composition. Naphtha solvents will initially spread on surface water or be dispersed

as fine droplets. They will evaporate from the water surface to the atmosphere, adsorb to

suspended solids, or disperse into the water column as fine droplets.

2. For scenarios (15a and 16a), the active ingredient disperses as fine liquid droplets free of the

solvent, modeled as an insoluble particulate that does not volatilize or degrade. This is the

worst-case scenario for the active ingredient being left after the naphtha volatilizes or degrades.

Spill Scenario 15 – Product B: Aromatic Naphtha Mixture

Product B, an oil soluble corrosion inhibitor, has the following components:

• Heavy aromatic naphtha

• Isopropanol

• Amides/Imidazolines

• Polyglycols

• Fatty acid dimers

• Ethoxylated amine

Scenario 15 is 400 gal. of the following mixture:

• 84% naphtha

• 3.5% isopropyl alcohol

• 12.5% amides/imidazolines and other active ingredients (fatty acid dimers, polyglycol,

ethoxylated amines, amine salts)
130

In addition to the naphtha solvent and the active ingredients, isopropyl alcohol is an

ingredient. An additional run of isopropyl alcohol is made (Scenario 15I).

Spill Scenario 15a – Amides/Imidazolines, Amines and Amine Salts

This scenario models oil-soluble organic materials that are applied in aromatic solvents.

Amides/Imidazolines, amines and amine salts were selected as representative of this type. They

are components of Product B. These materials are used in corrosion inhibitors. They were

selected because they represent potentially toxic materials. These chemicals are stored offshore

in relatively small amounts, 50 gal. or less, therefore spills of these chemicals are likely to be

small with respect to volume.

When spilled, the solution will spread on the water surface and evaporate or disperse into

the water column as fine droplets. The active ingredient will disperse as a fine dispersion of

liquid droplets once free of the solvent.

Spill Scenario 16 – Product C: Aromatic Naphtha Mixture

Scenario 16 is 700 gal. of Product C, an oil-soluble emulsion breaker, having the

following components:

• Heavy aromatic naphtha 40%

• Alkyl benzenesulfonic acids 60%

Spill Scenario 16a – Alkyl Benzenesulfonic Acids

This scenario models oil-soluble organic materials that are applied in aromatic solvents.

They are components of Product C. They were selected because they represent potentially toxic

materials. These chemicals are stored offshore in relatively small amounts, 300 gal. or less;

therefore spills of these chemicals are likely to be small with respect to volume.

When spilled, the solution will spread on the water surface and evaporate or disperse into

the water column as fine droplets. The active ingredient will disperse as a fine dispersion of

liquid droplets once free of the solvent.

Scenario 17

For scenario 17, a spill of barite in deep water (> 1,000 m), both single scenario and

stochastic modeling were performed. The spill site selected was in the middle of the habitat-depth

grid and also in water > 1,000 m. Barite is an insoluble particulate, about 10 microns in diameter

and with a very high density. The high density of barite causes it to sink, but the small particle

size causes it to sink slowly. More neutrally buoyant particulates and dissolved substances would

not sink, but would disperse at about the same rate as the barite plume. Because of the small

particulate size, the particulate sinks only very slowly and disperses widely. Scenario 17 may be

considered a typical dispersion pattern for any non-reactive chemical.
131

7.8 Spill Modeling Assumptions

Table 26 lists the chemical properties assumed in the modeling. Much of the data are

from French et al. (1996a). Solids were assumed released as powder of 5-25 micron diameter, as

indicated in Table 26. Liquids were assumed released as 5 mm droplets, a typical particle size for

oil releases under low turbulence (Delvigne and Sweeney 1988).

Those chemicals indicated as dissolved in Table 26 were released in that state. Thus,

dissolution rates and solubility were not used for these chemicals. For undissolved chemicals, the

dissolution rate was set based on the solubility, as data for dissolution rates are not available. For

chemicals with solubility > 10%, dissolution was assumed very rapid, such that 99% would

dissolve in just over an hour (rate = 100/day). For other chemicals, dissolution rate was assumed

proportionately slower.

Vapor pressure of methanol, ethylene glycol, and glutaraldehyde are from Section 8.0.

For other chemicals, vapor pressures are from French et al. (1996a). The chemical type code is

used to select parameters for the temperature correction to vapor pressure (see French et al.

1996a). Thus, its value is immaterial if the vapor pressure is zero.

THPS degradation to sulfate ion, phosphate ion and carbon dioxide was assumed slow,

with a half-life of 25 days, based on information from the supplier (collected at pH = 8, with no

oxygen supplied to the system). However, the half-life for degradation to the reportedly less

toxic product THPO is about 6 hours (Amides/Imidazolines, quaternary ammonium chloride, and

alkylbenzene sulfonic acids were assumed to degrade extremely slowly (rate = 0.001/day). Other

degradation rates are from French et al. (1996a). (The degradation rates for acids and bases are

for neutralization, rather than true degradation.) Values of sorption/partition coefficient (log KOC)

are from French et al. (1996a) or assumed as for similar chemical

Table 25

Spill Model Assumptions

Spill

Model

#

Scenario

Name

Chemical Name State Release

Depth

(m)

Amount

Spilled

Model

Duration

(days)

1 MAcid1 Hydrochloric acid

solution GOM

14% aqueous

solution

1 3,361 gal. 14

2 MNaOH1 Sodium hydroxide Powder 1 43,545 kg 14

3 MKCl1 Potassium chloride Powder 1 4,717 kg 14

4 MZnBR1 Zinc bromide solution

GOM

54% aqueous

solution

1 45,000

gal.

14

5 MNaSO31 Sodium bisulfite

solution GOM

40% aqueous

solution

1 500 gal. 14

6 MBarite1 Barite Powder 1 7,257.55

MT

14

7 MDesco1 DESCO/

Lignosulfonate

Powder 1 95,797 kg 14
132

Table 25

Spill Model Assumptions (continued)

Spill

Model

#

Scenario

Name

Chemical Name State Release

Depth

(m)

Amount

Spilled

Model

Duration

(days)

8 MLignite Lignite Powder 113 52,786 kg 14

9 Mmeth1 Methanol Pure liquid 1 96,000

gal.

14

10 Methgly1 Ethylene glycol Pure liquid 113 106,447

gal.

14

11 MglutS1 Glutaraldehyde

solution GOM

25% aqueous

solution

1 500 gal. 4

12 MglutB1 Glutaraldehyde

solution GOM

25% aqueous

solution

113 500 gal. 4

13 MTHPS1 THPS solution GOM 20% aqueous

solution

1 500 gal. 4

14 m M14 m-1 Methanol Liquid 1 231 gal. 1 (20 runs)

14aa M14aa-1 Acetic acid Liquid 1 16.5 gal. 1 (20 runs)

14np M14np-1 Nonylphenol Liquid 1 16.5 gal. 7

14a M14a-1 Amides/Imidazolines

and quaternary

ammonium chloride

(miscible organic

mixture)

Insoluble

particulate

1 165 gal. 4

15a M15a-1 Amides/Imidazolines Insoluble

particulate

1 50 gal. 4 (not run,

see 14a)

15n M15n-1 653 Aromatic solvent

(naphtha) – run as

naphthalene

Liquid 1 336 gal. 4 (not run,

see 15t)

15t M15t-1 Amides/Imidazolines

in 653 Aromatic

solvent (naphtha) –

run total mixture as

naphthalene

Liquid 1 386 gal. 4

15I M15i-1 Isopropyl alcohol Liquid 1 14 gal. 1 (20 runs)

16a M16a-1 Alkylbenzene sulfonic

acids

Insoluble

particulate

106 280 gal. 4

16n M16n-1 653 Aromatic solvent

(naphtha) – run as

naphthalene

Liquid 106 420 gal. 4 (not run,

see 16t)

16t M16t-1 Alkylbenzene sulfonic

acids in 653 Aromatic

solvent (naphtha) –

run total mixture as

naphthalene

Liquid 106 700 gal. 4

17 BarDeep1 Barite Powder 1 7,257.55

MT

14
133

Table 26

Chemical Properties Assumed For Model Runs

Model

Scenario

#

Chemical

Modeled

Particle

Size

Density

(g/cm3)

Seawater

Solubility

(mg/l)

Dissolution

Rate (day-1)

Vapor

Pressure

(atm)

Chemical

Type Code

Sorption/partition

coefficient

(Log KOC)

1 Hydrochloric

acid

(dissolved) 1.16 100% 100 0 101 0.31 

2 Sodium

hydroxide

10 um 2.13 42% 100 0 102 0.49 

3 Potassium

chloride

25 um 2.04 34.4% 100 0 103 0.31 

4 Zinc bromide (dissolved) 4.22 5 ppm - 0 133 0.31 5 Sodium

sulfite

(dissolved) 1.51 33% - 0 103 0.59 

6, 17 Barite 10 um 4.3 0 0 0 190 0.1 

7 DESCO/

Lignosulfonate

5 um 1.3 > 10% 100 0 242 0.1 

8 Lignite 5 um 1.7 0.2 ppm 1.0 0 242 0.1 

9, 14 m Methanol 5 mm 0.791 > 10% 100 0.168 201 0.92 

10 Ethylene

glycol

5 mm 1.14 100% 100 0.0001 201 0.59 

11, 12 Glutaraldehyde (dissolved) 1.08 > 10% - 0.022 202 0.31 

13 THPS (dissolved) 1.1637 > 10% - 0 252 0.31 

14aa Acetic acid 5 mm 1.05 57% 100 0.015 203 1.21 

14np Nonylphenol 5 mm 0.95 1.0 ppm 0.01 0 224 6.18 

133
134

Table 26

Chemical Properties Assumed For Model Runs (continued)

Model

Scenario

#

Chemical

Modeled

Particle

Size

Density

(g/cm3)

Seawater

Solubility

(mg/l)

Dissolution

Rate (day-1)

Vapor

Pressure

(atm)

Chemical

Type Code

Sorption/partition

coefficient

(Log KOC)

14a Amides/

imidazolinesandquaternaryammoniumchloride

10 um 1.01 0 0 0 206 3.0 

15a Amides/

imidazolines

10 um 1.01 0 0 0 206 3.0 

15n, 15t,

16n, 16t

Naphthalene 5 mm 1.162 22 ppm 0.1 0.0001 230 3.14 

15I Isopropyl

alcohol

5 mm 0.785 25% 100 0.0567 201 1.38 

16a Alkylbenzene

sulfonic acids

10 um 1.01 0 0 0 206 3.0 

134
135

7.9 Summary

The model run results are one of the important factors in determining which chemicals

would be of concern in causing impacts if they were spilled. The objective was to evaluate the

potential areas and volumes surrounding a spill site that could be contaminated at any

concentration above ~0.01 ppb. The resolution of the grid used was necessarily 533 m X 601 m

(= 320,573 m2 for each cell) in order to cover the potential distances chemicals might be

transported. Thus, details at a finer scale were not saved on the grid.

The model outputs represent a simplified summary for the purpose of screening which

chemicals pose an ecological risk. This summary is necessary because the model calculates

concentration in three dimensions and over time (in fine scale and at hourly increments), which

generates an inordinate amount of data for each of the 100 runs for each scenario (and chemical

within a scenario).

Additional model runs could evaluate the fine-scale exposure above specified thresholds

of actual concern for impacts. The spill modeling results, combined with the results of the

research on toxicity, which will be presented Section 8.0, may be used to define smaller scale

grids with which to project results.

The results of the 17 model scenarios may be used to infer potential impacts within

specified distances of a spill site. The shelf results (Scenarios 1-16) are most transferable along

the outer shelf, where the current patterns are very similar. As the currents are usually winddriven and relatively weak (except when eddies move on to the outer shelf), spills can move in

any direction.

Scenario 17 shows the dilution of a spill of a conservative substance occurring in the

offshore region of the western Gulf of Mexico (slope and deep water > 1,000 m). Loop current

eddies will be likely in this area, and more likely than in the outer shelf region. The one-year

current data record used for this offshore area is assumed representative for the region and over

time. No other measured current data are presently available, but on-going studies will show how

representative the mooring GG data are to the region.
137

8.0 PROFILES OF SELECTED CHEMICALS AND THEIR ASSOCIATED RISK

CHARACTERIZATION

8.1 Introduction

One of the objectives of this study included the development of detailed chemical profiles

for selected chemicals used in deepwater exploration and production operations. The approach,

as described in Section 2.0, was to select a subset of representative chemical or product types

used offshore and present the information in a series of profiles, rather than researching only the

“worst” or highest risk chemicals. Using this approach, information on the majority chemicals

used in the Gulf of Mexico (GOM) can be estimated by referencing one of the representative

chemical or product profiles.

This section provides detailed chemical profiles for 21 selected chemicals and

assumptions and results of spill models in both shallow and deep water in the Gulf of Mexico. It

also provides a risk characterization of the modeled chemicals based on available toxicological

data and spill model results. Since there is very limited or no information on deepwater

biological communities, as discussed in detail in Section 6.0, a complete risk evaluation was not

possible. Table 27 contains a summary of the spill modeling and risk characterization results.

Table 27

Chemical Risk Characterization Summary

Chemical 

Class

Amount 

Spilled

Worst-Case 

Environmental 

Exposure

Toxicity 

Type

Toxicity 

Value Receptor

Margin of 

Safety (1)

Potential 

Impact

CSW 3,400 gal. 1.0 ppm LC50 33 ppm

Crangon crangon (brown shrimp, 

marine crustacean) 0.03 No

CSW NM NM NM NM NM NM

DF,PT NM - NM NM NM NM NM

PT,DF 500 gal. 0.1 ppm LC50 6 ppm

Crangon crangon (brown shrimp, 

marine crustacean) 0.02 No

PT 165 gal. 0.1 ppm LC50 0.9 ppm Unspecified crustacean 0.1 No

PT 500 gal. 0.1 ppm LC50 119 ppm

Oncorhynchus mykiss (rainbow 

trout, freshwater fish) 0.001 No

CSW 45,000 gal. 10 ppm LC50 0.5 ppm

Daphnia magna (freshwater 

crustacean) 20 Yes

CSW NM - LC50 1,000 ppm

Crangon crangon (brown shrimp, 

marine crustacean) - No

CSW NM 1.0 ppm LC50 0.24 ppm

Salmo salar (Atlantic salmonsaltwater species) 4.17 Yes

DF 44,000 kg. 10 ppm

Threshold 

Limit Median 15 ppm

Daphnia magna (water flea, 

freshwater crustacean) 0.67 No

DF,CSW 4,700 kg. 1.0 ppm LC50 368.5 ppm

Puntius conchonius (freshwater 

fish) 0.003 No

PT 50-165 gal. 0.1 ppm LC50 2.0 ppm Unspecified crustacean 0.05 No
138

Table 27

Chemical Risk Characterization Summary (continued)

NM – Not Modeled

Notes:

(1) The worst-case margin of the safety is equal to the maximum exposure concentration divided by the toxicity

value. Values in this column greater than one indicate a potential for impact. These comparisons are one-hour

peak exposure concentrations versus 48-96 hour LC50 toxicity data and provide a conservative estimate of risk.

Actual exposure dosage and toxicity comparisons are discussed in the text.

(2) Although a spill of ammonium chloride was not modeled it would be similar to a spill of potassium chloride,

therefore we used the estimated concentrations for potassium chloride as a surrogate to estimate the risk from a

spill of ammonium chloride.

(3) Although a spill of triethylene glycol was not modeled it would be similar to a spill of ethylene glycol, therefore

we used the estimated concentrations for ethylene glycol as a surrogate to estimate the risk from a spill of

triethylene glycol.

8.2 Profile Explanation

8.2.1 Summary

Each profile is a description of the subject chemical and contains information in the

following order; summary, background information (i.e., fate in the environment, fate in the

process system, other components, CAS number, chemical formula, and important synonyms

and trade names), chemical and physical properties, health and safety properties, use and

handling properties, environmental concentrations and toxicological effects, spill modeling

results, aquatic toxicity levels, risk characterization, references, and spill modeling results in the

form of tables and figures.

Each profile represents chemical or product types. These 21 profiles should contain at

least one profile similar to every chemical or product type used in offshore E&P operations.

Chemical 

Class

Amount 

Spilled

Worst-Case 

Environmental 

Exposure

Toxicity 

Type

Toxicity 

Value Receptor

Margin of 

Safety (1)

Potential 

Impact

PT 400 gal. 0.1 ppm LC50 250 ppm

Mutilus edulis ( blue mussel, 

marine bivalve mollusk) 

Crassostrea gigas (Japanese 

oyster, marine bivalve mollusk) 0.0004 No

DF 53,000 kg. 10 ppm LC50 163,000 ppm Mysidopsis bahia (marine shrimp) 6.1E-05 No

PT 96,000 gal. 0.1 ppm LC50 12,539 ppm

Nitroca spinipes (harpacticoid 

copepod, marine crustacean) 8.0E-06 No

PT 106,000 gal. 100 ppm LC50 34,400 ppm

Ceriodaphnia dubia (water flea, 

freshwater crustacean) 0.003 No

PT NM 100 ppm LC50 10,000 ppm

Daphnia magna (water flea, 

freshwater crustacean) 0.1 No

PT 500 gal. 0.1 ppm

No toxicity 

data found

No toxicity 

data found No toxicity data found

No toxicity 

data found

No toxicity 

data found

DF 7,300 MT 1,000 ppm EC50 16200 ppm

Pandalus danae larvae ( coonstripe shrimp, marine species) 0.06 No

DF,C 96,000 kg. 1.0 ppm LC50 290,000 ppm

Pandalus danae (coon-stripe 

shrimp, marine crustacean) 0.003 No

PT 400-700 gal. 1.0 ppm LC50 3.0 ppm Elasmopus pectenicrus 0.3 No
139

The data in these profiles were gathered from:

• Operating companies who provided information on chemicals used, concentrations used, and

amounts stored

• Chemical suppliers who augmented the operating companies’ information and provided

explanations on how chemicals are used and transported

• MSDSs for the chemicals used by the operating companies and provided by their chemical

suppliers

• Standard reference books (e.g., CRC Handbook of Chemistry and Physics)

• Spill models prepared and run by Applied Science Associates, Inc. (ASA)

• Literature on toxicity collated by Applied Marine Sciences, Inc. (AMS)

• Industry technical and trade literature (e.g., World Oil or Journal of Petroleum Technology)

The following model profile shows the form of the information presentation and provides

a detailed explanation on each individual section within a profile.

8.2.2 Model Profile

Profile Number (#)

Single Component/Product

Summary

The summary describes which of the four chemical classes the single component/product

falls into (Drilling Fluids, Cementing Chemicals, Completion, Stimulation and Workover

Chemicals, or Production-treating Chemicals), the component’s function, phase, and form, and

the component’s potential impacts if discharged to the marine environment.

Background Information

Fate in the Environment

Fate in the environment describes the physical and chemical fate of the chemical or

product when it enters the marine environment and where it may ultimately end up, due to either

physical properties and/or chemical reactions.

Fate in the Process System

Fate in the process system describes how the chemical or product is used in the process

system, how the chemical leaves the system, and where the chemical ultimately goes upon

leaving the system.
140

The following information helps identify and explain the nature of the chemical or

product.

Other Components

CAS Number

Chemical Formula

Important Synonyms and Trade Names

Chemical and Physical Properties

Property Component (1) Product

Molecular Weight 233.39 Same as Component

Boiling Point 1,600o C Same as component

Melting Point 1,580o C Same as component

Specific Gravity 4.5 @ 15 oC Same as component

Solubility in Water Insoluble Same as component

Solubility in Organics Insoluble (2) Same as component

Vapor Pressure NA Same as component

Vapor Density (Air = 1) NA Same as component

Physical State (Phase) Solid Powder Same as Component

Chemical Reactivity in the

Environment

None Same as Component

Health and Safety Properties and Effects

Property Component Product (2)

Autoignition Temperature NA Same as Component

Flash Point NA (3) Same as component

Upper Explosive Limit NA (3) Same as component

Lower Explosive Limit NA (3) Same as component

Air Toxicity TLV 10 mg/m3 total dust containing

no asbestos and < 1% crystalline silica

(1)

Same as component

OSHA PEL (8) 15 mg/m3 total dust, 5 mg/m3

respirable dust (1)

Same as component

Notes: NA = Not Available

In this section, chemical and physical data for both

the chemical being profiled, and the product that it

is being supplied in, is presented. This data was

obtained from manufacturer MSDS sheets and

various standard technical reference books (as

referenced).

This table provides Health and Safety

information for the chemicals profiled and the

product that they are components of.

A qualitative discussion from information

provided in MSDS sheets and standard safety

tables is provided following presentation of this

table.
141

Use and Handling Properties

Use and Handling Properties covers typical and maximum offshore storage volumes,

transport containers, and handling practices offshore. This allowed for a qualitative assessment

of the amount of chemical that might be spilled offshore and how storage containers could

potentially impact a release into the marine environment. Information was collected and

synthesized from a variety of sources, including operator data from actual sites in the Gulf,

chemical supplier documents, etc. These data sources are discussed in detail in Section 3.0.

Environmental Concentrations and Toxicological Effects

This section contains modeled average peak exposure and worst-case peak exposure

concentrations from the modeling scenarios described in Section 7.0. Spill models were only

completed for 16 (of the 21) chemicals selected for detailed chemical profiling.

The chemical profiles were coordinated with the various spill scenarios in cooperation

with ADL, MMS, Applied Science Associates, Inc. (ADL’s spill modeling subcontractor), and

Applied Marine Sciences, Inc. (ADL’s toxicological data research subcontractor). Data from the

spill scenarios were used to estimate distributions in the marine environment. For most of the

chemical profiles, this information was obtained from spill scenarios for the same chemical, and

for several others, concentrations and fate were estimated from spill scenario results for similar

chemicals.

Spill Modeling Results

If a spill scenario was developed for the chemical being profiled, the objective was to

evaluate the potential areas and volumes surrounding a spill site that could be impacted. The spill

model results are presented on a series of tables and figures within each profile.

Contour maps show plots of the peak exposure concentrations at each location around the

spill site. This is calculated as follows.

• For each individual run (for each spill date and time run), the maximum amount over all time

after the spill is saved for each location (cell) in the model grid. This is the peak exposure

concentration for each location for a single randomly selected spill date and time.

• For the worst-case maximum amount for all possible releases (i.e., maximum peak exposure

for 100 randomly-selected spill dates and times), the 100 runs are evaluated to determine the

highest amount possible at each location.

• For the mean expected maximum amount for all possible releases (i.e., mean-peak exposure

of all randomly selected dates and times), the 100 runs are evaluated to determine the mean

peak exposure (mean amount for all runs) at each location.

Note that these amounts are not additive over all locations. These represent maximum

possible or mean amounts that would ever reach each site, considered individually. Different

sites are affected at different times after the spill.
142

Peak exposure plots are included for all forms of chemical where concentrations exceed

0.01 mg/m3 (~0.01 ppb) or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step)

following the spill. These extremely low thresholds were used so that the entire fate of the

chemical could be shown in the figures. The presence of these low concentration contours do not

imply toxicological impact. The chemical forms are:

• Dissolved concentration

• Particulate (solids or liquid droplets) concentration

• Concentration adsorbed to suspended sediment

• Mass loading to the bottom sediment (g/m2

)

• Surface slick (mass per unit area, g/m2

)

• Shoreline contamination (mass loading, g/m2

)

The figures vary in scale, depending on how far away from the spill site the 0.01 mg/m3

(~0.01ppb) threshold falls. Note the distance scale in the lower right corner of each figure as well

as the form of the chemical in the concentration plot.

The concentrations are calculated as total weight of the chemical, in the spilled form,

divided by volume of seawater. The notation ppb for mg/m3 is used herein for convenience. A

conversion was not made to account for the weight of the seawater being slightly greater than 1

g/ml.

For each of the chemical forms above, habitat areas exposed to peak concentrations or

mass loadings within range intervals were tabulated. The peak exposure concentration is

averaged over the depth of the plume. Since, for the shelf scenarios, the plume quickly (within a

day) mixes over the entire water column, the plume depth generally equals the water depth near

the spill site (114 m). In most cases, the chemical dispersed to < 1 mg/m3 (~1ppb) within less

than 10-50 km of the spill site. Thus, the plume is local to the spill site, and volume (m3

) exposed

would be about 100 times the area (m2) exposed.

Also, total dosage measures (concentration or mass per area times exposure time) are

calculated:

• Concentrations in water: Habitat area exposed at each dosage level (concentration-time, i.e.,

mg-m-3-hrs = ppb-hrs). Volume (m3) exposed would be about 100 times the area (m2)

exposed.

• Water surface: Slick thickness times time present (mass per area - time) for each dosage

level (g-m-2-hrs)

• Mass loading to sediments and shorelines: Mass per unit area times time present (mass per

area - time) for each dosage level (g-m-2-hrs)
143

Dosage is calculated in the model by summing, over all time steps, the concentration (or

mass per unit area) for that time step times the length of the time step in hours. Acute toxicity

(LC50) is known to decrease with increasing time of exposure (see review in French et. al.

1996a). If it is assumed that LC50 decreases linearly with time of exposure, this dosage index

may be used in comparison to LC50 data from bioassays performed at several days of exposure.

A dosage of 100 ppb-hours is equivalent to 100 ppb for 1 hour of exposure, or 10 ppb for 10

hours of exposure, or 1 ppb for 100 hours of exposure. Thus, if a 96-hour LC50 is the toxicity

endpoint of concern, a dosage level of 96 times the LC50 concentration is equivalent. The peak

exposure concentration may only have been present for an hour, and may not be comparable to a

96-hour LC50 (depending on the time for dilution). For this reason, the dosage is a better index

of exposure.

Output tables summarize the areas of habitat affected at different peak exposure and

dosage levels. The statistics include the mean, standard deviation, and the maximum and

minimum habitat area affected, based on the individual simulation results. The tables also

include the number of runs where zero area was affected above the threshold level. Habitat areas

are for exposure within intervals and for greater than a particular level. Thus, if areas affected

above several toxic endpoints are desired the appropriate threshold should be considered when

interpreting the data in the tables (i.e., tables are only included if there were some non-zero

results).

Note that these model runs represent a first cut at determining which chemicals may

cause potential impacts if they were spilled. The resolution of the grid used was necessarily 533

m X 601 m, in order to cover the potential distances chemicals might be transported. Thus,

details at a finer scale are not saved on the grid (although the model simulates the chemical

distribution at very fine scale each time step).

In addition, while the model calculates concentration in three dimensions and over time

(in fine scale and at hourly increments), this generates a tremendous amount of data for each of

the 100 runs for each scenario. The model outputs used here represent a simplified summary for

the purpose of screening chemicals with potential ecological impacts.

The results may be used to infer potential impacts within specified distances of a spill

site. As the plumes are generally circular in distribution the radial distance (r) to an impact

threshold (“endpoint” in EPA ecological risk parlance) is approximated by r = (A/π)

-2, where A =

the cumulative area affected above the threshold. The results of spill scenarios 1-16 are most

transferable along the outer shelf, where the current patterns are very similar.

When comparing some modeling results to reported toxicity end points, it was necessary

to make certain assumptions regarding distribution of the spilled chemical within the water or

sediments. Some model runs assumed that the spilled chemical would form a slick on the surface

of the water (e.g., for methanol) or a layer upon the sea floor (e.g., for barite). Chemical

concentrations were estimated by making the following assumptions:
144

• Seawater has a specific gravity of 1.0

• Sediments have a specific gravity of 2.0

• Spilled chemicals diffused into the top 1.0 centimeter of water and mixed into the top 0.5

centimeter of sediment

Average and worst case peak exposure concentrations were estimated using the spill

modeling. The time histories of multiple simulation runs under varying environmental conditions

were used to calculate the areas/volumes exposed at different levels of contamination. Each

simulation was evaluated to determine the maximum (peak) exposure concentration (over time

after the spill) for each location (model grid cell) around the spill site at any time after the spill.

The worst case (i.e., caused by worst case environmental conditions), and the average (i.e., mean

of all environmental conditions) over all simulations, of the peak exposure concentrations are

calculated for each location (grid cell) affected. The grid cells are 320,573 m2

 in area (for all

locations) and 114 m deep at the spill site. The peak concentrations are for 1 hour or more of

exposure, which is the time step used in the model runs. Of course, concentrations at the spill site

at time zero are at the maximum, i.e., at the concentration in the spill volume. At the spill site,

the peak concentrations calculated by the model are those at one hour after the spill, averaged

over one grid cell of volume (36,000,000 m3

). For surrounding grid cells, the peak concentration

is the maximum for any hour after the spill averaged over one grid cell of volume (36 million

m3). Concentrations continue to decrease from these levels over time.

Aquatic Toxicity Levels

A chemical spill in open water will rapidly dilute and dissipate within days, reducing the

likelihood of chronic toxicity. Therefore this report focuses on acute endpoints and less on

chronic effects. Available aquatic toxicity data were collected from numerous sources including

databases, technical journals, and relevant studies. Specific data sources are noted within each

profile and are included in References (see Section 9.0). Although an exhaustive literature search

was performed to find information on the toxicity of the prescribed drilling mud components,

several components had no published data, nor was it available from chemical manufacturers. An

effort was also made to obtain toxicity data from previous and current studies performed in the

North Sea region, however the toxicity database is proprietary and is not currently available to

the public and was not available for this study. Specifically, an attempt was made to obtain

toxicity data from these proprietary European sources:

• The Oslo and Paris Commission (OSPARCOM), an international agency acting on a broad

range of items that collects data on offshore chemicals used and stored by five countries

(Norway, the United Kingdom, The Netherlands, Denmark, and Germany)

• The Department of Trade and Industry (DTI), a United Kingdom-based organization to

increase competitiveness and scientific excellence in order to generate higher levels of

sustainable growth and productivity in a modern economy. Currently, DTI administers the

Offshore Chemical Notification Scheme (OCNS) using scientific and environmental advice

from CEFAS.

