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TEXAS COMMISSION ON ENVIRONMENTAL QuAlflIn'filVISION Bryan W. Shaw, Ph.D., Chairman

Buddy Garcia, Commissioner

Carlos Rubinstein, Commissioner

Mark R. Vickery, P.G., Executive Director

Protecting Texas by Reducing andPreventing Pollution April 1,2010

Docket No. 2009-0801-SIP Project No. 2009-018-SIP-NR**y",·~:·** -,...r;·,

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:::**~-~!'** Alfredo "AI" Armendariz, Ph.D., Regional Administrator
U.S. Environmental Protection Agency

- Region 6
1445 Ross Avenue Dallas, Texas 75202-2733 w

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Dear Dr. Armendariz:

On March 10,2010, the Texas Commission on Environinental Quality (Commission) adopted a revision to the

state implementation plan (SIP) for demonstration of reasonable further progress for the Houston-GalvestonBrazoria (HGB) 1997 eight-hour ozone nonattainment area.

The Commission adopted the HGB Reasonable Further Progress (RFP) SIP revision, demonstrating that the

RFP emissions reduction requirement will be met for the six-year period (2003-2008) beginning Janumy 1 of the

year following the year used for the baseline emissions inventory (2002) and all remaining three-year periods

after the first six-year period (2009-2011, 2012-2014, and 2015-2017) out to the area's attainment date (2019).

This SIP revision also sets the nitrogen oxides (NOx) and volatile organic compounds (VOC) motor vehicle
emissions budgets (MVEB) for transportation conformity purposes for the milestone years 2008, 2011, 2014, 2017, and 2018.

Enclosed are the proposed revision to the SIP, a public hearing certification, a complete record of the public hearings, and the accompanying order. I look forward to your expeditious approval ofthis SIP revision.

Sincerely,

# ~~;dAtv- Bryan W. Shaw, Ph.D.
Chairman

BWS/ts

Enclosures

cc: The Honorable Rick Perry, Governor of Texas

Mr. Toby Baker, Office of Budget, Planning and Policy, Office of the Governor

.Mr. MarkR. Vickery, P.G., Executive Director, Texas Commission on Environmental Quality

P.O. Box 13087 Austin, Texas 78711-3087 512-239-1000 Internet address:www.tceq.state.tx.us

'.' " 'dTexas Commission on Environmental Quality Public Hearings October 28 and 29. 2009

Concerning Revisions to the HGB Eight-Hour Ozone Reasonable Further Progress SIP Project No. 2009-018-SIP-NRREVISION TO THE STATE IMPLEMENTATION PLAN FOR

THE CONTROL OF OZONE AIR POLLUTION

HOUSTON-GALVESTON-BRAZORIA 1997 EIGHT-HOUR

OZONE STANDARD NONATTAINMENT AREA

TCEQ

TEXAS COMMISSION ON ENVIRONMENTAL QUALITY

P.O. BOX 13087 AUSTIN, TEXAS 78711-3087

Houston-Galveston-Brazoria Reasonable Further Progress State Implementation Plan Revision for th e1997 Eight-Hour Ozone Standard

PROJECT NO. 2009-018-SIP-NR

Adopted March 10, 2010HGB Reasonable Further Progress SIP Revisi on for the 1997 Eight-Hour Ozone Standard

ix LIST OF APPENDICES

Appendix Appendix Name

Appendix 1 HGB Reasonable Further Progress Demonstration Calculations Spreadsheet

Appendix 2 Development of Reasonable Further Progress Point Source Inventories

Appendix 3 Development of Reasonable Further Progress Area Source Inventories

Appendix 4 Development of Reasonable Further Progress Non-Road Mobile Source Emissions Inventories for Source Categories in the EPA’s NONROAD 2005

Model

Appendix 5 Development of Reasonable Further Progress Non-Road Mobile Source Emissions Inventories for Airports

Appendix 6 Development of Reasonable Further Progress Non-Road Mobile Source

Emissions Inventories for Locomotives

Appendix 7 Development of Reasonable Further Progress Non-Road Mobile Source

Emissions Inventories for Commercial Marine Vessels

Appendix 8 Development of Reasonable Further Progress Non-Road Mobile Source Emissions Inventories for Drilling Rigs

