SINTEF REPORT

TITLE

Weathering properties of Endicott, Milne Point Unit, High Island

Composite, the Alpine Composite, the Neptune Field Composite,

and North Star oil samples

AUTHOR(S)

Frode Leirvik, Tina J. Schrader and Merete Øverli Moldestad

CLIENT(S)

SINTEF Applied Chemistry

Address: N-7465 Trondheim,

NORWAY

Location: Sem Sælands vei 2A

Telephone: +47 73 59 28 73

Fax: +47 73 59 69 95

Enterprise No.: NO 948 007 029 MVA

U.S. Department of the Interior Minerals Management Service

(MMS)

REPORT NO. CLASSIFICATION CLIENTS REF.

STF66 A02114 Unrestricted Richard Prentki

CLASS. THIS PAGE ISBN PROJECT NO. NO. OF PAGES/APPENDICES

Unrestricted 82-14-02696-2 661189.40 131

ELECTRONIC FILE CODE PROJECT MANAGER (NAME, SIGN.) CHECKED BY (NAME, SIGN.)

MMS-report 151002.doc Merete Øverli Moldestad Per S. Daling

FILE CODE DATE APPROVED BY (NAME, POSITION, SIGN.)

2002-11-07 Tore Aunaas, Research Director

ABSTRACT

Based on the findings from the Phase I review “Revision of MMS Offshore Continental Shelf OilWeathering Model: Evaluation,” OCS Study MMS 98-0031 for MMS, SINTEF Applied Chemistry has

continued with Phase II and III; the “Revision of the OCS Oil-Weathering Model”. The main objectives

of Phase II and III are:

to adapt the SINTEF Oil Weathering Model (OWM) to MMS needs,

to expand the OWM oil library to include oils of interest to MMS, and

to develop and collate data sets identified in Phase I from experimental oil spills for validation testing

of algorithms and OWM’s.

During Phase II and III SINTEF have performed weathering studies of total six crude oils supplied by

MMS. The results from these weathering studies have been added to the OWM library for use by MMS

in Environmental Impact Assessment studies and presented in this final report.

KEYWORDS ENGLISH NORWEGIAN

GROUP 1 Chemistry Kjemi

GROUP 2 Environmental Miljø

SELECTED BY AUTHOR Weathering Forvitring
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TABLE OF CONTENTS

1 Background ...........................................................................................................................5

2 The weathering predictions obtained from the SINTEF OWM........................................6

2.1 Fixed and variable parameters used in the SINTEF OWM..............................................6

2.1.1 Spill scenario .........................................................................................................6

2.1.2 Oil film thickness ..................................................................................................7

2.1.3 Sea temperature .....................................................................................................7

2.1.4 Wind speed ............................................................................................................8

2.2 Input data for the SINTEF OWM ....................................................................................8

2.3 Weathering properties related to response .......................................................................9

2.3.1 Mechanical response .............................................................................................9

2.3.2 Chemical dispersion ..............................................................................................9

2.4 How to use the prediction charts, an example................................................................10

2.5 Prediction charts for Alaskan oils ..................................................................................11

2.5.1 Prediction charts and summary of the Endicott crude oil’s weathering properties

at sea ....................................................................................................................12

2.5.2 Prediction charts and summary of the Alpine Composite oil’s weathering

properties at sea ...................................................................................................23

2.5.3 Summary of the Milne Point Unit Oil’s weathering properties at sea ................34

2.5.4 Prediction charts and summary of the North Star Oil’s weathering properties at

sea........................................................................................................................35

2.6 Prediction charts for Gulf of Mexico oils.......................................................................46

2.6.1 Prediction charts and summary of the Neptune Field Composite’s weathering

properties at sea ...................................................................................................47

2.6.2 Prediction charts and summary of the High Island Composite’s weathering

properties at sea ...................................................................................................56

Appendix A: The behavior of crude oils on the sea surface ....................................................66

A1 The chemical composition of crude oils...............................................................................67

A1.1 Hydrocarbons..........................................................................................................67

A1.2 Hetroatomic organics..............................................................................................68

A2 Physical properties of crude oils ..........................................................................................68

A2.1 Density....................................................................................................................68

A2.2 Viscosity .................................................................................................................68

A2.3 Pour point................................................................................................................70

A2.4 Distillation curve ....................................................................................................70

A2.5 Flash point ..............................................................................................................71

A3 The behavior of crude oil spilt at sea ...................................................................................72

A3.1 Evaporation.............................................................................................................73

A3.2 Spreading ................................................................................................................74

A3.3 Drift of an oil slick..................................................................................................74

A3.4 Water-in-oil (w/o) emulsion ...................................................................................75

A3.5 Oil-in-water (o/w) dispersion..................................................................................77

A3.6 Water solubility.......................................................................................................78

A3.7 Photo-oxidation.......................................................................................................78
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A3.8 Biodegradation........................................................................................................78

A3.9 Sedimentation .........................................................................................................78

A3.10 Submersion .............................................................................................................79

Appendix B: Experimental Design of the Bench-Scale and Meso-scale Laboratory Testing80

B1 Oil Samples .........................................................................................................................81

B1.1 Detailed information of the Endicott crude oil sample .................................................81

B1.2 Detailed information of the Milne Point Unit oil sample .............................................81

B1.3 Detailed information of the Alpine Central Production Facility oil sample (Alpine

Composite) .........................................................................................................................81

B1.4 Detailed information of the North Star oil sample........................................................81

B1.5 Detailed information of the Neptune Field Composite sample.....................................82

B1.6 Detailed information of the High Island Composite .....................................................82

B2 Test temperatures ..................................................................................................................82

B3 Bench-scale laboratory testing..............................................................................................83

B3.1 Evaporation ...................................................................................................................83

B3.2 Water-in-oil (w/o) emulsification..................................................................................83

B3.3 Physical and chemical analysis .....................................................................................84

B4 Meso-scale laboratory testing ...............................................................................................85

B4.1 Description of the meso-scale flume.............................................................................85

B4.2 Oil weathering in the meso-scale flume........................................................................86

B4.3 In-situ chemical dispersion............................................................................................86

Appendix C: Experimental results from the bench-scale and meso-scale laboratory testing87

C1 Bench-scale laboratory testing .............................................................................................88

C1.1 Chemical composition...................................................................................................88

C1.1.1 Gas chromatographic analysis ............................................................................88

C1.1.2 Asphaltene and wax content ...............................................................................96

C1.1.3 Classification of the oil samples.........................................................................96

C1.2 Physical properties ........................................................................................................96

C1.2.1 Evaporative loss..................................................................................................96

C1.2.2 Density................................................................................................................97

C1.2.3 Pour Point ...........................................................................................................98

C1.2.4 Viscosity .............................................................................................................99

C1.2.6 Interfacial tension .............................................................................................100

C1.3 W/o emulsion properties .............................................................................................102

C1.3.1 W/o-emulsion rate of formation .......................................................................102

C1.3.2 Stability of the w/o-emulsions and the effect of an emulsion breaker .............103

C1.3.3 Viscosity of the w/o-emulsions ........................................................................106
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C2 Meso-scale laboratory testing of the High Island Composite..........................................107

C2.1 Visual observations .....................................................................................................107

C2.2 Evaporation .................................................................................................................108

C2.3 W/o-emulsification......................................................................................................109

C2.2.1 Water uptake.....................................................................................................109

C2.3.2 Stability of the w/o-emulsions..........................................................................110

C2.3.3 Viscosity of the w/o-emulsion..........................................................................110

C2.4 In-situ chemical dispersion..........................................................................................111

C2.5 Mass balance ...............................................................................................................111

Appendix D: Input data for the SINTEF Oil Weathering Model.........................................116

D1 Endicott .......................................................................................................................117

D2 Alpine Composite ..........................................................................................................119

D3 North Star oil..................................................................................................................121

D4 The Neptune Field Composite .......................................................................................123

D5 High Island Composite ..................................................................................................125

Appendix E: List of abbreviations, symbols and acronyms ..................................................127

Appendix F: Literature list.......................................................................................................129
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1 Background

SINTEF Applied Chemistry completed the Phase I review “Revision of MMS Offshore

Continental Shelf Oil-Weathering Model: Evaluation,” OCS Study MMS 98-0031 for MMS in

1998. This review recommended:

• upgrading to an existing state-of-the-art Oil Weathering Model (OWM)

• additional improvements needed to maintain state-of-the-art and to meet needs of MMS users

• spill data sets that would be suitable for algorithm and model testing and validation.

Based on these findings, MMS initiated the ongoing Phase II and III “Revision of the OCS OilWeathering Model”. The main objectives of Phase II and III are:

- to obtain and adapt the SINTEF OWM to MMS needs,

- to expand the SINTEF OWM oil library to include oils of interest to MMS

In Environmental Impact Assessment (EIA) studies and when planning the most effective

response it is important to have reliable predictions of how specific oils properties will change

during a spill. The efficiency of various oil spill combat methods (e. g. mechanical, dispersion

and/or burning) depends greatly on the physico-chemical properties of the oil at the time of action.

In the literature, several approaches on how to predict oil properties have been established.

SINTEF has chosen a direct empirical approach and in addition to crude oil data (Crude Oil

Assay), the SINTEF OWM uses experimental weathering data obtained from both bench and

meso-scale laboratory weathering testing of the actual crude oil as input data. Experience and data

generated from full-scale field studies during the past 25 years has provided the basis for a

continuous evolution of the algorithms used in the model. In recent years comparisons of the

predictions obtained from the SINTEF OWM with field data have shown the strength in the

prediction quality (Fiocco et al., 1999 and Daling and Strøm, 1999).

SINTEF has performed weathering studies on the following six crude oils supplied by MMS:

Endicott, Neptune Oilfield, Alpine Oilfield, High Island Oilfield, Milne Point Unit, and North

Star. The Neptune Field and High Island oils are Gulf of Mexico oils, the rest are Alaskan oils.

The results of these weathering studies will be added to the OWM library for use by MMS in

Environmental Impact Assessment studies and are presented in this final report.
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2 The weathering predictions obtained from the SINTEF OWM

The SINTEF OWM relates oil properties to a chosen set of conditions (oil/emulsion film

thickness, sea state and sea temperature) and predicts the change of an oils properties and

behavior on the sea surface. The SINTEF OWM is schematically shown in Figure 2.1.

Predicted oil properties by time at 

chosen environmental conditions:

 Evaporative loss

 Density

 Viscosity

 Flash point

 Pour point

 Water content

 Viscosity of w/o-emulsion

 Natural dispersion

 Total oil mass-balance

 "Time window" for use of 

 dispersants 

SINTEF Oil 

Weathering 

Model

Environmental 

conditions

(Wind speed, sea temperature,

oil film thickness)

Laboratory data of fresh and

weathered oil samples:

 Distillation curve (TBP)

 Densities

 Viscosities

 Flash points

 Pour points

 Water uptake rates (t0.5-values)

 Maximum water uptake ability

 Viscosity ratios 

 (w/o-emulsion/parent oil)

 Viscosity limits for chemical 

 dispersion

Criteria used

in the model

ik41961100\tegner\fig-eng\model.eps

Figure 2.1: Schematic diagram of the input data to the SINTEF OWM and the predicted output oil

properties.

The predictions obtained from the SINTEF OWM are a useful tool in Environmental Impact

Assessment studies and for determining the most effective response. In this report the predictions

are presented over a time period of 15 minutes to 5 days after the oil spill has occurred. This

covers potential spill situations where the response time is short (e. g. close to terminals) to

offshore spills where the response time can be several days.

2.1 Fixed and variable parameters used in the SINTEF OWM

2.1.1 Spill scenario

The spill scenario (e. g. sub-sea or surface blowouts, tanker spills, pipeline leakage etc.) and

release rate chosen when using the SINTEF OWM is of importance. In this project a surface

release at a rate of 1,33 metric tons per minute (i.e. 80 tons over one hour) was chosen as the spill

scenario.
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2.1.2 Oil film thickness

In the SINTEF OWM the oils are categorised into condensates, low emulsifying crudes,

emulsifying crudes, heavy bunker fuels or refined distillates based on experimental results

obtained in the bench-scale testing. A default for the initial oil and terminal w/o-emulsion film

thickness is given for each category of oil in the model.

From the experimental results of the bench-scale testing (see Appendix C) Endicott, High Island

Composite, Alpine Composite and North Star are described as emulsifying crude oils whereas, the

Neptune Field Composite, which did not form stable w/o-emulsions, is described as a low

emulsifying crude oil.

The spill conditions, oil categories and initial and terminal film thickness’ are summarized in

Table 2.1.

Table 2.1: The spill criteria chosen for Endicott, the Alpine Composite and the Neptune Field

Composite crude oils in this project.

Oil Oil Category Initial film

thickness [mm]

Terminal film

thickness [mm]

Endicott Emulsifying crude

oil 20 1,0

Neptune Field

Composite

Low emulsifying

crude oil 20 0,5

Alpine

Composite

Emulsifying crude

oil 20 1,0

High Island

Composite

Emulsifying crude

oil 20 1,0

Milne Point

Unit

Emulsifying crude

oil 20 1,0

North Star Emulsifying crude

oil 20 1,0

2.1.3 Sea temperature

The prevailing weather conditions greatly influence the weathering rate of oil on the sea surface.

Two sets of predictions are given in this report, one at the average summer temperature the other

at the average winter temperature for the area of interest. The temperatures are chosen on

background of climate statistics for the two regions and are given in table 2.2.
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Table 2.2: The average summer and winter sea temperatures* used for Endicott, the Alpine

Composite, the Neptune Field Composite, the High Island composite, the Milne

Point Unit and the North Star crude oils in the SINTEF OWM.

Oil type

Region Summer

temperature

[°C]

Winter

temperature

[°C]

Endicott

Alpine Composite

Milne Point Unit

North Star

Alaska

10 0

Neptune Field Composite

High Island Composite

Gulf of

Mexico 29 20

*Information provided from the Live Access to Climate Data server at the NOAA/ Pacific Environmental Laboratory.

2.1.4 Wind speed

The relationship between the wind speed and the significant wave heights used in the prediction

charts obtained from the SINTEF OWM are shown in Table 2.3.

Table 2.3: The relationship between the wind speed and the significant wave heights used in the

SINTEF OWM.

Wind speed

[m/s]

Beaufort

wind Wind type Wave height[m]

Wave height

[ft]

2 2 Light breeze 0,1-0,3 0.2-0.60

5 3 Gentle to moderate breeze 0,5-0,8 1-1.5

10 5 Fresh breeze 1,5-2,5 3-5

15 6-7 Strong breeze 3-4 6-8

2.2 Input data for the SINTEF OWM

In the bench scale laboratory testing, a systematic stepwise procedure developed at SINTEF

(Daling et al., 1990) is used to isolate and map the various weathering processes that take place

when an oil is spilled on the sea surface. The experimental design for the bench scale studies is

described in Appendix B and the results are presented in Appendix C. The input data to the

SINTEF OWM is given in Appendix D.