• The Center for Environment, Fisheries and Aquaculture Science (CEFAS), a United

Kingdom-based research and consultancy center.
145

The estimation of potential toxic impacts associated with spills of chemicals used in

offshore oil and gas operations required several steps. The estimation of impacts was based

primarily on available published or industry results of laboratory toxicity tests. The toxicity data

were then compared to average peak and worst-case chemical concentrations obtained with the

spill model.

The chemicals were categorized qualitatively relative to acute toxicity endpoints obtained

from the literature, because no toxicity data were found for the Gulf species potentially affected.

If modeled results were more than one order of magnitude below the lowest reported toxicity

endpoint, the chemical was categorized as unlikely to cause acute toxic impacts under the

modeled scenarios. If modeled results were within one order of magnitude of the lowest reported

toxicity endpoint, the chemical was categorized as potentially causing acute toxic impacts under

the modeled scenarios.

There are several toxicological endpoints found in published literature that differ in the

way they assess potential acute impacts. Moreover, endpoints may be measured over more than

one time span, incorporating the effect of exposure time. Each toxicological endpoint is

described as follows:

LC50 (Lethal Concentration 50) represents the concentration of material being tested that

is lethal for 50% of the test organisms over the time of exposure specified. Tests with the

LC50 endpoint can be performed over various exposure times. Various data sources used

exposure times that varied from 24 hours to 6 weeks. Obviously, achievement of 50%

lethality for the same concentration in half the time indicates a more toxic compound.

Nevertheless, because the rate of increasing mortality over time is not necessarily linear,

there is no way to meaningfully compare the LC50 for one exposure time with another.

EC50 (Effect Concentration 50) represents the concentration of material being tested that

has a prescribed effect on 50% of the test organisms. Tests with the EC50 endpoint also can

be performed over various exposure times. Reported exposure times ranged from 4 hours to 6

weeks. Effects usually involve reduction of a biological activity or process, such as feeding,

growth, fecundity, or embryonic development. Toxicity tests that measure effects on

biological processes are assumed to be more sensitive than those that measure mortality.

Nevertheless, because a return to normal activity or process probably occurs when the test

chemical is removed (except for embryonic development) a chemical that has an LC50 equal

to the EC50 of another chemical is the more toxic of the two.

LOEC (Lowest Observed Effect Concentration) is the lowest concentration at which an

effect is observed. Tests with an LOEC endpoint also can be performed over various

exposure times, although reported results incorporated in the study included only 7-day tests.

As with EC50, these tests usually measure effects on biological processes, but also may

include mortality.
146

NOEC (No Observed Effect Concentration) is the highest concentration at which no effect

is observed. Tests with an NOEC endpoint also can be performed over various exposure

times, although reported results incorporated in the study included only 7-day tests. As with

EC50, these tests usually measure effects on biological processes, but also may include

mortality.

TLM (Threshold Limit Median) refers to the median threshold limit. This endpoint can be

applied to either mortality, in which case it is synonymous with LC50, or to effects on

biological processes, in which case it is synonymous with EC50. Tests with a TLM endpoint

also can be performed over various exposure times, although reported results incorporated in

the study included only 96-hour tests.

Risk Characterization

This is a discussion of the potential impacts to the marine environment as a result of the

modeled spill using toxicity data of the chemical or product and exposure limits. It includes a

qualitative discussion of the potential for toxic impacts on the marine species such as would

occur in the GOM.

Contamination in the water column following a chemical spill changes rapidly in space

and time. Toxicity to marine organisms increases with time of exposure, such that organisms

may be unaffected by brief exposures to the same concentration that is lethal at long times of

exposure. For a brief exposure, a dosage measure of concentration times time is a more

appropriate index of toxicity than the peak concentration. For example, if a 96-hour LC50 is 1.0

mg/L, the dosage is 96 mg/L-1 hrs. Assuming a linear time-response model, the LC50 for a 1

hour exposure would be about 96 mg/L, and for a 10 hour exposure would be about 9.6 mg/L.

Total dosages (concentration-time, i.e., mg-m3

-hrs or ppb-hrs) are also calculated by the

modeling.

The chemical spill model also partitions the chemical into particulate (i.e., solid particles

or suspended liquid droplets and surface slicks, as appropriate), dissolved, and adsorbed (to

suspended sediment) phases in both water column and sediments. Concentrations in each phase

and mass loading to the sediments are computed in space and time. If the concentration exceeds

0.01 ppb for a model grid cell at any time after the spill, the area of that grid cell is included in

the summary data tables for the appropriate concentration interval. If no location would be

expected to exceed 0.01 ppb for the phase of concern, no data table is prepared for that phase

(i.e., particulate, dissolved, adsorbed, or sediment loading).

The modeled concentrations may be compared to concentrations that have been shown to

have toxic effects to determine the potential for impacts. Typically, toxicity tests are performed

with dissolved concentrations, so the comparison should be to the results for this phase.

Comparisons are made in the profiles for the peak (1 hour duration) concentrations at the spill

site. Calculations are also made of total habitat area exposed above a range of threshold

concentrations. Distance to these thresholds would be approximately the radius of a circle of that

exposed area. It should be noted that zero area/volume affected above a concentration threshold

indicates that the volume affected did not exceed one grid cell (of area 320,573 m2

 and volume

36 million m3

). Thus, the extent of the plume above this concentration threshold is less than 320

m from the spill site.
147

References

Sources for data presented in the profiles.

8.2.3 Uncertainties

The process we have used to estimate the ecological risks associated with spills of oilfield

chemicals is subject to several inherent sources of uncertainty. These sources of uncertainty

include the assumptions used in modeling the spill scenarios, the quality and quantity of existing

toxicological data for these oilfield chemicals, the use of different toxicological endpoints and

experimental protocols in the published literature, and the use of freshwater species for

estimating risk to marine species. In evaluating the potential impact of each chemical, it is

important for the reader to understand these uncertainties.

No toxicity data were found for the Gulf marine species actually potentially affected by

the chemicals. Uncertainties associated with the quality of the data and the absence of

quantitative descriptions of the biological communities in the region precluded a quantitative

evaluation of potential impacts of these chemicals. Many of the species for which data were

found are test species used in compliance testing for waste stream discharges.

All comparisons of toxicity data were to average or worst-case peak modeled

concentrations. Because these modeled peak concentrations would generally last only a short

time, comparison to toxicity results from standard 96-hour tests probably provides an

exaggerated estimate of acute impacts. Conversely, overall impacts may be underestimated

because we have included no consideration of long-term or chronic exposures to spilled

chemicals.

8.3 Twenty-one Profiles that Characterize the Qualitative Potential for Risk of

Chemicals Used in the Gulf of Mexico

The 21 representative chemical/product profiles are included below. These profiles cover

the entire range of chemicals used offshore, from the large volumes of single component

chemicals used in the drilling fluids at relatively few locations, to the small volumes of

production-treating formulations used at a large number of locations. The 21 chemicals selected

for detailed chemical profiles include:

Profile 1: Hydrochloric Acid (in water solution)

Profile 2: Hydrofluoric Acid (component of product) - no spill model

Profile 3: Polysiloxane (component of EC9034A) - no spill model

Profile 4: Glutaraldehyde (component of X-CIDE 0102 and EC6111A)

Profile 5: Quaternary Ammonium Compounds (component of Product A)

Profile 6: Tetrakishydroxymethyl Phosphonium Sulfate (THPS) (component of Magnicide 535)

Profile 7: Zinc Bromide (component of a Zinc Bromide/Calcium Bromide completion fluid)

Profile 8: Calcium Bromide (component of a Zinc Bromide/Calcium Bromide completion

fluid)- no spill model

Profile 9: Ammonium Chloride (single component) - no spill model

Profile 10: Sodium Hydroxide (single component)
148

Profile 11: Potassium Chloride (single component)

Profile 12: Amides/Imidazolines (component of Product B)

Profile 13: Amines and Amine Salts (component of Product B)

Profile 14: Lignite (single component)

Profile 15: Methanol (single component)

Profile 16: Ethylene Glycol (single component)

Profile 17: Triethylene Glycol (single component) - no spill model

Profile 18: Sodium Bisulfite (component of OSW3055)

Profile 19: Barite (single component)

Profile 20: Lignosulfonate (single component)

Profile 21: Naphtha, Aromatic (solvent for oil soluble products)
149

Profile 1

HYDROCHLORIC ACID (In Water Solution)

Summary

Hydrochloric acid is a mineral acid classified as a completion, stimulation and workover

chemical. It is used in stimulation procedures to remove corrosion products, water-formed scales,

and other solid materials from the formation around the wellbore, in the well, and in the

processing equipment. If discharged in the marine environment, it will initially change the pH of

the seawater. Ultimately, a chemical reaction with the natural buffering system will adjust the

seawater to its original concentration. The most important potential impact of this chemical is

worker safety. Discharge of quantities used offshore will not result in significant risk to the

marine environment.

Background Information

Fate in the Environment

Hydrochloric acid is used as a solution of hydrogen chloride gas in water. It is miscible in

seawater in all proportions. It is used in several standard concentrations, the most common being

15% solution by weight, in water. It is frequently used in a mixture with other acids and lesser

components.

When spilled in seawater, hydrochloric acid solution will mix into the water column.

Such mixing releases the heat of solution that will heat and agitate the receiving water. This

release of energy helps to mix the hydrochloric acid into the seawater where oceanographic and

meteorological forces provide additional mixing energy to disperse it through the water column.

Immediately on mixing with seawater, the acid reacts with the carbonate equilibrium system,

which acts to maintain the pH of the seawater (see Aquatic Toxicity Levels discussion below).

The concentrations of the various carbonate chemical species already found in the system and the

hydrogen ions released into the seawater are determined by the carbon dioxide concentration in

the atmosphere. Exchanges of carbon dioxide between the seawater and the atmosphere act to

convert the hydrogen ion component of the acid into bicarbonate and water. Since all the reaction

products of hydrochloric acid (hydrogen ions, bicarbonate, water, and chloride) are natural

components of seawater, these reaction products will ultimately mix with seawater and become

undetectable.

Fate in the Process System

Hydrochloric acid is applied to wells to remove acid soluble solids and clean up the

tubing and the formation around the well. During the treatment process the acid reacts with the

solids it is intended to remove and becomes partially neutralized. To perform this procedure the

well is taken out of service, the acid is injected, and the well is allowed to flow back to a

receiving tank. The returns are pretreated to allow them to be disposed of, either overboard into

the sea, into the produced water treating system then discharged into the sea, or hauled ashore for

appropriate disposal. Although most of the acid will return from the well over a period of a few

days, the pH concentration will be much lower due to the reactions for which it was applied.

Concentrations of acid in the returning fluids will yield pH values between 0 and 4.
150

Other Components

Water

CAS Number (Hydrochloric Acid)

7647-01-0

Chemical Formula (Hydrochloric Acid)

HCl (H+1 and Cl-1 in solution)

Important Synonyms and Trade Names

Hydrogen Chloride (in gas form); Muriatic Acid

Chemical and Physical Properties

Property Component (1) Product (2)

Molecular Weight 36.46 NA

Boiling Point - 84.9° C 110° C

Melting Point - 114.8o C Not established

Specific Gravity 1.0045 g/l (gas) 1.16

Solubility in Water 82.3 gm/100 gm water @ 0° C Soluble

Solubility in Organics Soluble in alcohol and ether NA

Vapor Pressure NA 13 mm Hg @ 20° C

Vapor Density (Air = 1) See specific gravity 1.3 (HCl)

Physical State (Phase) Gas Fuming Liquid

Chemical Reactivity in the

Environment

Very reactive, corrosive in water Very reactive with seawater

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component Product (2)

Autoignition Temperature Non-combustible NA

Flash Point NA NA

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity 5 ppm (ACGIH TLV) ND

OSHA PEL 5 ppm 5 ppm (2)

Notes: NA = Not Available; ND = Not Determined
151

There is no identified danger for fire or explosion. Liquid or concentrated vapors can

cause eye irritation, skin irritation and burns, and irritation of the respiratory tract. Ingestion can

cause burns of the mouth, nausea, pain, and vomiting, and depending on the amount swallowed,

could be fatal. (2)

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 3,000 gal.

Maximum = Application dependent.

Transport Container(s): Supplier’s plastic lined steel bulk tanks or boat tanks.

Storage Methods: Bulk tanks on platform (temporary) or supplier’s boat. The acid is

usually not stored on the platform; therefore, larger jobs are completed from the supplier’s boat.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Modeling Results

Hydrochloric acid was modeled as Spill Scenario 1. Results are shown in Figures 21 to

22 and Tables 23 to 29 (at the end of this section). The hydrochloric acid solution consists of

entirely dissolved chemical, i.e., H+ and Cl- or F- ions. The entire solution was modeled as HCl,

with a molecular weight of 36.5. Thus, for example, absent any buffering 1,000 mg/m3 is about

0.27 X 10-4 hydrogen ion concentration (pH 4.6). The concentration of H+ in seawater is

approximately 0.63 X 10-8 (pH 8.2).

Aquatic Toxicity Levels

The available literature for hydrochloric acid toxicity was reviewed and the results from

relevant studies are shown below.

Benthos

Crangon crangon (brown shrimp, marine crustacean) TLM = 272 ppm (3)

Crangon crangon (brown shrimp, marine crustacean) LC50 = 33-110 ppm (3)

Risk Characterization

The only toxicity data found for HCl was for benthos in sediment. The lowest toxicity

concentration found was 33 ppm (33,000 ppb), 96-hr LC50. Comparing this concentration with

toxicity thresholds (ppb) presented in Table 28 shows that no unit grid cell area was exposed to a

concentration of 33,000 ppb or greater, either average or worst case.

The impact of an accidental release of hydrochloric acid on the marine environment is to

lower the pH of seawater, at least locally and temporarily at the spill site. The modeled worst

case peak exposure concentration, 1.0 ppm, would correspond to 0.27 x 10-4 hydrogen ion

concentration (a pH of about 4.6), if it were not buffered. The natural concentration of hydrogen

ion in seawater is approximately 3.5 orders of magnitude lower, at 0.63 x 10-8 (pH = 8.2). The

lowest acute effect concentration (LC50) is 33 ppm, a concentration of hydrochloric acid that

would lower the pH of the seawater to about 3 without buffering. Based on the results of the
152

study, the test organisms could not tolerate pH values this low. However, because the modeled

concentrations do not reach 33 ppm, and because of the buffering capacity of seawater, no

significant acute aquatic toxicity effect would be expected from an accidental release of

hydrochloric acid.

References

(1) CRC Handbook of Chemistry and Physics (1985-1986)

(2) BJ Services Environmental Group (1998)

(3) Hudgins and Petrotech Consultants, Inc. (1991)
153

Table 28

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 1. Dissolved concentration

of hydrochloric acid and hydrofluoric acid (modeled as hydrochloric acid) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 166,038,560 1,445,103,744 7,270 21,447

10 23,024,884 307,103,840 2,707 9,887

100 1,621,471 35,672,364 718 3,370

1,000 - 1,945,766 - 787

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 29

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01-hours (0.01

ppb-hours): Scenario 1. Dissolved concentration of hydrochloric acid and hydrofluoric acid

(modeled as hydrochloric acid) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum

(m2)

% runs @

0

1H-10H 0.01-0.1 1.26E+08 1.19E+08 8.68E+08 2.01E+07 0

10H-100H 0.1-1.0 6.26E+08 4.78E+08 3.46E+09 2.16E+08 0

100H-1,000H 1.0-10.0 1.97E+09 8.17E+08 6.07E+09 9.85E+08 0

1,000H-10,000H 10.0-100.0 1.02E+09 4.84E+08 3.19E+09 4.80E+08 0

10,000H-100,000H 100.0-1,000.0 1.24E+08 4.76E+07 3.61E+08 6.00E+07 0

> 100,000H > 1,000.0 1.20E+07 2.39E+06 1.69E+07 6.81E+06 0

> 1H > 0.01 3.88E+09 1.43E+09 1.12E+10 2.14E+09 0

> 10H > 0.1 3.75E+09 1.35E+09 1.04E+10 2.08E+09 0

> 100H > 1.0 3.13E+09 1.03E+09 6.90E+09 1.79E+09 0

> 1,000H > 10.0 1.16E+09 5.10E+08 3.41E+09 5.89E+08 0

> 10,000H > 100.0 1.36E+08 4.74E+07 3.72E+08 7.04E+07 0

> 100,000H > 1,000.0 1.20E+07 2.39E+06 1.69E+07 6.81E+06 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
154

Figure 21. Peak exposure concentration (ppb) of hydrochloric acid dissolved in water at each

location: averaged over all simulations (Scenario 1).

Figure 22. Peak exposure concentration (ppb) of hydrochloric acid dissolved in the water at

each location: worst case of all simulations (Scenario 1).
155

Profile 2

HYDROFLUORIC ACID (Component of Product)

Summary

Hydrofluoric acid is a mineral acid classified as a completion, stimulation, and workover

chemical. It is used in stimulation procedures to remove solid materials from the formation

around the wellbore. It is almost always used in conjunction with another acid (usually

hydrochloric). Its function in these mixtures is to remove clays and other materials that are not

soluble in hydrochloric acid. If discharged into the marine environment, it will initially change

the pH of seawater. Ultimately, it will cause a chemical reaction with the natural buffering

system that will adjust the seawater to its original pH concentration. This acid differs from

hydrochloric because its anion, fluoride, is present in seawater in much lower amounts. Fluoride

may cause aquatic toxicity. It is normally used in much lower concentrations than hydrochloric

acid. Health and safety issues may be of concern, based on data for a hydrochloric/hydrofluoric

acid mixture.

Background Information

Fate in the Environment

Hydrofluoric acid is a solution of hydrogen fluoride in water. The product is miscible in

seawater. It is used in mixtures of acids as a secondary component. Total acid concentrations

vary, but a common total acid concentration is 15% by weight, in water. Hydrofluoric acid is

commonly found in concentrations of about 10% of the total acid concentration.

When spilled in seawater, hydrofluoric acid solution will mix into the water column.

Such mixing releases the heat of solution that will heat and agitate the receiving water. This

release of energy helps to mix the hydrofluoric acid into the seawater where oceanographic and

meteorological forces provide the mixing energy to disperse it through the water column. The

hydrofluoric acid reaction products are hydrogen ion and fluoride ion. Immediately upon mixing

with seawater, the hydrogen ion reacts with the carbonate equilibrium system already existing in

the seawater, which acts to maintain the pH (see Aquatic Toxicity Levels discussion below). The

concentrations of the various carbonate chemical species already found in the system and the

hydrogen ions released into the seawater are determined by the carbon dioxide concentration in

the atmosphere. Exchanges of carbon dioxide between the seawater and the atmosphere act to

convert the hydrogen ion component of the acid into bicarbonate and water. The fluoride

component of hydrofluoric acid becomes part of the natural concentration of fluoride in

seawater.

Fate in the Process System

Hydrofluoric acid is applied to wells to remove acid soluble solids and clean up the

tubing and the formation around the well. During the treatment process, the acid reacts with the

solids it is intended to remove and becomes partially neutralized. To perform this procedure, the

well is taken out of service, the acid is injected, and the well is then allowed to flow back to a

receiving tank. The returns are pretreated to allow them to be disposed of, either directly
156

overboard into the sea or into the produced water-treating system, followed by discharge into the

sea. Alternatively, the returns are hauled ashore for appropriate disposal. Disposal choices are

dictated by economics.

Other Components

Water, Hydrogen Chloride

CAS Number (Hydrofluoric Acid)

7664-39-3

Chemical Formula (Hydrofluoric Acid)

HF (H+1 and F-1 in solution)

Important Synonyms and Trade Names

Hydrogen Fluoride

Chemical and Physical Properties

Property Component (1) Product (2)

Molecular Weight 20.0 NA

Boiling Point 19.54° C Depends on acid

concentrations

Melting Point - 83.1o C Not established

Specific Gravity NA > 1,Varies with strength of

acid

Solubility in Water Soluble in all proportions Soluble

Solubility in Organics NA NA

Vapor Pressure NA Approaches constant boiling

mixture which boils @ 110° C

Vapor Density 0.901 g/l See Vapor Pressure

Physical State (Phase) Fuming liquid Fuming Liquid

Chemical Reactivity in the

Environment

H+1 reacts with carbonate buffering

system

Same as Component

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component (1) Product (2)

Autoignition Temperature Non-Combustible NA

Flash Point NA NA

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity TWA 3 ppm Same as Component

OSHA PEL 3 ppm Same as Component

Notes: NA = Not Available
157

There is no identified danger for fire or explosion. The vapors are highly irritating to the

tissue of the mucous membranes, upper respiratory tract, eyes, and skin. Liquid or concentrated

vapors of HCl: HF acid can rapidly cause burns when skin contact occurs. Hydrofluoric acid,

alone or in combination with hydrochloric acid, is very toxic by inhalation and by ingestion.

Exposures to vapor or liquid by any route can be fatal. (3)

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 3,000 gal. (total acid solution

typically containing 1.5% HF)

Maximum = Application dependent

Transport Container(s): Supplier’s plastic-lined steel bulk tanks or boat cargo tanks.

Storage Methods: Bulk tanks on platform (temporary) or supplier’s boat. The acid is

usually not stored on the platform; therefore, larger jobs are completed from the supplier’s boat.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Modeling Results

A hydrofluoric acid spill was not modeled.

Aquatic Toxicity Levels

The available literature was reviewed and no results were found specifically for

hydrofluoric acid. The data shown for calcium fluoride were the only data identified.

Algae and Invertebrates

Synechococcus leopoliensis (freshwater microalgae): concentrations > 1.1 μM resulted in

inhibition of growth(3) (1.1 μM of calcium fluoride is equal to 0.021 ppm fluoride ion).

Risk Characterization

Although a spill of hydrofluoric acid was not modeled, its behavior in the marine

environment would be identical to that of hydrochloric acid (see Profile 1), except for the

potential impact of the fluoride ion. Fluoride ions exhibit some toxicity, as the results of the

calcium fluoride study described above indicate, thus the potential toxicity of fluoride must be

considered.

The only toxicity data found for fluoride ion were measured on fresh water micro algae.

Thus, the aquatic toxicity value reported above (1.1 μM of calcium fluoride) is questionable for

application to the marine environment. A concentration of 0.021 ppm fluoride ion was found to

inhibit growth. However, the average concentration of fluoride ion in seawater is 1.3 ppm. (1) The

spill model for hydrochloric acid assumed a spill of 15% HCl by weight. A common use

concentration of HF is 1.5% by weight. Therefore, by analogy to the HCl spill model, a worstcase peak concentration of HF (where F is 95% of HF) would be approximately 0.1 ppm, which
158

is significantly lower than the average concentration of fluoride ion in seawater (i.e., 1.3 ppm). It

appears unlikely that an impact to the marine environment would result from a discharge of

hydrofluoric acid.

References

(1) CRC Handbook of Chemistry and Physics (1985-1986)

(2) BJ Services Environmental Group (1998)

(3) Nichol et al. (1987)
159

Profile 3

POLYSILOXANE (Component of EC9034A)

Summary

EC9034A is a solution containing a polysiloxane, an acetylenic diol, and 2-ethylhexanol

in kerosene. It is a production-treating chemical used to prevent foaming of crude oil during

oil/gas separations. Polysiloxane, the major active ingredient of EC9034A, is profiled here. The

most important environmental concern associated with this product is the potential toxicity of the

kerosene solvent (see Profile 21 for heavy aromatic naphtha).

Background Information

Fate in the Environment

EC9034A is oil soluble. The silicone component is an inorganic polymer (i.e., the

polymer “backbone” is an alternating oxygen/silicon chain) with two organic radicals attached to

each silicon atom. If spilled in seawater, the majority of the product will spread on the surface

and a very small quantity will dissolve into the water column. Ultimately, most of the kerosene

solvent component will evaporate into the atmosphere, and the alcohol will dissolve into the

water column. The silicone will become particulate matter and oceanographic and

meteorological forces will mix it into the water column. The magnitude of these forces will

determine how rapidly these processes take place.

No information was found concerning the ultimate fate of silicone in the environment.

Fate in the Process System

EC9034A is applied to the system after water is separated. It goes into the oil phase and

leaves the treatment facility in the oil export line.

Other Components

Acetylenic diol: 2-ethylhexanol; kerosene

CAS Number (Silicone)

63148-62-9(1) (For dimethyl siloxanes, the most common industrial polysiloxane: the

exact identification of the organic radical in this product is a trade secret.)

Chemical Formula (2) (Silicone)

Where R = CH3-, C2H5-, etc and n = number of repeating units

R

[ Si O ] n

R
160

Important Synonyms and Trade Names

Silicone

Chemical and Physical Properties

Property Component Product (3)

Molecular Weight Depends on R- and n NA

Boiling Point NA NA

Melting Point NA NA

Specific Gravity NA .84-.88 @ 60° F

Solubility in Water Insoluble (3) Insoluble

Solubility in Organics Soluble in oil Soluble in oil

Vapor Pressure NA 10.2 mm Hg @ 100° F

Vapor Density (Air = 1) ND NA

Physical State (Phase) Liquid Liquid

Viscosity NA 368 cst @ 60° F

Chemical Reactivity in the

Environment

NA NA

Notes: NA = Not Available; ND = Not Determined

Health and Safety Properties and Effects

Property Component Product

Autoignition Temperature NA NA

Flash Point NA 140° F (3)

Upper Explosive Limit None NA

Lower Explosive Limit None NA

Air Toxicity NA NA

OSHA TLV NA Kerosene = 100 ppm (3)

Notes: NA = Not Available

The most important health and safety concerns for this product offshore are due to the

solvent component. See Profile 21 for Naphtha solvents for more information.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 55 gal.

Maximum = 550 gal.

Transport Container(s): 5, 55, and 500 gal. totes (steel and/or HDPP).

Storage Methods: Shipping containers on offshore platform.
161

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

A polysiloxane spill was not modeled.

Aquatic Toxicity Levels

The available literature for polysiloxane toxicity was reviewed and the results from

relevant studies are shown below.

Algae and Invertebrates

Carcinus maenus (marine crustacean): LC50 (9-days) = 10,000 ppm (4)

Artemia sallina (marine crustacean): LC50 (9-days) = 20,000 ppm (4)

Fish

Scorpaena porcus (marine fish): LC50 (9-days) = 1,000 ppm (4)

Benthos (Sediment)

Nereis diversicolor (marine worm): LC50 (9-days) = 2,000 ppm (4)

Mytilus edulis (marine bivalve): LC50 (9-days) = 2,000 ppm (4)

Risk Characterization

Although no spill model was done for polysiloxanes (silicone), comparison with other

materials can give perspective to its possible environmental impact. Products containing

polysiloxanes are dissolved in mixed solvents, including naphtha solvents. Naphtha solvents are

discussed in Profile 21. Although these toxicity concentrations are for different species (i.e., fish

and crustaceans), comparing the lowest toxicity concentration for polysiloxane (listed above) to

the lowest toxicity concentrations for naphtha solvents in Profile 21, shows that they can be up to

about five orders of magnitude less toxic than the solvent in which they are dissolved.

Modeling of polysiloxanes spills is mathematically similar to that for amides/

imidazolines. Therefore the distribution of polysiloxane concentrations in the marine

environment following a spill would be the same order of magnitude as the modeled

concentration. Comparing a toxicity concentration of 1,000 ppm (1,000,000 ppb) 9-day LC50 to

these concentrations in Table 44 shows that no predicted exposure concentrations in a grid block

around a spill of polysiloxanes would exceed this toxicity level. These comparisons indicate that

polysiloxanes would pose minimal threat to the marine environment in the event of a spill.

References

(1) Mallinckrodt Baker, Inc. (1997)

(2) University of Southern Mississippi (1996)

(3) Nalco/Exxon Energy Chemical, L.P. (1992)

(4) Aubert (1985)
163

Profile 4

GLUTARALDEHYDE (Component of X-CIDE 0102 and EC6111A)

Summary

X-CIDE 0102 and EC6111A are water solutions containing glutaraldehyde. They are

production-treating chemicals used to control the growth of bacteria in production gathering and

treatment systems. Glutaraldehyde, as the active ingredient, is profiled here. If discharged to the

marine environment, it will ultimately be removed by biological degradation. Environmental

concerns include potential aquatic toxicity impacts.

Background Information

Fate in the Environment

Glutaraldehyde is the dialdehyde of glutaric acid and is soluble in seawater. When spilled

in seawater, glutaraldehyde solution will rapidly mix into the water column where oceanographic

and meteorological forces will disperse it. The magnitude of these forces determines how rapidly

glutaraldehyde disperses through the water column.

Glutaraldehyde will ultimately be removed from seawater by biological degradation.

Below toxic concentrations, it is degraded by bacteria. Glutaraldehyde has been shown to

degrade by more than 50% in less than 5 days in a standard BOD test. (1) Table 26 (Section 7.0)

presents the available degradation rates. The rates presented are instantaneous degradation rates.

The half-life in days can be calculated by the following formula: 0.693/Degradation Rate = 1/2

life (days).