Appendix 9 Houston-Galveston-Brazoria 1997 Eight- Hour Ozone Nonattainment Area Reasonable Further Progress On-Road M obile Source Emissions InventoriesAPPENDIX 8

DEVELOPMENT OF REASONABLE FURTHER PROGRESS NON-ROAD MOBILE

SOURCE EMISSIONS INVENT ORIES FOR DRILLING RIGSOilfield drilling rig diesel engines are included in the NONROAD model category “Other Oilfield Equipment” which includes various types of equipment. Due to the significant nature of the oil and gas exploration and production industry, the emissions inve ntory for diesel drilling rigs was selected to be included in a contract with Eastern Research Group, In c. This appendix consists of portions of the report developed by ERG, entitled Emissions from Oil and Gas Production Facilities , relevant to the development of an inventory for drilling rig emissions.ERG No. 0227.00.001.001



### EMISSIONS FROM OIL AND GA S PRODUCTION FACILITIES

DRAFT FINAL REPORT

TCEQ Contract 582-7-84003

Work Order No. 1

Prepared for:

Mr. Bertie Fernando, P.E. Texas Commission on Environmental Quality Air Quality Division

Mail Code 206

P.O. Box 13087 Austin, Texas 78711-3087

Prepared by:

Eastern Research Group, Inc.

1600 Perimeter Park Drive

Suite 200 Morrisville, North Carolina 27560

August 21, 2007TABLE OF CONTENTS

Section Page

LIST OF TABLES................................................................................................................. ........ iii

EXECUTIVE SUMMARY ........................................................................................................... vi

1. INTRODUCTION ........................................................................................................... 1-1

1.1 Purpose and Objectives........................................................................................ 1-1

1.2 Report Organization............................................................................................. 1-2

2. CHARACTERIZATION OF OIL AND GAS SOURCES INVENTORIED.................. 2-1

2.1 Definition of Oil and Gas Sources and SCCs ...................................................... 2-1

2.2 Emission and Activity Data Issues ...................................................................... 2-2 2.2.1 Onshore Exploration Sources .................................................................. 2-2

2.2.2 Onshore Production Sources.................................................................. 2-12

2.2.3 Offshore Production Sources ................................................................. 2-16

3. SUMMARY OF 2005 BASE YEAR EMISSIONS......................................................... 3-1

3.1 Oil and Gas Emissions Summary ........................................................................ 3-1

3.2 Source Category Contributions by Pollutant ..................................................... 3-27

3.2.1 Carbon Monoxide Emissions................................................................. 3-27 3.2.2 Nitrogen Oxide Emissions ..................................................................... 3-27 3.2.3 Volatile Organic Compound Emissions................................................. 3-28

3.2.4 Sulfur Dioxide Emissions ...................................................................... 3-28

3.2.5 Particulate Matter Emissions ................................................................. 3-28

3.3 Comparison of Emissions by County ................................................................ 3-29 3.3.1 Onshore Exploration .............................................................................. 3-29

3.3.2 Onshore Production ............................................................................... 3-40

3.3.3 Offshore Production Sources ................................................................. 3-41

3.4 Comparison of Emissions by Attainment Status ............................................... 3-42

iTABLE OF CONTENTS (Cont.)

Section Page

4. EMISSION PROJECTIONS ........................................................................................... 4-1

4.1 Projections Methodology..................................................................................... 4-1

4.2 Summary of Oil and Gas Area Sources Projected Emissions.............................. 4-5

5. REFERENCES ................................................................................................................ 5- 1

Appendix A – Documentation of Exploration Sources Emissions Appendix B – Documentation of Production Sources Emissions Appendix C – Documentation of Offshore Sources Emissions

iiLIST OF TABLES

Table Page

2-1a Identification of Source Categories A ddressed in the Texas Oil and Gas Emission Inventory in the Onshore Exploration Grouping ............................................................. 2-3 2-1b Identification of Source Categories Addr essed in the Texas Oil and Gas Emission Inventory in the Ons hore Production Grouping............................................................... 2-3 2-1c Identification of Source Categories A ddressed in the Texas Oil and Gas Emission Inventory in the Offshor e Production Grouping.............................................................. 2-4