The experimental weathering data obtained in the bench-scale testing are processed and used as

input for the SINTEF OWM. The following oil/emulsion properties obtained in the bench-scale

testing are used in the model:

• specific gravity

• pour point

• flash point

• viscosities of fresh and water-free residues (150°C+, 200°C+ and 250°C+)

• viscosities of the 50% and 75 % w/o-emulsions

• water uptake (maximum water content, stability and half-life-time)
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The SINTEF OWM is described in more detail in Johansen, 1991 and in the users guide for the

model.

2.3 Weathering properties related to response

The efficiency of various oil spill combat methods (e. g. mechanical recovery, dispersion and/or

burning) depends greatly on the physical and chemical properties of the oil at the time of action.

When planning the most effective response the predictions charts provide important information.

2.3.1 Mechanical response

Past experiences from Norwegian field trials have shown that the effectiveness of many

mechanical clean up operations is reduced due to a high degree of leakage of the confined oil or

w/o-emulsion from the oil spill boom (especially in high current). This leakage is especially

pronounced if the viscosity of the oil or the w/o-emulsion is lower than 1000 cP at a shear rate of

10s-1 (Nordvik et al., 1992). The lower viscosity limit for an optimal mechanical clean up

operation has therefore been set to 1000 cP.

The upper viscosity limit for an optimal mechanical clean up operation depends on the type of

skimmer used. For some disk-skimmers the collection capacity is reduced significantly at w/oemulsion viscosities exceeding 10 000 cP (ITOPF, 1986), however ITOPF, 1986 does not state

the shear rate.

Recent tests performed by SINTEF using a weir skimmer show that the efficiency may be reduced

for semi-solidified oils, i. e. oils with a large wax content and high pour point values, and for oils

with viscosities between 15000 and 20000 cP (Leirvik et.al.,2001).

2.3.2 Chemical dispersion

A dispersibility methodology, based on the viscosity increase due to weathering, was developed at

SINTEF (Daling and Strøm, 1999) in order to determine the window of opportunity for the

effective use of dispersants for different oils. Chemical dispersibility testing was not included in

this study. General limits for dispersibility based on pour point values are given in table 2.4.

These values are not valid for all oils and situations, and should only be regarded as guidelines.

Table 2.4: The chemical dispersibility used in the SINTEF OWM based on pour points.

Pour point

[°C] Chemical dispersibility

< 5°C above the sea temperature Dispersible

5-15°C above the sea temperature Reduced dispersibility

> 15°C above the sea temperature Not dispersible
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2.4 How to use the prediction charts, an example

If e.g. Endicott has drifted for a period of time on the sea surface the prediction charts can be

used to determine the remaining oil’s chemical, physical and emulsifying properties. Table 2.5

shows examples for the following scenario:

• Drift time: 24 hours

• Temperature: 0°C/10°C

• Wind speed: 10 m/s

Table 2.5: Weathering properties for Endicott obtained from the prediction charts.

Property Winter temperature

[0°C]

Summer temperature

[10°C]

Evaporation 13 vol% 15 vol%

Pour point 15 °C 17°C

Viscosity of the water free oil 5 000 cP 3 000 cP

Water content 50 % 58 %

Viscosity of the emulsion 12 000 cP 9 000 cP
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2.5 Prediction charts for Alaskan oils
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2.5.1 Prediction charts and summary of the Endicott crude oil’s weathering properties at

sea

Detailed information of the Endicott crude oil sample

Area/block: Alaskan North Slope

Common field name: Endicott

Well number: 133 G-12-00

Summary of the Endicott crude oil’s weathering properties at sea

Endicott is a heavy crude oil, with a density of 0,9131 g/mL. Endicott has a relative low content

of lighter molecular weight compounds, and at 10 m/s wind speed only 10 % of its original

volume will be evaporated 24 hours after the spill at summer temperatures.

Endicott will form w/o-emulsions with a maximum water content of approximately 60 % at winter

temperatures and 65 % at summer temperatures doubling the original spill volume. The w/oemulsions formed are very stable and in order to effectively dehydrate the w/o-emulsions when

using an emulsion breaker (e. g. Alcopol O 60 %) a minimum dosage of 2000 ppm should be

applied.

After approximately three hours at winter temperatures and half an hour at summer temperatures

the Endicott w/o-emulsion will have a viscosity of over 1000 cP which is the recommended lower

viscosity limit for an effective mechanical response. Viscosity of the Endicott emulsion will

exceed 20 000 cP within 1-3 days at high wind speed. This might cause lowered efficiencies in a

mechanical recovery operation using e.g. a weir or disk skimmer. At lower wind speeds this

should not be a problem.

Given the high viscosity of the Endicott emulsions, a limited time window for the use of

dispersants could be expected. A dispersibility study should be performed on the Endicott oil in

order to establish the time-frame in which the use of dispersants are feasible, and to determine the

optimal dosage of dispersants for an effective chemical treatment operation.

Due to the high viscosity of the Endicott emulsions a high “lifetime” should be expected for the

slick on the sea surface. At low wind speeds natural dispersion is almost neglectable, and even at

higher wind speeds the slick will endure for several days on the sea surface.

The prediction charts for the weathering of the Endicott crude oil at sea are given in Figure 2.2 to

Figure 2.7. The mass balance for Endicott at the mean summer and winter temperatures in the

Alaskan North Slope region at different wind speeds (2, 5, 10 and 15 m/s) are given in Figure 2.8

to Figure 2.11. These figures illustrate the degree of natural dispersion at varying sea conditions.
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Property: EVAPORATIVE LOSS

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 12, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 0 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

Sea surface temperature: 10 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

Figure 2.2: The predicted evaporative loss for Endicott at summer (10°C) and winter (0°C) mean

temperatures in Alaskan North Slope region.
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Figure 2.3: The Flash point for water-free Endicott at the mean summer (10°C) and winter (0°C)

temperatures for the Alaska North Slope region.

Property: FLASH POINT FOR WATER-FREE OIL

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

No fire hazard

Fire hazard in tankage (<60 °C)

Fire hazard at sea surface (below sea temperature)

Based on flash point measurements of weathered, water-free oil residues.

Sea surface temperature: 0 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

50

100

150

Sea surface temperature: 10 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

50

100

150

200
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Property: POUR POINT FOR WATER-FREE OIL

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 12, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Chemically dispersible

Reduced chemical dispersibility

Poorly / slowly chemically dispersible

Based on pour point measurements of weathered, water-free oil residues.

Sea surface temperature: 0 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

Sea surface temperature: 10 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

Figure 2.4: The predicted pour point for water-free Endicott at different wind speeds at the

summer (10°C) and winter (0°C) mean temperatures in the Alaskan North Slope

region.
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Property: VISCOSITY FOR WATER-FREE OIL

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 12, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 0 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

100

1000

10000

100000

Sea surface temperature: 10 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

100

1000

10000

100000

Figure 2.5: The predicted viscosity for water-free Endicott for different wind speeds at the

summer (10°C) and winter (0°C) mean temperatures in the Alaskan North Slope

region.
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Property: WATER CONTENT

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 12, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 0 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Sea surface temperature: 10 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.6: The predicted water content in the Endicott w/o-emulsions for different wind speeds at

the summer (10°C) and winter (0°C) mean temperatures in the Alaskan North

Slope region.
18

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: VISCOSITY OF EMULSION

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 12, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 0 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

100

1000

10000

100000

Sea surface temperature: 10 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

100

1000

10000

100000

Figure 2.7: The predicted viscosity of the Endicott w/o-emulsions for different wind speeds at the

summer (10°C) and winter (0°C) mean temperatures in the Alaskan North Slope

region.
19

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Property: MASS BALANCE

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 0 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 0 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.8: The mass balance for Endicott at the mean winter temperature (0°C) in the Alaskan

North Slope region at wind speeds of 2 and 5 m/s.
20

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 0 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 0 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.9: The mass balance for Endicott at the mean winter temperature (0°C) in the Alaskan

North Slope region at wind speeds of 10 and 15 m/s.
21

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 10 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 10 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.10: The mass balance for Endicott at the mean summer temperature (10°C) in the

Alaskan North Slope region at wind speeds of 2 and 5 m/s.
22

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ENDICOTT (2001)

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

The algorithm for prediction of natural dispersion is preliminary and is currently under improvement.Model 

predictions have been field-verified up to 4-5 days.

Temperature: 10 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 10 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.11: The mass balance for Endicott at the mean summer temperature (10°C) in the

Alaskan North Slope region at wind speeds of 10 and 15 m/s.
23

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2.5.2 Prediction charts and summary of the Alpine Composite oil’s weathering properties at

sea

Detailed information of the Alpine Composite

Area/block: Alpine Central Production Facility

Sample date: 07-23-2001

Company name: Phillips

Composite sample from all of the producing wells at Alpine.

Summary of the Alpine Composite’s weathering properties at sea

The Alpine Composite is a paraffinic crude oil, with a density of 0,834 g/mL. The Alpine

Composite contains a relatively large amount of lower molecular weight compounds and

approximately 25% of its original volume will be evaporated 24 hours after the spill at both

summer and winter temperatures.

The Alpine Composite contains approximately 4 wt% wax and less than 0,1 wt% asphaltenes. The

fresh oil has a pour point of -18°C and increases rapidly with weathering to approximately 10°C

and 15°C at the mean winter and summer mean temperatures at a wind speed of 10 m/s.

Alpine Composite will form w/o-emulsions with a maximum water content of 80 % at both winter

and summer temperatures, yielding approximately five times the original spill volume. The w/oemulsion formed after one day of weathering at sea is stable and in order to effectively dehydrate

the w/o-emulsions when using the emulsion breaker Alcopol O 60 % a minimum dosage of 2000

ppm should be applied.

After one day of weathering the Alpine Composite w/o-emulsions at winter and summer

temperatures will have a viscosity of over 1000 cP and the viscosity will only exceed 10 000 cP

after several days of weathering on the sea surface. High viscosity should not compromise the

success off a mechanical recovery operation, for at least a week after the time of the release.

The Alpine Composite will have a high degree of natural dispersion at high wind speeds. E.g. at

15 m/s wind speed the slick will be almost removed from the sea surface within a day.

The prediction charts for the weathering of the Alpine Composite oil at sea are given in Figure

2.12 to Figure 2.17.

The mass balance for the Alpine Composite at the mean summer and winter temperatures in the

Alaska North Slope region at different wind speeds (2, 5, 10 and 15 m/s) are given in Figure 2.18

to Figure 2.21. These figures illustrate the degree of natural dispersion at varying sea conditions.
24

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: EVAPORATIVE LOSS

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 05, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 0 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Sea surface temperature: 10 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Figure 2.12: The predicted evaporative loss for the Alpine Composite oil at summer (10°C) and

winter (0°C) mean temperatures.
25

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Figure 2.13: The Flash point for water-free Alpine Composite at the mean summer (10°C) and

winter (0°C) temperatures for the Alaska North Slope region.

Property: FLASH POINT FOR WATER-FREE OIL

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

No fire hazard

Fire hazard in tankage (<60 °C)

Fire hazard at sea surface (below sea temperature)

Based on flash point measurements of weathered, water-free oil residues.

Sea surface temperature: 0 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-50

0

50

100

150

Sea surface temperature: 10 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-50

0

50

100

150
26

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: POUR POINT FOR WATER-FREE OIL

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 05, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Chemically dispersible

Reduced chemical dispersibility

Poorly / slowly chemically dispersible

Based on pour point measurements of weathered, water-free oil residues.

Sea surface temperature: 0 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-40

-20

0

20

40

Sea surface temperature: 10 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-40

-20

0

20

40

Figure 2.14: The predicted pour point for water-free Alpine Composite at different wind speeds at

the summer (10°C) and winter (0°C) mean temperatures.
27

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: VISCOSITY FOR WATER-FREE OIL

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 05, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 0 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

100

1000

10000

Sea surface temperature: 10 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

10000

Figure 2.15: The predicted viscosity for water-free Alpine Composite for different wind speeds at

the summer (10°C) and winter (0°C) mean temperatures.
28

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: WATER CONTENT

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 05, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 0 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Sea surface temperature: 10 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.16: The predicted water content in the Alpine Composite w/o-emulsions for different

wind speeds at the summer (10°C) and winter (0°C) mean temperatures.
29

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: VISCOSITY OF EMULSION

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 05, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 0 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

100

1000

10000

100000

Sea surface temperature: 10 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

10000

100000

Figure 2.17: The predicted viscosity of the Alpine Composite w/o-emulsions for different wind

speeds at the summer (10°C) and winter (0°C) mean temperatures.
30

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 12, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 0 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 0 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.18: The mass balance for Alpine Composite at the mean winter temperature (0°C) in the

Alaskan North Slope region at wind speeds of 2 and 5 m/s.
31

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 12, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 0 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 0 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.19: The mass balance for Alpine Composite at the mean winter temperature (0°C) in the

Alaskan North Slope region at wind speeds of 10 and 15 m/s.
32

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 12, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 10 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 10 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.20: The mass balance for Alpine Composite at the mean summer temperature (10°C) in

the Alaskan North Slope region at wind speeds of 2 and 5 m/s.
33

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: ALPINE CPF 7/23/01 MMS

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Dec. 12, 2001

Evaporated

Surface

Naturally dispersed

The algorithm for prediction of natural dispersion is preliminary and is currently under improvement.Model 

predictions have been field-verified up to 4-5 days.

Temperature: 10 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 10 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.21: The mass balance for Alpine Composite at the mean summer temperature (10°C) in

the Alaskan North Slope region at wind speeds of 10 and 15 m/s.
34

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

2.5.3 Summary of the Milne Point Unit Oil’s weathering properties at sea

Detailed information of the Milne Point Unit oil sample

Area/block: Alaskan North Slope

Jerry cans marked: MPJ-01 CRUDE OIL

Summary of the Milne Point Unit oil’s weathering properties at sea

The Milne Point Unit oil sample were emulsified at arrival. The emulsion were extremely stable

and could not be broken without the addition of an excess of emulsion breaker and heating. The

laboratory evaporation of the oil, that forms the fundament of the weathering studies, could not be

performed on the emulsified oil. Predictions could therefore not be made for the Milne Point Unit

oil.

The Milne Point Unit oil is a heavy naphthenic oil with an approximate density of 0.95g/ml. The

oil seems to be highly biodegraded (i.e. no paraffinic components are present in the Gas

Chromatogram seen in fig C5) The emulsion is extremely stable and can only be dehydrated at

high temperatures and with the addition of a high dosage of demulsifier (approximately 10%).

Dehydration of the emulsion in a mechanical recovery operation could therefore prove difficult.

The water content of the arrived oil was 30-40%.

From previous studies at SINTEF, testing with a weir skimmer has showed poor recovery

efficiency at viscosities above 20.000. A 30% emulsion of the “fresh” Milne Point Unit oil has a

viscosity of approximately 8000 cP at 10°C. A high degree of evaporation is not expected for the

Milne Point Unit oil, but the viscosity will increase with weathering on the sea surface (both

evaporation and further emulsification), and high viscosities could cause problems in a

mechanical recovery operation for the Milne Point Unit oil, particularly at winter conditions.