Fate in the Process System

Glutaraldehyde is used in produced water streams and treatment vessels and will partition

to produced waters. Thus produced waters will contain residual concentrations of glutaraldehyde.

The produced waters containing the glutaraldhyde may either be discharged to the marine

environment or injected under ground.

Other Components

Water

CAS Number (Glutaraldehyde)

111-30-8

Chemical Formula (Glutaraldehyde)

Important Synonyms and Trade Names

1,5 Pentanedial

HC (CH2)3 CH

O O
164

Chemical and Physical Properties

Property Component (2) Product (1), (3)

Molecular Weight 100.13 NA

Boiling Point 187-189° C 213° C (1)

Melting Point NA - 7° F (1)

Specific Gravity NA 1.06 – 1.07@ 60° F

Solubility in Water Soluble Soluble

Solubility in Organics Benzene and Alcohols Alcohol

Vapor Pressure NA 16 mm Hg @ 20° C (1)

Vapor Density (Air = 1) NA Heavier than air

Physical State (Phase) Liquid Liquid

Viscosity NA 3.4 cp @ 69° F (1)

Chemical Reactivity in the

Environment

Biodegrades Biodegrades

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component Product

Autoignition Temperature NA (5) NA

Flash Point NA (5) > 93° C (3)

Upper Explosive Limit NA (5) NA

Lower Explosive Limit NA (5) NA

Air Toxicity NA NA

OSHA PEL None Established (5) None Established (5)

Notes: NA = Not Available

It is corrosive to the eyes on contact, with possible permanent damage depending on

exposure time. It can cause moderate skin irritation, can be fatal if ingested, and can cause severe

respiratory tract irritation.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 55 gal.

Maximum = 500 gal.

Transport Container(s): 5, 55, and 500 gal. totes (steel and/or HDPP)

Storage Methods: Shipping containers on offshore platform.
165

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Glutaraldehyde was modeled as Scenario 11 (surface release) and Scenario 12 (bottom

release).

Surface Release

Results are shown in Tables 30 to 31 and Figures 23 to 24. The surface release of

dissolved glutaraldehyde solution is dispersed nearly symmetrically, but less often to the

northwest.

Bottom Release

Results are shown in Tables 32 to 33 and Figures 25 to 26. The bottom release of

dissolved glutaraldehyde solution is dispersed primarily along-shelf with the prevalent direction

of the currents at that level.

Aquatic Toxicity Levels

The available literature for glutaraldehyde toxicity was reviewed and the results from

relevant studies are shown below.

Algae and Invertebrates

Artemia salina (brine shrimp, marine crustacean): LC50 (96-hr.) values range between

10 and 840 ppm; values cannot be compared with other LC50 values, as they were determined

through use of concentrations of treated mud diluted with seawater. (4)

Fish

Oncorhynchus tshawytscha (Chinook salmon, marine fish): high mortality at 62 mg/L. (5)

Benthos

Crangon crangon (brown shrimp, marine crustacean): LC50 (96-hr.) values range

between 6 and 2,200 ppm; these values were not determined for glutaraldehyde alone, but were

determined using treated mud diluted with seawater, which contains glutaraldehyde (Hudgins

and Petrotech Consultants, Inc. 1991).

Risk Characterization

The lowest toxic concentration values found for glutaraldehyde were gathered from

toxicity tests done on mud containing glutaraldehyde. A 96-hr LC50 of 6 ppm (6,000 ppb) was

reported. Examination of Tables 30 and 31 (surface release) and 30 and 31 (bottom release)

indicate that no unit grid cell area in either spill model scenario was exposed to a concentration

greater than 6,000 ppb. The highest average concentration affecting an entire unit grid block for

the surface release was 10 ppb and the highest average concentration affecting an entire unit grid

block for the bottom release was 100 ppb.
166

References

(1) NalcoExxon Energy Chemical, L.P. (1998)

(2) CRC Handbook of Chemistry and Physics (1985-1986)

(3) Baker Petrolite and Baker Hughes Co. (1997)

(4) Hudgins and Petrotech Consultants, Inc. (1991)

(5) Fitzpatrick et al. (1995)
167

Table 30

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 11. Dissolved concentration

of glutaraldehyde (surface release) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1.0 49,941,388.0 523,079,648.0 3,987.0 12,904.0

10.0 5,837,298.0 83,019,576.0 1,363.0 5,141.0

100.0 - 6,161,592.0 - 1,400.0

1,000.0 - - - -

10,000.0 - - - -

100,000.0 - - - -

1,000,000.0 - - - -

Table 31

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 11. Dissolved concentration of glutaraldehyde (surface

release) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum (m2) % runs @ 0

1H-10H 0.01-0.1 3.04E+07 1.27E+07 6.75E+07 6.16E+06 0

10H-100H 0.1-1.0 2.29E+08 1.12E+08 6.82E+08 7.75E+07 0

100H-1,000H 1.0-10.0 7.08E+08 2.12E+08 1.27E+09 3.64E+08 0

1,000H-10,000H 10.0-100.0 2.57E+08 8.32E+07 5.52E+08 1.26E+08 0

10,000H-100,000H 100.0-1,000.0 2.79E+07 8.74E+06 8.56E+07 1.14E+07 0

> 100,000H > 1,000.0 2.83E+06 5.94E+05 4.22E+06 1.62E+06 0

> 1H > 0.01 1.26E+09 3.15E+08 2.32E+09 8.20E+08 0

> 10H > 0.1 1.22E+09 3.10E+08 2.26E+09 8.02E+08 0

> 100H > 1.0 9.96E+08 2.37E+08 1.73E+09 6.28E+08 0

> 1,000H > 10.0 2.88E+08 8.38E+07 5.78E+08 1.67E+08 0

> 10,000H > 100.0 3.08E+07 8.63E+06 8.72E+07 1.43E+07 0

> 100,000H > 1,000.0 2.83E+06 5.94E+05 4.22E+06 1.62E+06 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
168

Table 32

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 12. Dissolved concentration

of glutaraldehyde (bottom release) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 25,619,236 196,845,920 2,856 7,916

10 3,891,531 26,267,824 1,113 2,892

100 324,294 1,945,766 321 787

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 33

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 12. Dissolved concentration of glutaraldehyde (bottom

release) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum

(m2)

% runs @ 0

1H-10H 0.01-0.1 2.38E+07 2.60E+07 2.61E+08 8.76E+06 0

10H-100H 0.1-1.0 1.60E+08 7.63E+07 4.99E+08 7.52E+07 0

100H-1,000H 1.0-10.0 4.27E+08 1.94E+08 1.26E+09 1.23E+08 0

1,000H-10,000H 10.0-100.0 1.41E+08 7.71E+07 6.01E+08 5.19E+07 0

10,000H-100,000H 100.0-1,000.0 1.99E+07 6.36E+06 4.31E+07 1.17E+07 0

> 100,000H > 1,000.0 2.28E+06 4.72E+05 3.57E+06 1.30E+06 0

> 1H > 0.01 7.75E+08 3.15E+08 2.41E+09 3.15E+08 0

> 10H > 0.1 7.51E+08 3.07E+08 2.35E+09 3.05E+08 0

> 100H > 1.0 5.91E+08 2.63E+08 1.91E+09 1.93E+08 0

> 1,000H > 10.0 1.64E+08 8.21E+07 6.43E+08 6.71E+07 0

> 10,000H > 100.0 2.22E+07 6.47E+06 4.48E+07 1.36E+07 0

> 100,000H > 1,000.0 2.28E+06 4.72E+05 3.57E+06 1.30E+06 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
169

Figure 23. Peak exposure concentration (ppb) of glutaraldehyde (surface release) dissolved in

the water at each location: averaged over all simulations (Scenario 11).

Figure 24. Peak exposure concentration (ppb) of glutaraldehyde (surface release) dissolved in

the water at each location: worst case of all simulations (Scenario 11).
170

Figure 25. Peak exposure concentration (ppb) of glutaraldehyde (bottom release) dissolved in

the water at each location: averaged over all simulations (Scenario 12).

Figure 26. Peak exposure concentration (ppb) of glutaraldehyde (bottom release) dissolved in

the water at each location: worst case of all simulations (Scenario 12).
171

Profile 5

QUATERNARY AMMONIUM COMPOUNDS (Component of Product A)

Summary

Product A is a water solution containing a quaternary ammonium chloride. It is a

production-treating chemical used to control corrosion in production gathering and treatment

systems. A quaternary ammonium chloride, one of the active ingredients, is profiled here. If

discharged to the marine environment, it will ultimately be removed by biological degradation.

Environmental concerns include possible aquatic toxicity.

Background Information

Fate in the Environment

Quaternary ammonium compounds are salts of substituted ammonium hydroxide bases.

They are soluble in water or a mixture of alcohol and water depending on their composition.

When spilled in seawater, Product A solution will rapidly mix into the water column where

oceanographic and meteorological forces will disperse it through the water column. The

magnitude of these forces determines how rapidly it spreads through the water column.

In the water column, Product A separates into an alcohol component and a quaternary

component. The alcohol component of Product A will dissolve in the water column and the

quaternary component will dissolve or disperse in the water column as tiny droplets. Quaternary

ammonium compounds will ultimately be removed from the environment by biological

degradation. Although quaternary ammonium compounds are also used to control bacteria, at

low concentrations they are degraded by bacteria. Table 26 (Section 7.0) presents the available

degradation rates. The rates presented are instantaneous degradation rates. The half-life in days

can be calculated by the following formula: 0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Product A is used in produced water streams and treatment vessels to protect against

corrosion. It is designed to adsorb to the internal surfaces of piping and vessels, react with active

corrosion sites and form a protective layer. Product A is designed to disperse into the produced

water that carries it to the surfaces to be treated. Therefore, produced waters will contain residual

concentrations of quaternary ammonium compounds. The produced waters containing the

residual treating chemical may either be discharged to the marine environment or injected under

ground for disposal.

Other Components

Water, methanol, isopropyl alcohol, acetic acid, ethoxylated nonylphenol and

amides/imidazolines.

CAS Number (Quaternary Ammonium)

NA
172

Chemical Formula (Quaternary Ammonium)

Important Synonyms and Trade Names

NA

Chemical and Physical Properties

Property Component Product (1)

Molecular Weight NA NA

Boiling Point NA ND

Melting Point NA ND

Specific Gravity NA .926 @ 25° C

Solubility in Water Slightly soluble Soluble

Solubility in Organics Soluble in alcohols and hydrocarbons NA

Vapor Pressure NA > 1

Vapor Density (Air = 1) NA > 1

Physical State (Phase) NA Liquid

Viscosity NA 8.5 cps

Chemical Reactivity in the

Environment

None None

Notes: NA = Not Available; ND = Not Determined

Health and Safety Properties and Effects

Property Component Product (1)

Autoignition Temperature NA NA

Flash Point NA 17o C

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity NA NA

OSHA PEL NA NA

Notes: NA = Not Available

The solvent for Product A is methanol and it comprises over 40% of the product. Most of

the reported health and safety effects of this product are due to methanol. See Profile 15 for

methanol.

R N CH3

CH3

Cl –

CH3

+
173

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 550 gal.

Maximum = 3,000 gal.

Transport Container(s): 55 gal. drums and/or 500 gal. HDPP plastic totes.

Storage Methods: In shipping containers or steel or plastic bulk tanks on the production

platform.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Quaternary ammonium compounds for Product A were modeled as Scenario 14a.

Results for all of Product A’s components are shown in Figures 37 to 42 and areas

exposed above threshold concentrations of quaternary ammonium compounds are shown in

Table 34 and Table 35.

The active ingredients of the miscible organic solution – amides/imidazolines, and

quaternary ammonium chloride – are modeled as insoluble particulate representing liquid droplets

(Figures 27 to 28 and Tables 34 to 35). Thus, all concentrations are in that form. The particulate

disperses only by current transport and diffusion in this simulation. If the active ingredient were

dissolved, it would disperse at the same rate to similar concentrations. As noted above, after the

model runs were made, the corrosion inhibitor mixture was corrected slightly to include 11.2%

quaternary ammonium chloride instead of 15% quaternary ammonium chloride. Thus, the model

runs were made with slightly more chemical mass spilled (165 gal.) than the corrected composition

(144 gal.) would indicate. Thus, the corrected results would be 87% of the concentrations predicted

by the model.

Aquatic Toxicity Levels

The available literature for quaternary ammonium chloride toxicity was reviewed and is

shown below. (2)

Algae and Invertebrates

Unspecified crustacean: LC50 = 0.9 ppm. (2)

Artemia salina (brine shrimp, marine crustacean): LC50 (96-hr.) = 10 ppm. (2)

Risk Characterization

The lowest toxicity concentration found for quaternary ammonium compounds was 0.9

ppm (900 ppb) 96-hr LC50. Comparing this concentration with toxicity thresholds presented in

Table 34 shows that no predicted exposure concentration in a unit grid cell area would be greater

than 1,000 ppb for either average or worst case concentration distributions.
174

References

(1) Supplier’s MSDS for Product A (See Appendix B)

(2) Hudgins and Petrotech Consultants, Inc. (1991)
175

Table 34

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 14a. Particulate

concentration of miscible organic solution (amides/imidazolines and quaternary ammonium

chloride) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 62,588,932 506,865,248 4,463 12,702

10 6,810,181 95,342,824 1,472 5,509

100 - 10,701,712 - 1,846

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 35

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 14a. Particulate concentration of miscible organic

solution(amides/imidazolines and quaternary ammonium chloride) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum

(m2)

% runs

@ 0

1H-10H 0.01-0.1 3.96E+07 1.90E+07 1.06E+08 4.22E+06 0

10H-100H 0.1-1.0 3.01E+08 1.48E+08 8.58E+08 9.63E+07 0

100H-1,000H 1.0-10.0 8.51E+08 2.40E+08 1.58E+09 5.20E+08 0

1,000H-10,000H 10.0-100.0 3.54E+08 1.27E+08 9.67E+08 1.97E+08 0

10,000H-100,000H 100.0-1,000.0 3.90E+07 8.16E+06 5.71E+07 2.24E+07 0

100,000H-10^6H 1,000-10,000 3.81E+06 7.51E+05 5.19E+06 1.89E+06 0

10^7H-10^8H 10,000-100,000 1.07E+05 1.88E+05 3.46E+05 0 75

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 1.59E+09 3.78E+08 2.80E+09 1.09E+09 0

> 10H > 0.1 1.55E+09 3.72E+08 2.79E+09 1.05E+09 0

> 100H > 1.0 1.25E+09 3.02E+08 2.55E+09 8.16E+08 0

> 1,000H > 10.0 3.97E+08 1.26E+08 1.01E+09 2.30E+08 0

> 10,000H > 100.0 4.29E+07 8.05E+06 6.03E+07 2.63E+07 0

> 100,000H > 1,000.0 3.91E+06 6.73E+05 5.19E+06 2.27E+06 0

> 1,000,000H > 10,000 1.07E+05 1.88E+05 3.46E+05 0 75

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
176

Figure 27. Peak exposure concentration (ppb) of miscible organic solution

(amides/imidazolines and guaternary ammonium chloride) as particulate in the

water at each location: averaged over all simulations (Scenario 14a).

Figure 28. Peak exposure concentration (ppb) of miscible organic solution

(amides/imidazolines and guaternary ammonium chloride) as particulate in the

water at each location: worst case of all simulations (Scenario 14a).
177

Profile 6

Tetrakishydroxymethyl Phosphonium Sulfate (THPS)

(Component of Magnicide 535)

Summary

Magnicide 535 is a water solution containing Tetrakishydroxymethyl Phosphonium

Sulfate (THPS). It is a production-treating chemical used to control the growth of bacteria in

production gathering and treatment systems. Tetrakishydroxymethyl phosphonium sulfate

(THPS), the active ingredient, is profiled here. If discharged to the marine environment, it will

ultimately be removed by reaction with oxygen. Environmental concerns include possible

aquatic toxicity.

Background Information

Fate in the Environment

Tetrakishydroxymethyl phosphonium sulfate (THPS) is soluble in seawater. It degrades

to THPO (trishydroxymethylphosphine oxide) in the presence of oxygen. Subsequently, it

degrades to phosphate ion and water. Its value as a biocide is based not only on efficiency, but

also on its ability to be rapidly removed from the environment by oxidation.

When spilled in seawater, THPS solution will rapidly mix into the water column where

oceanographic and meteorological forces provide the mixing energy to disperse it through the

water column. The magnitude of these forces determines how rapidly THPS will spread through

the water column.

When THPS mixes with oxygenated seawater it will begin to degrade by reacting with

the oxygen in seawater to form THPO. Within a few hours, the THPS will be gone from the

environment. Table 26 (Section 7.0) presents the available degradation rates. The rates presented

are instantaneous degradation rates. The half-life in days can be calculated by the following

formula: 0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

THPS is used in produced water streams and treatment vessels and partitions to the

produced water. The produced water contains residual concentrations of THPS when discharged

to the marine environment or injected under ground.

Other Components

Water

CAS Number (THPS)

55566-30-8
178

Chemical Formula (THPS)

(C4H10O4)2SO4

Important Synonyms and Trade Names

Tolcide

Chemical and Physical Properties

Property Component (1) Product (2)

Molecular Weight 406.3 NA

Boiling Point NA NA

Melting Point - 43° C 28° F

Specific Gravity 1.37 @ 20° C 1.164 @ 60° F

Solubility in Water Soluble Soluble

Solubility in Organics NA NA

Vapor Pressure NA NA

Vapor Density (Air = 1) NA > 1

Physical State (Phase) Liquid Liquid

Viscosity 31 cps 25° C 21.1 cps @ 77° F

Chemical Reactivity in the

Environment

Reacts with oxygen Reacts with oxygen

Notes: NA = Not Available

The component supplied by the manufacturer is a 75% solution in water. The data

presented for the product here were taken from an MSDS for a 35% solution in water. When the

spill models were planned, an MSDS was not available for this product, and a 20% solution was

modeled because it was the most common concentration applied offshore.

Health and Safety Properties and Effects

Property Component (1) Product (2)

Autoignition Temperature Non Flammable Non Flammable

Flash Point Non Flammable Non Flammable

Upper Explosive Limit Non Flammable Non Flammable

Lower Explosive Limit Non Flammable Non Flammable

Air Toxicity ND ND

OSHA PEL ND ND

Notes: ND =Not Determined

THPS can cause significant eye irritation and ingestion can cause significant irritation to

the digestive tract. Inhalation is expected to cause significant irritation to the lungs, upper

respiratory tract and nose.
179

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 55 gal.

Maximum = 500 gal.

Transport Container(s): 5, 55, and 500 gal. totes (steel and/or HDPP).

Storage Methods: Shipping containers on offshore platform.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

THPS was modeled as Scenario 13. The exposure concentrations presented below are

derived from the results of this modeling.

Results are shown in Figures 29 and 30 and Tables 36 and 37. The dissolved THPS

solution is dispersed nearly symmetrically, but less often to the northwest.

In the modeling, the degradation half-life is assumed (25-days). However, as noted

above, the intermediate product THPO, generated with a half-life of 6-hours, is reportedly much

less toxic than THPS. Thus, the THPS concentrations calculated by the model are for THPS and

its products. Comparison of this total concentration to LC50s for THPS would overestimate

toxicity to the degree that the THPO is less toxic.

Aquatic Toxicity Levels

The available literature for THPO and THPS toxicity was reviewed and the results from

relevant studies are shown below.

Algae and Invertebrates for THPO

Skeletonema costatum (marine algae): EC50 = 2,090 mg/L (3)

Daphnia magna (freshwater crustacean): LC50 (acute) = > 1,000 mg/L (3)

Acartia tonsa (marine copepod crustacean): NOEC > 1,000 mg/L (3)

Fish for THPO

Onchorynchus mykiss (rainbow trout, freshwater fish): LC50 = > 500 mg/L (3)

Benthos (Sediment) for THPO

Mytilus edulis (marine bivalve mollusk): EC50 > 872 mg/L (3)

Fish

Oncorhynchus mykiss (rainbow trout, freshwater fish): LC50 (96-hr) = 119 mg/L (3)

Benthos (Sediment)

Crangon crangon (brown shrimp, marine crustacean): LC50 (96-hr) = 340 mg/L (3)
180

Risk Characterization

The lowest toxicity concentration found for THPS was 119 mg/L (approximately 119

ppm or 119,000 ppb) for a fresh water species. Comparing this concentration with the modeled

concentrations presented in Table 36 shows that no predicted exposure concentration in a unit

grid cell area would be greater than 119,000 ppb for either average or worst case concentration

distributions. In fact, the highest concentration modeled for a complete unit grid cell area was

100 ppb.

The biocide THPS degrades to THPO with a half-life of approximately 6 hours. The

degradation rate is dependent on oxygen concentration, temperature, THPS concentration, and

the presence of catalysts, such as heavy metals. This reaction ensures that THPS will exist in the

environment for only a short time.

References

(1) Albright and Wilson Americas Inc. (1997)

(2) Baker Petrolite and Baker Hughes Co. (1998)

(3) Downward et al. (1997)
181

Table 36

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 13. Dissolved concentration

of THPS in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1.0 38,915,324.0 447,196,256.0 3,520.0 11,931.0

10.0 3,891,531.0 67,453,368.0 1,113.0 4,634.0

100.0 - 5,837,298.0 - 1,363.0

1,000.0 - - - -

10,000.0 - - - -

100,000.0 - - - -

1,000,000.0 - - - -

Table 37

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 13. Dissolved concentration of THPS in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum

(m2)

% runs @ 0

1H-10H 0.01-0.1 2.41E+07 1.04E+07 5.58E+07 5.84E+06 0

10H-100H 0.1-1.0 2.02E+08 1.09E+08 8.33E+08 4.38E+07 0

100H-1,000H 1.0-10.0 6.01E+08 1.87E+08 1.12E+09 3.23E+08 0

1,000H-10,000H 10.0-100.0 2.03E+08 6.56E+07 4.41E+08 1.09E+08 0

10,000H-100,000H 100.0-1,000.0 2.24E+07 7.05E+06 6.68E+07 1.01E+07 0

> 100,000H > 1,000.0 2.26E+06 4.93E+05 3.24E+06 6.49E+05 0

> 1H > 0.01 1.05E+09 2.70E+08 1.99E+09 6.80E+08 0

> 10H > 0.1 1.03E+09 2.66E+08 1.94E+09 6.62E+08 0

> 100H > 1.0 8.28E+08 2.00E+08 1.42E+09 5.28E+08 0

> 1,000H > 10.0 2.27E+08 6.59E+07 4.62E+08 1.36E+08 0

> 10,000H > 100.0 2.46E+07 6.96E+06 6.84E+07 1.23E+07 0

> 100,000H > 1,000.0 2.26E+06 4.93E+05 3.24E+06 6.49E+05 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
182

Figure 29. Peak exposure concentration (ppb) of THPS dissolved in the water at each location:

averaged over all simulations (Scenario 13).

Figure 30. Peak exposure concentration (ppb) of THPS dissolved in the water at each location:

worst case of all simulations (Scenario 13).
183

Profile 7

ZINC BROMIDE

(Component of a Zinc Bromide/Calcium Bromide Completion Fluid)

Summary

Zinc bromide is a solid inorganic salt. It is used as a constituent in completion,

stimulation, and workover chemicals. Its ions are natural constituents of seawater and, at higher

concentrations, zinc ion reacts with various other constituents of seawater to form insoluble

compounds. Bromide ion will ultimately dilute to ambient seawater concentrations.

Environmental concerns about this chemical are its potential aquatic toxicity.

Background Information

Fate in the Environment

When spilled in seawater, zinc bromide solution will rapidly disperse in seawater. In

solution, it is present as separate zinc and bromide ions. Zinc ion reacts with the hydroxide ion in

seawater to form insoluble zinc hydroxide. During and after reaction, oceanographic and

meteorological forces will act to dilute zinc ion and bromide ion to normal seawater

concentrations. The magnitude of these forces determines how rapidly these ions spread through

the water column.

Fate in the Process System

Zinc bromide is used in stimulation and workover work on wells. It is placed in wells to

hold pressure on the formation during casing perforation and during setting of packers and tubing

in wells. During these operations, some of it will be lost to the formation. In some wells, the zinc

bromide will remain in the annulus between the tubing and the casing and serve as a packer fluid.

Ultimately, the zinc bromide will leave the well or production system as waste. Normally it will

end up as part of the produced water stream. The produced water will ultimately be disposed of

overboard into the marine environment or injected under ground.

Other Components

Water, Calcium Bromide

CAS Number (Zinc Bromide)

7699-45-8

Chemical Formula (Zinc Bromide)

ZnBr2 (Zn+2 and Br-1 in water solution)

Important Synonyms and Trade Names

Zinc Dibromide
184

Chemical and Physical Properties

Property Component (1) Product (2)

Molecular Weight 225.18 NA

Boiling Point 697o C 275o F

Melting Point 394o C ND

Specific Gravity 4.22 2.3

Solubility in Water Complete (100%) Soluble

Solubility in Organics ND ND

Vapor Pressure Not Applicable (1) 17.5 mm Hg @ 68o F

Vapor Density (Air = 1) 7.8 ND

Physical State (Phase) Solid (granular powder) @ standard

conditions

Liquid solution

Viscosity NA NA

Chemical Reactivity in the

Environment

Reacts with hydroxide in seawater Reacts hydroxide in seawater

Notes: NA = Not Available; ND = Not Determined

The only health hazard found for the component, is skin irritation due to improper

handling. See Appendix B for Product MSDS sheet.

Health and Safety Properties and Effects

Property Component (1) Product (2)

Autoignition Temperature NA ND

Flash Point NA ND

Upper Explosive Limit NA ND

Lower Explosive Limit NA ND

Air Toxicity None Established (1) NA

OSHA PEL None Established (1) NA

Notes: NA = Not Available; ND = Not Determined

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 45,000 gal.

Maximum = Varies with well design.

Transport Container(s): Steel bulk tanks provided by supplier or cargo tanks on boats.

Storage Methods: In bulk tanks on the drilling rig or on the supplier’s boat.
185

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Zinc bromide was modeled as spill scenario 4. The exposure concentrations presented

below are derived for the results of this modeling.

Results are shown in Figures 31 and 32 and Tables 38 and 39. The zinc bromide is spilled

as a dissolved solution. Zinc may react with constituents of seawater to form a precipitate, some

of which would settle to the sediment if the particulates become large enough to overcome

turbulence. The model does not include these precipitation reactions. Thus, the dissolved

concentrations may be construed as total concentrations (of zinc bromide, molecular weight 225

g/mole), with the assumption that the zinc precipitate does not settle significantly.

In the concentration plot, the high concentrations near shore (not part of the symmetric

plume around the spill size) are an artifact of the compression of mass into a shallow water

column, as the current data from offshore aimed the modeled mass in the shoreward direction. If

detailed actual currents were available, shoreward transport would, by physical laws, be balanced

by offshore transport, and there would be no increase in concentration towards shore.

Aquatic Toxicity Levels

The available literature for zinc bromide toxicity was reviewed. No data were found for

zinc bromide. The following results are for zinc ion.

Algae and Invertebrates

Daphnia magna (freshwater crustacean) LC50 (48-hr) = 1.22 mg/L. (3)

Ceriodaphnia dubia (freshwater crustacean) LC50 (48-hr) = 0.5 mg/L. (3)

Fish

Pimelphales promelas (fathead minnow, freshwater fish) LC50 (7-days) = 0.78 mg/L. (3)

Risk Characterization

No marine toxicity data were found for zinc bromide. In seawater, zinc bromide

chemically changes to zinc hydroxide or zinc carbonate. If toxicity tests on seawater were

available the effect of precipitated zinc compounds would automatically be part of the bioassay

test. The fresh water toxicity data listed above indicates that zinc ion has significant toxicity. It

ranges from 0.5 mg/l (approximately 0.5 ppm or 500 ppb) 48-hr LC50 to 1.22 mg/l

(approximately 1,220 ppb) 48-hr LC50. While 100% of the zinc bromide will not dissociate into

zinc ion, a conservative comparison of these concentrations to the toxicity thresholds presented

in Table 38 shows that significant areas are exposed to concentrations of zinc bromide greater

than 500 ppb. On average, zinc bromide concentrations from a spill of the simulated volume

would exceed 1ppm for at least one hour in an area of 11 million m2

 (11 km2, volume of 11

million m2 x 114 m deep = 1,254 million m3) around the spill site. This indicates that, based on

fresh water toxicity studies, there could be an adverse impact of a zinc bromide spill. For the

most sensitive species tested, the dose required to cause 50% of the test organisms in freshwater

to die in 48 hours is 24,000 ppb-hrs (500 ppb x 48 hours). From Table 39, an area of

approximately 100 million m2 (100 km2, volume of 11,400 million m3) around the spill site

would be exposed to a dosage of 24,000 ppb-hrs or greater. However, based on the reaction of
186

zinc bromide in seawater vs. freshwater (i.e., zinc ion reacts with hydroxide ion in seawater to

form insoluble zinc hydroxide within minutes of mixing), and the absence of marine toxicity

data, it is not possible to definitively determine the potential toxicity posed by the accidental

release of zinc bromide under modeled conditions.

The potential for marine environmental impacts are affected by the chemical fate of zinc

in seawater. The nominal concentration of zinc in seawater is 0.01 mg/L. (4) Dilution of zinc

bromide spilled in the seawater would eventually reduce the zinc concentration to this level.

Dissolved zinc is removed from the water column by reaction with hydroxide ion and carbonate

ion in seawater. At the pH of seawater, the equilibrium concentration of zinc ion is 2 mg/L.