2-2a Assignment of SCCs to Texas Oil and Gas Sources in the Onshore Exploration Grouping ...................................................................................................................... .... 2-4 2-2b Assignment of SCCs to Texas Oil and Gas Sources in the Onshore Production Grouping ...................................................................................................................... .... 2-5 2-2c Assignment of SCCs to Texas Oil an d Gas Sources in the Offshore Production Grouping ...................................................................................................................... .... 2-8

3-1 Summary of Annual Statewide Cr iteria Pollutant Emissions.......................................... 3-2 3-2 Summary of Ozone Season Daily (OSD) Statewide Criteria Pollutant Emissions ......... 3-4 3-3 Summary of Oil and Gas Category Emi ssion Contribution Rankings by Pollutant........ 3-6

3-4a County-Level Annual and Ozone Season Da ily (OSD) Criteria Pollutant Emissions for Exploration Sources ................................................................................................... 3-8 3-4b County-Level Annual and Ozone Season Da ily (OSD) Criteria Pollutant Emissions

for Production Sources................................................................................................... 3-16 3-4c County-Level Annual and Ozone Season Da ily (OSD) Criteria Pollutant Emissions

for Offshore Platforms ................................................................................................... 3-24

3-5 Combined County-Level Emission Es timates for All Sources Included in the Inventory.............................................................................................................. 3-30

3-6 Summary of Oil and Gas Area Source Emissions by Attainment Status ...................... 3-43

4-1a Texas Counties in the Ons hore-Gulf Coast EIA Region ................................................. 4-2

4-1b Texas Counties in the Ons hore-Southwest EIA Region.................................................. 4-3

4-1c Texas Counties in the On shore-Shallow EIA Region...................................................... 4-3 4-1d Area-Blocks in the Offshore-Deep EIA Region .............................................................. 4-4

4-2a Projected EIA Production ................................................................................................ 4-5 4-2b Projected EIA Production (MMBtu)................................................................................ 4-5 4-2c Final Projection Fa ctors by EIA Region.......................................................................... 4-5

iiiLIST OF TABLES (Continued)

Table Page

4-3a CO Projected Emissions by Location and Type .............................................................. 4-6

4-3b NO

x Projected Emissions by Location and Type............................................................. 4-6

4-3c PM 10 PRI Projected Emissions by Location and Type .................................................... 4-6

4-3d PM 2.5 PRI Projected Emissions by Location ................................................................... 4-7

4-3e SO 2 Projected Emissions by Location and Type ............................................................. 4-7 4-3f VOC Projected Emissions by Location and Type ........................................................... 4-7

ivLIST OF ACRONYMS

Acronym Definition

API American Petroleum Institute

CAPP Canadian Associati on of Petroleum Producers

CBM Coal Bed Methane

CERR Consolidated Emissions Reporting Rule

CO Carbon Monoxide

DOE U.S. Department of Energy

EIA Energy Information Administration

ERG Eastern Research Group

GPA Gas Processors Association

HARC Houston Advanced Research Center hp Horsepower

H 2 S Hydrogen Sulfide

MMBBL Million Barrels

MMBTU Million British Thermal Units

MMS Minerals Management Service

MMscf Million Standard Cubic Feet

Mscf Thousand Standard Cubic Feet

MW Molecular Weight

NEI National Emissions Inventory

NH 3 Ammonia

NIF NEI Input Format

NO

x Nitrogen Oxides

OFW Offshore Federal Waters

OSW Offshore State Waters

OE Onshore Exploration

OP Onshore Production

OSD Ozone Season Daily

PM Particulate Matter

PM 10 PM with particle diameter less than 10 micrometers

PM 2.5 PM with particle diameter less than 2.5 micrometers

SCC Source Classification Code

scf Standard Cubic Feet

SIP State Implementation Plan

SO 2 Sulfur Dioxide TCEQ Texas Commission on Environmental Quality

TexAER Texas Air Emissions Repository

THC Total Hydrocarbons

TRC Texas Railroad Commission

TXCO Texas Exploration Company

US EPA United States Environmental Protection Agency

VOC Volatile Organic Compounds

WRAP Western Regional Air Partnership WYDEQ Wyoming Department of Environmental Quality

vEXECUTIVE SUMMARY

The purpose of this study was to compile a comprehensive emissions inventory for onshore and offshore oil and gas exploration and pr oduction facilities in Texas for the base year 2005. The inventory was compiled for criteria pollutant emissions and ammonia (NH 3 ) emissions as permissible with available emission factors. The emissions inventory will be used for general inventory compilation and tracking purposes, trends an alysis, and potential control strategy development purposes. Related to this, the inventory will also potentially serve as improved input data to photochemical air qua lity dispersion modeling, emissions sensitivity analyses, State Implementation Plan (SIP), and rule development activities.