SINTEF recommend a non emulsified Milne Point oil is supplied if possible, and the weathering

properties are further investigated.
35

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

2.5.4 Prediction charts and summary of the North Star Oil’s weathering properties at sea

Detailed information of the North Star oil sample

Sample no : 1.08

Client: BP Alaska

Installation: North Star

Date: 5.6-02

Bottle no.: n/a

Well: NS-08

Test: test1

Time: 21:25

Sample Nature: Atmospheric oil

Sampling point: Separator Oil Line

Sample bottle: 5gallon can

Job no.: NAM 1076

Summary of the North Star oil’s weathering properties at sea

The North Star oil is a light paraffinic crude oil, with a density of 0.8155 g/mL. The North Star oil

contains a relatively large amount of lower molecular weight compounds and approximately 30 %

of its original volume will evaporate 24 hours after the spill at both summer and winter

temperatures. The wax content of the North Star oil is 5.9 wt%. The pour point for the North Star

oil is very low for a paraffinic crude at –39°C for the fresh crude.

A viscosity of 1000 cP is considered to be a lower limit for efficient mechanical oil recovery. This

is due to leakage under the oil booms at lower viscosities (Norvik et.al. 1992). The North Star oil

will have viscosities below this limit initially and in a span of time highly dependent on wind and

temperature (e.g. 2 hours for 0°C and 15m/s wind speed, and 2 days for 10°C and 2 m/s wind

speed). During mechanical combat operations loss of oil could be expected within this timeframe.

No laboratory study is performed to assess the window of opportunity for the use of chemical

dispersants. The natural dispersion, however, will be of significance at high wind speeds. At both

summer and winter temperatures and 15 m/s wind speed the oil slick is expected to vanish from

the sea surface within a day due to natural dispersion. At lower wind speeds the oil could be

persistent on the sea surface for several days.

The prediction charts for the weathering of the North Star oil at sea are given in Figure 2.22 to

Figure 2.27. The mass balance for the North Star oil at the mean summer and winter temperatures

in the Alaska North Slope region at different wind speeds (2, 5, 10 and 15 m/s) are given in

Figure 2.28 to Figure 2.31.
36

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Figure 2.22: The predicted evaporative loss for the North Star oil at the mean summer (10°C) and

winter (0°C) temperatures for the Alaska North Slope region.

Property: EVAPORATIVE LOSS

Oil Type: NORTH STAR

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 0 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Sea surface temperature: 10 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

60
37

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Figure 2.23: The predicted viscosity for water-free North Star oil at the mean summer (10°C) and

winter (0°C) temperatures for the Alaska North Slope region.

Property: VISCOSITY FOR WATER-FREE OIL

Oil Type: NORTH STAR

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 0 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

1

10

100

1000

10000

Sea surface temperature: 10 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

1

10

100

1000

10000
38

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Figure 2.24: The Flash point for water-free North Star oil at the mean summer (10°C) and winter

(0°C) temperatures for the Alaska North Slope region.

Property: FLASH POINT FOR WATER-FREE OIL

Oil Type: NORTH STAR

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

No fire hazard

Fire hazard in tankage (<60 °C)

Fire hazard at sea surface (below sea temperature)

Based on flash point measurements of weathered, water-free oil residues.

Sea surface temperature: 0 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-50

0

50

100

150

Sea surface temperature: 10 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-50

0

50

100

150

200
39

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Figure 2.25: The predicted pour point for water-free North Star oil at the mean summer (10°C)

and winter (0°C) temperatures for the Alaska North Slope region.

Property: POUR POINT FOR WATER-FREE OIL

Oil Type: NORTH STAR

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Chemically dispersible

Reduced chemical dispersibility

Poorly / slowly chemically dispersible

Based on pour point measurements of weathered, water-free oil residues.

Sea surface temperature: 0 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-40

-20

0

20

40

Sea surface temperature: 10 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-40

-20

0

20

40
40

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Figure 2.26: The predicted water uptake for North Star oil at the mean summer (10°C) and winter

(0°C) temperatures for the Alaska North Slope region.

Property: WATER CONTENT

Oil Type: NORTH STAR

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 0 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

Sea surface temperature: 10 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80
41

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Figure 2.27: The predicted emulsion viscosity for North Star oil at the mean summer (10°C) and

winter (0°C) temperatures for the Alaska North Slope region.

Property: VISCOSITY OF EMULSION

Oil Type: NORTH STAR

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 0 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

10000

100000

Sea surface temperature: 10 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

1

10

100

1000

10000
42

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Figure 2.28: The mass balance for the North Star oil at the mean winter temperature (0°C) for the

Alaska North Slope region at wind speeds of 2 and 5 m/s.

Property: MASS BALANCE

Oil Type: NORTH STAR

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2002), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Evaporated

Surface

Naturally dispersed

Temperature: 0 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 0 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100
43

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Figure 2.29: The mass balance for the North Star oil at the mean winter temperature (0°C) for the

Alaska North Slope region at wind speeds of 10 and 15 m/s.

Property: MASS BALANCE

Oil Type: NORTH STAR

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2002), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Evaporated

Surface

Naturally dispersed

Temperature: 0 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 0 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100
44

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Figure 2.30: The mass balance for the North Star oil at the mean summer temperature (10°C) for

the Alaska North Slope region at wind speeds of 2 and 5 m/s.

Property: MASS BALANCE

Oil Type: NORTH STAR

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2002), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Evaporated

Surface

Naturally dispersed

Temperature: 10 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 10 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100
45

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Figure 2.31: The mass balance for the North Star oil at the mean summer temperature (10°C) for

the Alaska North Slope region at wind speeds of 10 and 15 m/s.

Property: MASS BALANCE

Oil Type: NORTH STAR

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2002), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Evaporated

Surface

Naturally dispersed

The algorithm for prediction of natural dispersion is preliminary and is currently under improvement.Model 

predictions have been field-verified up to 4-5 days.

Temperature: 10 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 10 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100
46

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

2.6 Prediction charts for Gulf of Mexico oils
47

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

2.6.1 Prediction charts and summary of the Neptune Field Composite’s weathering

properties at sea

Detailed information of the Neptune Field Composite sample

Area/block: VK 826

MMS Structure name: A

Sample date: 14. November 2000

Sample number: DGM 5870

Common field name: Neptune

Field/unit: VK 825

Company name: Kerr-McGee

MMS Platform ID: VK 826A

Composite sample from the following API well numbers:

Well A-1 through A-10, A-12st, 825-4, 825-5 and 826-12.

Summary of the Neptune Field Composite’s weathering properties at sea

The Neptune Field Composite is a paraffinic crude oil, with a density of 0,869 g/mL. The Neptune

Field Composite contains a relatively large amount of lower molecular weight compounds and

over 30 % of its original volume will be evaporated 24 hours after the spill at both summer and

winter temperatures. The wax content of the Neptune Field Composite is medium (∼ 4 wt%). The

fresh oil has a pour point of -9°C and increases with weathering to approximately 15°C at a wind

speed of 10 m/s.

The experimental results showed that the Neptune Field Composite did not form stable w/oemulsions. One normally would expect that a crude oil with a wax and asphalthene content similar

to the Neptune Field Composite will form stable w/o-emulsions. SINTEF suspects that

production/process chemicals are present in the oil sample thereby reducing the w/o-emulsion

process. This suspicion is supported by the un-normal low interfacial tension value measured for

the fresh crude (6 mN/m). SINTEF proposes that MMS inquire if offshore chemicals are present

in this crude oil sample, and that a follow up study of an untreated oil should be discussed based

on the findings.

The viscosity of the Neptune Field Composite only exceeds the lower viscosity limit for an

effective mechanical response (1000 cP at shear rate 10s-1) after 5 days. The viscosity will not

increase drastically with weathering since the Neptune Field Composite does not form stable w/oemulsions on the sea surface. The initial spill volume will not increase significantly and the

Neptune Field Composite will most likely spread quickly on the sea surface. In a mechanical

clean up operation the Neptune Field Composite may have a significant degree of leakage from

the oil spill boom due to the oils low viscosity (< 1000 cP) (Nordvik et.al. 1992), even after

several days of weathering on the sea surface. Chemical dispersion may be a possible response

operation since the viscosity and pour point of the Neptune Field Composite are low, however,

this was not investigated in this study.

The prediction charts for the weathering of the Neptune Field Composite at sea are given in

Figures 2.32 to 2.35. The mass balance for the Neptune Field Composite at the mean summer and

winter temperatures in the GOM region at different wind speeds (2, 5, 10 and 15 m/s) are given in

Figures 2.36 to 2.40. These figures illustrate that the natural dispersion process of the Neptune

Field Composite is high (at wind speeds above 10 m/s) due to the low viscosity and that the oil

does not form stable w/o-emulsions (i. e. the Neptune Field Composite will have a short lifetime

on the sea surface).
48

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: EVAPORATIVE LOSS

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 27, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 20 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Sea surface temperature: 29 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Figure 2.32: The predicted evaporative loss for the Neptune Field Composite at the mean summer

(29°C) and winter (20°C) temperatures for the GOM region.
49

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Figure 2.33: The Flash point for water-free Neptune Field Composite at the mean summer (29°C)

and winter (20°C) temperatures for the GOM region.

Property: FLASH POINT FOR WATER-FREE OIL

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Sep. 13, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

No fire hazard

Fire hazard in tankage (<60 °C)

Fire hazard at sea surface (below sea temperature)

Based on flash point measurements of weathered, water-free oil residues.

Sea surface temperature: 20 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

50

100

150

200

Sea surface temperature: 29 °C

Flash Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

50

100

150

200

250
50

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: POUR POINT FOR WATER-FREE OIL

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 27, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Chemically dispersible

Reduced chemical dispersibility

Poorly / slowly chemically dispersible

Based on pour point measurements of weathered, water-free oil residues.

Sea surface temperature: 20 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-20

0

20

40

Sea surface temperature: 29 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-20

0

20

40

Figure 2.34: The predicted pour point for the Neptune Field Composite at the mean summer

(29°C) and winter (20°C) temperatures for the GOM region.
51

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Property: VISCOSITY FOR WATER-FREE OIL

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

2.0

© 2001

Pred. date: Sep. 27, 2001

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 20 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

10000

100000

Sea surface temperature: 29 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

10000

100000

Figure 2.35: The predicted viscosity for water-free Neptune Field Composite at the mean summer

(29°C) and winter (20°C) temperatures for the GOM region.
52

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

Copyright 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 20 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 20 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.36: The mass balance for the Neptune Field Composite at the mean winter temperature

(20°C) for the GOM region at wind speeds of 2 and 5 m/s.
53

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

Copyright 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 20 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 20 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.37: The mass balance for the Neptune Field Composite at the mean winter temperature

(20°C) for the GOM region at wind speeds of 10 and 15 m/s.
54

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

Copyright 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

Temperature: 29 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 29 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.38: The mass balance for the Neptune Field Composite at the mean summer

temperature (29°C) for the GOM region at wind speeds of 2 and 5 m/s.
55

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: MASS BALANCE

Oil Type: NEPTUNE FIELD COMPOSITE

Description: TBP from SINTEF

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/0.5 mm

Release rate: 1.33 metric tons/minute

Copyright 2001

Pred. date: Oct. 03, 2001

Evaporated

Surface

Naturally dispersed

The algorithm for prediction of natural dispersion is preliminary and is currently under improvement.Model 

predictions have been field-verified up to 4-5 days.

Temperature: 29 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 29 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.39: The mass balance for the Neptune Field Composite at the mean summer temperature

(29°C) for the GOM region at wind speeds of 10 and 15 m/s.
56

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2.6.2 Prediction charts and summary of the High Island Composite’s weathering

properties at sea

Detailed information of the High Island oil sample

Area/block: High Island Block A573

MMS structure name: A

Sample date: December 8, 2000

Sample number: DGM 6013

Common field name: none

Field name: HIA573A

Company name: UNOCAL

Well number: A006

API well number: 427094016200

Composite sample from the following API well numbers:

Well A-1 through A-10, A-12st, 825-4, 825-5 and 826-12.

Summary of the High Island oil’s weathering properties at sea

The High Island oil were emulsified at arrival (~15%). Water was removed by leaving the

emulsion at rest for approximately a month in a 10 litre flask. At this time the oil/emulsion had

formed a gradient with no water in the top layers of the flask increasing to an emulsion of

80%water in the bottom of the flask. The water free upper layer of the flask was used in the

further weathering study. The meso-scale flume experiment, however, was performed on the

emulsion as delivered, and yield supplementary data as input to the OWM.

The High Island oil is a naphthenic crude oil, with a density of approximately 0.85 g/mL. The

High Island oil contains medium amount of lower molecular weight compounds and over 20 % of

its original volume will evaporate 24 hours after the spill at both summer and winter temperatures.

The wax content of the High Island oil is low (1.6 wt%). and the pour point for the High Island oil

is also low (–16°C for the fresh crude).

Results from the meso scale flume shows that High Island oil form unstable emulsions with low

viscosity. Maximum water content is high at 70%, but observations from the meso scale flume

shows that emulsions dehydrate almost completely within an hour when left at rest (e.g. in a tank).

A viscosity of 1000 cP is considered to be lower limit for efficient mechanical oil recovery. This

is due to leakage under the oil booms at lower viscosities (Nordvik et.al. 1992). The High Island

oil will have viscosities below this limit for at least four days of weathering at the sea surface, and

problems with leakage under the boom could be expected during recovery.

No laboratory study is performed to assess the window of opportunity for the use of chemical

dispersants. However, dispersibility testing in the meso scale flume shows fairly good

dispersibility after 3 days of weathering in the flume basin. Natural dispersion is high at high wind

speeds and the slick will have an estimated lifetime of 12 hours and 3 days respectively for 15 m/s

and 10 m/s wind speed. For lower win speeds the slick will be persistent on the sea surface, and

the lifetime will exceed 5 days.

The prediction charts for the weathering of the High Island oil at sea are given in Figures 2.40 to

2.44. The mass balance for the High Island oil at the mean summer and winter temperatures in the

GOM region at different wind speeds (2, 5, 10 and 15 m/s) are given in Figures 2.45 to 2.48.
57

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: EVAPORATIVE LOSS

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Jun. 06, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 20 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Sea surface temperature: 29 °C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50

Figure 2.40: The predicted evaporative loss for the High Island oil at the mean summer (29°C)

and winter (20°C) temperatures for the GOM region.
58

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: VISCOSITY FOR WATER-FREE OIL

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Jun. 06, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 20 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

Sea surface temperature: 29 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

Figure 2.41: The predicted viscosity for water-free High Island oil at the mean summer (29°C)

and winter (20°C) temperatures for the GOM region.
59

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: POUR POINT FOR WATER-FREE OIL

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Jun. 06, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Chemically dispersible

Reduced chemical dispersibility

Poorly / slowly chemically dispersible

Based on pour point measurements of weathered, water-free oil residues.

Sea surface temperature: 20 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-40

-20

0

20

40

Sea surface temperature: 29 °C

Pour Point (°C)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

-40

-20

0

20

40

60

Figure 2.42: The predicted pour point for water-free High Island oil at the mean summer (29°C)

and winter (20°C) temperatures for the GOM region.
60

I:\CH661189 MMS OWM Phases II and III\Task4 Weathering\Adm\Rapporten\6_oljer\MMS-report 151002.doc

Property: WATER CONTENT

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Nov. 10, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 20 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

Sea surface temperature: 29 °C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

Figure 2.43: The predicted water uptake for High Island oil at the mean summer (29°C) and

winter (20°C) temperatures for the GOM region.
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Property: VISCOSITY OF EMULSION

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Nov. 10, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Based on viscosity measurements carried out at a shear rate of 10 reciprocal seconds.