Assuming that zinc above that concentration would precipitate, the potential impact zone is

likely much smaller than the model results indicate. Dilution would further reduce this zinc

concentration within a short period of time, certainly less than the 14 days modeled in spill

scenario 4. The solid precipitate formed by chemical reaction would initially become suspended

solids in the water column and eventually settle onto the sediment. A direct assessment of the

potential impact of a zinc bromide spill on the marine environment would require toxicity data

on marine organisms exposed to both zinc ion added to seawater and insoluble zinc compounds,

studies of reaction products of zinc ion with seawater, and modeling of important chemical

processes in the spill scenario.

References

(1) Mallinckrodt Baker Inc. (1996a)

(2) M-I Drilling Fluids (1998a)

(3) Magliette et al. (1995)

(4) CRC Handbook of Chemistry and Physics (1985-1986)
187

Table 38

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 4. Dissolved concentration

of zinc bromide in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 3,176,494,592 25,957,097,472 31,798 90,898

10 542,861,248 3,883,581,952 13,145 35,159

100 88,856,904 834,720,448 5,318 16,300

1,000 11,026,006 152,742,752 1,873 6,973

10,000 324,294 17,511,886 321 2,361

100,000 - - - -

1,000,000 - - - -

Table 39

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 mg/m3-

hours (0.01 ppb-hours): Scenario 4. Dissolved concentration of zinc bromide in all subtidal

habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev.

(m2)

Maximum

(m2)

Minimum

(m2)

% runs

@ 0

1H-10H 0.01-0.1 9.11E+08 3.99E+08 2.56E+09 2.47E+08 0

10H-100H 0.1-1.0 3.73E+09 1.35E+09 7.60E+09 9.69E+08 0

100H-1,000H 1.0-10.0 1.04E+10 2.99E+09 2.06E+10 1.68E+09 0

1,000H-10,000H 10.0-100.0 1.35E+10 3.23E+09 2.76E+10 3.86E+09 0

10,000H-100,000H 100.0-1,000.0 5.57E+09 2.14E+09 1.17E+10 2.03E+09 0

100,000H-10^6H 1,000-10,000 5.96E+08 4.13E+08 3.23E+09 1.81E+08 0

10^7H-10^8H 10,000-100,000 1.54E+08 1.17E+08 9.89E+08 4.03E+07 0

10^8H-10^9H 100,000-1,000,000 1.58E+07 9.76E+06 6.93E+07 4.22E+06 0

> 10^9H > 1,000,000 8.85E+05 1.54E+06 5.33E+06 0.00E+00 21

> 1H > 0.01 3.49E+10 3.96E+09 4.79E+10 1.91E+10 0

> 10H > 0.1 3.40E+10 3.78E+09 4.67E+10 1.89E+10 0

> 100H > 1.0 3.03E+10 3.26E+09 4.26E+10 1.79E+10 0

> 1,000H > 10.0 1.98E+10 2.76E+09 3.02E+10 1.53E+10 0

> 10,000H > 100.0 6.34E+09 2.41E+09 1.53E+10 2.44E+09 0

> 100,000H > 1,000.0 7.66E+08 4.42E+08 3.64E+09 2.70E+08 0

> 1,000,000H > 10,000 1.71E+08 1.28E+08 1.06E+09 4.46E+07 0

> 10,000,000H > 100,000 1.66E+07 1.13E+07 7.47E+07 4.22E+06 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
188

Figure 31. Peak exposure concentration (ppb) of zinc bromide dissolved in the water at each

location: averaged over all simulations (Scenario 4).

Figure 32. Peak exposure concentration (ppb) of zinc bromide dissolved in the water at each

location: worst case of all simulations (Scenario 4).
189

Profile 8

CALCIUM BROMIDE

(Component of a Zinc Bromide/Calcium Bromide Completion Fluid)

Summary

Calcium bromide is a solid inorganic salt. It is used as a constituent in Completion,

stimulation, and workover chemicals. Its ions are natural constituents of seawater. At higher

concentrations, calcium ion reacts with various other constituents of seawater to form insoluble

compounds. Bromide ion will ultimately dilute to seawater concentrations. This chemical is

unlikely to pose potential aquatic toxicity.

Background Information

Fate in the Environment

When spilled in seawater, calcium bromide solution will rapidly disperse in seawater. In

solution, it is present as separate calcium and bromide ions. Calcium ion reacts with the

carbonate system in seawater to form insoluble calcium carbonate. At equilibrium with seawater,

the calcium ion concentration will be reduced to 400 mg/L (1). During and after reaction,

oceanographic and meteorological forces will act to dilute calcium ion and bromide ion back to

normal seawater concentrations. The magnitude of these forces will determine how rapidly these

ions spread through the water column.

Fate in the Process System

Calcium bromide is used in stimulation and workover on wells. It is placed in wells to

hold pressure on the formation during casing perforation and during setting of packers and tubing

in wells. During these operations, some of it will be lost to the formation. In some wells, the

calcium bromide will remain in the annulus between the tubing and the casing and serve as a

packer fluid. Ultimately, the calcium bromide will leave the well or production system as waste

(i.e., it will normally end up as part of the produced water stream). The produced water will

ultimately be disposed of overboard into the marine environment or injected under ground.

Other Components

Water, Zinc Bromide

CAS Number (Calcium Bromide)

7789-41-5

Chemical Formula (Calcium Bromide)

CaBr2•2H20 (In water solution: Ca+2, Br-1)

Important Synonyms and Trade Names

None
190

Chemical and Physical Properties

Property Component (2) Product (3)

Molecular Weight 235.92 NA

Boiling Point No information found 275o F

Melting Point No information found ND

Specific Gravity No information found 2.3

Solubility in Water Complete Soluble

Solubility in Organics Insoluble ND

Vapor Pressure NA 17.5 mm Hg @ 68o F

Vapor Density (Air = 1) NA ND

Physical State (Phase) Solid (crystals or granules) @ standard

conditions

Liquid solution

Viscosity NA NA

Chemical Reactivity in the

Environment

Reacts with carbonate in seawater Reacts with carbonate in

seawater

Notes: NA = Not Available; ND = Not Determined

Health and Safety Properties and Effects

Property Component Product (3)

Autoignition Temperature NA ND

Flash Point NA ND

Upper Explosive Limit NA ND

Lower Explosive Limit NA ND

Air Toxicity None Established (2) NA

OSHA PEL None Established (2) NA

Notes: NA = Not Available; ND = Not Determined

The only health hazard found for the component is skin irritation due to improper

handling. See Appendix B for Product MSDS sheet.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 45,000 gal.

Maximum = Varies with well design.

Transport Container(s): Steel bulk tanks provided by supplier or cargo tanks on boats.

Storage Methods: In bulk tanks on the drilling rig or on boats.
191

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

No spill model was run for calcium bromide.

Aquatic Toxicity Levels

The available literature for calcium bromide toxicity was reviewed and the results from

relevant studies are shown below.

Fish

Puntius conchonius (freshwater fish) LC50 (24-96 hr) = 2,791 mg/L. (4)

Benthos (Sediment)

Planorbarius corneus (freshwater snail) EC50 (6 week test) = 50% survival or cell

number reduction > 1,202 ppm; concentration reduced fecundity. (5)

Crangon crangon (brown shrimp, marine crustacean) LC50 (96-hr) > 1,000 ppm. (6)

Risk Characterization

Calcium bromide exists in water solution as calcium ions and bromide ions. Both calcium

ions and bromide ions are natural constituents of seawater. A toxicity level of 1,000 ppm

(1,000,000 ppb) 96-hr LC50 for one marine species was found for calcium bromide. The spill

model results for calcium bromide would be mathematically similar to the model results for zinc

bromide, as the model simply dilutes and disperses the ions and no degradation is assumed.

Using the results of the zinc bromide spill modeling and assuming a similar amount was spilled,

Table 38 can be used to approximate a potential impact for calcium bromide. As may be seen in

Table 38, 10,000 ppb is not exceeded over the area of a model grid cell. This concentration is

two orders of magnitude lower than the 96-hr LC50 concentration.

The chemical fate of calcium in seawater will also affect the potential for impact on the

marine environment. The nominal concentration of calcium in seawater is 400 mg/L(1). Dilution

alone would ultimately reduce the calcium concentration to this level. However the nominal

concentration of calcium in seawater is determined by reaction with carbonates. At the pH of

seawater, this equilibrium reaction acts to maintain the calcium ion concentration at 400 mg/L.

This means that there are two forces acting to dilute the calcium ion in seawater: dilution and

reaction. The solid precipitate formed by chemical reaction would initially become suspended

solids in the water column and eventually settle on to the sediment.

References

(1) CRC Handbook of Chemistry and Physics (1985-1986)

(2) Mallinckrodt Baker Inc. (1996b)

(3) M-I Drilling Fluids L.L.C. (1998a)

(4) Pant and Gill (1984)

(5) Mazuran et al. (1999)

(6) Hudgins and Petrotech Consultants, Inc. (1991)
192
193

Profile 9

AMMONIUM CHLORIDE (Single Component)

Summary

Ammonium chloride is a solid inorganic salt. It is used as a constituent of several

different types of completion, stimulation, and workover chemicals. Other ammonium

compounds are also used (i.e., ammonium hydroxide). If discharged to the marine environment,

it will ultimately be removed by biological activity. The major environmental concern associated

with this chemical is its potential aquatic toxicity.

Background Information

Fate in the Environment

When ammonium chloride dissolves in seawater, it immediately undergoes several

reactions, dissociating into ammonium and chloride ions. Chloride ions are a major natural

constituent of seawater. The ammonium ions further react with the hydroxide in seawater to form

the undissociated molecule ammonium hydroxide (NH4OH), the predominant ammonium

species in seawater. A small fraction of the ammonium hydroxide dissociates into ammonium

ions and hydroxide ions. Thus, the concentration of ammonium dissolved in seawater is the sum

of the ammonium hydroxide and the ammonium ion concentrations. Ammonium is very soluble

in seawater. It can decompose into ammonia gas and water and the ammonia gas can escape into

the atmosphere.

Fate in the Process System

Ammonium chloride is used in stimulation and workover work on wells, and will be lost

to the formation during this activity. When the well is returned to production, most of the

ammonium chloride will be returned as part of the produced stream, and becomes a component

of the produced water. The produced water is ultimately disposed of overboard into the seawater

or is injected under ground.

Other Components

None

CAS Number (Ammonium Chloride)

12125-02-9

Chemical Formula (Ammonium Chloride)

NH4Cl

Important Synonyms and Trade Names

Sal Ammoniac; Ammonium Muriate
194

Chemical and Physical Properties

Property Component (1) Product

Molecular Weight 53.49 Same as Component

Boiling Point 520o C Same as Component

Melting Point 338o C Same as Component

Specific Gravity 1.53 Same as Component

Solubility in Water 29.7g / 100g water @ 0o C Same as Component

Solubility in Organics Trace solubility in organic solvents Same as Component

Vapor Pressure 1.0 mm Hg @ 160o C Same as Component

Vapor Density (Air = 1) 1.9 Same as Component

Physical State (Phase) Solid (powder) @ standard conditions Same as Component

Chemical Reactivity in the

Environment

Reacts with hydroxide in seawater to

form undissociated ammonium

hydroxide

Same as Component

Health and Safety Properties and Effects

Property Component (1) Product

Autoignition Temperature NA Same as Component

Flash Point NA Same as Component

Upper Explosive Limit NA Same as Component

Lower Explosive Limit NA Same as Component

Air Toxicity 20 mg/m3 STEL (4) Same as Component

OSHA PEL NA (5) Same as Component

Notes: NA = Not Available

There is no identified danger for fire or explosion. Contact with skin, eyes, or respiratory

tract can cause irritation. Ingestion or inhalation of ammonium chloride can cause coughing,

difficulty in breathing, nausea, vomiting, or diarrhea.

Use and Handling Properties (assumed to be similar to Potassium Chloride)

Storage Volumes Offshore (deep water): Typical = varies with well depth.

Maximum = 11,000 lbs.

Transport Container(s): 50 lb. paper sacks on pallets.

Storage Methods: In sacks on pallets (usually in the offshore drilling rig’s mud room).
195

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

A spill of ammonium chloride was not modeled.

Aquatic Toxicity Levels

The toxicity information below is for ammonium chloride. The available literature for

ammonium chloride toxicity was reviewed and the results from relevant studies are shown

below. Freshwater toxicity values are reported as total ammonia and marine toxicity values are

reported as unionized ammonia. Unionized ammonia can be absorbed through gill tissues and is

more toxic to fish species. The relationship between unionized and total ammonia concentration

can be calculated empiricaly if the pH, temperature and salinity of the water is known. The

general relationship between unionized and total ammonia concentrations results in total

ammonia concentrations higher than unionized ammonia concentrations, therefore the use of

unionized ammonia toxicity data may result in a conservative risk estimate.

Fish

Pimephales promelas (fathead minnow - freshwater species) LC50 = 3.55 mg/L .(2)

Scophthalmus maximum (turbot - saltwater species) LC50 (4-6 weeks) = 2.6 mg/L.(3)

Sparus aurata (gilthead seabream - saltwater species) LC50 (4-6 weeks, 6-136 g fish) =

2.6 mg/L. (3)

Sparus aurata (gilthead seabream - saltwater species) LC50 (4-6 weeks, 0.4-3 g fish) =

2.6 mg/L. (3)

Salmo salar (Atlantic salmon - saltwater species) LC50 (4-6 weeks) = 0.24-0.34 mg/L. (3)

Risk Characterization

Although a spill of ammonium chloride was not modeled, it would be mathematically

similar to a spill of potassium chloride. A potassium chloride spill was modeled in Spill Scenario

3. Both chemicals are highly soluble. Potassium chloride is not volatile and degrades slowly,

whereas ammonium is volatile and biodegradable (as a nutrient for plants and bacteria). Thus,

the modeled dilution of potassium chloride over-estimates the concentrations that would result

from an ammonium chloride spill.

Unlike potassium ion, ammonium ion reacts with seawater components. Such reactions

distribute the ammonium between the chemical species ammonium ion (NH4+) and ammonium

hydroxide (NH4OH). The effect of this distribution is accounted for in toxicity testing because

the same distribution occurred in the test solutions.

Marine LC50 toxicity values range between 0.24 and 2.6 mg/L(approximately 0.24 ppm

to 2.6 ppm or 240 ppb to 2,600 ppb). Using these concentrations and the modeling results in

Table 42 it is apparent that, on average, a complete unit grid area of 5.5 million m2 would be

expected to exceed a concentration of 100 ppb, but the area exceeding 1,000 ppb would be less

than one grid cell. Thus, the toxic effect levels could be exceeded. The maximum concentration

under worst case environmental conditions would exceed 1,000 ppb over an area of 5.8 million

m2.
196

Table 43 shows the dose that water column organisms would be exposed to, calculated as

integrations of concentration over time. The toxicity test for the most sensitive species indicates

a 50% lethal concentration of 240 ppb for 4 to 6 weeks. Calculating the lethal dose that the test

species were exposed to one finds a dose of 240 x 4 x 7 x 24 = 161,280 ppb-hrs. From Table 43,

the area where this dose would be exceeded is approximately 3 million m2

. Given that

biodegradation and volatilization of ammonium are not accounted for in the potassium chloride

simulation results used for this analysis, potential impacts of ammonium chloride spills should be

evaluated in future research.

References

(1) Mallinckrodt Baker, Inc. (1999a)

(2) Versteeg and Shorter (1992)

(3) Person-Le Ruyet et al. (1997)

(4) American Conference of Governmental Industrial Hygienists (1994-1995)

(5) U.S. Department of Health and Human Services (1994)
197

Profile 10

SODIUM HYDROXIDE (Single Component)

Summary

Sodium hydroxide is a strong base used as a drilling fluid chemical. It is used to adjust

the pH of drilling fluids and cause clays to hydrate and thicken. It also acts to dissolve lignite

which is soluble in water only above pH 8. In this manner it aids in creating the viscosity

necessary for the mud to lift cuttings. High pH facilitates this process. If discharged into the

marine environment, it will initially affect the pH of the water. Eventually chemical reaction with

the natural buffering system will adjust the seawater to its original concentrations. The most

important potential impact of this chemical is associated with the health and safety of the

workers. Accidental discharge of amounts used offshore will not result in significant localized

impacts to the environment.

Background Information

Fate in the Environment

When spilled on the seawater surface, sodium hydroxide will dissolve into the water

column. Such mixing releases the heat of solution, which can heat and agitate the receiving

water. This release of energy helps to mix the sodium hydroxide into the seawater where

oceanographic and meteorological forces provide additional mixing energy to disperse it through

the water column. Immediately on mixing with seawater, the hydroxide reacts with the carbonate

equilibrium system, which acts to maintain the pH of the seawater. Since all the reaction

products are natural components of seawater, ultimately the seawater will return to its natural

state. The concentration of the various carbonate chemical species and the hydroxide ion

concentration are determined by the carbon dioxide concentration in the atmosphere. Exchanges

of carbon dioxide with the atmosphere act to convert the hydroxide ion component of the sodium

hydroxide into carbonate ion and water. The sodium component of sodium hydroxide becomes

part of the natural concentration of sodium ion in seawater.

Fate in the Process System

Sodium hydroxide is a component of drilling fluid, usually water-based fluids. It will

eventually exit the system as a waste in one of three ways: clinging to cuttings that are disposed

of; as excess drilling fluid that is disposed of; or at the completion of the well when all the

remaining drilling fluid is disposed of. Outside the territorial seas, waste drilling fluids are

discharged to the sea. Inside the territorial seas, waste drilling fluids are sent to landfills for

disposal.

Other Components

None

CAS Number (Sodium Hydroxide)

1310-73-2
198

Chemical Formula (Sodium Hydroxide)

NaOH

Important Synonyms and Trade Names

Caustic Soda; Lye

Chemical and Physical Properties

Property Component (1), (2), (3) Product

Molecular Weight 40 Same as Component

Boiling Point 2,130° C Same as Component

Melting Point 318.4° C Same as Component

Specific Gravity 2.13 Same as Component

Solubility in Water 42 g/100 ml @ 0° C Same as Component

Solubility in Organics Alcohol and glycol Same as Component

Vapor Pressure NA Same as Component

Vapor Density (Air = 1) NA Same as Component

Physical State (Phase) Solid Same as Component

Chemical Reactivity in the

Environment

Reacts with seawater buffering system Same as Component

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component Product (2), (3)

Autoignition Temperature Non combustible (7) Same as component

Flash Point Non combustible (7) Same as component

Upper Explosive Limit Non combustible (7) Same as component

Lower Explosive Limit Non combustible (7) Same as component

Air Toxicity TLV 2 mg/m3 Ceiling (8) NA

OSHA PEL 2 mg/m3 Ceiling (8) NA

Notes: NA = Not Available

Sodium hydroxide is a strong base that can cause eye and skin burns. Contact with the

product is severely irritating to the eyes, skin, and respiratory tract and may cause severe injury.

It is reactive with water, and contact with water or moisture may generate sufficient heat to ignite

combustible materials. (2)
199

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 100,000 lbs.

Maximum = 150,000 lbs.

Transport Container(s): 50 lb. paper sacks on pallets.

Storage Methods: In sacks on pallets (usually in drilling rig mud room).

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

A sodium hydroxide spill was modeled as spill scenario 2. The exposure concentrations

presented below are derived for the results of this modeling.

Results are shown in Figures 33 and 34 and Tables 40 to 41. The sodium hydroxide

begins as particulate, but dissolves so quickly the particulate concentration is not relevant. In the

dissolved concentration plots (Figures 33 and 34), the high concentrations near shore (not part of

the symmetric plume around the spill size) are an artifact of the compression of mass into a

shallow water column, as the current data from offshore aimed the modeled mass in the

shoreward direction. If detailed actual currents were available, shoreward transport would, by

physical laws, be balanced by offshore transport, and there would be no increase in concentration

towards shore.

As the molecular weight of NaOH is 40, and the concentration of hydroxide ion in

seawater is 2.5 X 10-8, 1,000 mg NaOH/m3 (~1 ppm) might be considered a threshold of

significance. The average exposed area with peak concentration above 1 ppm is 5.2 km2, with an

approximate volume of 590 million m3. This is a much more significant volume than expected

for the acid spill (because of the larger mass assumed spilled).

Aquatic Toxicity Levels

The available literature for sodium hydroxide was reviewed and the results from relevant

studies are shown below.

Algae and Invertebrates

Daphnia magna (water flea, freshwater crustacean): TLM (Threshold Limit Median) =15

ppm (4)

Mysidopsis bahia (mysid shrimp, marine crustacean): LC50 (96-hr SPP test) 163,000 -

1,000,000 ppm; concentrations ranged from 0-5 lbs. per barrel in EPA muds 2, 3, 5, 6, 7,

8 (5)

Fish

Lepomis macrochirus (bluegill, freshwater fish): LC50 (96-hr) = 32.3 ppm (6)
200

Risk Characterization

None of the toxicity data for sodium hydroxide are directly relevant to this study. The

only seawater toxicity study is for ion muds containing sodium hydroxide. This data is relevant

for mud discharges, but not for spills of sodium hydroxide, since in muds sodium hydroxide

reacts with other mud constituents. Assuming that sodium hydroxide is more toxic to freshwater

organisms, since marine species are used to higher pH values and seawater is buffered by the

carbonate system, using freshwater toxicity results in this study results in conservatively high

predicted impacts.

Fresh water toxicity ranges from 15 ppm to 32.3 ppm (15,000 ppb to 32,300 ppb). Using

these concentrations and the modeling results in Table 40, under average environmental

conditions, no complete unit grid cell area would be expected to exceed a concentration of 1,000

ppb, indicating that the impact would be localized around the spill site in most cases.

Under worst case environmental conditions; i.e., with minimal dispersion rates and

assuming no buffering, the maximum modeled concentration would exceed 10,000 ppb over an

area of 6.8 million m2

. Table 41 shows dose or integrations of concentration over time. The

lowest toxicity level was 15,000 ppb for 96 hours of exposure. The dose that the test species was

exposed to was 15,000 x 96 = 1,440,000 ppb-hrs. This dose level was not exceeded over a unit

grid cell area under any environmental conditions, including worst case. Comparison of Tables

40 and 41 shows that 109 m2

 exceeded 1,000 ppb under worst case conditions (Table 40) and this

same area could receive a dose of 1,000 ppb-hrs (Table 41). Thus, the average exposure time to

concentrations above 1,000 ppb was 1 hour (i.e., the maximum dose was 1,000 ppb-hrs).

Therefore, the dose to the environment from this spill was three orders of magnitude lower than

the dose required to produce the toxic effect.

References

(1) CRC Handbook of Chemistry and Physics (1985-1986)

(2) M-I Drilling Fluids L.L.C. (1998b)

(3) Baker Hughes Inteq (1994a)

(4) Hudgins and Petrotech Consultants, Inc. (1991)

(5) Jones et al. (1986)

(6) Bailey (1984)

(7) U.S. Department of Health and Human Services (1994)

(8) Mallinckrodt Baker Inc. (1998)
201

Table 40

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 2. Dissolved concentration

of sodium hydroxide in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 1,779,835,008 13,390,407,680 23,802 65,286

10 325,263,968 2,280,958,720 10,175 26,945

100 47,022,724 487,407,968 3,869 12,456

1,000 5,188,709 88,856,904 1,285 5,318

10,000 - 6,810,181 - 1,472

100,000 - - - -

1,000,000 - - - -

Table 41

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01-hours (0.01

ppb-hours): Scenario 2. Dissolved concentration of sodium hydroxide in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum

(m2)

% runs @ 0

1H-10H 0.01-0.1 8.39E+08 3.55E+08 1.71E+09 1.32E+08 0

10H-100H 0.1-1.0 3.95E+09 1.41E+09 7.74E+09 6.32E+08 0

100H-1,000H 1.0-10.0 1.11E+10 3.29E+09 2.65E+10 1.69E+09 0

1,000H-10,000H 10.0-100.0 9.59E+09 1.98E+09 1.56E+10 4.65E+09 0

10,000H-100,000H 100.0-1,000.0 2.81E+09 1.39E+09 9.05E+09 1.02E+09 0

> 100,000H > 1,000.0 3.26E+08 1.40E+08 1.14E+09 1.89E+08 0

> 1H > 0.01 2.86E+10 3.74E+09 4.15E+10 1.57E+10 0

> 10H > 0.1 2.77E+10 3.56E+09 4.06E+10 1.56E+10 0

> 100H > 1.0 2.38E+10 2.95E+09 3.60E+10 1.48E+10 0

> 1,000H > 10.0 1.27E+10 2.08E+09 1.79E+10 8.92E+09 0

> 10,000H > 100.0 3.13E+09 1.49E+09 1.02E+10 1.24E+09 0

> 100,000H > 1,000.0 3.26E+08 1.40E+08 1.14E+09 1.89E+08 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
202

Figure 33. Peak exposure concentration (ppb) of sodium hydroxide as dissolved in the water at

each location: mean case of all simulations (Scenario 2).

Figure 34. Peak exposure concentration (ppb) of sodium hydroxide dissolved in the water at

each location: worst case of all simulations (Scenario 2).
203

Profile 11

POTASSIUM CHLORIDE (Single Component)

Summary

Potassium chloride is a solid inorganic salt. It is used as a constituent in several different

types of completion, stimulation, and workover chemicals. It is a natural constituent of seawater

and, if discharged to the marine environment, it will ultimately dilute to seawater concentrations.

Potassium is an essential nutrient in low concentrations, (1) and its potential toxicity is low.

Background Information

Fate in the Environment

When spilled in seawater, potassium chloride will rapidly dissolve in seawater. In

solution, it dissociates into potassium and chloride ions. Both ions are normal constituents of

seawater, and oceanographic and meteorological forces will act to dilute them to normal

seawater concentrations. The magnitude of these forces determines how rapidly potassium

chloride spreads through the water column.

Because potassium ion is one of the three common nutrients for plants, some of it is

needed in the environment, but an excess can cause toxicity in some marine organisms. (1) For

example, if an excess exists after an accidental discharge, a short-term impact may occur.

Fate in the Process System

Potassium chloride is used in stimulation and workover work on wells, and it will be lost

to the formation during this process. When the well is returned to production status, most of the

potassium chloride will be recycled as part of the produced stream, thus becoming part of the

produced water. The produced water will ultimately be disposed of overboard into the marine

environment or injected under ground.

Other Components

None

CAS Number (Potassium Chloride)

7447-40-7

Chemical Formula (Potassium Chloride)

KCl (K+1, Cl-1 in water solution)

Important Synonyms and Trade Names

Muriate of Potash
204

Chemical and Physical Properties

Property Component (2) Product

Molecular Weight 74.55 Same as Component

Boiling Point 1,500o C (sublimes) Same as Component

Melting Point 770o C Same as Component

Specific Gravity 1.984 Same as Component

Solubility in Water 28.1 g / 100g water @ 0o C (3) Same as Component

Solubility in Organics Soluble in ether and glycol Same as Component

Vapor Pressure NA Same as Component

Vapor Density (Air = 1) NA Same as Component

Physical State (Phase) Solid (powder) @ STP Same as Component

Chemical Reactivity in the

Environment

Non-reactive Same as Component

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component (3) Product

Autoignition Temperature NA NA

Flash Point NA NA

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Airborne Exposure Limits (PEL) 15 mg/m3 total dust, 5 mg/m3

respirable fraction for nuisance dusts

Same as Component

Airborne Exposure Limits (ACIGH

TLV)

10 mg/m3 total dust containing no

asbestos and < 1% crystalline silica for

Particulates Not Otherwise Classified

Same as Component

Notes: NA = Not Available

High concentrations of dust may cause irritation to the eyes. Ingesting large quantities

can cause can cause vomiting and lead to weakness and circulatory problems. Contact of dust

with moist skin can cause irritation.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 11,000 lbs.

Maximum = varies with well depth and

perforated interval.

Transport Container(s): 50 lb. sacks on pallets

Storage Methods: In sacks on pallets (usually in the offshore drilling rig’s mud room)
205

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Potassium chloride was modeled as spill scenario 3. The exposure concentrations

presented below are derived from the results of this modeling.

Results are shown in Figures 35 to 36 and Tables 42 to 43. As for sodium hydroxide, the

potassium chloride begins as particulate, but dissolves so quickly the particulate concentration is

instantaneous. Thus, dissolved concentrations are of interest. The more likely directions for the

plume to move are along-shelf, as indicated by the east-west stretching of the concentration

plots. (This pattern is evident in the results for most scenarios.)

Aquatic Toxicity Levels

The available literature for potassium chloride toxicity was reviewed and the results from

relevant studies are shown below.

Algae and Invertebrates

Mysidopsis bahia (mysid shrimp, marine crustacean) (tested in drilling mud): LC50 (96-

hr SPP test) = 27,000 ppm (6)

Mysidopsis bahia (mysid shrimp, marine crustacean): Predicted LC50 (48-hr) Deficiency

= 115 mg/l; Excess = 790 mg/l (1) .