This project addressed the development of an emissions inventory for oil and gas industry

sources in Texas that have not been well charact erized previously. The oil and gas exploration and production industry is a large and complex one with many different potential sources of air pollution. The larger sources such as refineries , bulk plants, and large transmission/distribution stations are generally well identi fied and typically treated as ma jor point sources for inventory purposes. The Texas Commission on Environmenta l Quality (TCEQ) already has good quality inventories on these sources. The industry, how ever, contains many smaller and much more

diffuse sources that occur in the course of e xploring for oil and gas and bringing these products to the marketplace. Many of these sources fit the definition of being non- point or area sources, i.e., they have emissions below major source th resholds, they are large in number, and are geographically dispersed. Hist orically many of these area oil and gas sources have not been adequately inventoried. These “missing” source emissions, their identifi cation and locations can be significant.

The goals of this study were to identify the extent of the ar ea oil and gas source categories, including defining new categories not previously identified, and to develop preliminary baseline emissions estimates for as many of the identified categories as possible using readily available data from studies comp leted in the last few years. The emissions estimates were developed using top-down, area source methods (i.e., the inventory was not intended to be on a source-by-source, bottom-up basis). This approach was taken to be

consistent with the resources that are available for the project. The oil and gas industry in Texas is very large and diverse. Co mpiling an inventory on a point sour ce basis for a state the size of Texas would be very resource intensive and co stly. By applying th ese broader area source methods, preliminary emission estimates could be obtained that start to give some reference points for the level of emissions a ttributable to these previously unc haracterized sources. It also helps provide input on where effort should be placed in the future to refine and improve the data.

The oil and gas source categories that were the focus of initial investigations included the following. Sources were organized into thr ee groups – onshore explor ation, onshore production, and offshore production.

Exploration sources:

• Drilling Rigs

• Gas Well Completions

• Oil Well Completions

vivii • Gas Well Pneumatic Devices

• Oil Well Pneumatic Devices

Production sources:

• Wellheads

• Compressor Engines

• Dehydrators

• Heater Treaters

• Oil and Condensate Storage Tanks

• Loading of Oil and Condensate for Transportation

• Pump and Piping Compone nt Fugitive Losses

• Coal Bed Methane (CBM) Engines

Offshore platforms:

• Oil and Gas Platforms Operating in Texas State Waters (0-10 miles from shore)

• Oil and Gas Platforms Operating in Fede ral Waters (>10-25 miles from shore)

These are the source types included in the emi ssions inventory. In some cases, these source categories have multiple emission sources associated with them. For example, for Drill Rigs,

emission estimates were assembled for drill ri g power engines and for mud degassing operations.

Emission estimates were constructed for each source at the county level. Both annual and ozone season daily emission estimates were cal culated. Much of the activity data used to develop the emission estimates came from records maintained by the Texas Railroad Commission (TRC). The 2005 base year emission estimates were also projected to future years. Projection years included 2010, 2015, and 2020. A procedure involving the use of U.S Department of Energy (DOE), Energy Informa tion Administration (EIA ) oil and gas production growth estimates for the Texas region was used to perform the projections.