Sea surface temperature: 20 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

10000

Sea surface temperature: 29 °C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

Figure 2.44: The predicted emulsion viscosity for High Island oil at the mean summer (29°C)

and winter (20°C) temperatures for the GOM region.
62

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Property: MASS BALANCE

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Nov. 10, 2002

Evaporated

Surface

Naturally dispersed

Temperature: 20 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 20 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.45: The mass balance for the High Island oil at the mean winter temperature (20°C) for

the GOM region at wind speeds of 2 and 5 m/s.
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Property: MASS BALANCE

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Nov. 10, 2002

Evaporated

Surface

Naturally dispersed

Temperature: 20 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 20 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.46: The mass balance for the High Island oil at the mean winter temperature (20°C)

for the GOM region at wind speeds of 10 and 15 m/s.
64

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Property: MASS BALANCE

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Nov. 10, 2002

Evaporated

Surface

Naturally dispersed

Temperature: 29 °C Wind speed: 2 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 29 °C Wind speed: 5 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.47: The mass balance for the High Island oil at the mean summer temperature (29°C)

for the GOM region at wind speeds of 2 and 5 m/s.
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Property: MASS BALANCE

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Nov. 10, 2002

Evaporated

Surface

Naturally dispersed

The algorithm for prediction of natural dispersion is preliminary and is currently under improvement.Model 

predictions have been field-verified up to 4-5 days.

Temperature: 29 °C Wind speed: 10 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Temperature: 29 °C Wind speed: 15 m/s

Mass (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

100

Figure 2.48: The mass balance for the High Island oil at the mean summer temperature (29°C)

for the GOM region at wind speeds of 10 and 15 m/s.

.
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Appendix A: The behavior of crude oils on the sea surface
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A1 The chemical composition of crude oils

Crude oil is a complex mixture of thousands of chemical components. The relative compositions

vary, giving rise to crude oils with different chemical and physical properties. The components

found in crude oil are classified into two main chemical groups, these are hydrocarbons and

heteroatomic organics, see Figure A1.

Hydrocarbons

Hetroatomic

organics

n-alkanes

iso-alkanes

Naphthenes

Aromatics

Resins

Asphaltenes

Paraffins

6621/handboker/grafisk/fig-eng/crudeoil2.eps

Figure A1: The chemical composition of crude oil.

A1.1 Hydrocarbons

The majority of compounds in crude oil are hydrocarbons. Hydrocarbons are compounds that

contain carbon (C) and hydrogen (H) and include both saturated and unsaturated molecules in

linear, branched and cyclic configurations. Volatile gases, such as methane (CH4) as well as

complex molecules containing more than one hundred carbon atoms (C>100) are included in this

group.

Hydrocarbons are further classified into aliphatic and aromatic compounds. The two main groups

of aliphates are paraffins and naphthalenes.

Paraffins

Paraffins include n-alkanes and iso-alkanes aliphatic compounds. The common term for paraffinic

molecules, which consist of more than twenty carbon atoms (C>20), is wax. At elevated

temperatures the wax will be present in solution, however, at lower temperatures the wax can

precipitate. The wax content of crude oils can vary from 0,5 to 50 wt%, however the majority

have a wax content of 2 to 15 wt%.

Naphthenes

Naphthenes are saturated cyclic hydrocarbons with one or more rings. Each ring can have one or

more paraffinic side chains.
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Aromatics

Aromatics are a specific type of unsaturated cyclic hydrocarbons. Benzene, toluene and xylenes

are examples of mono-ring aromatics, naphthalenes are di-ring aromatics and polynuclear

aromatic hydrocarbons (PAH) contain three or more aromatic rings.

A1.2 Hetroatomic organics

Hetroatomic organics can, in addition to carbon and hydrogen, contain small amounts of sulphur

(S), nitrogen (N), oxygen (O) and trace amounts of vanadium (V) and nickel (Ni). Resins and

asphaltenes are important subgroups of organic non-hydrocarbons.

Carboxylic acids, sulphoxides and phenol compounds are relatively polar compounds classified as

resins. Asphaltenes consist of high molecular weight polycyclic aromatic compounds.

A2 Physical properties of crude oils

The physical properties of specific oils are a result of their chemical compositions. The most

important physical properties in oil spill scenarios are discussed below.

A2.1 Density

The density of crude oil normally lies between 0,78 to 0,95 g/mL at 15,5°C. Paraffinic oils have

lower density values, while oils that contain large amounts of high molecular weight aromatic,

naphthenes and asphalthenic compounds usually have higher density values.

A2.2 Viscosity

The viscosity of crude oil expresses its resistance to flow and is of special interest when pumping

mechanically collected oil. The viscosity of crude oils can vary from 3 to 2000 cP at 13°C. In

comparison water has a viscosity of 1 cP and syrup a viscosity of 120 000 cP at 20°C.

The viscosity is temperature dependent. For liquids the viscosity decreases with increasing

temperatures. Figure A2 shows the variations in viscosity as a function of temperature for various

crude oils and oil products. Viscous crude oils or crude oils that contain wax can exhibit nonNewtonian behaviour (viscosity varies with shear rate), especially close to or below their pour

point.
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0 10 20 30 40 50 60 

100 000

10 000

1000

100

10

1

Viscostiy (cSt)

Kinematic

viscosity (cSt) 

Dynamic

viscosity (cP)

Density (kg/L)

2

20

200

2000

IF-240

Temperature ( ̊C)

IF-30

Marin Diesel

=

Endicott

Alaska North Slope

Statfjord C

Neptune Field Composite

Alpine CPF 7/23/01

66118900MMS\grafisk\viskonANS.eps

Figure A2: The variation in viscosity as a function of temperature for several crude oils and oil

products. The figure is not valid below the oil’s pour points.

The viscosity of an oil increases with evaporation since the heavier, more viscous components

remain. The difference in viscosity for crude oils is approximately 3 to 2000 cP for fresh crude

oils and several hundred/thousand cP for their residues.

Water-in-oil (w/o) emulsions are generally more viscous than the parent crude oil, this is

illustrated in Figure A3.
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0 20 40 60 80

Water content (vol. %)

100

1000

100

10

0

Viscosity ratio

ik41911100\tegner\fig-eng\fig2-5.eps

B

Figure A3: An example of the viscosity ratio as a function of increasing water content (Mackay et

al., 1980).

Due to the shear thinning rheological properties, the viscosity of w/o-emulsions will decrease with

increasing shear rate. A w/o-emulsion can therefore flow under turbulent conditions on the sea

surface, but can become more viscous under calmer sea conditions or if washed on shore.

Viscosity measurements must therefore be made under controlled conditions in the laboratory.

A2.3 Pour point

The temperature when an oil ceases to flow when cooled without disturbance under standardised

conditions in the laboratory (ASTM-D97) is defined as the oils pour point. In oil spill clean up

situations the pour point provides important information when determining the efficiency of

various skimmers, pumping rates and the use of dispersion agents.

The pour point is related to the chemical composition of the parent crude oil, particularly its wax

content. The ASTM Pour Point test is performed under static conditions. Field experience shows

that under dynamic conditions on the sea surface, effects of oil solidification will occur 10-15°C

below the laboratory generated pour points.

The pour point of an oil with a high wax content will increase dramatically with weathering as the

lower weight molecules that contribute in keeping the wax in solution are lost. The pour point of

oils with high wax contents can reach 30°C, while low viscous naphthenic (highly biodegraded)

oils can have pour points as low as –40°C.

A2.4 Distillation curve

Distillation curves for crude oils give important information about the relative amount of lighter

compounds in the oil and is therefore fundamental for determining the degree of evaporative loss

after it is spilled on the sea surface. The curve is obtained by plotting the vapour temperature as a

function of the amount of distillate. Figure A4 shows segments of the distillation curves for

selected crude oils.
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0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 700 800

vapour temerature (°C)

percent distilled (vol%)

Endicott

Alpine

Neptune Fields

High Island

North Star

Figure A4: Distillation curves for the crude oils tested during the project.

A2.5 Flash point

The flash point is the lowest temperature at which the gas or vapour generated by heating an oil

can be ignited by a flame. The flash point depends on the proportion of low molecular weight

components. Fresh crude oils normally have a low flash point (from –40°C to 30°C).

From a safety point of view flash points are of most significance at or slightly above the

maximum temperature that may be encountered in storage or transport. The flash point is an

approximate indicator of the relative fire and explosion hazard of an oil.

A rule of thumb says that moving in an oil spill where the flash point of the oil is close to or lower

than the sea temperature implies a fire and explosion hazard. Natural weathering processes like

evaporation and emulsification formation contribute in reducing the potential hazard by increasing

the flash point. There is therefore a relatively short fire and/or explosion danger in the initial

stages of an oil spill.

In the laboratory, the flash point is measured in a closed system where there is equilibrium

between the components in the oil and gas. In the field, however, the weather situation will

influence the flammability of the air above the slick. For instance the gas concentration will be

high just above the oil film in calm weather and high temperatures, whereas the concentration will

be low in cold and windy weather due to dilution and transport and a lower degree of evaporation.
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A3 The behavior of crude oil spilt at sea

When a crude oil is spilt at sea a number of natural processes take place, which change the

volume and the chemical properties of the oil. These natural processes are evaporation, water-inoil (w/o) emulsification, oil-in-water (o/w) dispersion, release of oil components into the water

column, spreading, sedimentation, oxidation and biodegradation. A common term for all of these

natural processes is weathering. The relative contribution of each process varies during the

duration of the spill. Figure A5 illustrates the various weathering processes and Figure A6 shows

their relative importance with time.

Uptake by biota

Dissolution of water soluble 

components

Sedimentation

Adsorption to particles

Resurfacing of larger oil droplets

Horizontal diffusion

Microbiological

Vertical diffusion degradation

Wind

Drifting Water-in-oil

emulsion

Photolysis Evaporation

Spreading

 Oil-in-water dispersion

Uptake and release from sediment

Figure A5: The weathering processes that take place when an oil is spilt on the sea surface.
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Evaporation

Dissolution

Photo-oxidation

Biodegradation

Sedimentation

Water-in-oil

emulsification

Oil-in-water

dispersion

Spreading

Drifting

0

Hours

1 10

Day

100

Week Month

1000

Year

10000

Unstable

emulsion

Stable "mousse"

6621\handboker\grafiske\fig-eng\emulsion.eps

Figure A6: Weathering processes’ relative importance with time.

The weathering of oil depends on the oil type (chemical and physical properties), the weather

conditions (wind, waves, temperature and sunlight) and the properties of the seawater (salinity,

temperature, bacteria flora etc.).

A3.1 Evaporation

Evaporation is one of the natural processes that helps in removing spilt oil from the sea surface.

The evaporation process starts immediately after the oil is spilled and the evaporation rate

decreases exponentially throughout the duration of the oil spill.

The amount evaporated depends on the chemical composition of the oil in addition to the

prevailing weather conditions, sea temperature and the oil film thickness.

The rate of evaporation will vary for different oil types. Light refinery products (e.g. gasoline and

kerosene) may completely evaporate after a few hours/days on the sea surface. Condensates and

lighter crude oils can loose 50 % or more of their original volume during the first days after an oil

spill.

The most significant difference caused by evaporation is the loss of volatile and semi-volatile

compounds increases the relative amounts of higher molecular weight compounds. The chemical

and physical properties of the remaining oil change, for example the density, viscosity, pour point

and the relative wax and asphaltene contents will increase with increased evaporation.
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A3.2 Spreading

Oil spilt at sea will spread on the sea surface. Spreading is often the dominating process in the

initial stages of an oil spill, however see Figure A6, its importance decreases as the viscosity and

density of the remaining oil increases. The spreading process is also retarded if the oil’s pour

point is 10-15°C below the sea temperature.

Oceanographic conditions (e. g. wind, waves and current) will affect the spreading process. The

oil slick will be broken into windrows aligned in the wind direction, see Figure A7. The oil film

thickness of the oil slick will vary, often differing with a factor of several thousand. Past

experience has shown that 90 vol% of the oil spilt will consist of patches of w/o-emulsion with a

film thickness of 1 to 5 mm that often constitute for less than 10 % of the total oil slick area. The

remaining 10 vol% will cover 90 % of the spill area in the form of a sheen (<1 μm oil thickness).

Sheen (< 1μm) Windrows

Tick oil and 

water-in-oil

emulsion (mm)

Wind

ik41961100/tegner/fig-eng/sheen.eps

Figure A7: The spreading of oil spilt on the sea surface and the distribution within the oil slick.

A3.3 Drift of an oil slick

Prevailing surface currents cause the oil slick to drift, see Figure A8. Surface currents are

controlled by currents in the water column but will also be influenced by wind speed and

direction. This influence will be about 3% off the wind speed and direction compared to the drift

contribution from currents.
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Wind - 20 knots

3 %

100 %

ik41961100/tegner/fig-eng./wind.eps

Figure A8: An illustration showing how wind and current can influence the drift of an oil slick.

A3.4 Water-in-oil (w/o) emulsion

The formation of w/o-emulsions is one of the major weathering processes that contributes in

keeping oil on the sea surface. A w/o-emulsion has a higher viscosity than the parent crude oil and

the emulsification process will therefore retard/delay the evaporation and the natural dispersion

process.

The minimum criteria for the formation of w/o-emulsions is the presence of breaking waves (i. e.

a wind speed of 5 m/s), however, a slow water uptake can also take place during calmer weather.

Surface active components present in crude oil will promote the formation of w/o-emulsions and

contribute in stabilising the emulsion. These components contain both hydrophilic and

hydrophobic groups.

The maximum water uptake will vary for different crude oils. Tests performed at SINTEF have

shown that the maximum water uptake is fairly independent of the prevailing weather conditions

as long as the lower energy barrier for the formation of w/o-emulsions is exceeded, however, the

rate of emulsification depends highly on the weather conditions. Previous tests of asphalthenic

oils performed at SINTEF show that the water uptake is in inverse ratio with the viscosity.

The rate of formation of the w/o-emulsion varies for different oil types since it is dependent on the

chemical composition if the oil. A large amount of wax will for instance increase the rate of

formation. Another important factor that influences the rate of formation is the prevailing weather

conditions. Figure A9 shows an example of how the wind speed influences the rate of formation.
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100

80

60

40

20

0

0 6 12 18 24

Water content (vol.%)

Time (hours)

Windspeed = 10 m/s

Windspeed = 5 m/s

ik41911100\tegner\fig-eng\fig2-3a.eps

A

Figure A9: An example of how the prevailing weather conditions influence the rate of the w/oemulsion formation for a typical crude oil.

The stability of the w/o-emulsion depends on the water droplet size in the emulsion. Not all of the

water droplets in the emulsion are stabile. The largest droplets may coalesce and settle out of the

w/o-emulsion. Larger water droplets may be reduced in size by the flexing, stretching and

compressing motion of a slick due to wave action. After a period of time the emulsion may only

contain small water droplets with a diameter of 1 to 10 μm. Figure A10 illustrates the effect of

rotation time on the water droplet size in a w/o-emulsion formed in the laboratory.