Fish

Puntius conchonius (freshwater fish): LC50 (24 - 96 hr.) = 368.5 mg/L; concentrations

resulted in elevated blood glucose, and decreased amino acid nitrogen, muscle water

content erythrocyte count, and hemoglobin (4)

Pimephales promelas (fathead minnow, freshwater fish): LOEC (7-day, survival) =

1,000 mg/L (5)

Pimephales promelas (fathead minnow, freshwater fish) NOEC (7-day, survival) = 500

mg/L (5)

Pimephales promelas (fathead minnow, freshwater) LOEC (7-day, growth) = 500 mg/L(5)

Risk Characterization

Most of the toxicity data found for potassium chloride is not directly relevant to this

study. One reference is to studies done in drilling mud, and all but one of the others are tests on

freshwater species. Pillard et al. (2000) gives relevant data for a marine species. Since potassium

is an essential nutrient for some marine species, his work determined both deficiency toxicity

and excess toxicity for potassium ion. The deficiency toxicity is not relevant here. The excess

toxicity reported is 790 mg/l (approximately 790 ppm or 790,000 ppb). Using this concentration

and the results report in Table 42 it is apparent that the lowest predicted exposure concentration

in any unit grid cell area would be at least three orders of magnitude lower than the toxic

concentration.
206

References

(1) Pillard (2000)

(2) CRC Handbook of Chemistry and Physics (1985-1986)

(3) Mallinckrodt Baker Inc. (1999b)

(4) Pant and Gill (1984)

(5) Pickering et al. (1996)

(6) Jones et al. (1986)
207

Table 42

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 3. Dissolved concentration

of potassium chloride in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 316,832,480 2,227,764,992 10,042 26,629

10 50,589,980 451,412,000 4,013 11,987

100 5,513,003 86,911,128 1,325 5,260

1,000 - 5,837,298 - 1,363

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 43

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 mg/m3-

hours (0.01 ppb-hours): Scenario 3. Dissolved concentration of potassium chloride in all

subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum

(m2)

Minimum

(m2)

% runs

@ 0

1H-10H 0.01-0.1 2.65E+08 2.51E+08 1.84E+09 7.91E+07 0

10H-100H 0.1-1.0 1.12E+09 9.81E+08 6.31E+09 3.64E+08 0

100H-1,000H 1.0-10.0 3.63E+09 1.58E+09 9.16E+09 1.76E+09 0

1,000H-10,000H 10.0-100.0 2.39E+09 8.49E+08 5.92E+09 9.33E+08 0

10,000H-100,000H 100.0-1,000.0 3.19E+08 1.38E+08 1.00E+09 1.18E+08 0

100,000H-10^6H 1,000-10,000 1.47E+07 3.07E+06 2.43E+07 7.62E+06 0

10^7H-10^8H 10,000-100,000 1.29E+07 4.18E+06 2.67E+07 5.44E+06 0

10^8H-10^9H 100,000-1,000,000 3.22E+06 1.30E+06 6.64E+06 7.92E+05 0

> 10^9H > 1,000,000 3.65E+05 8.42E+04 5.82E+05 1.51E+05 0

> 1H > 0.01 7.75E+09 2.58E+09 1.76E+10 4.90E+09 0

> 10H > 0.1 7.48E+09 2.42E+09 1.64E+10 4.75E+09 0

> 100H > 1.0 6.36E+09 1.74E+09 1.22E+10 4.20E+09 0

> 1,000H > 10.0 2.74E+09 9.27E+08 6.33E+09 1.14E+09 0

> 10,000H > 100.0 3.50E+08 1.40E+08 1.04E+09 1.51E+08 0

> 100,000H > 1,000.0 3.12E+07 6.44E+06 5.35E+07 1.65E+07 0

> 1,000,000H > 10,000 1.65E+07 5.56E+06 3.39E+07 6.38E+06 0

> 10,000,000H > 100,000 3.59E+06 1.38E+06 7.23E+06 9.43E+05 0

> 100,000,000H > 1,000,000 3.65E+05 8.42E+04 5.82E+05 1.51E+05 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
208

Figure 35. Peak exposure concentration (ppb) of potassium chloride dissolved in water at each

location: averaged over all simulations (Scenario 3).

Figure 36. Peak exposure concentration (ppb) of potassium chloride dissolved in the water at

each location: worst case of all simulations (Scenario 3).
209

Profile 12

AMIDES / IMIDAZOLINES (Component of Product B)

Summary

Product B is an oil-soluble mixture containing an amide/imidazoline, which comprises

less than 5% of Product B. Product B is a production-treating chemical used to control corrosion

in production gathering and treatment systems. If discharged to the marine environment, it will

ultimately be removed by biological degradation. A lack of aquatic toxicity data preclude

conclusions about the possible toxic impacts of amides/imidazolines.

Background Information

Fate in the Environment

Imidazolines are nitrogen containing organic compounds with a five-member ring

structure. Amides are organic compounds containing a carbon double bonded to an oxygen and

bonded to an -NH2 radical. These functional groups are frequently in the same molecule for

compounds used as corrosion inhibitors. They may be soluble in either water/alcohol mixtures or

in an organic solvent. When spilled in seawater, Product B solution will spread on the water

surface and the hydrocarbon solvent portion of the product will either evaporate or be dispersed

in the water column, separating from the amine compound. Once separated from the solvent, the

amine component will be dispersed in the water column as liquid droplets or will dissolve in the

water. Oceanographic and meteorological forces will disperse it through the water column and

the magnitude of these forces determines how rapidly amides/imidazolines spread through the

water column. Ultimately, the amide/imidazoline component will be removed from the

environment through biological degradation. Table 26 (Section 7.0) presents the available

degradation rates. The rates presented are instantaneous degradation rates. The half-life in days

can be calculated by the following formula: 0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Product B is used in produced streams and treatment vessels to protect against corrosion.

It will mix with the oil phase and be distributed throughout the system. It is designed to adsorb to

the internal surfaces of piping and vessels, react with active corrosion sites, and form a protective

layer. Residual amounts of it will disperse into the produced water, but the majority of it will

leave the system in the crude oil sales line. Therefore, produced waters will contain residual

concentrations of amide/imidazoline compounds, and the produced waters containing the

residual treating chemical may either be discharged to the marine environment or injected under

ground for disposal.

Other Components

Heavy Aromatic Naphtha, Isopropyl Alcohol, Ethoxylated Amine, Fatty Acid Dimers,

and Polyglycol

CAS Number (Amides/Imidazolines)

NA
210

Chemical Formula (Amides/Imidazolines)

This varies with the specific compound. The basic imidazoline structure is a fivemembered ring containing two nitrogen atoms that are attached to two of the bonds of a carbon

atom between them. One of the nitrogen atoms may also be bonded to a carbonyl group. The ring

also has an alkyl radical attached.

Important Synonyms and Trade Names

NA

Chemical and Physical Properties

Property Component Product (1)

Molecular Weight NA NA

Boiling Point NA ND

Melting Point NA ND

Specific Gravity NA 0.918 @ 60° F

Solubility in Water NA Insoluble

Solubility in Organics Soluble in alcohols and hydrocarbons Soluble in oil

Vapor Pressure NA 1.144 psia (Reid)

Vapor Density (Air = 1) NA > 1

Physical State (Phase) NA Dark brown liquid with

aromatic odor

Viscosity NA NA

Chemical Reactivity in the

Environment

None None

Notes: NA = Not Available; ND = Not Determined

H H

R C N CH2 C

O H NH2

Amide

R1

H

R CN

N CH

Imidazoline

R1

CH2
211

Health and Safety Properties and Effects

Property Component Product (1)

Autoignition Temperature NA NA

Flash Point NA 32o C

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity NA NA

OSHA PEL NA NA

Notes: NA = Not Available

No health hazards were found for the component; however, the formulation that carries

this material contains alcohols and aromatic solvents that have potential health and safety effects

to human health. See Appendix B for Product MSDS sheet.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 550 gal.

Maximum = 3,000 gal.

Transport Container(s): 55 gal. drums, 500 gal. HDPP plastic totes.

Storage Methods: In shipping containers or steel or plastic bulk tanks on the production

platform.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Amide/Imidazoline compounds in Product B were modeled as part of Scenario 15t. The

total concentrations of all ingredients in Product B, including amides/imidazolines and amines,

were modeled together. It is assumed that these materials behave similarly in the environment.

The amides/imidazolines portion is approximately 60% of the total concentration of amineamide/imidazoline ingredients, which in turn were assumed in the modeling as 30% of the total

product. The exposure concentrations presented below are derived from the results of model

scenario 15t (see Section 7.8) by applying a factor 0.18 to the resulting concentrations. See

discussion of spill modeling for Product B above.

The amides/imidazolines are highly surface active (as are the compounds in naphtha),

and would predominantly exist as particulates, either alone (as suspended droplets) or adsorbed

to suspended sediments. Because suspended sediment concentrations in the open Gulf of Mexico

are low, most of the mass remains as “droplets.” Thus, concentrations for amides/imidazolines

are shown in scenario 15t (droplets) in Tables 44 and 47.
212

Aquatic Toxicity Levels

The available literature for amide/imidazoline toxicity was reviewed. No data were found

except that presented for amides/imidazolines by Hudgins. (2)

Algae and Invertebrates

Unspecified crustacean: LC50 = 2.0 ppm (96-hr). (2)

Risk Characterization

Only one source of toxicity data was found for amides/imidazolines. A toxicity of 2.0

ppm (2,000 ppb) was reported. After adjusting the modeled concentrations for scenario 15t by a

factor of 0.18 (the fraction of the chemical that was amides/imidazolines) and comparing the

resulting concentrations to the reported toxicity value, it is apparent that less than one unit grid

cell area would contain exposure concentrations exceeding 180 ppb (listed as 1,000 ppb of total

Product B in Table 44), even under worst case environmental conditions. Table 47 shows dose or

integrations of concentration over time. The toxicity test found a 50% lethal concentration of

2,000 ppb for a 96-hr exposure. The 50% lethal dose was 2,000 x 96 = 192,000 ppb-hrs. This

dose is not exceeded over a grid cell area (Table 47).

References

(1) Supplier’s MSDS for Product B (See Appendix B)

(2) Hudgins and Petrotech Consultants, Inc. (1991)
213

Table 44

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 15t. Concentration of

amides/imidazolines in naphtha (modeled as naphthalene) as droplets in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 143,338,400 1,039,346,176 6,755 18,189

10 19,781,944 217,600,352 2,509 8,323

100 1,621,471 33,726,588 718 3,277

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 45

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 15t. Dissolved concentration

of amides/imidazolines in naphtha (modeled as naphthalene) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 2,918,648 145,932,704 964 6,816

10 - 5,513,003 - 1,325

100 - - - -

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 46

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 15t. Concentration of

amides/imidazolines in naphtha (modeled as naphthalene) adsorbed to suspended sediments in

all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 - 45,401,244 - 3,802

10 - 324,294 - 321

100 - - - -

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -
214

Table 47

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 15t. Particulate concentration of amides/imidazolines in

naphtha (modeled as naphthalene) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 6.58E+07 3.56E+07 1.96E+08 1.65E+07 0

10H-100H 0.1-1.0 4.48E+08 1.87E+08 1.04E+09 1.74E+08 0

100H-1,000H 1.0-10.0 1.03E+09 2.51E+08 1.77E+09 6.29E+08 0

1,000H-10,000H 10.0-100.0 5.23E+08 1.52E+08 1.03E+09 3.17E+08 0

10,000H-100,000H 100.0-1,000.0 8.50E+07 2.59E+07 2.11E+08 3.53E+07 0

100,000H-10^6H 1,000-10,000 9.33E+06 2.19E+06 1.56E+07 5.19E+06 0

10^7H-10^8H 10,000-100,000 1.12E+06 4.48E+05 1.84E+06 4.32E+05 0

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 2.16E+09 4.64E+08 3.55E+09 1.32E+09 0

> 10H > 0.1 2.09E+09 4.40E+08 3.36E+09 1.28E+09 0

> 100H > 1.0 1.65E+09 3.20E+08 2.51E+09 1.10E+09 0

> 1,000H > 10.0 6.18E+08 1.58E+08 1.13E+09 4.01E+08 0

> 10,000H > 100.0 9.55E+07 2.53E+07 2.20E+08 4.51E+07 0

> 100,000H > 1,000.0 1.05E+07 2.00E+06 1.65E+07 6.49E+06 0

> 1,000,000H > 10,000 1.12E+06 4.48E+05 1.84E+06 4.32E+05 0

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
215

Table 48

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 15t. Dissolved concentration of amides/imidazolines in

naphtha (modeled as naphthalene) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 3.96E+07 2.67E+07 1.26E+08 3.24E+05 0

10H-100H 0.1-1.0 2.85E+08 1.92E+08 1.08E+09 6.10E+07 0

100H-1,000H 1.0-10.0 7.32E+08 3.04E+08 1.61E+09 2.50E+08 0

1,000H-10,000H 10.0-100.0 1.92E+08 8.21E+07 4.61E+08 6.00E+07 0

10,000H-100,000H 100.0-1,000.0 7.36E+06 4.87E+06 2.85E+07 9.73E+05 0

100,000H-10^6H 1,000-10,000 2.57E+05 5.42E+05 3.89E+06 0 79

10^7H-10^8H 10,000-100,000 3.85E+04 2.07E+05 1.95E+06 0 97

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 1.26E+09 5.12E+08 2.99E+09 4.50E+08 0

> 10H > 0.1 1.22E+09 4.92E+08 2.90E+09 4.34E+08 0

> 100H > 1.0 9.32E+08 3.34E+08 2.03E+09 3.53E+08 0

> 1,000H > 10.0 2.00E+08 8.46E+07 4.72E+08 6.16E+07 0

> 10,000H > 100.0 7.65E+06 4.79E+06 2.85E+07 9.73E+05 0

> 100,000H > 1,000.0 2.95E+05 5.65E+05 3.89E+06 0 79

> 1,000,000H > 10,000 3.85E+04 2.07E+05 1.95E+06 0 97

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
216

Table 49

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 15t. Concentration of amides/imidazolines in naphtha

(modeled as naphthalene) adsorbed to suspended sediments in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 2.79E+06 1.61E+07 1.17E+08 0 93

10H-100H 0.1-1.0 1.96E+07 8.53E+07 5.19E+08 0 91

100H-1,000H 1.0-10.0 4.82E+07 1.84E+08 1.01E+09 0 50

1,000H-10,000H 10.0-100.0 5.93E+07 2.04E+08 1.36E+09 0 47

10,000H-100,000H 100.0-1,000.0 8.96E+07 1.58E+08 9.09E+08 0 47

100,000H-10^6H 1,000-10,000 7.53E+06 3.07E+07 2.13E+08 0 85

10^7H-10^8H 10,000-100,000 2.98E+07 1.06E+08 7.35E+08 0 85

10^8H-10^9H 100,000-1,000,000 5.60E+07 1.22E+08 8.27E+08 0 85

> 10^9H > 1,000,000 1.13E+09 1.14E+09 2.82E+09 0 85

> 1H > 0.01 1.44E+09 1.39E+09 4.25E+09 0 47

> 10H > 0.1 1.44E+09 1.38E+09 4.24E+09 0 47

> 100H > 1.0 1.42E+09 1.36E+09 4.14E+09 0 47

> 1,000H > 10.0 1.37E+09 1.33E+09 3.63E+09 0 47

> 10,000H > 100.0 1.31E+09 1.29E+09 3.17E+09 0 47

> 100,000H > 1,000.0 1.22E+09 1.22E+09 2.94E+09 0 85

> 1,000,000H > 10,000 1.21E+09 1.36E+09 4.38E+09 0 85

> 10,000,000H > 100,000 1.18E+09 1.26E+09 3.65E+09 0 85

> 100,000,000H > 1,000,000 1.13E+09 1.14E+09 2.82E+09 0 85

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
217

Figure 37. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets at each location: averaged over all simulations

(Scenario 15t).

Figure 38. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets in the water at each location: worst case of all

simulations (Scenario 15t).
218

Figure 39. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: averaged over all simulations

(Scenario 15t).

Figure 40. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: worst case of all simulations

(Scenario 15t).
219

Figure 41. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location:

averaged over all simulations (Scenario 15t).

Figure 42. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location: worst

case of all simulations (Scenario 15t).
220
221

Profile 13

AMINES AND AMINE SALTS (Component of Product B)

Summary

Product B is an oil-soluble mixture containing an amine, in this case an ethoxylated

amine. It is a production-treating chemical used to control corrosion in production gathering and

treatment systems. An ethoxylated amine, one of the major active ingredients, is profiled here.

The ethoxylated amine typically is less than 5% of the total product. If discharged to the marine

environment, it will ultimately be removed by biological degradation. There are few

environmental concerns associated with ethoxylated amines.

Background Information

Fate in the Environment

Amines and amine salts (the reaction product of an amine and an acid) are nitrogencontaining organic compounds, which are essentially ammonium compounds (NH4

+

) with one or

more of the hydrogens replaced by organic radicals. They may be soluble in either water/alcohol

mixtures or in an organic solvent. In Product B, the amine component contains an ethoxylated

radical (a radical also containing carbon-oxygen bonds). When spilled in seawater, Product B

solution will spread on the water surface and the hydrocarbon solvent portion of Product B (such

as naphtha and alcohols) will either evaporate or be dispersed in the water column. When the

solvent evaporates or dissolves the amine component will be dispersed in the water column as

liquid droplets, or will be dissolved. Oceanographic and meteorological forces will disperse it

through the water column and the magnitude of these forces determines how rapidly the amine

component will spread through the water column. Ultimately, the amine component will be

removed from the environment through biological degradation. Table 26 (Section 7.0) presents

the available degradation rates. The rates presented are instantaneous degradation rates. The halflife in days can be calculated by the following formula: 0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Product B is used in produced streams and treatment vessels to protect against corrosion.

It will mix with the oil phase and be distributed throughout the system. It is designed to adsorb to

the internal surfaces of piping and vessels, react with active corrosion sites, and form a protective

layer. Residual amounts will disperse into the produced water but the majority will leave the

system as part of the crude oil (i.e., commercially sold product). Therefore, produced waters will

contain residual concentrations of amine and amine salt compounds. Produced waters containing

the residual treating chemicals may either be discharged to the marine environment or injected

under ground for disposal.

Other Components

Heavy Aromatic Naphtha, Isopropyl Alcohol, Amides/Imidazolines, Fatty Acid Dimers,

and Polyglycol

CAS Number (Amines and Amine Salts)

Varies, one example (not a component of Product B) being diethylenetriamine 111-40-0
222

Chemical Formula (Amines)

CH3(CH2)11NH2

Important Synonyms and Trade Names

NA

Chemical and Physical Properties

Property Component Product (1)

Molecular Weight NA NA

Boiling Point NA ND

Melting Point NA ND

Specific Gravity NA 0.918 @ 60° F

Solubility in Water NA Insoluble

Solubility in Organics Soluble in alcohols and hydrocarbons Soluble in oil

Vapor Pressure NA 1.144 psia (Reid)

Vapor Density (Air = 1) NA > 1

Physical State (Phase) NA Dark brown liquid with

aromatic odor

Viscosity NA NA

Chemical Reactivity in the

Environment

None None

Notes: NA = Not Available; ND = Not Determined

Health and Safety Properties and Effects

Property Component Product (1)

Autoignition Temperature NA NA

Flash Point NA 32o C

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity NA NA

OSHA PEL NA NA

Notes: NA = Not Available

No health hazards were found for the component; however, the formulation that carries

this material contains alcohols and aromatic solvents that have potential health and safety effects

to human health. See Appendix B for Product MSDS sheet.
223

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 550 gal.

Maximum = 3,000 gal.

Transport Container(s): 55 gal. drums, 500 gal. HDPP plastic totes.

Storage Methods: In shipping containers or steel or plastic bulk tanks on the production

platform.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Amine compounds in Product B were modeled as part of spill scenario 15t. The amine

portion was approximately 5% of the total. The exposure concentrations presented below are

derived from the results of this modeling. The use of the total concentrations to represent the

concentrations of amines is a conservative approach. See discussion of spill modeling for

Product B above.

The amines are highly surface active, active (as are the compounds in naphtha), and would

predominantly exist as particulates, either alone (as suspended droplets) or adsorbed to suspended

sediments. Because suspended sediment concentrations in the open Gulf of Mexico are low, most

of the mass remains as “droplets.” Thus, concentrations for amines are shown in scenario 15t

(droplets) in Tables 50 and 53.

Aquatic Toxicity Levels

The available literature for amine toxicity was reviewed and the results from relevant

studies are shown below.

Algae and Invertebrates

Mysidopsis bahia (mysid shrimp, marine crustacean): LC50 (96 hr.) = 29,000 to 78,000

ppm (2)

Fish

Oncorhynchus mykiss (rainbow trout, freshwater fish): LC50 (96 hr.) 271 to 779 μg/L (3)

Pimephales promelus (fathead minnow, freshwater fish): LC50 (96hr.) = 0.07-47,000

mg/L (4)

Benthos

Mytilus edulis (blue mussel, marine bivalve mollusk) LC50 (96-hr.) < 250 mg/L (5)

Mytilus edulis (blue mussel, marine bivalve mollusk) NOEL = 100 mg/L (5)

Crassostrea gigas (Japanese oyster, marine bivalve mollusk) LC50 (96-hr.) < 250 mg/L(5)

Crassostrea gigas (Japanese oyster, marine bivalve mollusk) NOEL = 100 mg/L (5)
224

Risk Characterization

The lowest toxic concentration for marine species was found to be for benthic species

exposed to concentrations in water; 250 mg/l (approximately 250 ppm or 250,000 ppb) as 96-hr

LC50s for two species. Particulate (droplet) concentrations in the water (Table 50) did not

exceed 50 ppb and sediment concentrations did not exceed 100 ppb (total Product B) over any

unit grid cell area. These results show that the modeled concentrations are more than three orders

of magnitude lower than the lowest toxic concentration.

References

(1) Supplier’s MSDS for Product B (See Appendix B)

(2) Jones et al. (1986)

(3) Goodrich et al. (1991)

(4) Newsome et al. (1991)

(5) Knezovich and Crosby (1985)
225

Table 50

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 15t. Concentration of

amides/imidazolines in naphtha (modeled as naphthalene) as droplets in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 143,338,400 1,039,346,176 6,755 18,189

10 19,781,944 217,600,352 2,509 8,323

100 1,621,471 33,726,588 718 3,277

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 51

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 15t. Dissolved concentration

of amides/imidazolines in naphtha (modeled as naphthalene) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 2,918,648 145,932,704 964 6,816

10 - 5,513,003 - 1,325

100 - - - -

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 52

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 15t. Concentration of

amides/imidazolines in naphtha (modeled as naphthalene) adsorbed to suspended sediments in

all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 - 45,401,244 - 3,802

10 - 324,294 - 321

100 - - - -

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -
226

Table 53

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 15t. Particulate concentration of amides/imidazolines in

naphtha (modeled as naphthalene) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 6.58E+07 3.56E+07 1.96E+08 1.65E+07 0

10H-100H 0.1-1.0 4.48E+08 1.87E+08 1.04E+09 1.74E+08 0

100H-1,000H 1.0-10.0 1.03E+09 2.51E+08 1.77E+09 6.29E+08 0

1,000H-10,000H 10.0-100.0 5.23E+08 1.52E+08 1.03E+09 3.17E+08 0

10,000H-100,000H 100.0-1,000.0 8.50E+07 2.59E+07 2.11E+08 3.53E+07 0

100,000H-10^6H 1,000-10,000 9.33E+06 2.19E+06 1.56E+07 5.19E+06 0

10^7H-10^8H 10,000-100,000 1.12E+06 4.48E+05 1.84E+06 4.32E+05 0

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 2.16E+09 4.64E+08 3.55E+09 1.32E+09 0

> 10H > 0.1 2.09E+09 4.40E+08 3.36E+09 1.28E+09 0

> 100H > 1.0 1.65E+09 3.20E+08 2.51E+09 1.10E+09 0

> 1,000H > 10.0 6.18E+08 1.58E+08 1.13E+09 4.01E+08 0

> 10,000H > 100.0 9.55E+07 2.53E+07 2.20E+08 4.51E+07 0

> 100,000H > 1,000.0 1.05E+07 2.00E+06 1.65E+07 6.49E+06 0

> 1,000,000H > 10,000 1.12E+06 4.48E+05 1.84E+06 4.32E+05 0

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
227

Table 54

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 15t. Dissolved concentration of amides/imidazolines in

naphtha (modeled as naphthalene) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 3.96E+07 2.67E+07 1.26E+08 3.24E+05 0

10H-100H 0.1-1.0 2.85E+08 1.92E+08 1.08E+09 6.10E+07 0

100H-1,000H 1.0-10.0 7.32E+08 3.04E+08 1.61E+09 2.50E+08 0

1,000H-10,000H 10.0-100.0 1.92E+08 8.21E+07 4.61E+08 6.00E+07 0

10,000H-100,000H 100.0-1,000.0 7.36E+06 4.87E+06 2.85E+07 9.73E+05 0

100,000H-10^6H 1,000-10,000 2.57E+05 5.42E+05 3.89E+06 0 79

10^7H-10^8H 10,000-100,000 3.85E+04 2.07E+05 1.95E+06 0 97

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 1.26E+09 5.12E+08 2.99E+09 4.50E+08 0

> 10H > 0.1 1.22E+09 4.92E+08 2.90E+09 4.34E+08 0

> 100H > 1.0 9.32E+08 3.34E+08 2.03E+09 3.53E+08 0

> 1,000H > 10.0 2.00E+08 8.46E+07 4.72E+08 6.16E+07 0

> 10,000H > 100.0 7.65E+06 4.79E+06 2.85E+07 9.73E+05 0

> 100,000H > 1,000.0 2.95E+05 5.65E+05 3.89E+06 0 79

> 1,000,000H > 10,000 3.85E+04 2.07E+05 1.95E+06 0 97

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
228

Table 55

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 15t. Concentration of amides/imidazolines in naphtha

(modeled as naphthalene) adsorbed to suspended sediments in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 2.79E+06 1.61E+07 1.17E+08 0 93

10H-100H 0.1-1.0 1.96E+07 8.53E+07 5.19E+08 0 91

100H-1,000H 1.0-10.0 4.82E+07 1.84E+08 1.01E+09 0 50

1,000H-10,000H 10.0-100.0 5.93E+07 2.04E+08 1.36E+09 0 47

10,000H-100,000H 100.0-1,000.0 8.96E+07 1.58E+08 9.09E+08 0 47

100,000H-10^6H 1,000-10,000 7.53E+06 3.07E+07 2.13E+08 0 85

10^7H-10^8H 10,000-100,000 2.98E+07 1.06E+08 7.35E+08 0 85

10^8H-10^9H 100,000-1,000,000 5.60E+07 1.22E+08 8.27E+08 0 85

> 10^9H > 1,000,000 1.13E+09 1.14E+09 2.82E+09 0 85

> 1H > 0.01 1.44E+09 1.39E+09 4.25E+09 0 47

> 10H > 0.1 1.44E+09 1.38E+09 4.24E+09 0 47

> 100H > 1.0 1.42E+09 1.36E+09 4.14E+09 0 47

> 1,000H > 10.0 1.37E+09 1.33E+09 3.63E+09 0 47

> 10,000H > 100.0 1.31E+09 1.29E+09 3.17E+09 0 47

> 100,000H > 1,000.0 1.22E+09 1.22E+09 2.94E+09 0 85

> 1,000,000H > 10,000 1.21E+09 1.36E+09 4.38E+09 0 85

> 10,000,000H > 100,000 1.18E+09 1.26E+09 3.65E+09 0 85

> 100,000,000H > 1,000,000 1.13E+09 1.14E+09 2.82E+09 0 85

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
229

Figure 43. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets at each location: averaged over all simulations

(Scenario 15t).

Figure 44. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) as pure liquid droplets in the water at each location: worst case of all

simulations (Scenario 15t).
230

Figure 45. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: averaged over all simulations

(Scenario 15t).

Figure 46. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) dissolved in the water at each location: worst case of all simulations

(Scenario 15t).
231

Figure 47. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location:

averaged over all simulations (Scenario 15t).

Figure 48. Peak exposure concentration (ppb) of amides/imidazolines (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location: worst

case of all simulations (Scenario 15t).
232
233

Profile 14

LIGNITE (Single Component)

Summary

Lignite is a naturally occurring organic material used as a drilling fluid chemical. It is

used as a filtrate reducer, a temperature stability agent, and a dispersant. If discharged to the

marine environment, it will ultimately be removed by biological degradation.

Background Information

Fate in the Environment

Lignite is a naturally occurring organic material resulting from prehistoric decomposition

of plant material that also contains some clay and silica impurities. It is supplied as a very fine

powder material. If it is discharged into the marine environment in its pure form, it will disperse

into the water column. It is not water soluble at low pH values, but is soluble at up to 20-22% in

water depending on the source of the lignite at pH values above 8. Thus, the solubility is pH

dependent, with more lignite dissolving at higher pH values. Once lignite is diluted enough in

seawater, the normal seawater pH (i.e., normal range of 8 to 8.2) will dissolve it.

Fate in the Process System

Lignite is a component of water-based drilling fluids. Such fluids usually are formulated

with pH values of 10 or higher, so that the lignite goes into solution. As an offshore well is

drilled, drilling fluid is lost in one of three ways: (1) clinging to bits of formation (i.e., cuttings)

removed from the well which are then disposed of; (2) as excess drilling fluid that is disposed

during the drilling operation; or (3) when the well drilling has been completed, and all the

remaining drilling fluid is disposed of. Outside the territorial seas, waste drilling fluids are

discharged to the sea. Inside the territorial seas, waste drilling fluids are captured and sent ashore

for disposal (i.e., to landfills).

Other Components

None

CAS Number (Lignite)

1415-93-6

Chemical Formula (Lignite)

No proven structure. A complex mixture of partially unsaturated structures containing

oxygen and nitrogen functional groups.