For emissions of nitrogen oxides (NO

x ), onshore drilling rig engine and compressor engine sources were found to contribute the greate st amounts to statewide area source emissions. These two categories were responsible for roughly 95% of statewide emissions from oil and gas area sources. The largest sources of volatile organic compounds (VOC), comprising 62.4% of the state area sources total, were found to be onshore production glyc ol dehydrators (26.9%), onshore condensate storage tanks (22.9%), and onshore gas production wellheads (12.6%). Sulfur dioxide (SO 2 ) emissions were dominated by onshore dr ill rig engines (97.4%). Similarly for carbon monoxide (CO), the largest oil and gas area sources were onshore production compressor engines (70.5%), onshore drill rig engines (21.8%), offshore platform compressor engines (3.6%), and onshore producti on gas well completions (1.7%). Emissions of particulate matter (PM), PM 10 and PM 2.5 , were found to be dominated by onshore production drill rig engines (53.8% for PM 10 and 53.3% for PM 2.5 ) and onshore compresso r engines (42.5% for

PM 10 and 43% for PM 2.5 ). The final 2005 emission estimates were put into National Emissions Inventory (NEI) Input Format (N IF) to facilitate reporting to EP A under Consolidated Emissions Reporting Rule (CERR) requirements.1.0 INTRODUCTION

1.1 Purpose and Objectives

The purpose of this study is to compile a comprehensive emissions inventory for onshore oil and gas exploration and producti on facilities in Texas and for offshore production platforms (within 25 miles of the Texas coast) for the base year 2005. The list of onshore oil and gas sources ad dressed in the study, as defined in the Work Order, is as

follows.

Exploration sources including:

• Drilling Rigs - diesel engines - degassing of drilling muds

• Gas Well Completions - flaring - venting

• Oil Well Completions - flaring - venting

• Gas Well Pneumatic Devices

• Oil Well Pneumatic Devices

Production sources including:

• Wellheads

• Compressor Engines

• Dehydrators

• Heater Treaters

• Oil and Condensate Storage Tanks

• Loading of Oil and Condensate for Transportation

• Pump and Piping Compone nt Fugitive Losses

• Coal Bed Methane (CBM) Pump Engines

Offshore oil and gas production platforms were inventoried in both state waters off the coast, which spans from shore out to a distance of 10 miles, and in federal waters out to a distance of 25 miles (basically the band be tween 10 and 25 miles). The inventory was compiled for both criteria pollutant emissions and ammonia emissions.

This study primarily pertains to the devel opment of an emissions inventory for oil and gas industry sources in Texas that have not been well characterized previously. The oil and gas exploration and production industry is a large and complex one in Texas with many different potential sources of air pollution. The larger sources in the state such as refineries, bulk plants, and large transmi ssion/distribution stations are generally well identified and typically treated as major poi nt sources for inventory purposes. The TCEQ already has good quality inventories on thes e sources. The industry though contains many smaller and much more diffuse sources that occur in the course of exploring for oil

8and gas and bringing these products to the ma rketplace. Many of these sources fit the definition of being non-point or area sources , i.e., they have emissions below major sources thresholds, they are large in nu mber, and are geographically dispersed. Historically, many of these area oil and gas s ources have not been ad equately identified and inventoried. Identifying, locating, and qua ntifying these “missing” source emissions is a significant task.

The goals of this study are to identify th e extent of these area oil and gas source categories, including defining new categories not previously inventor ied, and to develop preliminary baseline emissions estimates for 200 5 for as many of the identified categories as possible using currently available data (i.e., time and resources for extensive surveys and/or new source testing are not available). Studies within the last three years by TCEQ, the Houston Advanced Research Ce nter (HARC), and th e Western Regional Partnership (WRAP) have produced data a nd methods that can be applied for the purposes of this inventory (HARC, 2 005; HARC, 2006a; HARC, 2006b; WRAP, 2005). The emissions estimates were developed us ing top-down, area source methods (i.e., the inventory was not estimated on a source-by-source, bottom-up basis). Compiling an inventory on a point source basis would be ve ry resource intensive and take much more

calendar time than was available for th is study. By applying broader area source methods, preliminary emission estimates can be obtained that start to give some reference points for the level of emissions attributable to these previous ly uncharacterized sources. It also helps provide input on where effort should be placed in the future to refine and improve the data. The study results will be used for general inventory compilation and tracking purposes, trends analysis, and potenti al control strategy development purposes. The results can also serve as improved input data to photochemical air quality dispersion modeling, emissions sensitivity analyses, SI P planning, and possible rule development

activities.