 A B

 

Figure A10: A picture taken with a microscope of the water droplet size in a w/o-emulsion after

(A) 1 hour and (B) 24 hours in a rotating cylinder.

Another factor that influences the w/o-emulsion’s stability is the amount of surface-active

components present in the parent oil. Resins and asphaltenes have hydrophobic and hydrophilic

properties and will concentrate at the interface between the water and oil thereby forming a layer

that stabilises the water droplets. The hydrophobic properties can lead to the concentration of wax

along the water droplets, which further stabilises the interfacial “skin” layer. The interfacial layer

between the oil and water forms a physical barrier hindering coalescence and will stabilise the

w/o-emulsion by hindering the fusion of water droplets. The stabilisation of the water droplets by

asphaltenes and by asphaltenes and wax are shown in Figure A11.
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WATER PHASE

Water droplet ~ 1 μm in diameter 

Unstabilized Asphaltene

& wax 

stabilized

Wax

stabilized

Asphaltene

stabilized

OIL PHASE

Asphaltene "particles"

Wax crystals

Resins

ik41961100:tegner\fig_eng\interfac.eps

Figure A11: Stabilization of the interfacial layer between the water and oil in a w/o-emulsion by

wax and asphaltenes.

Oils that contain a large amount of wax and little asphaltenes can form w/o-emulsions that may

appear to be stabile. These w/o-emulsions appear to be stabled by the continuos phase’s

rheological strength (viscosity and elasticity). This strength is due to the wax structure formed by

precipitated wax. Wax stabilised emulsions are characterised by large water droplets and are fairly

stabile when stored, however, they may break when stress is applied and/or when the emulsion is

heated to e. g. 40-50°C.

A3.5 Oil-in-water (o/w) dispersion

Natural o/w dispersion will take place if there is sufficient energy on the sea surface, i. e. if there

are breaking waves present. The waves will break the slick into droplets typically with a diameter

between 1 to1000 μm which are mixed into the water masses. The largest oil droplets will

resurface forming a sheen (see 0) behind the oil slick.

In addition to weather conditions the dispersion rate depends highly on the oil type and can be one

of the main processes that determine the lifetime of an oil slick on the sea surface. The natural o/w

dispersion will gradually decrease since evaporation of the lighter components will increase the

viscosity of the remaining oil.

The purpose of applying chemical dispersion agents is to increase the natural o/w dispersion rate.

When effective chemical dispersion is achieved small oil droplets are formed with a diameter of 5

to 50 μm. The dispersion agent reduces the interfacial tension between the water and oil and

promotes dispersion.
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A3.6 Water solubility

The water solubility of saturated hydrocarbons (<C4) is very low, while lower molecular weight

aromatic compounds are water-soluble. Within the various types of hydrocarbons the water

solubility decreases from aromatics to naphthenes and from iso-paraffins to n-paraffins. In each

series the water solubility decreases with increasing molecular weight.

Evaporation and the release of oil components in to the water masses are competitive processes

since most of the water-soluble components are also volatile. The evaporation process is

approximately 10 to 100 times faster than the dissolution into the water column. The

concentration of soluble oil components in the water column during an oil spill is quite low (<1

mg/L). The dissolution of oil components into the water column does not contribute in removing

the oil from the sea surface. However the water-soluble fraction (WSF) is of great interest since it

has a high bioavailability and therefore the potential to cause acute toxic effects on marine

organisms.

A3.7 Photo-oxidation

Under the influence of sunlight some of the oil components will slowly be oxidised to resins and

eventually asphaltenes. This contributes to the stability of w/o-emulsions and therefore has a large

influence on the oils persistence on the sea surface. The photo-oxidised components will stabilise

the w/o-emulsions. After a long period of weathering at sea, tar-balls can be formed. Tar-balls are

broken down very slowly both at sea and on beaches.

A3.8 Biodegradation

Theoretically, seawater contains micro-organisms that can break down all types of oil

components. The various micro-organisms prefer specific oil components as an energy source.

Several factors influence the biodegradation rate, among these are temperature, the supply of

nutritive substances that contain nitrogen and phosphor, the oxygen supply, oil type and the

degree of weathering. Bacteria can only degrade oil that is in contact with seawater and is

dependent of the water/oil interface area. The interface area increases as the oil is spread over the

sea surface as a thin layer or by chemical or natural dispersion of oil in the water masses. An area

increase due to chemical and/or natural dispersion will increase the degradation rate in the water

mass to 10 to 100 times the rate at the water/oil interface.

A3.9 Sedimentation

Crude oil and oil residues rarely sink into the water masses since there are few oils that have a

density higher than water, even after extreme weathering. Oil can, however, sink if sticking to

particular material present in the water masses. The increased density will make oil-soiled

particles sink more readily.
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A3.10 Submersion

Highly weathered oils can temporarily submerge from the sea surface. This can greatly influence

the effectiveness of combating oil pollution in the marine environment. The oil density and

viscosity in addition to the weather conditions influence submersion. W/o-emulsions have a

higher density value than the parent oil and can therefore submerge more easily.
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Appendix B: Experimental Design of the Bench-Scale and Meso-scale

Laboratory Testing
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B1 Oil Samples received for the study

SINTEF received two fresh oil samples from the Alaskan North Slope (Endicott and Milne Point

Unit) on the 14th of November 2000, two fresh oil samples from the Gulf of Mexico (Neptune

Field Composite and High Island Composite) on the 30th of January 2001 and an oil sample from

the North Slope (Alpine Central Production Facility) on the 15th of August 2001. At 11th of June

2002, the last Alaskan North Slope oil arrived (North Star Oil). These oil samples were supplied

by MMS.

Alaskan North Slope samples

B1.1 Detailed information of the Endicott crude oil sample

Area/block: Alaskan North Slope

Common field name: Endicott

Well number: 133 G-12-00

B1.2 Detailed information of the Milne Point Unit oil sample

Area/block: Alaskan North Slope

Jerry cans marked: MPJ-01 CRUDE OIL

B1.3 Detailed information of the Alpine Central Production Facility oil sample (Alpine

Composite)

Area/block: Alpine Oilfield

Sample date: July 23, 2001

Composite sample of all of the producing wells at Alpine.

B1.4 Detailed information of the North Star oil sample

Sample no : 1.08

Client: BP Alaska

Installation: North Star

Date: 5.6-02

Bottle no.: n/a

Well: NS-08

Test: test1

Time: 21:25

Sample Nature: Atmospheric oil

Sampling point: Separator Oil Line

Sample bottle: 5gallon can

Job no.: NAM 1076
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Gulf of Mexico Oils

B1.5 Detailed information of the Neptune Field Composite sample

Area/block: VK 826

MMS Structure name: A

Sample date: November 14, 2000

Common field name: Neptune

Field/unit: VK 825

Company name: Kerr-McGee

MMS Platform ID: VK 826A

Composite sample from the following API well numbers:

Well A-1 through A-10, A-12st, 825-4, 825-5 and 826-12

B1.6 Detailed information of the High Island Composite

Area/block: High Island Block A573

MMS structure name: A

Sample date: December 8, 2000

Common field name: none

Field name: HIA573A

Company name: UNOCAL

Well number: A006

API well number: 427094016200

B2 Test temperatures

The temperatures chosen for the bench-scale laboratory testing are:

Endicott: 10°C

Milne Point Unit: 10°C

Alpine Composite: 10°C

North Star 10°C

The Neptune Field Composite: 23°C

High Island Composite: 23°C
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B3 Bench-scale laboratory testing

In order to isolate and map the various weathering processes that take place when an oil is spilled

on the sea surface, the weathering of the oils is carried out using a systematic, stepwise procedure

developed at SINTEF (Daling et al., 1990). The weathering process is illustrated in Figure B1.

Evaporation

Emulsification with water

WOR = 1

WOR = 3

WOR = max

Figure B1: Flow chart for the bench-scale laboratory weathering of a crude oil.

B3.1 Evaporation

Evaporation of the lighter components from the fresh crude oil is carried out according to a

modified ASTM-D86/82 distillation procedure (Stiver and Mackay, 1984). The fresh crude oil is

distilled, in a simple one step distillation, to a vapor temperature of 150, 200 and 250°C. This will

give oil residues with an evaporation loss typically corresponding to 0,5-1 hour, 0,5-1 day and 2-5

days of weathering of an oil slick on the sea surface. These residues are referred to as 150°C+,

200°C+ and 250°C+ respectively.

B3.2 Water-in-oil (w/o) emulsification

The procedures used in the w/o-emulsification studies are described in detail by Hokstad et al.,

1993.

The w/o-emulsification of the fresh crude oil is carried out based on the rotating cylinder method

developed by Mackay and Zagorski, 1982. Oil (30 mL) and seawater (300 mL) are rotated (30

rpm) in a separating funnel (0,5 L), see Figure B2. The emulsification kinetics are mapped by

measuring the water content at fixed rotation times. The maximum water content is determined

after 24 hours of rotation.
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Before mixing

Oil 

(30 mL)

Seawater

(330 mL)

Axis of

rotation

(30 rpm)

24 hours

mixing

WOR

0-

2-

4-

6-

8-

24 hours mixing and 

24 hours settling

6621/handbøker/grafisk/fig-eng/3skilletrakter.eps

Figure B2: Principle of the rotating cylinder method.

To test the effectiveness of the emulsion breaker Alcopol O 60 %, two dosages (500 ppm and

2000 ppm relative to the oil volume) were added drop wise to the w/o-emulsion. After a contact

period of 5 minutes and a rotation time of 5 minutes (30 rpm), the treated emulsion stood for 24

hours before the amount of water drained from the emulsion was determined.

The distilled residues were emulsified with 50 vol% and 75 vol% water in addition to the

maximum water content w/o-emulsion. Four parallel runs were performed to map the w/oemulsion kinetics and two of the parallel runs were performed with the addition of Alcopol O

60%. Several physical and chemical properties of the twelve weathered samples (see Figure B1)

were determined. A detailed description of the various analyses is given in B3.3.

B3.3 Physical and chemical analysis

The viscosity, density, pour point, flash point and interfacial tension of the water free residues and

w/o emulsions were determined. The analytical procedures used are given in Table B1.

Table B1: Summary of the analytical methods used in the determination of the physical

properties.

Physical property Analytical method Instrument

Viscosity McDonagh et al., 1995 Physica MCR 300

Density ASTM method D4052-81 Anton Paar, DMA 4500

Pour Point ASTM method D97 -

Interfacial tension De Nouy Ring method Kruss tensiometer

Flash point ASTM D 56-82 Pensky-Martens, PMP1, SUR

The wax content and “hard” asphaltene content will be determined using the analytical procedures

given in Table B2.
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Table B2: Summary of the analytical methods used in the determination of the chemical

properties.

Chemical property Analytical method

Wax content Bridiè et al., 1980

“hard” asphaltene IP 234/84

B4 Meso-scale laboratory testing

In the bench scale testing the oils are distilled and emulsified in separate processes. In an oil spill

situation at sea these processes will occur simultaneously and affect each other. It is therefore

important that the oils are weathered under realistic conditions when studying how the oils

behaviour when spilled on the sea surface.

A meso-scale flume basin (Singsaas et al., 1993) located at SINTEF is routinely used to study the

weathering processes simultaneously under controlled conditions. The experimental data obtained

from the meso-scale testing provides a link between the bench scale testing and field trials and is

important input in the OWM. In this study a meso-scale flume basin experiment is therefore

performed as a supplement to the limited bench scale study to be conducted on the heavily

emulsified High Island oil sample.

B4.1 Description of the meso-scale flume

Approximately 1,7 m3 seawater circulates in the 10 meter long flume. The flume is located in a

conditioning room (20°C – 50°C). To fans (3) placed in a covered wind-tunnel allow various wind

speeds. The evaporation- and emulsification rate is calibrated to simulate a wind speed of 5-10

m/s. A schematic drawing of the flume is given in Figure B3.

2

1. Wave generator

2. Photolysis (sun-lamp)

3. Wind-tunnel

4. Sub-surface sampling

4

1

4 m

3

Boss\ik41961100/tegner/fig-eng/mesoflu_e.eps

Figure B3: A schematic drawing of the meso-scale flume.
86

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B4.2 Oil weathering in the meso-scale flume

The emulsified oil sample (10 L) is carefully released on the water surface. The oil is weathered

for a total of 72 hours. Surface oil residue, w/o-emulsion and subsurface water samples are taken

after 0 min., 15 min., 30 min., 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours 12 hours, 1 day,

2 days and 3 days of weathering. The following physical properties are determined:

- water content

- viscosity

- density

- evaporation loss

B4.3 In-situ chemical dispersion

After 72 hours of weathering in the flume the dispersion agent Corexit9500 is sprayed onto the

w/o-emulsion, see Table B3, where

DOR is the dispersion agent to oil ratio

DER is the dispersion to w/o-emulsion ratio

Table B3: The application time and amount of the dispersion agent Corexit 9500.

Weathering

[h]

Amount of Dasic NS

applied [mL]

Cumulative DOR

[%]

Cumulative DER

[%]

72 56 0.9 0.3

Water samples are taken 3 min., 10 min., 30 min. and 2 hours after the dispersion agent is applied

in order to determine the effect of the dispersion agent in addition to observations of the surface

film and w/o-emulsion.
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Appendix C: Experimental results from the bench-scale and meso-scale

laboratory testing
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C1 Bench-scale laboratory testing

In this chapter the experimental results obtained for Endicott, the Neptune Field Composite,

Alpine Composite and the North Star oils in the bench-scale laboratory testing are presented and

compared.

The Milne Point Unit and the High Island oil samples were emulsified on arrival. A standard

bench scale weathering study of these two oil samples could therefore not be performed. Both

samples have water contents well above the safety limit for the laboratory distillation of crude oils

enabling the artificial weathering of the oil samples.

The High Island Oil was emulsified on arrival at SINTEF. Three phases were formed after

allowing the w/o-emulsion to settle for several weeks. A dark brown oil phase (water content less

than 1%), a light brown phase (water content approximately 10%) and a water phase. The upper

water free layer were “artificially” evaporated (described in B3.1), and used for obtaining data on

the physical and chemical properties of the water free residues of the oil upon weathering. A meso

scale experiment were performed to obtain data on the properties of the emulsions formed in a

weathering situation.

The Milne Point Unit sample was an extremely stable emulsion and water could only be separated

from the sample after an excess of emulsion breaker (approximately 10% of Alcopol O 60 %) was

added to the sample, and the mixture were heated. The water content of the sample did not

increase using the rotating cylinder method. A meso-scale laboratory study was not regarded

appropriate for obtaining more information about this sample.

C1.1 Chemical composition

C1.1.1 Gas chromatographic analysis

Fresh samples of Endicott, the Alpine Composite, the Neptune Field Composite, the North Star

and their evaporated residues (150°C+, 200°C+ and 250°C+) were analysed by a gas

chromatograph with a flame ionisation detector (GC-FID). The gas chromatograms are given in

Figure C1-C6.