Important Synonyms and Trade Names

Humic Acid
234

Chemical and Physical Properties

Property Component (1), (2) Product

Molecular Weight Unknown Same as Component

Boiling Point ND Same as Component

Melting Point ND Same as Component

Specific Gravity 1.6-1.8 @68° F Same as Component

Solubility in Water Insoluble Same as Component

Solubility in Organics NA Same as Component

Vapor Pressure NA Same as Component

Vapor Density (Air = 1) NA Same as Component

Physical State (Phase) Solid powder Same as Component

Chemical Reactivity in the

Environment

Biodegrades Same as Component

Notes: NA = Not Available; ND = Not Determined

Health and Safety Properties and Effects

Property Component Product

Autoignition Temperature ND (1) Same as Component

Flash Point 309o C (PM closed cup) (1) Same as Component

Upper Explosive Limit ND (1) Same as Component

Lower Explosive Limit ND (1) Same as Component

Air Toxicity 2 mg/m3 TWA (1) Same as Component

OSHA PEL NA Same as Component

Notes: NA = Not Available; ND = Not Determined

Health hazards for this chemical are related to the fact that it is a fine powder that can

cause irritation to the skin, eyes, and throat. Explosive dust and air mixtures are possible. See

Appendix B for MSDS sheet.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 100,000 lbs.

Maximum = 150,000 lbs.

Transport Container(s): 50 lb. paper sacks on pallets.

Storage Methods: In sacks on pallets (usually in drilling rig mud room).
235

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

A lignite spill was modeled as Scenario 8. The exposure concentrations presented below

are derived from the results of this modeling.

Results are shown in Figures 49 to 54 and Tables 56 to 61. Lignite is spilled as

particulate, and takes some time to dissolve. Thus, both particulate and dissolved concentrations

are of interest. Particulate also settles to the sediments, predominantly east and west of the spill

site (along-shelf direction).

The extension to the southwest of the main concentration area is caused by a single rare

event of southwest-directed current, which catches only a few Lagrangian particles representing

the spilled mass in the model.

Aquatic Toxicity Levels

The available literature for lignite toxicity was reviewed and the results from relevant

studies are shown below. The only literature found included data on lignite in a mud formulation,

where the toxicity of lignite was calculated from mud component, matrix studies. (3)

Algae and Invertebrates

Mysidopsis bahia (marine shrimp): LC50 (96-hr. SPP test) = 163,000 to 654,000 ppm of

processed lignite; concentrations of 3-10 lbs. per barrel in EPA mud 2,3,7,8. (3)

Mysidopsis bahia (marine shrimp): LC50 (96-hr SPP test) > 1,000,000 ppm causticized

lignite. (3)

Risk Characterization

The only toxicity data found for lignite was measured on lignite in drilling mud and thus

is not relevant to this study. In addition to its function as a drilling mud additive, lignite is used

as a soil improver for agricultural crops, where it has shown no toxicity for terrestrial plants.

Assuming the toxicity measured in mud is applicable, 163,000 ppm (163,000,000 ppb) is used to

estimate the potential impact of a lignite spill. Using this concentration and the results reported in

Tables 56, 57, and 58, it is apparent that the highest predicted exposure concentration in any unit

grid cell area to is at least three orders of magnitude lower than the toxic concentration.

References

(1) M-I Drilling Fluids L.L.C. (1998c)

(2) Baker Hughes Inteq (1994b)

(3) Jones et al. (1986)
236

Table 56

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 8. Particulate concentration

of lignite in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 442,331,936 3,293,261,312 11,866 32,377

10 110,260,440 622,636,096 5,924 14,078

100 21,727,708 144,635,552 2,630 6,785

1,000 3,567,237 20,430,532 1,066 2,550

10,000 324,294 2,270,060 321 850

100,000 - - - -

1,000,000 - - - -

Table 57

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 8. Dissolved concentration

of lignite in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 924,548,224 8,123,730,432 17,155 50,851

10 110,260,440 752,027,008 5,924 15,472

100 7,458,770 89,505,496 1,541 5,338

1,000 - 3,242,943 - 1,016

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 58

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 8. Mass loading of lignite

onto sediments in all subtidal habitats.

Threshold (g/m2) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 176,091,488 840,557,632 7,487 16,357

0.10 19,133,356 840,557,632 2,468 16,357

1.0 1,297,177 27,889,294 643 2,980

10 - 324,294 - 321

100 - - - -

1,000 - - - -

10,000 - - - -
237

Table 59

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 8. Particulate concentration of lignite in all subtidal habitats.

Exposure Range Dose

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 1.49E+07 9.66E+07 9.61E+08 0.00E+00 63

10H-100H 0.1-1.0 1.28E+08 8.20E+08 8.15E+09 0.00E+00 57

100H-1,000H 1.0-10.0 5.69E+08 1.25E+09 8.80E+09 1.46E+07 0

1,000H-10,000H 10.0-100.0 2.41E+09 2.52E+09 9.65E+09 1.57E+08 0

10,000H-100,000H 100.0-1,000.0 4.40E+09 2.97E+09 1.10E+10 8.72E+07 0

> 100,000H > 1,000.0 1.22E+09 1.91E+09 9.56E+09 3.21E+07 0

> 1H > 0.01 8.74E+09 3.86E+09 1.66E+10 1.89E+09 0

> 10H > 0.1 8.72E+09 3.85E+09 1.66E+10 1.89E+09 0

> 100H > 1.0 8.60E+09 3.81E+09 1.65E+10 1.88E+09 0

> 1,000H > 10.0 8.03E+09 3.72E+09 1.62E+10 1.43E+09 0

> 10,000H > 100.0 5.61E+09 3.81E+09 1.55E+10 1.50E+08 0

> 100,000H > 1,000.0 1.22E+09 1.91E+09 9.56E+09 3.21E+07 0

Table 60

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 8. Dissolved concentration of lignite in all subtidal habitats.

Exposure Range Dose (1)

ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 7.92E+08 2.35E+08 1.26E+09 1.07E+07 0

10H-100H 0.1-1.0 3.96E+09 1.05E+09 5.86E+09 7.77E+08 0

100H-1,000H 1.0-10.0 1.19E+10 2.44E+09 1.70E+10 1.29E+09 0

1,000H-10,000H 10.0-100.0 9.45E+09 2.28E+09 1.46E+10 1.42E+09 0

10,000H-100,000H 100.0-1,000.0 2.06E+09 1.50E+09 8.05E+09 2.25E+08 0

> 100,000H > 1,000.0 2.82E+08 9.66E+08 9.78E+09 1.65E+07 0

> 1H > 0.01 2.84E+10 3.33E+09 3.26E+10 3.74E+09 0

> 10H > 0.1 2.76E+10 3.24E+09 3.18E+10 3.73E+09 0

> 100H > 1.0 2.37E+10 3.00E+09 2.83E+10 2.95E+09 0

> 1,000H > 10.0 1.18E+10 3.27E+09 2.02E+10 1.66E+09 0

> 10,000H > 100.0 2.34E+09 1.88E+09 1.24E+10 2.44E+08 0

> 100,000H > 1,000.0 2.82E+08 9.66E+08 9.78E+09 1.65E+07 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
238

Table 61

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.0001 (g/m2)-

hours: Scenario 8. Mass loading of lignite onto sediments in all subtidal habitats.

Exposure Range Dose

(g/m2)-hrs)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

10H-100H 0.1-1.0 3.00E+07 1.69E+07 7.95E+07 8.11E+06 0

100H-1,000H 1.0-10.0 7.29E+06 4.64E+06 2.69E+07 6.49E+05 0

1,000H-10,000H 10.0-100.0 2.92E+05 3.04E+05 1.30E+06 0.00E+00 37

10,000H-100,000H 100.0-1,000.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

> 100,000H > 1,000.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

> 1H > 0.01 3.76E+07 2.02E+07 9.34E+07 1.07E+07 0

> 10H > 0.1 3.76E+07 2.02E+07 9.34E+07 1.07E+07 0

> 100H > 1.0 7.58E+06 4.65E+06 2.76E+07 6.49E+05 0

> 1,000H > 10.0 2.92E+05 3.04E+05 1.30E+06 0.00E+00 37

> 10,000H > 100.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

> 100,000H > 1,000.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100
239

Figure 49. Peak exposure concentration (ppb) of lignite as particulate in the water at each

location: averaged over all simulations (Scenario 8).

Figure 50. Peak exposure concentration (ppb) of lignite as particulate in the water at each

location: worst case of all simulations (Scenario 8).
240

Figure 51. Peak exposure concentration (ppb) of lignite dissolved in the water at each location:

averaged over all simulations (Scenario 8).

Figure 52. Peak exposure concentration (ppb) of lignite dissolved in the water at each location:

worst case of all simulations (Scenario 8).
241

Figure 53. Peak exposure mass per unit area (g/m2

) of lignite in the sediment averaged over all

simulations (Scenario 8).

Figure 54. Peak exposure mass per unit area (g/m2

) of lignite in the sediment at each location:

worst case of all simulations (Scenario 8).
242
243

Profile 15

METHANOL (Single Component)

Summary

Methanol is a single carbon alcohol, widely used as an industrial solvent. It is a

production-treating chemical used primarily to prevent gas hydrate formation in gas gathering

systems. If discharged to the marine environment, it will ultimately be removed by biological

degradation. The most important potential impacts of this chemical are the human safety issues

associated with its potential for fire and explosion offshore. Very high concentrations of

methanol are required to produce measurable aquatic toxicity.

Background Information

Fate in the Environment

Methanol is an organic liquid. It is miscible in seawater at all proportions. When spilled

on the seawater surface, methanol will rapidly mix into the water column where oceanographic

and meteorological forces provide the mixing energy to disperse it through the water column.

The magnitude of these forces determines how rapidly methanol spreads through the water

column. In the water column, methanol will ultimately be removed from the environment by

biological degradation. Table 26 (Section 7.0) presents the available degradation rates. The rates

presented are instantaneous degradation rates. The half-life in days can be calculated by the

following formula: 0.693/Degradation Rate = 1/2 life (days).

Methanol is also volatile and a portion of the spilled methanol would be lost to the

atmosphere, since methanol has a relatively high vapor pressure. Since alcohols are very soluble

in water, the portion lost to volatilization will be less than that dissolved in the water.

In the atmosphere, oxidation of the methanol will occur.

Fate in the Process System

Methanol in the production system equilibrates with the gas, oil, and water phases and

distributes between them. A large proportion of the methanol remains in the produced water and

will be disposed of with the produced water, usually into the sea.

Other Components

None

CAS Number (Methanol)

67-56-1

Chemical Formula (Methanol)

CH3OH

Important Synonyms and Trade Names

Methyl Alcohol; Wood Alcohol
244

Chemical and Physical Properties

Property Component Product

Molecular Weight 32.04 (2) Same as Component

Boiling Point 64.5° C (2) Same as Component

Melting Point -94° C (2) Same as Component

Specific Gravity 0.791 @ 20° C (2) Same as Component

Solubility in Water Miscible (2) Same as Component

Solubility in Organics Soluble in alcohol, other alcohol’s,

acetone, ether, benzene, and

chloroform

Same as Component

Vapor Pressure 96 mm Hg @ 20° C (2) Same as Component

Vapor Density (Air =1) 1.11 (1) Same as Component

Physical State (Phase) Liquid @ standard conditions (1) Same as Component

Chemical Reactivity in the

Environment

None Same as Component

Health and Safety Properties and Effects

Property Component (1) Product

Autoignition Temperature 725° F (385° C) Same as Component

Flash Point 12° C (closed cup) Same as Component

Upper Explosive Limit 36.0% Same as Component

Lower Explosive Limit 6.7% Same as Component

Air Toxicity 200 ppm Same as Component

OSHA PEL 200 ppm Same as Component

The most important health and safety concern offshore is the danger of fire and

explosion. However, this danger is no greater than that from the natural gas produced on the

platform (i.e., if normal safety precautions are observed). Vapor toxicity also presents a potential

health concern on offshore platforms. Although ingestion of methanol and large concentrations

in vapor are reported to cause serious health effects, including blindness and death, protective

measures used offshore limit exposure to these conditions. Chronic exposures to low levels of

methanol are not expected to have serious health effects.
245

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 7,500 gal.

Maximum = 100,600 gal.

(modeled in Scenario 9).

Transport Container(s): 550 gal. HDPP totes (typical).

Storage Methods: Shipping container or stationary bulk tank on offshore platform.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Methanol was modeled as Scenario 9. The exposure concentrations presented below are

derived from the results of this modeling.

Results are shown in Tables 62 to 67 and Figures 55 to 60. Methyl alcohol (methanol) is

buoyant in water, but also very soluble, and so dissolves quickly. Thus, droplets of methanol

(“particulate”) are short-lived in the water column, and surfaced methanol forms slicks for a very

brief time. The plots for these are, therefore, patchy and blocky in appearance, and

concentrations last only an hour or so. The dissolved concentration plume is much more

extensive, and of interest in terms of potential toxic effects. There is also some partitioning of the

methanol onto suspended sediments (adsorbed concentration).

Aquatic Toxicity Levels

The available literature for methanol toxicity was reviewed and the results from relevant

studies are shown below.

Algae and Invertebrates

Artemia salina (brine shrimp): LC50 (96-hr) = 10,000 mg/L (3)

Artemia salina (brine shrimp): LC50 (24-hr) = 10,000 mg/L; generated using most

sensitive stage of species (72 hr) (4)

Rhodomonas baltica (marine microalgae): EC50 (4-hr) = 100,000 mg/L; significantly

reduced survival at reported concentrations (5)

Tetraselmis chuii Butcher (marine microalgae): EC50 (4-hr) = 250,000 mg/L

significantly reduced survival at reported concentrations (5)

Isochrysis aff. galbana (strain T-ISO) Parke (marine microalgae): EC50 (4-hr) =

250,000 mg/L significantly reduced survival at reported concentrations (5)

Nannochloropsis gaditana Lubian (marine microalgae): EC50 (4-hr) = 200,000 mg/L

significantly reduced survival at reported concentrations (5)

Nannochloris atomus Butcher (marine microalgae): EC50 (4-hr) = 200,000 mg/L

significantly reduced survival at reported concentrations (5)

Chaetoceros gracilis Schutt (marine microalgae): EC50 (4-hr) = 200,000 mg/L

significantly reduced survival at reported concentrations (5)
246

Fish

Lepomis macrochiris (bluegill, freshwater fish): LC50 (96-hr) = 10,000 mg/L (6)

Salmo gairdneri (rainbow trout, freshwater fish): LC50 (96-hr) = 20,100 mg/L (6)

Pimephales promelas (fathead minnow, freshwater fish): LC50 (96-hr) = 28,100 mg/L (9)

Alburnas alburnas (bleak, freshwater fish): LC50 (96-hr) = 28,000 ppm (8)

Benthos

Mytilus edulis (blue mussel, marine bivalve mollusk): LC50 (96 hr) = 15,900 mg/L (7)

Mytilus edulis (blue mussel, marine bivalve mollusk): NOEC = 7,960 mg/L (7)

Nitroca spinipes (harpacticoid copepod, marine crustacean): LC50 (96 hr) = 12,539

mg/L (8)

Risk Characterization

Toxicity data on methanol were found for planktonic and benthic species. Data for fish

were for freshwater species. The lowest 96-hr LC50 toxicity level found for benthic species was

12,539 mg/l (approximately 12,539 ppm or 12,539,000 ppb) 96-hr LC50. Using a concentration

of 12,539,000 ppb and comparing it to the results in Table 64 it is apparent that the highest

predicted exposure concentration in any grid unit cell area would be approximately two orders of

magnitude lower than the toxic concentration.

References

(1) Air Products and Chemicals (1987)

(2) CRC Handbook of Chemistry and Physics (1986-1986)

(3) Price et al. (1974)

(4) Barahona-Gomariz et al. (1994)

(5) Canavate and Lubian (1994)

(6) Poirier et al. (1986)

(7) Helmstetter et al. (1996)

(8) Tarkpea and Svanberg (1982)

(9) Veith et al. (1983)
247

Table 62

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 9. Mass per unit area (g/m2)

of methyl alcohol as slicks in all subtidal habitats. Note that these slicks occur only

instantaneously after the spill, as dissolution would be immediate.

Threshold (g/ m2) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 27,565,000 35,348,068 2,962 3,354

0.10 11,674,594 35,348,068 1,928 3,354

1.0 3,891,531 26,267,824 1,113 2,892

10 - 10,053,124 - 1,789

100 - 1,945,766 - 787

1,000 - - - -

10,000 - - - -

Table 63

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 9. Concentration of methyl

alcohol slicks and pure liquid droplets in all subtidal habitats. Note that these concentrations

occur only instantaneously after the spill, as dissolution would be immediate.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 72,642,104 82,046,688 4,809 5,110

10 51,562,868 78,155,136 4,051 4,988

100 21,727,708 72,642,104 2,630 4,809

1,000 9,404,536 49,292,796 1,730 3,961

10,000 3,567,237 17,836,180 1,066 2,383

100,000 - 6,485,887 - 1,437

1,000,000 - - - -

Table 64

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 9. Dissolved concentration

of methyl alcohol in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 5,127,787,008 28,561,301,504 40,401 95,349

10 972,218,560 6,753,776,640 17,592 46,366

100 152,742,752 1,322,498,688 6,973 20,517

1,000 15,241,828 254,244,896 2,203 8,996

10,000 2,270,060 32,753,704 850 3,229

100,000 - 5,188,709 - 1,285

1,000,000 - - - -
248

Table 65

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 9. Concentration of methyl

alcohol adsorbed to suspended sediments in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 62,264,636 2,245,604,352 4,452 26,736

10 5,188,709 374,231,456 1,285 10,914

100 - 57,724,492 - 4,287

1,000 - 4,215,825 - 1,158

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 66

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 9. Dissolved concentration of methyl alcohol in all subtidal

habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 8.23E+08 3.69E+08 2.15E+09 1.09E+08 0

10H-100H 0.1-1.0 3.67E+09 1.36E+09 6.63E+09 5.53E+08 0

100H-1,000H 1.0-10.0 1.01E+10 3.22E+09 2.00E+10 1.28E+09 0

1,000H-10,000H 10.0-100.0 1.16E+10 2.68E+09 1.86E+10 2.85E+09 0

10,000H-100,000H 100.0-1,000.0 5.97E+09 2.23E+09 1.30E+10 2.12E+09 0

> 100,000H > 1,000.0 1.25E+09 5.90E+08 3.01E+09 3.85E+08 0

> 1H > 0.01 3.34E+10 5.44E+09 4.42E+10 1.54E+10 0

> 10H > 0.1 3.25E+10 5.25E+09 4.29E+10 1.52E+10 0

> 100H > 1.0 2.89E+10 4.46E+09 3.74E+10 1.47E+10 0

> 1,000H > 10.0 1.88E+10 3.25E+09 2.51E+10 1.16E+10 0

> 10,000H > 100.0 7.22E+09 2.58E+09 1.52E+10 2.70E+09 0

> 100,000H > 1,000.0 1.25E+09 5.90E+08 3.01E+09 3.85E+08 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
249

Table 67

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 9. Concentration of methyl alcohol adsorbed to suspended

sediments in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

10H-100H 0.1-1.0 7.13E+04 7.13E+05 7.13E+06 0.00E+00 99

100H-1,000H 1.0-10.0 2.50E+05 1.48E+06 1.17E+07 0.00E+00 96

1,000H-10,000H 10.0-100.0 3.42E+06 1.86E+07 1.28E+08 0.00E+00 96

10,000H-100,000H 100.0-1,000.0 1.63E+07 1.02E+08 8.46E+08 0.00E+00 96

> 100,000H > 1,000.0 1.15E+09 5.68E+09 2.96E+10 0.00E+00 96

> 1H > 0.01 1.17E+09 5.77E+09 2.99E+10 0.00E+00 96

> 10H > 0.1 1.17E+09 5.77E+09 2.99E+10 0.00E+00 96

> 100H > 1.0 1.17E+09 5.77E+09 2.99E+10 0.00E+00 96

> 1,000H > 10.0 1.17E+09 5.77E+09 2.98E+10 0.00E+00 96

> 10,000H > 100.0 1.17E+09 5.75E+09 2.98E+10 0.00E+00 96

> 100,000H > 1,000.0 1.15E+09 5.68E+09 2.96E+10 0.00E+00 96

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
250

Figure 55. Peak exposure mass per unit area (g/m2

) of methyl alcohol as slicks on the water

surface at each location: worst case of all simulations (Scenario 9).

Figure 56. Peak exposure concentration (ppb) of methyl alcohol as slicks and pure liquid

droplets in the water at each location: worst case of all simulations (Scenario 9).
251

Figure 57. Peak exposure concentration (ppb) of methyl alcohol dissolved in the water at each

location: averaged over all simulations (Scenario 9).

Figure 58. Peak exposure concentration (ppb) of methyl alcohol dissolved in the water at each

location: worst case of all simulations (Scenario 9).
252

Figure 59. Peak exposure concentration (ppb) of methyl alcohol adsorbed to suspended

sediment in the water at each location: averaged over all simulations (Scenario 9).

Figure 60. Peak exposure concentration (ppb) of methyl alcohol adsorbed to suspended

sediment in the water at each location: worst case of all simulations (Scenario 9).
253

Profile 16

ETHYLENE GLYCOL (Single Component)

Summary

Ethylene glycol is a di-alcohol, widely used as an industrial solvent. It is a productiontreating chemical used primarily to prevent gas hydrate formation in gas-gathering systems. If

discharged to the marine environment, it will disperse through the water column and ultimately

be removed by biological degradation.

Background Information

Fate in the Environment

Ethylene glycol is an organic liquid. It is miscible in seawater at all proportions. When

spilled on the seawater surface, ethylene glycol will rapidly mix into the water column where

oceanographic and meteorological forces provide the mixing energy to disperse it through the

water column. The magnitude of these forces determines how rapidly ethylene glycol spreads

through the water column. In the water column, ethylene glycol will ultimately be removed from

the environment by biological degradation. If released below the seawater surface (i.e., bottom

release), ethylene glycol will mix and disperse into the water column and the solution will be

transported down current. Table 26 (Section 7.0) presents the available degradation rates. The

rates presented are instantaneous degradation rates. The half-life in days can be calculated by the

following formula: 0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Ethylene glycol is added to production streams to prevent gas hydrate formation. Once in

the production system, it equilibrates with the gas, oil, and water phases and distributes between

them. While a proportion of the ethylene glycol normally remains in the produced water and may

be disposed of with the produced water, it is also often recovered, recycled and reused.

Other Components

None

CAS Number (Ethylene Glycol)

107-21-1

Chemical Formula (Ethylene Glycol)

Important Synonyms and Trade Names

Ethylene Alcohol; Glycol; 1,2-Ethanediol

H H

O CCOH

H H

H
254

Chemical and Physical Properties

Property Component (1) Product

Molecular Weight 62.07 Same as Component

Boiling Point 197.6o C Same as Component

Melting Point -13o C Same as Component

Specific Gravity 1.1 @ 20o C / 4o C Same as Component

Solubility in Water Miscible Same as Component

Solubility in Organics Soluble in alcohol, ether, and acetone

(4)

Same as Component

Vapor Pressure 0.06 @ 20o C Same as Component

Vapor Density (Air = 1) 2.14 Same as Component

Physical State (Phase) Liquid (clear) @ standard conditions (1) Same as Component

Viscosity NA Same as Component

Chemical Reactivity in the

Environment

None Same as Component

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component (1) Product

Autoignition Temperature 398o C Same as Component

Flash Point 111o C Same as Component

Upper Explosive Limit 15.3% by Volume Same as Component

Lower Explosive Limit 3.2% by Volume Same as Component

Air Toxicity 50 ppm Ceiling (vapor) Same as Component

OSHA PEL 50 ppm Ceiling Same as Component

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = Depends on facility

Maximum = 110,000 gal.

Transport Container(s): 550 gal. HDPP totes (typical) or steel bulk tanks.

Storage Methods: Shipping container or stationary bulk tank on offshore platform.
255

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Ethylene glycol was modeled as Scenario 10. The exposure concentrations presented

below are derived from the results of this modeling.

Results are shown in Figures 66 to 69 and Tables 63 to 66. Ethylene glycol is denser than

seawater and extremely soluble. Thus, there is a short-lived lens of ethylene glycol resting on the

sediment following the hypothetical bottom release (from the umbilical). It dissolves quickly and

disperses widely.

The extension to the southwest of the main concentration area is caused by a single rare

event of southwest-directed current (same phenomenon as in the lignite scenario), which catches

only a few Lagrangian particles representing the spilled mass in the model.

Aquatic Toxicity Levels

The available literature for ethylene glycol toxicity was reviewed and the results from

relevant studies are shown below.

Algae and Invertebrates

Ceriodaphnia dubia (water flea, freshwater crustacean): LC50 (48-hr) = 34,400 mg/L. (3)

Fish

Oncorhynchus mykiss (rainbow trout, freshwater fish): LC50 (96-hr) = 0.91 mol/L

(56,483 mg/L). (2)

Pimephales promelas (fathead minnow, freshwater fish): LC50 (96-hr) = 1.1 mol/L

(68,277 mg/L). (2)

Pimephales promelas (fathead minnow, freshwater fish): LC50 (96-hr) = 72,860 mg/L (3)

No toxicity data were found for ethylene glycol exposures to benthos in sediment.

Risk Characterization

No relevant marine toxicity data on ethylene glycol were found. The fresh water toxicity

data listed above were found. Freshwater toxicity values range from 34,400 mg/L (approximately

34,400 ppm or 34,400,000 ppb) to 72,860 mg/L (approximately 72,860 ppm or 72,860,000 ppb).

Assuming that it applies to marine waters the lowest toxicity concentration found was

34,400,000 ppb. Using this concentration and the results reported in Table 68 it is apparent that

the highest predicted exposure concentration in any unit grid cell area would be an order of

magnitude lower than the toxic concentration.
256

References

(1) Mallinckrodt Baker Inc. (1999c)

(2) Greene and Kocan (1997)

(3) Pillard (1995)

(4) CRC Chemical Handbook of Chemistry and Physics (1985-1986)
257

Table 68

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 10. Dissolved concentration

of ethylene glycol in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 5,381,878,272 35,399,925,760 41,390 106,152

10 874,607,872 4,477,650,432 16,685 37,753

100 149,175,584 909,306,688 6,891 17,013

1,000 23,673,472 169,281,440 2,745 7,341

10,000 3,567,237 20,430,532 1,066 2,550

100,000 324,294 1,945,766 321 787

1,000,000 - - - -

Table 69

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 10. Mass loading of

ethylene glycol onto sediments in all subtidal habitats.

Threshold (g/m2) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 3,242,943 3,242,943 1,016 1,016

0.10 2,918,648 3,242,943 964 1,016

1.0 1,621,471 3,242,943 718 1,016

10 324,294 1,945,766 321 787

100 - 1,297,177 - 643

1,000 - - - -

10,000 - - - -
258

Table 70

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 10. Dissolved concentration of ethylene glycol in all subtidal

habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 6.84E+08 2.13E+08 1.69E+09 0.00E+00 1

10H-100H 0.1-1.0 2.62E+09 8.24E+08 5.60E+09 1.07E+07 0

100H-1,000H 1.0-10.0 7.38E+09 2.13E+09 1.57E+10 5.45E+07 0

1,000H-10,000H 10.0-100.0 1.35E+10 2.45E+09 1.94E+10 1.07E+08 0

10,000H-100,000H 100.0-1,000.0 7.84E+09 2.17E+09 1.38E+10 1.77E+08 0

> 100,000H > 1,000.0 1.84E+09 1.72E+09 1.54E+10 3.20E+08 0

> 1H > 0.01 3.38E+10 4.18E+09 4.34E+10 7.11E+08 0

> 10H > 0.1 3.31E+10 4.04E+09 4.17E+10 7.11E+08 0

> 100H > 1.0 3.05E+10 3.53E+09 3.62E+10 7.00E+08 0

> 1,000H > 10.0 2.32E+10 2.89E+09 2.73E+10 6.46E+08 0

> 10,000H > 100.0 9.68E+09 2.99E+09 1.80E+10 5.38E+08 0

> 100,000H > 1,000.0 1.84E+09 1.72E+09 1.54E+10 3.20E+08 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.

Table 71

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.0001 (g/m2)-

hours: Scenario 10. Mass loading of ethylene glycol onto sediments in all subtidal habitats.

Exposure Range Dose

(g/m2)-hrs)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs @ 0

1H-10H 0.01-0.1 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

10H-100H 0.1-1.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

100H-1,000H 1.0-10.0 3.60E+05 2.76E+05 9.73E+05 0.00E+00 27

1,000H-10,000H 10.0-100.0 3.50E+05 2.75E+05 9.73E+05 0.00E+00 29

10,000H-100,000H 100.0-1,000.0 8.43E+04 1.57E+05 6.49E+05 0.00E+00 76

> 100,000H > 1,000.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

> 1H > 0.01 7.95E+05 3.95E+05 1.30E+06 0.00E+00 6

> 10H > 0.1 7.95E+05 3.95E+05 1.30E+06 0.00E+00 6

> 100H > 1.0 7.95E+05 3.95E+05 1.30E+06 0.00E+00 6

> 1,000H > 10.0 4.35E+05 3.10E+05 1.30E+06 0.00E+00 23

> 10,000H > 100.0 8.43E+04 1.57E+05 6.49E+05 0.00E+00 76

> 100,000H > 1,000.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100
259

Figure 61. Peak exposure concentration (ppb) of ethylene glycol dissolved in the water at each

location: averaged over all simulations (Scenario 10).