For planning purposes, the 2005 base year estimates were projected to future years 2010, 2015, and 2020. Also, the final base year inventory estimates were provided in National Emissions Inventory (NEI) Input Format (NIF) for the purposes of submittal to EPA in order to comply with Consolidated Emissions Reporting Rule (CERR) requirements, and to facilitate entry of the data into the state’s TexAER ( Tex as A ir

E missions R epository) database.

1.2 Report Organization

Section 2.0 of this report more thoroughl y identifies the oil and gas source categories addressed in the emissions inve ntory and describes how each emission source is being treated in terms of the inventory de velopment. The emissions aspects of each category are described, along with an identificat ion of the pollutants being inventoried for each. Each emission source is assigned a S ource Classification C ode (SCC) for tracking purposes and a table of all SCCs is presente d. Section 2.0 provides explanations of any assumptions or manipulations that had to be made to source categories to facilitate the development of area source emission estimates.

9The summary results of the 2005 emissions inventory development process are presented in Section 3.0. Su mmary emissions tables are provided on a statewide and county level basis for both annual and oz one season daily (OSD) emissions. The

emissions estimates are described in terms of known uncertainties and weaknesses, and suggestions for possible improvements are pr ovided. Discussion and analysis is also provided to compare and contrast how s ources rank relative to each other for each pollutant. Emissions are also presented to show geographic concentrations by county.

Section 4.0 presents information and data on the projection of the 2005 base year estimates to three future years (2010, 2015, and 2020). The data and methods used to construct projection technique s are described and statewid e and county level emission estimate are provided for all three projection years. Section 5.0 contains reference citations for the report.

The full documentation and detailed count y level 2005 emissions estimates data for each inventoried source category are provided in Appendices A, B, and C. The appendices address the onshore explorati on, onshore production, and offshore production source groupings, respectively. Each appendi x discussion provides fu ll and transparent documentation on how each category’s estimates were derived, the procedures and assumptions used, and the input emission factor and activity data app lied to determine all

emission estimates.

102.0 CHARACTERIZATION OF OIL AND GAS SOURCES INVENTORIED

2.1 Definition of Oil and Gas Sources and SCCs

The majority of the list of onshore oil and gas explor ation and production source categories addressed in this project was ta ken from a Western Regi onal Air Partnership (WRAP) study on area source oil and gas emi ssions (WRAP, 2005). In the WRAP study, volatile organic compounds ( VOC), nitrogen oxides (NO

x ), carbon monoxide (CO), and sulfur dioxide (SO 2 ) emission estimates were generate d for several non-point oil and gas sources in 14 states of the WRAP region (note: not all applicable pollutants were estimated for every source). Many of these sa me sources are prevalent in Texas. Other oil and gas emissions sources were specified by TCEQ and in oil and gas industry data produced by the Minerals Management Servi ce (MMS) for offshore oil and gas platforms

in Texas state waters and federal wa ters (MMS, 2004; TCEQ, 2007b). The TCEQ provided information on the names and locat ion coordinates for over 200 oil and gas platforms located within 25 miles of the Texas coastline. The MMS information characterizes emissions from 16 platform emission unit types (e.g., boiler, engines, turbines, amine units, glycol de hydrators, fugitives) at the eq uipment level for base year 2005. Currently, base year 2005 estimates are being finalized ; however, MMS has provided authorization for TCEQ to use these dr aft data for the purposes of this project, provided the data are marked as draft and are not released, cite d, quoted, or otherwise used outside of TCEQ until such time as MMS publishes the data as final.

In this project, the oil and gas source categories have been divided into three major groups: onshore exploration sources, onshore production sources, and offshore production platforms. For exploration and production, depending on the definition of the operations used, there is clearly some pot ential for overlap occurring between some emission sources, i.e., a source such as completion venting could be considered exploration or production. For the purpos es of this project and this memorandum, exploration, production, and offshore sources are defined as follows.

Exploration sources include:

• Drilling Rigs

• Gas Well Completions

• Oil Well Completions

• Gas Well Pneumatic Devices

• Oil Well Pneumatic Devices

Production sources include:

• Wellheads

• Compressor Engines

• Dehydrators

• Heater Treaters

• Oil and Condensate Storage Tanks

• Loading of Oil and Condensate for Transportation

11• Pump and Piping Compone nt Fugitive Losses

• Coal Bed Methane Pump Engines Offshore stationary sources include:

• Oil and Gas Platforms Operating in Texas State Waters (sources 0-10 miles from shore)

• Oil and Gas Platforms Operating in Fe deral Waters (sources >10-25 miles from shore)

Emission totals in Section 3.0 are pres ented according to these groupings.