The components with the lowest boiling points are seen first in the chromatogram. Some of the

more complex components, e.g. resins, NSO-components and naphthenes are difficult to separate

using this analysis technique and are seen as a broad, poorly defined envelope. This is described

as Unresolved Complex Material (UCM). The n-alkanes are seen as systematic, narrow peaks

protruding the UCM envelope. Heavier compounds (>C40) cannot be analysed by this technique.

From the gas chromatograms given in Figures C1-C6 it can be seen that Endicott, the Alpine

Composite, the Neptune Field Composite and the North Star have paraffinic peaks protruding the

UCM envelope. Endicott contains fewer lower molecular weight components and has a larger

UCM envelope than both the Alpine Composite and the Neptune Field Composite that is therefore

the heaviest of the three oils.

The Milne Point Unit’s chromatogram (Figure C5) differs from the others in the total lack of nalkane peaks. This indicates a high degree of biodegradation.
89

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Gas chromatography is an important tool in identifying oil spills due to the diversity of the n-C17

and pristane and n-C18 and phytane ratios for different oil types. The ratios for Endicott, the

Alpine Composite, the Neptune Field Composite and the North Star oil are given in Table C1.

Table C1: nC17/Pristane and nC18/Phytane ratios, calculated from peak height, for Endicott, the

Alpine Composite, the Neptune Field Composite and the North Star.

Crude oil n-C17/pristane n-C18/phytane

Endicott 2.0 2.8

Neptune Field Composite 2.3 3.4

Alpine Composite 1.7 3.1

North Star 2.4 3.3

High Island Composite 1.4 1.7
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5 10 15 20 25 30 35 40 45 min

counts

20000

40000

60000

80000

100000

120000

140000

160000

 FID1 A, (I:\HPCHEM\1\DATA\66118910\00-66902.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

UCM

Pristane

Phytane

5 10 15 20 25 30 35 40 45 min

counts

5000

10000

15000

20000

25000

30000

 FID1 A, (I:\HPCHEM\1\DATA\66118910\00-66901.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Phytane

Pristane

UCM

5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

60000

70000

 FID1 A, (I:\HPCHEM\1\DATA\66118910\00-66900.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

UCM

Pristane

Phytane

Figure C1: Gas chromatogram for fresh Endicott and it’s evaporated residues.

5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

60000

 FID1 A, (I:\HPCHEM\1\DATA\66118910\00-66905.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Pristane

Phytane

UCM

26.5 min

counts

10000

15000

20000

25000

30000

35000

 FID1 A, (I:\HPCHEM\1\DAT nC-17 nC-18 Pristane Phytane

Fresh

150°C+

200°C+

250°C+
91

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5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

60000

70000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00001.D) nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

60000

70000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00002.D) nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

5 10 15 20 25 30 35 40 45 min

counts

20000

40000

60000

80000

100000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00003.D) nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Figure C2: Gas chromatograms for the fresh Alpine Composite and its evaporated residues.

5 10 15 20 25 30 35 40 45 min

counts

5000

10000

15000

20000

25000

30000

35000

40000

45000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\PHILIPS0.D) nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

25.525.7526 26.2526.526.7527 27m

counts

5000

10000

15000

20000

25000

30000

FID1 A, (I:\HPCHEM\1\DATA\6611 nC-17 nC-18 Pristane Phytane

Fresh

150°C+

200°C+

250C°+
92

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5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

60000

70000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\001-0043.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Phytane

Pristane

5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

60000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\001-0042.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Pristane

Phytane

5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\001-0041.D)

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Phytane

Pristane

Figure C3: Gas chromatogram for the fresh Neptune Field Composite and it’s evaporated

residues.

5 10 15 20 25 30 35 40 45 min

counts

2500

5000

7500

10000

12500

15000

17500

20000

22500

 FID1 A, (I:\HPCHEM\1\DATA\66118940\001-0044.D) nC-9

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Pristane

Phytane

26.5 min

counts

2500

5000

7500

10000

12500

15000

17500

20000

 FID1 A, (I:\HPCHEM\1\DATA\661 nC-17 nC-18 Pristane Phytane

150°C+

200°C+

250°C+

Fresh
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0 10 20 30 40 min

counts

10000

20000

30000

40000

50000

 FID1 A, (I:\HPCHEM\1\DATA\MMS_HIA\VIGDIS04.D)

 nC-10

 nC-11

 nC-12

 n-C13

 nC-14

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

5 10 15 20 25 30 35 40 45 min

counts

5000

10000

15000

20000

25000

30000

35000

40000

45000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\60130003.D)

 nC-11

 nC-13

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Figure C4: Gas chromatogram for the fresh High Island Composite and the 250°C+ residue.

250°C+

Fresh

26 27 28 min

counts

10000

15000

20000

25000

30000

 FID1 A, (I:\HPCHEM\1\DATA\MMS_HIA\VIGDIS n-C17 n-C18 pristane phytane
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5 10 15 20 25 30 35 40 45 min

counts

2500

5000

7500

10000

12500

15000

17500

20000

22500

 FID1 A, (I:\HPCHEM\1\DATA\661189~1\MMS00001.D)

Figure C5: Gas chromatogram for the fresh Milne Point Unit oil.

Fresh
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5 10 15 20 25 30 35 40 45 min

counts

10000

20000

30000

40000

50000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00000.D)

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

5 10 15 20 25 30 35 40 45 min

counts

20000

40000

60000

80000

100000

120000

140000

160000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00001.D)

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

5 10 15 20 25 30 35 40 45 min

counts

20000

40000

60000

80000

100000

120000

140000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00002.D)

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

5 10 15 20 25 30 35 40 45 min

counts

20000

40000

60000

80000

100000

120000

140000

160000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS00003.D)

 nC-15

 nC-17

 nC-18

 nC-20

 nC-25

 nC-30

Figure C6: Gas chromatogram for the fresh North Star oil and it’s evaporated residues.

26 27 min

counts

5000

10000

15000

20000

25000

 FID1 A, (I:\HPCHEM\1\DATA\66118940\MMS nC-17 nC-18 pristane phytane

Fresh

150°C+

200°C+

250°C+
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C1.1.2 Asphaltene and wax content

Wax and asphaltenes are important parameters for water uptake ability and w/o-emulsion

stability. The (“hard”) asphaltene and wax content of Endicott, the Alpine Composite and the

Neptune Field Composite and their evaporated residues are given in Table C3.

C1.1.3 Classification of the oil samples

From the experimental results all the crude oil sample, but the Milne Point Unit and the High

Island Composite are classified as paraffinic crude oils. Endicott is the heaviest of the paraffinic

oils with an asphaltene content of 1,6 wt% and a wax content of 5,5 wt%. The Alpine Composite

has the lowest asphaltene and wax content of the three oils. The Neptune Field Composite

contains a large amount of lighter weight compounds and has a relatively low asphaltene content

(0,3 wt%).

Milne Point Unit is a heavily biodegraded heavy crude oil. Information obtained from the

chromatogram indicates a low wax content. The extreme stability of the emulsion could indicate a

high amount of asphaltenes.

The High Island oil is also biodegraded but not to the same degree as the Milne Point Unit oil.

C1.2 Physical properties

C1.2.1 Evaporative loss

Endicott, Alpine Composite, Neptune Field Composite and North Star were distilled to a vapour

temperature of 150, 200 and 250°C. The volume percent evaporated during the distillation is

given in Figure C7

0

10

20

30

40

50

60

Endicott Alpine Neptune Field Composite North Star

Evaporative loss (vol%)

150°C+

200°C+

250°C+
97

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Figure C7: Evaporative loss of Endicott, the Alpine Composite ,the Neptune field composite

and the North Star crude oils.

Endicott contains a larger amount of higher weight compounds and the volume spilled on the sea

surface will decrease slowly. The Alpine and North Star oils have a high amount of lighter

components, and evaporative loss will yield great changes in physical properties for the oil.

C1.2.2 Density

The density of Endicott, the Alpine Composite the Neptune Field Composite, the North Star and

their evaporated residues are given in Figure C8.

0,81

0,83

0,85

0,87

0,89

0,91

0,93

0,95

Fresh 150°C+ 200°C+ 250°C+

Oil residue

Density (g/mL)

Endicott

Alpine

Neptune Field Composite 

North Star

Figure C8: Density of Endicott, the Alpine Composite and the Neptune Field Composite and

their evaporated residues at 15,5°C.

The densities of the water free oil residue increase with evaporation, see Figure C8. Fresh

Endicott has the highest density of the three crude oils indicating that it contains fewer lower

weight molecules and a larger amount of heavier compounds than the others do. The North Star

crude oil is the lightest of the four crude oils. This is in agreement with the results obtained from

the GC analysis and the evaporation data (see chapters C.1.1 and C1.2).
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C1.2.3 Pour Point

The pour points of fresh Endicott, the fresh Neptune Field Composite, the North Star and their

evaporated residues are given in Figure C9.

-40

-20

0

20

Fresh 150°C+ 200°C+ 250°C+

Oil residue

Pour point (°C)

Endicott

Alpine

Neptune Field Composite 

North Star

Figure C9: Pour points of Endicott, the Alpine Composite and the Neptune Field Composite

and their evaporated residues.

The Alpine Composite and the North Star oil have the lowest initial pour points at –18°C and –

39°C respectively. The low pour points are due to high amounts of light components in the oils,

keeping heavier components as wax in solution. Upon evaporative loss the chemical composition

changes, and as e.g. wax is allowed to precipitate the pour point is getting higher. As the Alpine

and North Star oils have the greatest evaporative loss of the four, they also display the greatest

change in pour point with evaporation.
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C1.2.4 Viscosity

The viscosity of the fresh crude oils and their evaporated residues measured at shear rate 10 s-1 is

given in Table C2.

Table C2: Measured viscosity for fresh Endicott, the Alpine Composite, the North Star, the

Neptune field Composite and The High Island Composite.

Oil type Viscosity at 10s-1

[cP]

Pour point

[°C]

Fresh 510 6

150°C+ 840 9

200°C+ 1 630 15

Endicott

10°C

250°C+ 5 150 18

Fresh 100 -18

150°C+ 120 -3

200°C+ 840 9

Alpine

Composite

10°C

250°C+ 1 160 18

Fresh 10 -39

150°C+ 45 -9

200°C+ 380 3

Alaskan North

Slope

North Star

10°C

250°C+ 2272 18

Fresh 10 -9

150°C+ 50 0

200°C+ 110 3

Neptune

Field

Composite

23°C 250°C+ 300 9

Fresh 23 -36

- -

- -

Gulf of

Mexico High

Island

Composite

23°C 250°C+ 83 -15

As the more volatile components are lost by evaporation, the viscosity of the remaining residue

will increase. This is seen in Table C2 for all five crude oils.

The viscosities of Endicott 150°C+, 200°C+, 250°C+ , Alpine Composite 250°C+ and North Star

250°C+ were measured close or below their pour points and the values obtained are therefore

quite high.
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C1.2.5 Flash point

The flashpoint of the fresh crude oils and their evaporated residues were determined and are given

in Table C3.

C1.2.6 Interfacial tension

The interfacial tension of the fresh crude oils and their evaporated residues were determined and

are given in Table C3.

The experimental results showed that the Neptune Field Composite did not form stable w/oemulsions. One normally would expect that a crude oil with a wax and asphaltene content similar

to the Neptune Field Composite will form stable w/o-emulsions. SINTEF suspects that production

chemicals are present in the oil sample thereby reducing the w/o-emulsion process. This suspicion

is supported by the low interfacial tension value measured for the fresh crude (6 mN/m). SINTEF

proposes that MMS inquire if offshore chemicals are present in this crude oil sample and that a

follow up study be discussed based on the findings.
101

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he High Island

Composite and the North Star. The viscosities for Endicott, the Alpine Composite, the North Star, the Neptune Field Composite and the HighIsland Composite and the were measured at 10°C, 10°C , 10°C, 23°C and 23°C respectively.

Oil type Evaporated [vol%] Residue [wt%] Density at 15,5°C [g/mL] Pour point [°C] Viscosity at 10 s-1 [cP] Flash point [°C] Interfacial tension [mN/m] Wax content [wt%] Asphaltenes “hard” [wt%]

Fresh 0 100 0,913 6 510 <20 24 5,5 1,6

150°C+ 6 95 0,923 9 840 56 24 5,7 1,7200°C+ 12 89 0,931 15 1630 85 25 6,1 1,8 Endicott250°C+ 19 84 0,940 18 5150 121 25 6,5 1,9

Fresh 0 100 0,834 -18 103 <20 18 3,2 0,06

150°C+ 22 81 0,867 -3 118 38 20 3,9 0,07200°C+ 34 69 0,885 9 839 82 27 4,6 0,09

Alpine

Composite

250°C+ 44 60 0,898 18 1160 123 16 5,3 0,1

Fresh 0 100 0.816 -39 10 <20 20 5,8 0,016

150°C+ 24.7 78.5 0.850 -9 45 37 21 7,3 0,021200°C+ 38.5 65.3 0.866 3 380 77 23 8,8 0,025

Alaskan North Slope

North Star

250°C+ 50.2 53.8 0.881 18 2272 119 24 10,7 0,030

Fresh 0 100 0,869 -9 10 <20 6 3,7 0,3

150°C+ 11 90 0,887 0 50 46 6 4,1 0,4200°C+ 22 81 0,900 3 110 93 7 4,6 0,4

Neptune

Field

Composite 250°C+ 30 73 0,911 9 300 128 8 5,0 0,4

Fresh 0 100 0,847 -15 23 - 14 1,6 0,03

150°C+ - - - - - - - - -200°C+ - - - - - - - - -

Gulf of Mexico High Island

Composite 250°C+ 33 70 0,879 0 83 - 16 2,3 0,04
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C1.3 W/o emulsion properties

The formation of w/o-emulsions on the sea surface delay the evaporation and the natural

dispersion weathering processes increasing the lifetime for the oil on the sea surface. When

determining the most effective plan of action after an oil spill it is important to know the

emulsifying properties (e.g. the rate of formation and stability) of the oil that has been spilled.

C1.3.1 W/o-emulsion rate of formation

The rates of formation of the Endicott, the Alpine Composite, the Neptune Field Composite and

the North Star w/o-emulsions were mapped using the rotating cylinder method (Mackay, 1982) at

10°C, 10°C, 23°C and 10°C respectively. The kinetics of formation are expressed by the t1/2-

values, which is the time (in hours) it takes for the emulsions to reach half of their maximum

water content. The calculated t1/2-values for Endicott, Alpine Composite, the Neptune Field

Composite and the North Star are given in Table C4.

The maximum water content of the Endicott w/o-emulsions is quite high (all are above 50%). The

rate of formation is relatively slow, after approximately 10 hours the Endicott emulsions have

reached their maximum water content. A slow rate of formation is typical for crude oils with a

high asphaltene content.

The maximum water content of the Alpine Composite w/o-emulsions is high (all are above 80%).

The rate of formation is relatively fast, after approximately 30 minutes the Alpine Composite w/oemulsions have reached a water content above 50 vol%.

The Neptune Field Composite w/o-emulsions contain little water (all water contents are below 10

vol%). The rate of formation is fast, after approximately 1⁄2 hour the emulsions have reached their

maximum water content. These w/o-emulsion were not stable, see C1.3.2.