Figure 62. Peak exposure concentration (ppb) of ethylene glycol dissolved in the water at each

location: worst case of all simulations (Scenario 10).
260

Figure 63. Peak exposure mass per unit area (g/m2

) of ethylene glycol in the sediment at each

location: averaged over all simulations (Scenario 10).

Figure 64. Peak exposure mass per unit area (g/m2

) of ethylene glycol in the sediment at each

location: worst case of all simulations (Scenario 10).
261

Profile 17

TRIETHYLENE GLYCOL (Single Component)

Summary

Triethylene glycol is a complex alcohol consisting of three ethylene glycol units

condensed into a single molecule. It is a production-treating chemical used primarily to prevent

gas hydrate formation in gas-gathering systems. If discharged to the marine environment, it will

disperse through the water column and ultimately be removed by biological degradation.

Environmental concerns include potential aquatic toxicity.

Background Information

Fate in the Environment

Triethylene glycol is an organic liquid. It is miscible in seawater at all proportions. When

spilled on the seawater surface, triethylene glycol will rapidly mix into the water column where

oceanographic and meteorological forces provide the mixing energy to disperse it through the

water column. The magnitude of these forces determines how rapidly triethylene glycol spreads

through the water column. In the water column, triethylene glycol will ultimately be removed

from the environment by biological degradation. Table 26 (Section 7.0) presents the available

degradation rates. The rates presented are instantaneous degradation rates. The half-life in days

can be calculated by the following formula: 0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Triethylene glycol is added to production streams to prevent gas hydrate formation. Once

in the production system it equilibrates with the gas, oil and water phases and distributes between

them. While a proportion of the triethylene glycol normally remains in the produced water and

may be disposed of with the produced water, it is also often recovered, recycled and reused.

Other Components

None

CAS Number (Triethylene glycol)

112-27-6

Chemical Formula (Triethylene glycol)

Important Synonyms and Trade Names

TEG

HH HH HH

CCOCCOCCOH

HH HH HH

H O
262

Chemical and Physical Properties

Property Component (1) Product

Molecular Weight 150.20 Same as Component

Boiling Point 285o C Same as Component

Melting Point -5o C Same as Component

Specific Gravity 1.1274 @ 15o C / 4o C Same as Component

Solubility in Water Miscible Same as Component

Solubility in Organics Soluble in alcohol and benzene (2) Same as Component

Vapor Pressure < 0.01 @ 20o C Same as Component

Vapor Density (Air = 1) 5.17 Same as Component

Physical State (Phase) Liquid (colorless) @ standard

conditions

Same as Component

Viscosity NA Same as Component

Chemical Reactivity in the

Environment

None Same as Component

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component (1) Product

Autoignition Temperature 398o C Same as Component

Flash Point 111o C Same as Component

Upper Explosive Limit 15.3% by Volume Same as Component

Lower Explosive Limit 3.2% by Volume Same as Component

Air Toxicity 50 ppm Ceiling (vapor) Same as Component

OSHA PEL 50 ppm Ceiling Same as Component

Triethylene glycol is mildly irritating to the eyes and skin and has a low order of acute

oral toxicity for ingestion. However, small quantities of diethylene glycol byproduct are present

in triethylene glycol that may cause kidney or liver damage if ingested and could be fatal.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = Depends on facility.

Maximum = 110,000 gal.

Transport Container(s): 550 gal. HDPP totes (typical) or steel bulk tanks.

Storage Methods: Shipping container or stationary bulk tank on offshore platform.
263

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

A triethylene glycol spill was not modeled.

Aquatic Toxicity Levels

The available literature for triethylene glycol toxicity was reviewed and the results from

relevant studies are shown below.

Algae and Invertebrates

Daphnia magna (water flea, freshwater crustacean): LC50 (48-hr) = 35,000 μl/L. (2)

Daphnia magna (water flea, freshwater crustacean): LC50 (96-hr) = 10,000 ppm. (3)

Artemia salina (brine shrimp, marine crustacean): LC50 (96-hr) = 10,000 ppm. (3)

Fish

Carassius auratus (goldfish, freshwater fish): LC50 (96-hr) = 5,000 ppm. (3)

No toxicity data were located for triethylene glycol exposures to benthos in sediment.

Risk Characterization

Although no spill model was run for triethylene glycol, it is mathematically similar to

ethylene glycol, if it were spilled in similar amounts. One source of marine toxicity data on

triethylene glycol was found. The toxicity level was 10,000 ppm (10,000,000 ppb). Using this

concentration and the results reported in Table 68 from the ethylene glycol spill model, it is

apparent that the highest predicted exposure concentration in any unit grid cell area would be an

order of magnitude lower than the toxic concentration.

References

(1) Mallinckrodt Baker Inc. (1996c)

(2) Le Blanc and Suprenant (1983)

(3) Hudgins and Petrotech Consultants, Inc. (1991)
264
265

Profile 18

SODIUM BISULFITE (Component of OSW3055)

Summary

OSW3055 is a water solution containing sodium bisulfite. It is a production-treating

chemical used to remove oxygen from produced water and waterflood water. Sodium bisulfite,

as the active ingredient, is profiled here. If discharged to the marine environment, it will

ultimately be removed by chemical reaction with oxygen. Environmental concerns include the

potential for sodium bisulfite to cause oxygen depletion in the seawater.

Background Information

Fate in the Environment

When spilled in seawater, OSW3055 will mix immediately into the surface where

oceanographic and meteorological forces will provide the mixing energy to disperse it into the

water column. The magnitude of these forces will determine how rapidly bisulfite spreads

through the water column. Sodium bisulfite is very soluble in seawater and exists in water

solution as sodium and bisulfite ions. In the presence of heavy metals naturally occurring in

seawater, it reacts rapidly with oxygen to form sulfate and hydroxide ions, both major

components of seawater. One part per million oxygen will react with 5 parts per million sodium

bisulfite. The average peak concentrations resulting from a spill of OSW3055 will use up less

than 0.2 ppm of the 6 to 8 ppm oxygen in seawater.

Fate in the Process System

Sodium bisulfite is used in produced water streams and treatment vessels and will

partition to produced waters. Thus produced waters will contain residual concentrations of

sodium bisulfite. The produced waters containing the sodium bisulfite may either be discharged

to the marine environment or injected under ground.

Other Components

Water

CAS Number (Sodium Bisulfite)

7631-90-5

Chemical Formula (Sodium Bisulfite)

NaHSO3

Important Synonyms and Trade Names

Sodium Acid Sulfite; Sulfurous Acid, Monosodium Salt; Sodium Hydrogen Sulfite
266

Chemical and Physical Properties

Property Component (1) Product (2)

Molecular Weight 104 NA

Boiling Point NA ND

Melting Point 150o C NA

Specific Gravity 1.48 1.29 @ 60o F

Solubility in Water Very soluble in water Completely soluble

Solubility in Organics Insoluble Insoluble

Vapor Pressure No information found 17.5 mm Hg @ 70o F

Vapor Density (Air = 1) No information found > 1

Physical State (Phase) Solid (coarse white granules) @

standard conditions

Water solution

Viscosity NA ND

Chemical Reactivity in the

Environment

Reacts with oxygen in seawater to

form sulfate ion and hydroxide ion

See component

Notes: NA = Not Available; ND = Not Determined

Health and Safety Properties and Effects

Property Component (1) Product

Autoignition Temperature NA NA

Flash Point NA NA

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity TLV 5 mg/m3 TWA NA

OSHA PEL NA NA

Notes: NA = Not Available

The most important human health and safety concern offshore is exposure to sulfite dust

because of its potential air toxicity, and potential exposure to sulfur dioxide if the product is

overheated (i.e., as a result of a fire).

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 55 gal.

Maximum = 500 gal.

Transport Container(s): 5, 55, and 500 gal. totes (steel and/or HDPP).

Storage Methods: Shipping containers on offshore platform.
267

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Sodium bisulfite was modeled as Scenario 5. The exposure concentrations presented

below are derived for the results of this modeling.

Results are shown in Figures 65 and 66 and Tables 72 and 73. The sodium bisulfite spill

was modeled as sodium sulfite as a dissolved solution. On contacting seawater containing

oxygen, the bisulfite ion will react to form sulfate ion, a common constituent of seawater.

Dissociation and chemical changes in seawater would be complex, and modeling of this

chemistry was not attempted. The sodium sulfite was simply diluted over time. Thus, the

predicted concentrations are conservatively high.

Aquatic Toxicity Levels

None found

Risk Characterization

Although no toxicity test data could be found for sodium bisulfite, its chemical reactivity

ensures that it will not persist in the environment for longer than a few minutes, limiting its

potential toxicity. Table 72 shows that a 96-hr LC50 concentration for sodium bisulfite would

have to be lower than 0.1 ppm in order to cause more than a minimal impact.

Bisulfite ion is used to remove oxygen from water streams. Stoichiometrically, 1 ppm

oxygen will remove 5 ppm bisulfite. The oxygen content of seawater in the GOM ranges from 6

to 8 ppm (at the surface) and reaction with the bisulfite concentrations modeled will remove only

0.2 ppm of the available oxygen in seawater, thus will not significantly change the oxygen

concentration. At standard conditions, this reaction takes less than 15 minutes.

References

(1) Mallinckrodt Baker Inc. (1999d)

(2) Baker Petrolite and Baker Hughes Co. (1996)
268

Table 72

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 5. Dissolved concentration

of sodium bisulfite (modeled as sodium sulfite) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 72,966,400 661,874,944 4,819 14,515

10 8,431,654 122,583,688 1,638 6,247

100 324,294 14,593,240 321 2,155

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 73

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 mg/m3-

hours (0.01 ppb-hours): Scenario 5. Dissolved concentration of sodium bisulfite (modeled as

sodium sulfite) in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 5.25E+07 4.88E+07 4.53E+08 1.30E+06 0

10H-100H 0.1-1.0 3.25E+08 2.00E+08 1.07E+09 1.21E+08 0

100H-1,000H 1.0-10.0 9.99E+08 3.11E+08 2.86E+09 5.71E+08 0

1,000H-10,000H 10.0-100.0 4.55E+08 1.71E+08 1.16E+09 2.51E+08 0

10,000H-100,000H 100.0-1,000.0 4.83E+07 1.33E+07 1.04E+08 2.63E+07 0

> 100,000H > 1,000.0 4.78E+06 9.84E+05 7.46E+06 2.59E+06 0

> 1H > 0.01 1.88E+09 4.69E+08 4.25E+09 1.26E+09 0

> 10H > 0.1 1.83E+09 4.53E+08 4.19E+09 1.23E+09 0

> 100H > 1.0 1.51E+09 3.50E+08 3.43E+09 1.01E+09 0

> 1,000H > 10.0 5.08E+08 1.73E+08 1.21E+09 2.97E+08 0

> 10,000H > 100.0 5.30E+07 1.32E+07 1.08E+08 2.98E+07 0

> 100,000H > 1,000.0 4.78E+06 9.84E+05 7.46E+06 2.59E+06 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
269

Figure 65. Peak exposure concentration (ppb) of sodium bisulfite (modeled as sodium sulfite)

dissolved in the water at each location: averaged over all simulations (Scenario 5).

Figure 66. Peak exposure concentration (ppb) of sodium bisulfite (modeled as sodium sulfite)

dissolved in the water at each location: worst case of all simulations (Scenario 5).
270
271

Profile 19

BARITE (Single Component)

Summary

Barite is a naturally occurring inorganic salt material mined in various locations

throughout the world. It is used as a weighting agent to adjust the density of drilling fluids.

Barite is supplied as a fine powder and is insoluble in water. If discharged to the marine

environment, it will ultimately end up in the sediment where it is a natural constituent of many

marine sediments.

Background Information

Fate in the Environment

Due to its high density and insolubility in seawater, barite will initially disperse into the

water column and ultimately settle into marine sediment. Because of the product’s small particle

size, it will spread over a wide area.

Fate in the Process System

Barite is added to water-based drilling fluids in high concentrations by weight to give the

drilling fluids the necessary density. As a well is drilled, drilling fluid is lost in one of three

ways: (1) clinging to bits of the formation (i.e., cuttings) removed from the well, that are then

disposed of; (2) as excess drilling fluid that is disposed during the drilling operation; or (3) when

the well drilling has been completed, and all the remaining drilling fluid is to be disposed of.

Outside the territorial seas, waste drilling fluids are discharged to the sea. Inside the territorial

seas, waste drilling fluids are captured in waste tanks and sent ashore for disposal (i.e., to

landfills).

Other Components

None

CAS Number (Barite)

7727-43-7

Chemical Formula (Barite)

BaSO4

Important Synonyms and Trade Names

Barium Sulfate; Barium Salt of Sulfuric Acid; Baroid, Mil-Bar
272

Chemical and Physical Properties

Property Component (1) Product

Molecular Weight 233.39 Same as Component

Boiling Point 1,600o C Same as Component

Melting Point 1,580o C Same as Component

Specific Gravity 4.5 @ 15o C Same as Component

Solubility in Water Insoluble Same as Component

Solubility in Organics Insoluble (2) Same as Component

Vapor Pressure NA Same as Component

Vapor Density (Air = 1) NA Same as Component

Physical State (Phase) Solid Powder Same as Component

Chemical Reactivity in the

Environment

None Same as Component

Notes: NA = Not Available

Health and Safety Properties and Effects

Property Component Product (2)

Autoignition Temperature NA Same as Component

Flash Point NA (3) Same as Component

Upper Explosive Limit NA (3) Same as Component

Lower Explosive Limit NA (3) Same as Component

Air Toxicity TLV 10 mg/m3 total dust containing no

asbestos and < 1% crystalline silica (1)

Same as Component

OSHA PEL (8) 15 mg/m3 total dust, 5 mg/m3

respirable dust (1)

Same as Component

Notes: NA = Not Available

Health hazards for this chemical are related to the fact that it is a fine powder that can

cause mechanical irritation to the skin, eyes, and throat. See Appendix B for MSDS sheet.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 4,000 tons

Maximum = 8,000 tons

Transport Container(s): 100 lb. paper sacks on pallets or in bulk boat tanks and transfer

by blower to bulk tanks on the drilling rig.

Storage Methods: In sacks on pallets (usually in the drilling rig mud room) or in bulk

tanks on the drilling rig.
273

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

A barite spill was modeled as spill scenario 6 (shallow water) and 17 (deep water). The

exposure concentrations presented below are derived from the results of this modeling.

Results are shown in Figures 67 to 70, 81 and 82 and Tables 74 to 79. Barite is an

insoluble particulate, about 10 microns in diameter and with a very high density. Because of the

small particle size, the particulate sinks only very slowly and disperses widely, with a bias alongshelf (the more frequent current directions). However, settling does occur, again primarily in the

along-shelf direction, extending several hundred kilometers.

For scenario 17, a spill of barite in deep water (> 1,000 m), both single scenario and

stochastic modeling were performed. Because of the depth of the water column (> 1,000 m), the

plume does not mix vertically the entire distance to the bottom, as it does on the shelf. Thus,

single scenarios were examined to evaluate the movement of the plume both horizontally and

vertically over time.

Time series plots for an example spill on 1 January 1992 are in Figures 71 to 80. For this

example spill date, the plume moved directly westward. For other example runs on different

dates (not shown), the plume moved other directions, but underwent the same dispersion and

vertical movement.

Barite, because of its small particulate size, will sink very slowly and disperse widely.

This is evident in the plots of concentration over time after the spill. For example, after 1 week,

the barite plume of > 1 mg/m3 (~1ppb) has a radius of 50 km and is about 85 m thick, centered

about 100 m below the surface. After 2 weeks, the barite plume of > 1 mg/m3 (~1ppb) has a

radius of about 100 km and is about 70 m thick, centered about 200 m below the surface. The

direction and distance of horizontal movement is subject to the current field at the time of the

spill. The dispersion rate is common to all the spill dates modeled.

In the example case (Figures 71 to 80), the plume eventually intersects the sediment on

the continental slope at about 300 m depth. However, at that time (2 weeks after the spill), it is so

dispersed that the sediment loading is extremely low, and lower than the threshold used in this

analysis (for plotting).

Figures 81 to 82 and Tables 78 to 79 summarize the stochastic modeling results for spill

scenario 17. The figures show the peak exposure concentration of barite as particulate in the

water column and as a maximum in the vertical. Barite loading to the sediments is negligible as

mass per unit area, because it is well dispersed before it ultimately reaches the sediments.

Tables 78 and 79 were prepared as follows. For the particulate in the water column, water

volume exposed within ranges and above thresholds is tabulated. The peak exposure

concentration is averaged over the vertical thickness of the plume. The plume where

concentrations exceed about 1ppb does not extend over the entire water column, remaining about

100 m thick for a few weeks after the spill.
274

Scenario 17 may be considered a typical dispersion pattern for any non-reactive

chemical. The high density of barite causes it to sink, but the small particle size causes it to sink

slowly. More neutrally buoyant particulates and dissolved substances would not sink, but would

disperse at about the same rate as the barite plume.

Aquatic Toxicity Levels

The available literature for barite toxicity was reviewed and the results from relevant

studies are shown below.

Algae and Invertebrates

Mysidopsis bahia (marine shrimp): LC50 (96-hr) > 1,000,000 ppm (non-toxic); (5) this

value cannot be compared with other LC50 values, as it was determined through use of

concentrations of treated mud diluted with seawater.

Mysidopsis bahia (marine shrimp): LC50 (96-hr SPP test) > 1,000,000 ppm; (6)

concentrations ranged from 50 - 180 ppb in EPA muds 4, 5, and 6.

Cancer magister larvae (Dungeness crab, marine species): EC50 (96-hr) = 71.4 g/L; (4)

concentrations caused cessation of larval swimming.

Pandalus danae larvae (coon-stripe shrimp, marine species): EC50 (96-hr) = 16.2 g/L; (4)

concentrations caused cessation of larval swimming.

Benthos

Abra alba (marine mollusk): EC50 (5 days) = no toxicity; (4) no changes to fecal pellet

production at concentrations up to 100,000 mg/kg in clean sediments.

Branchiostoma caribaeum (marine chordate): LC50 (168-hr) = no toxicity ; (7) toxicity to

drilling muds found, but pure barite was non-toxic.

Risk Characterization

Toxicity data found for barite shows it to have very low toxicity. No conclusive LC50

values could be measured on barite. EC50 data was found on two marine species. The lowest

EC50 was 16.2 g/l (approximately 16,200 ppm or 16,200,00 ppb) 96-hr EC50. Using this

concentration and the results reported in Tables 74, 75, and 78, it is apparent that the highest

predicted exposure concentration in any unit grid cell area would be at least two orders of

magnitude lower than the toxic concentration. Both shallow water and deepwater spill models

were run.

References

(1) Mallinckrodt Baker Inc. (1996d)

(2) Baker Hughes Inteq (1994c)

(3) Carls and Rice (1984)

(4) Clark and Patrick (1987)

(5) Hudgins and Petrotech Consultants, Inc. (1991)

(6) Jones et al. (1986)

(7) Stromgren et al. (1993)

(8) U.S. Department of Health and Human Services (1994)
275

Table 74

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 6. Particulate concentration

of barite in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 46,451,613,696 104,086,855,680 121,598 182,022

10 10,299,490,304 65,495,502,848 57,258 144,388

100 1,449,644,672 11,351,220,224 21,481 60,110

1,000 281,160,800 2,013,692,800 9,460 25,318

10,000 45,076,948 464,059,232 3,788 12,154

100,000 6,161,592 72,642,104 1,400 4,809

1,000,000 - 6,161,592 - 1,400

10,000,000 - - - -

Table 75

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 6. Mass loading of barite

onto sediments in all subtidal habitats.

Threshold (g/m2) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 11,548,906,496 11,548,906,496 60,631 60,631

0.10 11,548,906,496 11,548,906,496 60,631 60,631

1.0 3,943,911,424 11,548,906,496 35,431 60,631

10 - 11,548,906,496 - 60,631

100 - 177,064,352 - 7,507

1,000 - - - -

10,000 - - - -
276

Table 76

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 6. Particulate concentration of barite in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 6.29E+08 2.43E+08 1.45E+09 1.44E+08 0

10H-100H 0.1-1.0 1.76E+09 5.58E+08 3.17E+09 4.97E+08 0

100H-1,000H 1.0-10.0 3.10E+09 9.66E+08 5.82E+09 9.81E+08 0

1,000H-10,000H 10.0-100.0 6.26E+09 2.82E+09 2.67E+10 1.51E+09 0

10,000H-100,000H 100.0-1,000.0 1.20E+10 2.93E+09 1.60E+10 3.77E+09 0

> 100,000H > 1,000.0 1.38E+10 5.03E+09 2.80E+10 7.52E+09 0

> 1H > 0.01 3.76E+10 3.88E+09 5.86E+10 2.28E+10 0

> 10H > 0.1 3.69E+10 3.74E+09 5.71E+10 2.26E+10 0

> 100H > 1.0 3.52E+10 3.49E+09 5.46E+10 2.17E+10 0

> 1,000H > 10.0 3.21E+10 3.14E+09 4.87E+10 2.01E+10 0

> 10,000H > 100.0 2.58E+10 3.20E+09 3.39E+10 1.74E+10 0

> 100,000H > 1,000.0 1.38E+10 5.03E+09 2.80E+10 7.52E+09 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.

Table 77

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 6. Particulate concentration of barite in all subtidal habitats.

Exposure Range Dose

(g/m2)-hrs

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

10H-100H 0.1-1.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

100H-1,000H 1.0-10.0 0.00E+00 0.00E+00 0.00E+00 0.00E+00 100

1,000H-10,000H 10.0-100.0 1.82E+08 1.10E+08 6.02E+08 0.00E+00 1

10,000H-100,000H 100.0-1,000.0 1.92E+08 1.34E+08 6.64E+08 0.00E+00 1

> 100,000H > 1,000.0 1.32E+07 1.59E+07 5.93E+07 0.00E+00 34

> 1H > 0.01 3.88E+08 2.30E+08 1.25E+09 0.00E+00 1

> 10H > 0.1 3.88E+08 2.30E+08 1.25E+09 0.00E+00 1

> 100H > 1.0 3.88E+08 2.30E+08 1.25E+09 0.00E+00 1

> 1,000H > 10.0 3.88E+08 2.30E+08 1.25E+09 0.00E+00 1

> 10,000H > 100.0 2.06E+08 1.36E+08 6.64E+08 0.00E+00 1

> 100,000H > 1,000.0 1.32E+07 1.59E+07 5.93E+07 0.00E+00 34
277

Table 78

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 17. Particulate concentration

of barite in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 32,118,591,488 107,615,076,352 101,112 185,081

10 6,800,575,488 42,051,883,008 46,526 115,696

100 1,039,645,376 7,408,780,800 18,191 48,562

1,000 173,813,664 1,141,768,448 7,438 19,064

10,000 32,078,576 221,930,880 3,195 8,405

100,000 5,237,320 43,535,196 1,291 3,723

1,000,000 - 3,927,990 - 1,118

10,000,000 - - - -

Table 79

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 17. Particulate concentration

of barite in all subtidal habitats.

Exposure Range Dose

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 1.0-10.0 1.14E+11 1.72E+10 1.67E+11 5.50E+10 0

10H-100H 10.0-100.0 6.93E+11 7.28E+10 8.19E+11 2.91E+11 0

100H-1,000H 100.0-1,000.0 1.46E+12 1.30E+11 1.87E+12 1.24E+12 0

1,000H-10,000H 1,000.0-10,000.0 5.51E+11 5.74E+10 7.88E+11 4.89E+11 0

10,000H-100,000H 10,000.0-100,000.0 2.20E+10 5.19E+09 3.18E+10 6.00E+09 0

> 100,000H > 100,000.0 2.28E+08 1.06E+08 4.88E+08 0.00E+00 9

> 1H > 1.0 2.84E+12 1.47E+11 3.44E+12 2.55E+12 0

> 10H > 10.0 2.72E+12 1.45E+11 3.28E+12 2.44E+12 0

> 100H > 100.0 2.03E+12 1.47E+11 2.52E+12 1.80E+12 0

> 1,000H > 1,000.0 5.73E+11 5.32E+10 8.00E+11 5.12E+11 0

> 10,000H > 10,000.0 2.22E+10 5.23E+09 3.18E+10 6.03E+09 0

> 100,000H > 100,000.0 2.28E+08 1.06E+08 4.88E+08 0.00E+00 9
278

Figure 67. Peak exposure concentration (ppb) of barite as particulate in the water at each

location: averaged over all simulations (Scenario 6).

Figure 68. Peak exposure concentration (ppb) of barite as particulate in the water at each

location: worst case of all simulations (Scenario 6).
279

Figure 69. Peak exposure mass per unit area (g/m2

) of barite in the sediment at each location:

averaged over all simulations (Scenario 6).

Figure 70. Peak exposure mass per unit area (g/m2

) of barite in the sediment at each location:

worst case of all simulations (Scenario 6).
280

Figure 71. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 12:00 hours on 1 January 1992: 12 hours after the spill.

Figure 72. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 2 January 1992: 24 hours after the spill.
281

Figure 73. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 3 January 1992: 2 days after the spill.

Figure 74. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 5 January 1992: 4 days after the spill.
282

Figure 75. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 7 January 1992: 6 days after the spill.

Figure 76. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 9 January 1992: 8 days after the spill.
283

Figure 77. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 11 January 1992: 10 days after the spill.

Figure 78. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 15 January 1992: 14 days after the spill.
284

Figure 79. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 21 January 1992: 20 days after the spill.

Figure 80. Particulate concentration of barite following a hypothetical surface release in the

offshore Gulf of Mexico at 00:00 hours on 29 January 1992: 28 days after the spill.
285

Figure 81. Peak exposure concentration (ppb) of barite as particulate in the water at each

location: averaged over all simulations (Scenario 17).

Figure 82. Peak exposure concentration (ppb) of barite as particulate in the water at each

location: worst case of all simulations (Scenario 17).
286
287

Profile 20

LIGNOSULFONATE (Single Component)

Summary

Lignosulfonate is an organic salt material used as a drilling fluid chemical as a thinner or

dispersant that adjusts the viscosity of the drilling fluid. It is made from nitrogen containing

waste from the pulp and paper industry where wood is processed to make paper. It contains

metal ions, usually chromium, and is supplied as a fine, water-soluble powder. If spilled in

seawater, it will initially disperse into the water column and dissolve. Ultimately, it will be

removed from the marine environment by biological action. An environmental concern

associated with lignosulfonates is their potential toxicity due mainly to added metal ions.

Background Information

Fate in the Environment

Lignosulfonate is supplied as a fine, water-soluble powder. It is soluble in seawater, and,

on being spilled, the lignosulfonate powder will disperse into the water column and dissolve.

Ultimately, it will be removed from the marine environment by biological action. Table 26

(Section 7.0) presents the available degradation rates. The rates presented are instantaneous

degradation rates. The half-life in days can be calculated by the following formula:

0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Lignosulfonate is a component of water-based drilling fluids, which circulate through the

drill string and bit and return to the mud pit. Eventually, drilling fluids become wastes. As a well

is drilled, drilling fluid is lost to the environment in one of three ways: (1) clinging to bits of the

formation removed from the well (cuttings) that are disposed of; (2) as excess drilling fluid that

is disposed during the drilling operation; or (3) when the well drilling has been completed, and

all the remaining drilling fluid is to be disposed. Outside the territorial seas, waste drilling fluids

are discharged directly to the marine environment. Inside the territorial seas, waste drilling fluids

are captured in cuttings boxes and are sent to landfills for disposal.

Other Components

None

CAS Number

7440-47-3 (Chromium (III) compounds)
288

Chemical Formula

Lignosulfonates are low molecular weight polymers of various combinations of the

monomers shown above which have been sulfonated. In the sulfonation process some of the

alcohol groups (-OH) have been replaced by sulfonate groups (-SO3

-1).

Important Synonyms and Trade Names

UNI-CAL, SPERSENE, Q-BROXIN

Chemical and Physical Properties

Property Component (1) Product

Molecular Weight NA Same as Component

Boiling Point NA Same as Component

Melting Point NA Same as Component

Specific Gravity 1.2 – 1.4 Same as Component

Solubility in Water Soluble Same as Component

Solubility in Organics Insoluble Same as Component

Vapor Pressure NA Same as Component

Vapor Density (Air = 1) NA Same as Component

Physical State (Phase) NA Same as Component

Chemical Reactivity in the

Environment

NA Same as Component

Notes: NA = Not Available

A

OH

CH

CH

CH2 OH

B

OH

CH

CH

CH2 OH

OCH3

C

OH

CH

CH

CH2 OH

CH3O OCH3

O

S O

O

C
289

Health and Safety Properties and Effects

Property Component (6) Product

Autoignition Temperature 450o C Same as Component

Flash Point 153.9o C Same as Component

Upper Explosive Limit ND Same as Component

Lower Explosive Limit ND Same as Component

Air Toxicity 0.5 mg/m3 TLV for Chromium (III)

compounds, respirable dust (1)

3 mg/m3 TLV for PNOC, respirable dust

(1)

Same as Component

OSHA PEL 0.5 mg/m3 TWA for Chromium (III)

compounds

5 mg/m3 TWA for PNOC

Same as Component

Notes: ND = Not Determined; PNOC = Particulates Not Otherwise Classified

Health hazards for this chemical are related to the fact that it is a fine powder that can

cause irritation to the skin, eyes, and throat. See Appendix B for MSDS sheet.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 70 tons

Maximum = 100 tons

Transport Container(s): 50 lb. paper sacks on pallets.