The North Star oil has a fast initial water-uptake and reaches 45% within 10 minutes. The water

content gradually increases to a maximum water content of 70-80%.

The fast emulsification rates are typical for the Alpine Composite and the North Star oil is typical

for paraffinic crude oils
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Table C4: The calculated t1/2–values and the maximum water content for Endicott, the Alpine

Composite, the North Star and the Neptune Field Composite w/o-emulsions at 10°C,

10°C, 10°C and 23°C respectively.

Oil type t1/2

[h]

max. water content

[vol%]

150°C+ 0,6 82

200°C+ 1,2 79

Endicott

250°C+ 2,8 64

150°C+ 0,1 80

200°C+ 0,2 80

Alpine

Composite

250°C+ 0,5 80

150°C+ 0.11 68

200°C+ 0.14 69

Alaskan

North

Slope

North Star

250°C+ 0.09 83

150°C+ 0,1 6

GOM 200°C+ 0,2 8

Neptune

Field

Composite 250°C+ 0,1 7

C1.3.2 Stability of the w/o-emulsions and the effect of an emulsion breaker

Unstable w/o-emulsions may dehydrate at storage or upon mechanical influence (e. g. stirring or

pumping). Stable w/o-emulsions, on the other hand, increase the volume that has to be collected

considerably. This can give storage problems. Responding boats are therefore recommended to

have an emulsion breaker available and it is important to know its effectiveness. A reduction of

the water content in a w/o-emulsion from 80 to 20% will decrease the volume of the emulsion 4

times. One of the most common emulsion breakers is Alcopol O 60% (Ross, 1986).

From the experimental results the fractional dehydration factor, D, is calculated using equation

C-1.

ref

ref x

x WOR

WOR WOR D − = (C-1)

where:

WORref = Volumetric water-to-oil ratio in the emulsion after 24 hours rotation

WORx = Maximum volumetric water-to-oil ratio in the emulsion after 24 hours rotation

and x hours settling

The fractional dehydration value lies between 0 and 1. An emulsion is defined as totally stable if

no water is separated from the emulsion during a 24 hour settling period (D = 0) and an increasing

D means reduced stability after the application of an emulsion breaker.

The calculated fractional dehydration factor for the Endicott, the Alpine Composite and the North

Star w/o-emulsions with and without application of Alcopol O 60% are given in table C6.
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Table C5: The calculated fractional dehydration of the Endicott, the Alpine Composite, and the

North Star w/o-emulsions with and without the application of Alcopol O 60% (500 ppm

and 2000 ppm) after 10 min settling and 24 hours settling with and without rotation at

10°C.

Oil residue Alcopol O 60%

[ppm] D24 hours D24 hours + rot

150°C+ 0 0

200°C+ 0,1 0,1

250°C+

0

0 0

150°C+ 0,2 0,2

200°C+ 0,2 0,4

250°C+

500

0,3 0,3

150°C+ 1,0 1,0

200°C+ 1,0 1,0

Endicott

250°C+

2000

0,7 0,9

150°C+ 1,0 1,0

200°C+ 0 0

250°C+

0

0,2 0,2

150°C+ 1,0 1,0

200°C+ 0,93 0,93

250°C+

500

0,93 0,93

150°C+ 1,0 1,0

200°C+ 1,0 1,0

Alpine

Composite

250°C+

2000

1,0 1,0

150°C+ 0 0

200°C+ 0 0

250°C+

0

0 0

150°C+ 0,82 0,82

200°C+ 0,89 0,89

250°C+

500

0,90 0,90

150°C+ 0,92 0,92

200°C+ 0,92 0,92

North Star

250°C+

2000

0,97 0,97

The asphaltene and wax content in Endicott stabilise the w/o-emulsion by preventing the fusion of

water droplets. In order to effectively dehydrate the Endicott w/o-emulsions when using Alcopol

O 60%, a minimum dosage of 2000 ppm should be applied in an oil spill situation. This will

enable an effective dehydration of all of the Endicott w/o-emulsions.

The wax content and asphaltene content in the Alpine Composite oil sample is quite low,

however, the relative amount of these stabilising components increase with weathering. This will

increase the stability of the w/o-emulsions formed. In addition the increase in viscosity of the

continuous phase (especially the 200°C+ and 250°C+ residues) decreasing the diffusion of water

droplets will lead to a more stable w/o-emulsion. A dosage of 500 ppm Alcopol O 60% will

dehydrate emulsions of the Alpine Composite oil to a water content of 6%, which should be

sufficient for most practical purposes. A total dehydration demands a higher ratio of demulsifier.
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The experimental results showed that the Neptune Field Composite obtained a water content

below 10 %, however, these w/o-emulsions were completely dehydrated after a settling period of

24 hours. The initial spill volume of the Neptune Field Composite will not increase significantly.

One normally would expect that a crude oil with a wax and asphaltene content similar to the

Neptune Field Composite will form stable w/o-emulsions. SINTEF suspects that production-

/process-chemicals are present in the oil sample thereby reducing the w/o-emulsion process. This

is supported by the low interfacial tension value measured for the fresh crude (6 mN/m), and as

mentioned earlier, a follow up study is recommended.

The North Star crude has a low asphaltene content, but will form emulsions stabilised by the high

wax content of the oil. Emulsions of the North Star oil is dehydrated to a water content of

approximately 7% at an emulsion/demulsifier rate of 500ppm. For further dehydration of the

emulsion a higher dosage (e.g. 2000ppm) will be needed.
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C1.3.3 Viscosity of the w/o-emulsions

The viscosities of the Endicott and the Alpine Composite w/o-emulsions with different water

contents were measured at 10°C, the results are given in Table C6. The viscosities measured are

used as input to the SINTEF Oil Weathering Model. Emulsification of Endicott will cause a

dramatic increase in viscosity. The viscosity of the Alpine Composite w/o-emulsion could not be

determined due to the emulsion’s unstability.

Table C6: Viscosities of the Endicott and Alpine Composite w/o-emulsions (0 vol%, 50 vol%,

75 vol% and maximum water content) measured at 10°C.

Oil residue Water content

[vol%]

Viscosity at shear 10s-1

[cP]

150°C+ 840

200°C+ 1 630

250°C+

0

5 150

150°C+ 1 530

200°C+ 3 330

250°C+

50

7 910

150°C+ 6 240

200°C+ 12 200

250°C+

75

-

150°C+ 82 (max) 15 300

200°C+ 79 (max) 21 400

Endicott

250°C+ 64 (max) 21 700

150°C+ 120

200°C+ 840

250°C+

0

1 160

150°C+ 120

200°C+ 920

250°C+

50

2 940

150°C+ 780

200°C+ 2 970

250°C+

75

7 130

150°C+ -

200°C+ 5 960

Alpine

Composite

250°C+

80 (max)

11 700

150°C+ 45

200°C+ 380

250°C+

0

2272

150°C+ 305

200°C+ 405

250°C+

50

882

150°C+ 624

200°C+ 1034

250°C+

75

1967

150°C+ 68 421

200°C+ 69 850

North Star

250°C+ 83 752

-: measurement not possible
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C2 Meso-scale laboratory testing of the High Island Composite

In this chapter the experimental results obtained for High Island oil in the meso-scale laboratory

testing are presented. The High Island oil were emulsified at arrival SINTEF. The emulsion was

difficult to break, and thus the untreated emulsion were used in the meso-scale laboratory test.

The experimental test temperature was 23°C. Results from the meso scale experiment are given in

table C8.

C2.1 Visual observations

The High Island Composite oil sample spread quickly after its application to the water surface in

the flume (Figure C14), an estimated 80-90% of the water surface was covered with oil within one

hour. The formation of a w/o-emulsion could be observed during the first hour after application of

High Island Composite.

An increase in the viscosity of the w/o-emulsion was observed throughout the experiment. The

surface w/o-emulsion samples taken 5 hours after application of High Island Composite were

dehydrated after a one-hour settling period, indicating the instability of the w/o-emulsion formed.

The w/o-emulsion formed after 6 hours weathering is seen in Figure C15

Figure 16 shows the w/o-emulsion formed after 3 days of weathering in the flume. The w/oemulsion formed after 3 days of weathering has a darker colour and has become more viscous.

Immediately after the first application of dispersant the w/o-emulsion was dehydrated (Figure

C17) and after 10 minutes most of the surface oil had dispersed (Figure C18). A second dispersant

application was therefore not necessary.
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C2.2 Evaporation

The evaporation results obtained in the meso-scale laboratory testing of High Island oil are

presented and compared with the predicted evaporation results from the SINTEF OWM in Figure

C10.

Figure C10: The evaporation results obtained for High Island Composite in the meso-scale

laboratory testing and the predicted results from the SINTEF OWM.

Predicted evaporative loss is in good accordance with results form the meso scale flume.

Property: EVAPORATIVE LOSS

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data used

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Pred. date: Jun. 10, 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 23  ̊C

Evaporated (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

10

20

30

40

50
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C2.3 W/o-emulsification

The w/o-emulsification results obtained in the meso-scale laboratory testing are plotted with the

predicted results from the SINTEF OWM in Figure C11 to Figure C12.

C2.2.1 Water uptake

Property: WATER CONTENT

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data used

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 23  ̊C

Water content (%)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

0

20

40

60

80

Pred. date: Nov. 10, 2002

Figure C11: Predicted water uptake for High Island Composite and the results obtained from the

meso-scale laboratory testing.

The water uptake observed in the meso scale flume experiment is used as input to the OWM. As

shown in figure C11, the predicted emulsification rate correlates with the results from the flume

experiment.
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C2.3.2 Stability of the w/o-emulsions

The surface w/o-emulsion samples taken 5 hours after application of High Island Composite were

dehydrated after a one-hour settling period, indicating an unstable emulsion. An increase in the

stability of the w/o-emulsions, however, was observed throughout the experiment.

C2.3.3 Viscosity of the w/o-emulsion

Viscosities of the emulsion formed in the meso scale flume is compared to predicted viscosities in

figure C14. As results form the meso scale flume experiment are used as input to the OWM, good

correlation is expected between predicted and measured values. Evaporation- and emulsification

rates in the meso scale flume is calibrated to simulate weathering conditions at 5-10m/s wind

speed. Measured viscosities are in good accordance with predicted values in this wind speed

interval.

Property: VISCOSITY OF EMULSION

Oil Type: HIGH ISLAND FLUME DATA

Description: 

Data Source: SINTEF Applied Chemistry (2001), Weathering data used

Initial/Terminal Oil film thickness: 20 mm/1 mm

Release rate: 1.33 metric tons/minute

2.0

© 2002

Wind Speed (m/s): 15

Wind Speed (m/s): 10

Wind Speed (m/s): 5

Wind Speed (m/s): 2

Sea surface temperature: 23  ̊C

Viscosity (cP)

Hours Days

0.25 0.5 1 2 3 6 9 12 1 2 3 4 5

10

100

1000

Pred. date: Nov. 10, 2002

Figure C12: Predicted viscosity of the High Island Composite w/o-emulsions and the results

obtained from the meso-scale laboratory testing.
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C2.4 In-situ chemical dispersion

In situ chemical dispersion of the surface emulsion was performed on the High Island oil after 3

days of weathering in the meso scale flume. The efficiency of the dispersant on the emulsion was

tested by analysing the concentration of dispersed oil in sub surface water.

At the application of the dispersant the emulsion were quickly dehydrated from approximately

70% to a water content of 10%. As the water content decreased a decrease in viscosity were

visually observed (to little surface oil for measurements). Analysis of the sub surface water in the

meso scale flume shows a high dispersibility compared to other oils tested in the flume, and

emulsions of the high Island oil is probably dispersable for at least 3 days in an oil spill situation.

Re-emulsification of the surface oil were slow and a second dispersant application were not

thought to be necessary.

C2.5 Mass balance

The main elements in a mass balance for a crude oil spilt at sea are:

- Evaporative loss

- Surface oil

- Dispersed oil

However, the initial sample and water volume in the flume is reduced throughout the test,

therefore the following parameters must taken into consideration:

- Amount of oil sampled

- Amount of water sampled

- Amount of oil adsorbed to the flume walls

The amount of oil evaporated, dispersed and sampled was calculated, and the oil adsorbed to the

flume walls was estimated. Table C7 shows the mass balance for High Island oil during

weathering in the meso-scale flume at 23°C.

Table C7: Mass balance for High Island Composite during the meso-scale laboratory test at

23°C.

After 72 hours of

weathering (%)

After the application

of dispersant (%)

Evaporated 35.2 35.2

Oil on water surface 53.1 30.7

Dispersed 4.1 26.3

Sampled amount of oil 2.6 2.8

Adsorbed to the flume walls 5.0 5.0

The mass balance for High Island Composite during the meso-scale laboratory testing was

predicted by the SINTEF OWM at 23°C and is given in Figure C13
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0,0

20,0

40,0

60,0

80,0

100,0

0 10 20 30 40 50 60 70

Time (hours)

Mass balance (wt%)

Evaporated

Surface oil

Dispersed

Sampled

Adsorbed

Applic ation of 56ml of Corexit9500

Figure C13: Mass balance for High Island Composite in the meso-scale laboratory test at 23°C.

Figure C14: High Island Composite 30 minutes after application in the meso-scale flume.
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Figure C15: High Island Composite 6 hours after application in the meso-scale flume.

Figure C16: High Island Composite 3 days after application in the meso-scale flume.
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Figure C17: High Island Composite immediately after application of dispersant in the meso-scale

flume.

Figure C18: High Island Composite 10 minutes after application of dispersant in the meso-scale

flume.
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Table C8 Results from the meso-scale flume testing of the High Island Composite at 23°C

Emulsion Waterfree residue

Sample Time

(hours)

Water content

(vol%)

Viscosity

(cP)

Evaporative loss

(wt%)

Dispersed oil

(wt%)

0 0.0 0 23 0 0

1 0.25 13 43 13 3.3

2 0.50 31 230 15 3.0

3 1.00 19 185 17 3.0

4 2.00 38 220 19 3.0

5 3.00 38 345 21 3.0

6 4.00 66 370 21 3.0

7 5.00 69 450 22 3.0

8 6.00 75 510 23 3.0

9 12.0 75 345 26 3.0

10 24.0 68 675 33 3.0

11 48.0 67 - 33 3.0

12 72.0 67 490 34 4.1

Application of 56 ml of Corexit 9500

13 72.05 12 - 34 26,3

14 72.2 12 - 34 30,9

15 72.5 20 - 34 35,6
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Appendix D: Input data for the SINTEF Oil Weathering Model
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D1 Endicott

Geographical area: Alaskan North Slope

Initial oil film thickness: 20 mm

Terminal oil film thickness: 2 mm

Release rate: 1,33 metric tons/minute

Sea temperature: 0°C and 10°C

Wind speed: 2 m/s, 5 m/s, 10 m/s and 15 m/s

The data used as input to the SINTEF OWM for Endicott are given in Table D.1 to Table D.3.

Table D.1: Physical and chemical data for Endicott

Chemical/physical property

Specific Gravity (60°F/15.56°C) 0,913

Pour Point 6°C

Reference temperature #1 10°C

Viscosity at reference temperature #1 510cP

Wax (wt%) 5.5

Asphaltenes (wt%) 1.6

Table D.2: The true boiling point values used for Endicott (obtained from Crude Assay at

http://www.etcentre.org/main/e/db/db.html).

Temperature

[°C]

Evaporated

[vol%]

66 0

93 1

121 3

149 6

204 11

232 16

260 21

287 27

315 34

343 40

371 46

427 57

482 66

537 74

565 77
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Table D.3: Experimental results from the bench-scale laboratory testing (see chapter C1) at

10°C:

Chemical/physical property Fresh 150°C+ 200°C+ 250°C+

Boiling point [°C] - 190 185 275

Evaporation [vol%] 0 6 12 19

Residue [wt%] 100 95 89 84

Specific gravity [g/L] 0.913 0.923 0.931 0.9340

Pour point [°C] 6 9 15 18

Viscosity at shear 10s-1 [cP] 510 840 1630 5150

Viscosity of 50% emulsion at shear 10s-1 [cP] - 1540 3330 7910

Viscosity of 75% emulsion at shear 10s-1 [cP] - 6240 12200 -

Viscosity of max water emulsion at shear 10s-1

[cP] - 15300 21400 21700

Maximum water content in emulsion [vol%] - 82 79 65

Halftime for water uptake [h] - 0.6 1.2 2.8

Stability ratio - 0.96 0.98 1.0

-: not determined
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D2 Alpine Composite

Geographical area: Alaskan North Slope

Initial oil film thickness: 20 mm

Terminal oil film thickness: 2 mm

Release rate: 1,33 metric tons/minute

Sea temperature: 0°C and 10°C

Wind speed: 2 m/s, 5 m/s, 10 m/s and 15 m/s

The data used as input to the SINTEF OWM for the Alpine Composite are given in Table D4 to

Table D6.

Table D.4: Physical and chemical data for the Alpine Composite

Chemical/physical property

Specific Gravity (60°F/15.56°C) 0.834

Pour Point -18

Reference temperature #1 (°C) 10

Viscosity at reference temperature #1 (cP) 103

Wax (wt%) 3.2

Asphaltenes (wt%) 0.06

Table D.5: The true boiling point values used for the Alpine Composite sample.

Temperature

[°C]

Evaporated

[vol%]

85 8

105 13

135 19

175 27

205 33

235 38

265 45

310 54

350 62

420 72

525 89
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Table D.6: Experimental results from the bench-scale laboratory testing (see chapter C1) at

10°C:

Chemical/physical property Fresh 150°C+ 200°C+ 250°C+

Boiling point [°C] - 167 246 296

Evaporation [vol%] 0 22 34 44

Residue [wt%] 100 81 69 60

Specific gravity [g/L] 0.8340 0.8668 0.8845 0.8981

Pour point [°C] -18 -3 9 18

Viscosity at shear 10s-1 [cP] 103 118 839 1160

Viscosity of 50% emulsion at shear 10s-1 [cP] - 120 920 2940

Viscosity of 75% emulsion at shear 10s-1 [cP] - 780 2970 7130

Viscosity of max water emulsion at shear 10s-1

[cP] - - 5960 11700

Maximum water content in emulsion [vol%] - 80 80 80

Halftime for water uptake [h] - 0.1 0.2 0.5

Stability ratio - 0 1 0.8

-: not determined
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D3 North Star oil

Geographical area: Alaska North slope

Initial oil film thickness: 20 mm

Terminal oil film thickness: 1 mm

Release rate: 1.33 metric tons/minute

Sea temperature: 0°C and 10°C

Wind speed: 2 m/s, 5 m/s, 10 m/s and 15 m/s

The data used as input to the SINTEF OWM for High Island Composite are given in Table D7 to

Table D9.

Table D.7: Physical and chemical data for North Star

Chemical/physical property

Specific Gravity (60°F/15.56°C) 0.816

Pour Point (°C) -39

Reference temperature #1 (°C) 10

Viscosity at reference temperature #1 (cP) 20

Wax (wt%) 5.8

Asphaltenes (wt%) 0.016

Table D.8: The true boiling point values used for the North Star.

Temperature

[°C]

Evaporated

[vol%]

60 1.3

100 6.9

120 11.9

140 18.3

160 25.5

180 31.3

200 36.4

220 41.3

240 46.0

250 48.6

310 61.1

360 69.2

420 75.2

525 86.2
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Table D.9: Experimental results from the bench-scale laboratory testing (see chapter C1) at

23°C.

Chemical/physical property Fresh 150°C+ 200°C+ 250°C+

Boiling point [°C] 160 231 280

Evaporation [vol%] 0 24.7 38.5 50.2

Residue [wt%] 100 78.5 65.3 53.8

Specific gravity [g/L] 0.816 0.850 0.866 0.881

Pour point [°C] -39 -9 3 18

Viscosity at shear 10s-1 [cP] 10 45 380 2272

Viscosity of 50% emulsion at shear 10s-1 [cP] 305 405 882

Viscosity of 75% emulsion at shear 10s-1 [cP] 624 1034 1967

Maximum water content in emulsion [vol%] 68 68 83

Viscosity of max water emulsion at shear 10s-1 [cP] 421 850 752

Halftime for water uptake [h] 0.11 0.15 0.09

Stability ratio 1 0.99 1
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D4 The Neptune Field Composite

Geographical area: Gulf of Mexico

Initial oil film thickness: 20 mm

Terminal oil film thickness: 0.5 mm

Release rate: 1.33 metric tons/minute

Sea temperature: 20°C and 29°C

Wind speed: 2 m/s, 5 m/s, 10 m/s and 15 m/s

The data used as input to the SINTEF OWM for the Neptune Field Composite are given in Table

D10 to Table D12.

Table D.10: Physical and chemical data for Neptune Field Composite

Chemical/physical property

Specific Gravity (60°F/15.56°C) 0.869

Pour Point (C°) -9

Reference temperature #1 (C°) 23

Viscosity at reference temperature #1 (cP) 10

Wax (wt%) 3.7

Asphaltenes (wt%) 0.3

Table D.11: The true boiling point values used for the Neptune Field Composite.

Temperature

[°C]

Evaporated

[vol%]

53 1

93 4

125 9

150 13

173 17

195 20

213 23

240 28

267 33

288 36

321 42

370 50

450 62
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Table D.12: Experimental results from the bench-scale laboratory testing (see chapter C1) at

23°C.

Chemical/physical property Fresh 150°C+ 200°C+ 250°C+

Boiling point [°C] - 200 256 305

Evaporation [vol%] 0 11 22 30

Residue [wt%] 100 90 81 73

Specific gravity [g/L] 0.869 0.887 0.900 0.911

Pour point [°C] -9 0 3 9

Viscosity at shear 10s-1 [cP] 10 50 110 300

Maximum water content in emulsion

[vol%] -000

Halftime for water uptake [h] - 0 0 0

Stability ratio - 0 0 0

-: not determined
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D5 High Island Composite

Geographical area: Gulf of Mexico

Initial oil film thickness: 20 mm

Terminal oil film thickness: 0,5 mm

Release rate: 1.33 metric tons/minute

Sea temperature: 20°C and 29°C

Wind speed: 2 m/s, 5 m/s, 10 m/s and 15 m/s

The data used as input to the SINTEF OWM for High Island Composite are given in Table D13 to

Table D15.

Table D.13: Physical and chemical data for High Island Composite

Chemical/physical property

Specific Gravity (60°F/15.56°C) 0.846

Pour Point (C°) -15

Reference temperature #1 (C°) 23

Viscosity at reference temperature #1 (cP) 23

Wax (wt%) 1.6

Asphaltenes (wt%) 0.03

Table D.14: The true boiling point values used for the High Island Composite.

Temperature

[°C]

Evaporated

[vol%]

120 3.0

140 5.7

150 7.0

160 8.6

170 10.7

180 12.8

190 15.3

200 18.2

210 20.3

220 23.0

230 25.5

240 26.8

250 31.9

280 40.0

300 45.0

350 56.0

380 61.0

400 64.0

425 68.0

450 72.0
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Table D.15: Experimental results from the bench-scale laboratory testing (see chapter C1) at

23°C.

Chemical/physical property Fresh 150°C+ 200°C+ 250°C+

Boiling point [°C] - - - 285

Evaporation [vol%] 0 7.0b 18.2b 32.7

Residue [wt%] 100 93.9c 83.5c 70

Specific gravity [g/L] 0.847 0.853c 0.864c 0.879

Pour point [°C] -36 -20* -10* 0

Viscosity at shear 10s-1 [cP] 23 40* 60* 83

Maximum water content in emulsion [vol%] - 70f 70f 70f

Viscosity of max water emulsion at shear

10s-1 [cP] - 200f 400f 500f

Halftime for water uptake [h] - 0.25f 0.25f 0.25f

Stability ratio - 0f 0f 0f

-: not determined

f: From meso scale flume data

b: From boiling point curve

c: Calculated from boiling point curve

*constructed data

The High Island Composite sample received for the weathering study were in fact an emulsion.

This disabled a proper weathering study, and a lot of the weathering data had to be extracted from

data obtained in the meso scale flume, calculated, or constructed with background in experience

from studies of similar oils. The results from the meso scale flume is, however, regarded realistic

compared to a real weathering situation, and should provide relevant input data to the OWM.
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Appendix E: List of abbreviations, symbols and acronyms
128

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Term Abbreviation, symbol or acronym

Benzene, toluene, etylbensen, o-, m- and p-xylenes BTEX

Carbon C

Centi Poise cP

Cubic meters m3

American Petroleum Index API

Degrees Celsius °C

Dehydrating D

Flame Ionization Detector FID

Gas Chromatograph/Gas Chromatography GC

Gram g

Hours h

Hydrogen H

Kilo Pascal kPa

Liter L

Meter m

Microliter μL

Micrometer μm

Milligram mg

Milliliter mL

Millimeter mm

Millimeters mm

Minute min

Nickel Ni

Nitrogen N

Nitrogen, Sulfur and Oxygen NSO

Oil Weathering Model OWM

Oil-in-water o/w

Oxygen O

Parts per million ppm

Percent %

Polynuclear Aromatic Compounds PAH

Reciprocal second s

-1

Rotations per minute rpm

Second s

Sulfur S

The American Society for Testing and Materials ASTM

The fractional dehydration factor after 24 hours rotation and x hour

settling

Dx

The fractional dehydration factor after 24 hours rotation and x hours

settling

D24

The fractional dehydration factor after 24 hours rotation, 24 hours

settling and 10 rotations

D24 + rot

The time it takes in hours before the oil has emulsified half of its

maximum water content

t1/2

Unresolved Chromatographic Material UCM

Vanadium V

Volume percent vol%

Volumetric water-to-oil ratio in the emulsion after 24 hours rotation

and x hours settling

WORx

Dispersant to Emulsion ratio DER

Dispersant to Oil Ratio DOR

Volumetric water-to-oil ratio in the emulsion after 24 hours rotation WORref

Water Soluble Fraction WSF

Water-in-oil w/o

Water-to-oil ratio WOR

Weight percent wt%
129

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Appendix F: Literature list
130

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Bridiè, A. L., Wanders, T. H., Zegweld, W. V. and den Heijde, H. B., 1980: Formation,

Prevention and Breaking of Seawater in Crude Oil Emulsions, Chocolate Mousse. Mar. Poll.

Bull., 11, 343-348.

Daling, P. S., Brandvik, P. J., Mackay, D. og Johansen, Ø., 1990: Characterization of crude oils

for environmental purposes. Paper at the 13th AMOP seminar, Edmonton, Canada 1990. DIWOreport no. 8. IKU rapport 02.0786.00/08/90. Open, 22pp.

Daling, P. S. and Strøm, T., 1999: Weathering of Oils at Sea: Model/Field Data Comparisons.

Spill Science and Tech. Bull., 5 (1), 63-74.

Fiocco, R. J., Daling, P. S., DeMarco, G., and Lessard, R., R., 1999: Advancing Laboratory/Field

Dispersant Effectiveness Testing. OSC, pp 177-185.

FOH, 1984: Oljers skjebne og effekter i havet, Avslutningsrapport, Miljøverndepartementet,

Norge.

Hokstad, J. N., Daling, P. S., Lewis, A., Strøm-Kristiansen, T., 1993: Methodology for testing

water-in-oil emulsions and demulsifiers. Description of laboratory procedures. In: Proceedings

Workshop on Formation and Breaking of W/O Emulsions. MSRC, Alberta, June 14-15, 24pp.

ITOPF 1986, Fate of Marine Oil Spills. Technical information paper no. 11/86. The

InternationalTankers Owners Pollution Federation Ltd., London, England.

Johansen, Ø., 1991, Numerical modelling of physical properties of weathered North Sea crude

oils. DIWO-report no. 15. IKU-report 02.0786.00/15/91. Open.

Leirvik, F.,Moldestad, M.Ø., Johansen, Ø., 2001: Kartlegging av voksrike råoljers tilflytsevne til

skimmere. SINTEF report STF 66F01157.

Mackay, D, Buist, I., Mascararenhas, R. and Paterson, S., 1980: Oil Spill Processes and models.

Report EE-8, Environment Canada, Ottawa, Ontario.

Mackay, D. and Zagorski, W., 1982: Studies of W/o Emulsions. Report EE-34: Environment

Canada, Ottawa, Ontario.

Martinsen, E.A., 1994: The operational oil drift system at DNMI. The Norwegian Meteorological

Institute, Technical Report No 125, Oslo, Norway, 51 pp.

McDonagh, M., Hokstad, J. N. og Nordvik, A. B., 1995: Standard procedure for viskosity

measurement of water-in-oil emulsions. Marine Spill Response Corporation, Washington D. C.,

MRSC Technical Report Series 95-030, 36pp.

Moldestad, M., Singsaas, I., Resby, J. L. M., Faksness, L.-G. og Hokstad, J. N., 2001: Statfjord A,

B og C. Egenskaper og forvitring på sjøen, karakterisering av vannløselige komponenter relatert

til beredskap. SINTEF rapport nr. STF66 A00138. Åpen. 121pp.

National Research Council (NRC), 1985: Oil in the sea. Input, fates, and effects. National

Academy Press, Washington D. C.
131

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Nordvik, A., B., Daling P., S. and Engelhardt, F. R., 1992: Problems in the interpretation of spill

response technology studies. In: Proceedings of the 15th AMOP Technical Seminar, June 10-12,

Edmonton, Alberta, Canada, pp. 211-217.

Singsaas, I., Daling, P. S. and Jensen, H. V., 1993: Meso-scale laboratory weathering of oils. IKU

report 22.2042.00/04/93, 81pp.

Ross, S. L., 1986: An experimental study of the oil spill treating agents that inhibit emulsification

and promote dispersion. Report EE-87, Environmental Canada, Ottawa, Ontario.

Stiver, W. and Mackay, D., 1984: Evaporation rate of spills of hydrocarbons and petroleum

mixtures. Environ, Sci. Technol., 18 (11), 834-840.

Strøm-Kristiansen, T., Daling, P.S., 1994: Forvitringsegenskaper på sjøen for Brage Råolje. En

håndbok for Norsk Hydro a.s.. IKU report no. 96.116.