Storage Methods: In sacks on pallets (usually in the drilling rig mud room).

Environmental and Toxicological Properties and Effects

Spill Model Results

A lignosulfonate spill was modeled as Scenario 7. The exposure concentrations presented

below are derived for the results of this modeling.

Results are shown in Figures 83 to 85 and Tables 80 to 82. The DESCO/lignosulfonate

begins as particulate, but dissolves so quickly the particulate concentration is instantaneous.

Thus, dissolved concentrations are of interest. While DESCO and lignosulfonate are considered

surface active, their partitioning behavior to suspended sediments has not been quantified. Thus,

partitioning is assumed negligible in the model simulations. The dissolved concentrations may be

considered as total concentrations of both dissolved and adsorbed material.

In the concentration plot, the high concentrations near shore (not part of the symmetric

plume around the spill size) are an artifact of the compression of mass into a shallow water

column, as the current data from offshore aim the modeled mass in the shoreward direction. If

detailed actual currents were available, shoreward transport would, by physical laws, be balanced

by offshore transport, and there would be no increase in concentration towards shore.
290

Aquatic Toxicity Levels

The available literature for lignite toxicity was reviewed and the results from relevant

studies are shown below.

Algae and Invertebrates

Pandalus danae (coon-stripe shrimp, marine crustacean) larvae: LC50 (96 hr.) = 290

g/L. (2)

Mysidopsis bahia (mysid shrimp, marine crustacean): LC50 (96 hr.) = 506,000 ppm to >

1,000,000 ppm for chrome lignosulfonate muds with lignosulfonate concentrations of 3-

15 lbs. per barrel in EPA muds 7 and 8. (5)

Mysidopsis bahia (mysid shrimp, marine crustacean): LC50 (96 hr.) 388,000 ppm to >

1,000,000 ppm for chrome-free lignosulfonate with lignosulfonate concentrations of 4-

7.2 lbs. per barrel in EPA mud 7. (5)

Cancer magister (Dungeness crab, marine crustacean) larvae: LC50 (96 hr.) = 1.44 g/L(2)

Benthos

Crangon crangon (brown shrimp, marine crustacean) LC50 (96 hr.) = 3,300 ppm. (4)

Patria mineata (sea star, marine echinoderm) EC50 (48 hr.) = 5% WSF (Water Soluble

Fraction) in embryo development test. (3)

Risk Characterization

Three of the toxicity data sources found for lignosulfonate are directly relevant to this

study. The others are measured in tests on drilling muds. Toxicity values range from 290 mg/L

(approximately 290 ppm or 290,000 ppb) 96-hr LC50 to 3,300 ppm (3,300,000 ppb) 96-hr LC50.

Using 290,000 ppb and the results reported in Tables 80 and 81, it is apparent that the highest

predicted exposure concentration in any unit grid cell area would be at least two orders of

magnitude lower than the toxic concentration.

References

(1) Baker Hughes Inteq (1994d)

(2) Carls and Rice (1984)

(3) Chaffee and Spies (1982)

(4) Hudgins and Petrotech Consultants, Inc. (1991)

(5) Jones et al. (1986)

(6) M-I Drilling Fluids L.L.C. (1998d)
291

Table 80

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 7. Particulate concentration

of DESCO/ lignosulfonate in all subtidal habitats. Note that these concentrations occur only

within the first hour after the spill, as dissolution would be immediate.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 34,699,476 77,182,248 3,323 4,957

10 12,323,182 65,831,892 1,981 4,578

100 4,215,825 32,105,116 1,158 3,197

1,000 - 8,107,359 - 1,606

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 81

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 7. Dissolved concentration

of DESCO/lignosulfonate in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

1 3,262,447,872 25,457,807,360 32,225 90,019

10 582,424,384 4,450,750,464 13,616 37,639

100 91,451,272 964,435,648 5,395 17,521

1,000 11,026,006 169,281,440 1,873 7,341

10,000 324,294 17,187,592 321 2,339

100,000 - - - -

1,000,000 - - - -
292

Table 82

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 7. Dissolved concentration of DESCO/lignosulfonate in all

subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 9.02E+08 4.22E+08 2.17E+09 1.07E+08 0

10H-100H 0.1-1.0 3.89E+09 1.50E+09 8.42E+09 6.67E+08 0

100H-1,000H 1.0-10.0 1.02E+10 3.17E+09 1.76E+10 1.62E+09 0

1,000H-10,000H 10.0-100.0 1.27E+10 2.93E+09 2.70E+10 3.18E+09 0

10,000H-100,000H 100.0-1,000.0 5.88E+09 2.21E+09 1.16E+10 2.15E+09 0

> 100,000H > 1,000.0 8.13E+08 3.86E+08 2.19E+09 3.83E+08 0

> 1H > 0.01 3.44E+10 4.69E+09 4.58E+10 1.82E+10 0

> 10H > 0.1 3.35E+10 4.43E+09 4.41E+10 1.81E+10 0

> 100H > 1.0 2.96E+10 3.47E+09 4.01E+10 1.74E+10 0

> 1,000H > 10.0 1.94E+10 2.45E+09 2.97E+10 1.52E+10 0

> 10,000H > 100.0 6.69E+09 2.41E+09 1.30E+10 2.58E+09 0

> 100,000H > 1,000.0 8.13E+08 3.86E+08 2.19E+09 3.83E+08 0

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
293

Figure 83. Peak exposure concentration (ppb) of DESCO/ lignosulfonate as particulate in the

water at each location: worst case of all simulations (Scenario 7).

Figure 84. Peak exposure concentration (ppb) of DESCO/ lignosulfonate dissolved in the water

at each location: averaged over all simulations (Scenario 7).
294

Figure 85. Peak exposure concentration (ppb) of DESCO/ lignosulfonate dissolved in the water

at each location: worst case of all simulations (Scenario 7).
295

Profile 21

NAPHTHA, AROMATIC (Solvent for Oil Soluble Products)

Summary

Production-treating chemicals such as oil soluble corrosion inhibitors, emulsion breakers,

oil/gas antifoaming chemicals, and other products, use aromatic naphthas as solvents. Product C,

an oil soluble emulsion breaker, is one such product. The solvent portion of Product C, aromatic

naphtha, is profiled here. A major component of aromatic naphtha is naphthalene. In the spill

modeling of Product C, naphtha was assumed to have the properties of naphthalene for

calculating distribution in the environment only. The main environmental impact of naphtha is its

potential aquatic toxicity.

Background Information

Fate in the Environment

When spilled into the marine environment, Product C will spread on the surface of the

water and some of the naphtha will be lost to the atmosphere. When the release to the

environment is near the bottom (i.e., ocean floor), the product will rise rapidly to the surface and

then spread on the surface. Oceanographic and meteorological forces will disperse the product

into the water column as droplets, where some of it will partition to the water as soluble material.

Dispersed droplets of Product C, and its naphtha component, will adhere to suspended solids and

to sediment. Ultimately, naphtha will be lost to the atmosphere or biologically degraded. Table

26 (Section 7.0) presents the available degradation rates. The rates presented are instantaneous

degradation rates. The half-life in days can be calculated by the following formula:

0.693/Degradation Rate = 1/2 life (days).

Fate in the Process System

Product C is used as an emulsion breaker to aid in the separation of emulsified water and

solids from oil, so that the oil will meet sales specifications and the water can be removed for

disposal. When applied to the produced stream, Product C will dissolve into the oil phase. Most

of it will ultimately leave the treatment facility in the crude oil (i.e., commercially sold product).

Small amounts of the chemical will be dispersed in the produced water, entering the produced

water treatment system, and may be disposed of as a part of the produced water. In the Territorial

Seas and the Outer Continental Shelf, produced water is disposed of into the sea, however, in

other areas it is injected underground for disposal.

Other Components (Product)

Alkyl benzenesulfonic acid

CAS Number (Naphtha)

653 Aromatic Solvent (a standard solvent of this type) – 64742-94-5
296

Chemical Formula (Naphtha)

Common constituents of naptha include:

653 Aromatic Solvent - a mixture of C9 to C11 aromatic hydrocarbons, primarily C10.

Two constituents are naphthalene (C10H8) and 1,2,4-Trimethyl-Benzene

Important Synonyms and Trade Names

Heavy Aromatic Naphtha, HAN, Aromatic Solvent

Chemical and Physical Properties

Property Component (1) Product (2)

Molecular Weight 128.9 (naphthalene)

120.20 (trimethyl-benzene)

NA

Boiling Range 184-205o C ND

Melting Point NA NA

Specific Gravity 0.90 @ 15.6o C .93 (7.76 lbs./gal.)

Solubility in Water Insoluble Insoluble

Solubility in Organics Soluble in hydrocarbons Soluble in hydrocarbons

Vapor Pressure 0.5 mm Hg @ 20o C 2.0 psia @ 38o C

Vapor Density (Air = 1) 4.6 > 1

Physical State (Phase) Liquid Liquid

Viscosity 1.33 cst @ 25o C NA

Chemical Reactivity in the

Environment

None None

Notes: NA = Not Available; ND = Not Determined

R

R1

R2

R1

R2

Substituted benzene

where R is 0 - 5

or or R2 R1

Where R is 0 - 3

R1

R3 R2

R1

R2

R3

Where R is 1 - 2

R1

Where R is 0 - 3
297

Health and Safety Properties and Effects

Property Component (1) Product (2)

Autoignition Temperature 443o C ND

Flash Point 63o C (TCCC ASTM D 56) 20o C (TCC ASTM D 56)

Upper Explosive Limit NA NA

Lower Explosive Limit NA NA

Air Toxicity - TLV-STEL 100 ppm 250 ppm

OSHA PEL - TWA NE 200 ppm

Notes: NA = Not Available; ND = Not Determined; NE = Not Established

Health hazards found for the component include effects on eyes, skin, respiratory tract,

and gastrointestinal tract. Contact may cause permanent damage to the eyes. Inhalation of high

concentrations may cause headache and nausea. Skin contact can result in toxic effects similar to

those for inhalation. Ingestion may cause severe irritation or burns to the mouth and the

gastrointestinal tract. See Appendix B for Product MSDS sheet.

Use and Handling Properties

Storage Volumes Offshore (deep water): Typical = 550 gal.

Maximum = 700 gal.

Transport Container(s): 55 gal. drums, 500 gal. steel or HDPP totes.

Storage Methods: In shipping containers on the platform or in steel or plastic bulk tanks

on the platform.

Spill Modeling Results, Aquatic Toxicity, and Risk Characterization

Spill Model Results

Product C spill was modeled in spill scenario 16. The exposure concentrations presented

below are derived from the results of this modeling. For Scenario 16t, the modeling assumed that

all of Product C behaved physically as naphtha, using the physical-chemical properties of

naphthalene. Since Product C is actually composed of only 60% naphtha, the naphtha values

shown here are 60% of the results of Scenario 16t. See Section 7.0 for other modeling

assumptions.

Results of scenario 16t are shown in Figures 86 to 92 and Tables 83 to 90. The

alkylbenzene sulfonic acids are in a naphtha solution. If it is assumed that the active ingredients

are transported with and have the same fate as the naphtha, scenario 16t (modeled as

naphthalene) represents the concentrations of naphtha plus alkylbenzene sulfonic acids.
298

Scenario 16t (Figures 86 to 92 and Tables 83 to 90) shows the expected behavior of

naphtha, with portions as suspended droplets (particulate), dissolved, and adsorbed to suspended

sediments. Because the release is at the bottom, some of the naphtha solution is dispersed onto the

sediments around the spill site, primarily along-shelf (along bathymetric contours). Dilution is by

dispersion primarily, as there is little exposure to the atmosphere.

The naphtha represents 60% of the spilled mass and resulting concentrations in scenario

16t. Thus, consideration of the naphtha alone (scenario 16n) would be identical in pattern, with

concentrations 60% of that shown in the figures for scenario 16t. (Thus, scenario 16n was not run.)

Since scenario 16t was a bottom release, such that the naphtha would not evaporate or

volatilize appreciably, scenario 16t would be representative of the entire solution if the

alkylbenzene sulfonic acids have a similar (low) solubility to naphtha. If alkylbenzene sulfonic

acids are not at all soluble, the results of scenario 16a are more representative for that chemical.

However, in comparing the patterns of the two scenarios in the figures, dissolution of alkylbenzene

sulfonic acids does not change the results appreciably.

Aquatic Toxicity Levels

Algae and Invertebrates

No aquatic toxicity data were found for naphtha. Toxicity information found for naphthalene, a

major constituent in most naphtha formulations, was used in this evaluation. The information

found for naphthalene is listed below.

Plankton (Water Column)

Daphnia magna (water flea, freshwater crustacean): EC50 (48-hr) = 2,305 μg/L; endpoint was immobility of test organisms (3)

Eurytemora affinis (marine copepod crustacean): concentration of 10 μg/L resulted in

shortened lifespan and brood size (4)

Marine bacterioplankton: two to seven day growth test, 1 mg/L concentration resulted in

reduced growth (5)

Benthos

Neanthes arenaceodentata (marine polychaete): TLM (96-hr) = 3.8 ppm (6)

Elasmopus pectenicrus (marine amphipod): LC50 (96-hr) > 3.0 ppm (7)

Chironomus attenuatus (freshwater insect): LC50 (24-hr) = 13 mg/L (8)

Tanytarsus dissimilis (freshwater insect): LC50 (24-hr) = 13 mg/L (8)

Risk Characterization

No marine toxicity data were found for naphtha. Naphthalene is a major constituent of

naphtha and the properties of naphthalene were used to evaluate potential impact of naphtha.

Data on toxicity to marine species included 96-hr LC50 data and effects data. Concentrations as

low as 10 μg/L (approximately 10 ppb) were reported to cause shortened lifespan and reduced

brood size in Eurytemora affinis. A two to seven day test at 1 mg/L (approximately 1 ppm or

1,000 ppb) resulted in reduced growth in marine bacterioplankton. Toxicity to one marine

amphipod was 3 ppm (3,000 ppb) (96-hr LC50). Using 3,000 ppb and the results reported in

Table 84, it is apparent that the highest predicted exposure concentration in any unit grid cell

area would be at least two orders of magnitude lower than the toxic concentration.
299

References

(1) Exxon Company, U.S.A. (1999)

(2) Supplier’s MSDS for Product C (See Appendix B)

(3) Muñoz and Tarazona (1993)

(4) Ott et al. (1978)

(5) Hudack and Furhman (1988)

(6) Rossi and Neff (1978)

(7) Lee and Nicol (1978)

(8) Darville and Wilhm (1983)
300

Table 83

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 16t. Concentration of

alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) as droplets in all subtidal

habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 2,497,301,504 8,885,822,464 28,194 53,183

0.10 535,078,304 2,843,709,440 13,051 30,086

1.0 86,262,536 515,945,312 5,240 12,815

10 12,647,476 80,749,504 2,006 5,070

100 1,297,177 10,701,712 643 1,846

1,000 - 972,883 - 556

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 84

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 16t. Dissolved concentration

of alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 1,130,482,304 6,963,142,656 18,970 47,079

0.10 83,668,168 1,183,351,680 5,161 19,408

1.0 4,864,414 54,157,236 1,244 4,152

10 324,294 3,242,943 321 1,016

100 - - - -

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -
301

Table 85

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 16t. Concentration of

alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) adsorbed to suspended

sediments in all subtidal habitats.

Threshold (ppb) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 245,164,832 4,298,101,248 8,834 36,988

0.10 5,513,003 427,738,976 1,325 11,668

1.0 - 36,969,548 - 3,430

10 - 1,621,471 - 718

100 - - - -

1,000 - - - -

10,000 - - - -

100,000 - - - -

1,000,000 - - - -

Table 86

Areas (m2

) and distance (m) from the spill site exposed above the indicated threshold levels

under average and worst case environmental conditions: Scenario 16t. Mass loading of

alkylbenzene sulfonic acids in naphtha (modeled as naphthalene) onto sediments in all subtidal

habitats.

Threshold (g/m2) Average (m2) Worst Case (m2) Average Radius (m) Worst Case Radius (m)

0.01 - 608,043,136 - 13,912

0.10 - 1,621,471 - 718

1.0 - - - -

10 - - - -

100 - - - -

1,000 - - - -

10,000 - - - -
302

Table 87

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 16t. Concentration of alkylbenzene sulfonic acids in naphtha

(modeled as naphthalene) as droplets in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 7.79E+07 3.34E+07 2.14E+08 2.92E+07 0

10H-100H 0.1-1.0 4.72E+08 1.24E+08 9.20E+08 1.92E+08 0

100H-1,000H 1.0-10.0 9.36E+08 1.84E+08 1.51E+09 5.16E+08 0

1,000H-10,000H 10.0-100.0 4.64E+08 1.98E+08 1.14E+09 9.76E+07 0

10,000H-100,000H 100.0-1,000.0 7.51E+07 3.47E+07 2.29E+08 2.76E+07 0

100,000H-10^6H 1,000-10,000 6.46E+06 2.12E+06 2.35E+07 4.32E+06 0

10^7H-10^8H 10,000-100,000 9.20E+05 4.76E+05 3.24E+06 0 1

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 2.03E+09 3.98E+08 3.32E+09 1.12E+09 0

> 10H > 0.1 1.95E+09 3.87E+08 3.21E+09 1.08E+09 0

> 100H > 1.0 1.48E+09 3.48E+08 2.69E+09 8.36E+08 0

> 1,000H > 10.0 5.46E+08 2.29E+08 1.30E+09 1.36E+08 0

> 10,000H > 100.0 8.24E+07 3.57E+07 2.54E+08 3.41E+07 0

> 100,000H > 1,000.0 7.38E+06 1.94E+06 2.43E+07 5.19E+06 0

> 1,000,000H > 10,000 9.20E+05 4.76E+05 3.24E+06 0 1

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
303

Table 88

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 16t. Dissolved concentration of alkylbenzene sulfonic acids in

naphtha (modeled as naphthalene) in all subtidal habitats.

Exposure Range Dose

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 4.69E+07 2.94E+07 2.04E+08 5.84E+06 0

10H-100H 0.1-1.0 2.71E+08 1.26E+08 6.78E+08 7.75E+07 0

100H-1,000H 1.0-10.0 7.15E+08 2.70E+08 1.61E+09 1.54E+08 0

1,000H-10,000H 10.0-100.0 2.11E+08 1.63E+08 9.75E+08 3.63E+07 0

10,000H-100,000H 100.0-1,000.0 6.92E+06 6.35E+06 5.51E+07 1.30E+06 0

100,000H-10^6H 1,000-10,000 2.92E+05 3.52E+05 2.27E+06 0 64

10^7H-10^8H 10,000-100,000 1.56E+05 2.64E+05 1.51E+06 0 80

10^8H-10^9H 100,000-1,000,000 0 0 0 0 100

> 10^9H > 1,000,000 0 0 0 0 100

> 1H > 0.01 1.25E+09 5.09E+08 3.22E+09 3.72E+08 0

> 10H > 0.1 1.20E+09 4.93E+08 3.12E+09 3.50E+08 0

> 100H > 1.0 9.33E+08 4.17E+08 2.59E+09 1.96E+08 0

> 1,000H > 10.0 2.18E+08 1.66E+08 9.82E+08 4.22E+07 0

> 10,000H > 100.0 7.36E+06 6.35E+06 5.58E+07 1.30E+06 0

> 100,000H > 1,000.0 4.48E+05 4.29E+05 2.27E+06 0 31

> 1,000,000H > 10,000 1.56E+05 2.64E+05 1.51E+06 0 80

> 10,000,000H > 100,000 0 0 0 0 100

> 100,000,000H > 1,000,000 0 0 0 0 100
304

Table 89

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.01 (mg/m3)-

hours (0.01 ppb-hours): Scenario 16t. Concentration of alkylbenzene sulfonic acids in naphtha

(modeled as naphthalene) adsorbed to suspended sediments in all subtidal habitats.

Exposure Range Dose (1)

(ppb-hours)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 2.53E+06 1.58E+07 1.47E+08 0 93

10H-100H 0.1-1.0 1.51E+07 6.54E+07 5.18E+08 0 90

100H-1,000H 1.0-10.0 2.76E+07 1.04E+08 5.90E+08 0 60

1,000H-10,000H 10.0-100.0 3.98E+07 1.33E+08 8.12E+08 0 56

10,000H-100,000H 100.0-1,000.0 5.29E+07 1.19E+08 6.95E+08 0 56

100,000H-10^6H 1,000-10,000 3.41E+05 9.84E+05 4.75E+06 0 98

10^7H-10^8H 10,000-100,000 3.24E+06 4.52E+06 1.43E+07 0 90

10^8H-10^9H 100,000-1,000,000 1.47E+07 1.81E+07 6.18E+07 0 89

> 10^9H > 1,000,000 9.77E+08 1.15E+09 3.04E+09 0 89

> 1H > 0.01 1.13E+09 1.29E+09 3.25E+09 0 56

> 10H > 0.1 1.13E+09 1.29E+09 3.25E+09 0 56

> 100H > 1.0 1.12E+09 1.27E+09 3.25E+09 0 56

> 1,000H > 10.0 1.09E+09 1.25E+09 3.25E+09 0 56

> 10,000H > 100.0 1.05E+09 1.22E+09 3.24E+09 0 56

> 100,000H > 1,000.0 9.95E+08 1.17E+09 3.12E+09 0 56

> 1,000,000H > 10,000 9.95E+08 1.17E+09 3.12E+09 0 89

> 10,000,000H > 100,000 9.91E+08 1.17E+09 3.10E+09 0 89

> 100,000,000H > 1,000,000 9.77E+08 1.15E+09 3.04E+09 0 89

(1) Peak exposure plots are included for all forms of chemical where concentrations exceed 0.01 mg/m3 (~0.01 ppb)

or mass loading exceeds 0.0001 g/m2

 for at least one hour (the time step) following the spill. These extremely

low thresholds were used so that the entire fate of the chemical could be shown in the figures. The presence of

these low concentration contours do not imply toxicological impact.
305

Table 90

Areas (m2

) impacted at each dosage level of exposure above a threshold of H=0.0001 (g/m2)-

hours: Scenario 16t. Mass loading of alkylbenzene sulfonic acids in naphtha (modeled as

naphthalene) onto sediments in all subtidal habitats.

Exposure Range Dose

(g/m2)-hrs)

Mean (m2) Std. Dev. (m2) Maximum (m2) Minimum (m2) % runs

@ 0

1H-10H 0.01-0.1 1.59E+07 1.18E+07 5.35E+07 0 1

10H-100H 0.1-1.0 2.10E+06 3.24E+06 2.04E+07 0 33

100H-1,000H 1.0-10.0 0 0 0 0 100

1,000H-10,000H 10.0-100.0 0 0 0 0 100

10,000H-100,000H 100.0-1,000.0 0 0 0 0 100

> 100,000H > 1,000.0 0 0 0 0 100

> 1H > 0.01 1.80E+07 1.40E+07 6.19E+07 0 1

> 10H > 0.1 2.10E+06 3.24E+06 2.04E+07 0 33

> 100H > 1.0 0 0 0 0 100

> 1,000H > 10.0 0 0 0 0 100

> 10,000H > 100.0 0 0 0 0 100

> 100,000H > 1,000.0 0 0 0 0 100
306

Figure 86. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) as pure liquid droplets in the water at each location: averaged over all

simulations (Scenario 16t).

Figure 87. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) as pure liquid droplets in the water at each location: worst case of all

simulations (Scenario 16t).
307

Figure 88. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) dissolved in the water at each location: averaged over all simulations

(Scenario 16t).

Figure 89. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) dissolved in the water at each location: worst case of all simulations

(Scenario 16t).
308

Figure 90. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location: over

all simulations (Scenario 16t).

Figure 91. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) adsorbed to suspended sediment in the water at each location: worst

case of all simulations (Scenario 16t).
309

Figure 92. Peak exposure concentration (ppb) of alkylbenzene sulfonic acids (modeled as

naphthalene) in the sediment at each location: worst case of all simulations

(Scenario 16t).

Summary

Chemicals perform critical functions during drilling; cementing; well completion,

stimulation, and workover processes; and producing processes. In offshore operations, chemicals

fall naturally into four major classes: (1) drilling fluid chemicals, (2) cementing chemicals, (3)

completion, stimulation, and workover chemicals and (4) Production-treating chemicals.

The liquid and solid drilling fluid chemicals used in the highest quantity in the GOM are:

• Shale Control Inhibitors (liquid)– 1,210,000 gal. (shallow water); 763,000 gal. (deep water)

• Weighting Materials – 326,000,000 lbs. (shallow water); 372,000,000 lbs. (deep water)

• Shale Control Inhibitors (solid) – 6,660,000 lbs. (shallow water); 14,100,000 lbs. (deep

water)

The cementing chemicals used in the highest quantity in the GOM are:

• Basic Cements – 203,000,000 lbs. (shallow water); 18,500,000 lbs. (deep water)

• Silica – 14,100,000 lbs. (shallow water); 1,780,000 lbs. (deep water)

• Extenders/density-reducers – 3,890,000 lbs. (shallow water); 365,000 lbs. (deep water)
310

Except for the chemically inert substances such as sand and ceramic proppants the

completion, stimulation and workover chemicals used in the highest quantity in the GOM are the

following acids and brine solutions:

• Water-based Completion Fluids – 16,200,000 gal. (shallow water); 760,000 gal. (deep

water), specific chemical amounts were: 9,100,000 gal. of calcium chloride (shallow water);

425,600 gal. (deep water) and 4,700,000 gal. sodium chloride (shallow water); 218,000 gal.

(deep water)

• Hydrochloric Acid – 2,500,000 gal. solution containing 2,800,200 lbs. HCl (shallow water);

94,112 gal. solution containing 103,260 lbs. HCl (deep water)

• Ammonium Chloride Overflush – 2,300,000 gal. of 5% solution containing 988,500 lbs. of

ammonium chloride (shallow water); 87,400 gal. of solution containing 37,000 lbs. of

ammonium chloride (deep water)

The production-treating chemicals used in the highest quantity in the GOM are:

• Hydration Inhibition Chemicals (Methanol) – 200,000,000 gal. (total)

• Corrosion Inhibitor – 2,500,000 gal. (total)

• Hydration Inhibition Chemicals (Glycols) – 5,200,000 gal. (total)

As part of this study, the types and volumes of hazardous substances used, handled, and

stored in offshore E&P operations were identified. Hazardous chemicals were defined as those

substances listed in the U.S. Code of Federal Regulations (CFR) – Chapter 40, Protection of the

Environment, Part 116, that designates hazardous substances per the Clean Water Act. Only

eight hazardous substances were found to be stored in amounts exceeding reportable quantities;

sodium hydroxide, potassium hydroxide, zinc bromide, diethylamine, toluene, xylene, and

naphthalene.

Twenty-one chemicals were selected for detailed study based on volume estimates,

screening-level toxicity data and professional judgement. For each of the selected chemicals a

detailed chemical profile was developed to obtain a more definitive characterization of their use,

storage, and potential for environmental impact. In addition, spill scenarios were developed and

modeled for seventeen of the twenty-one profiled chemicals using Applied Science Associates’

(ASA) chemical spill model CHEMMAP.

As part of the risk characterization, the results of the modeling effort were integrated with

the toxicity data collected for the chemical profiles. The results of this analysis indicate a

potential for impact from a release of either zinc bromide or ammonium chloride. The modeled

impacts for zinc bromide were predicted based on a 45,000 gal. release to the environment, a

predicted maximum exposure concentration of greater than 1ppm for at least one hour in an area

of 11 million m2

 (11 km2, volume of 11 million m2 x 114 m deep = 1,254 million m3) around the

spill site and an acute 48-hr LC50 toxicity threshold for Ceriodaphnia dubia (freshwater

crustacean) of 0.5 mg/L. While a spill of ammonium chloride was not modeled, a review of the

chemical’s structure and properties indicate that it would behave similarly to potassium chloride.

Utilizing the modeled maximum predicted exposure concentrations of potassium chloride as a
313

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The Department of the Interior Mission

As the Nation's principal conservation agency, the Department of the Interior has responsibility for

most of our nationally owned public lands and natural resources. This includes fostering sound use of

our land and water resources; protecting our fish, wildlife, and biological diversity; preserving the

environmental and cultural values of our national parks and historical places; and providing for the

enjoyment of life through outdoor recreation. The Department assesses our energy and mineral

resources and works to ensure that their development is in the best interests of all our people by

encouraging stewardship and citizen participation in their care. The Department also has a major

responsibility for American Indian reservation communities and for people who live in island territories

under U.S. administration.

The Minerals Management Service Mission

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) primary

responsibilities are to manage the mineral resources located on the Nation's Outer Continental Shelf

(OCS), collect revenue from the Federal OCS and onshore Federal and Indian lands, and distribute

those revenues.

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program

administers the OCS competitive leasing program and oversees the safe and environmentally sound

exploration and production of our Nation's offshore natural gas, oil and other mineral resources. The

MMS Royalty Management Program meets its responsibilities by ensuring the efficient, timely and

accurate collection and disbursement of revenue from mineral leasing and production due to Indian

tribes and allottees, States and the U.S. Treasury.

The MMS strives to fulfill its responsibilities through the general guiding principles of: (1) being

responsive to the public's concerns and interests by maintaining a dialogue with all potentially affected

parties and (2) carrying out its programs with an emphasis on working to enhance the quality of life for

all Americans by lending MMS assistance and expertise to economic development and environmental

protection.