Table 2-1 (a, b, and c) provides a summary of the source categories evaluated in the emissions inventory (according to their grouping), the specific operations or processes that generate air emissions, and an identific ation of the pollutants associated with each source. Table 2-2 (organized as a, b, and c for the three groupings) further delineates these source category types into specific emi ssion processes, and presents SCCs for each individual emissions process. For onshor e exploration and production sources, most of the SCC assignments originate as new c odes proposed by TCEQ (TCEQ, 2007a) or codes proposed by ERG as a resu lt of assessing all of the emission processes included in the inventory. The offshore SCC assignments are a combination of ones on the official EPA list and ones proposed by ERG.

2.2 Emission and Activity Data Issues

This discussion further describes and cl arifies the oil and gas emission sources included in the inventory. F actors affecting emissions are di scussed and the rationales for using certain assumptions (related to source operation) for the purposes of the inventory are explained. General information is provided on how source emissions will be estimated. The detailed procedural descri ption of the estimation processes and the accompanying input data and calculations are presented in Appendices A, B, and C.

2.2.1 Onshore Exploration Sources

Drilling Rigs/Engines

This category pertains to the engines used to generate power to run drilling rigs in the exploration field. These engines are assu med to be burning diesel fuel. Emission factors for diesel-fired engi nes operating drilling rigs were taken from AP-42 (US EPA, 1996). Drilling rig engines we re assumed to operate with a maximum horsepower (hp) greater than 600 hp (Engeser, 2004). For SO 2 emissions, the weight percent of sulfur used in the diesel fuel (low sulfur fuel) is assumed to be 3400 ppmv or 0.34% by weight for every county in Texas (EPA, 2004b). It is possible that some counties in Texas may be using fuels with a lower or higher sulfur content.

12Table 2-1a. Identification of Source Categor ies Addressed in the Texas Oil and Gas Emission Inventory in the Onshore Exploration Grouping

Onshore Exploration Source Type Specific Emission Sources Potential

Pollutants a

Diesel engines to run electricity generators SO 2 , NO

x , VOC,

PM 10 , PM 2.5 , CO Drilling Rigs Drill mud degassing (open pits or storage tanks) VOC

Emissions from flaring from the gas well completion phase CO, NO X , VOC Gas Well Completion Emissions from venting from the gas well completion phase VOC

Emissions from flaring from the oil well completion phase CO, NO X , VOC,

SO 2 Oil Well Completion Emissions from venting from the oil well completion phase VOC

Gas Well Pneumatic

Devices Fugitive emissions from pneumatic devices used during gas well exploration and production VOC

Oil Well Pneumatic

Devices Fugitive emissions from pneumatic devices used during oil well exploration and production VOC

a PM = Particulate Matter

Table 2-2a. Assignment of SCCs to Texas Oil and Gas Sources in the Onshore Exploration Grouping

Onshore Exploration Source Types and Emission Processes Proposed SCC SCC Description (abbreviated) a Drilling Rigs - Diesel Engines 2310001200 ERG proposed SCC; Drilling Rig Engines using diesel fuel - Mud Degassing 2310001100 ERG proposed SCC; Mud Degassing Activities Gas Well Completion – Flaring 2310021701 ERG proposed SCC; Flaring during Gas Well Completions Gas Well Completion – Venting 2310021702 ERG proposed SCC; Venting during Gas Well Completions Oil Well Completion – Flaring 2310011701 ERG proposed SCC; Flaring during Oil Well Completions Oil Well Completion – Venting 2310011702 ERG proposed SCC; Venting during Oil Well Completions Gas Well Pneumatic Pumps 2310021401 ERG proposed SCC; Gas Well Pneumatic Pumps Oil Well Pneumatic Pumps 2310011401 ERG proposed SCC; Oil Well Pneumatic Pumps

a Unless otherwise noted, SCCs were obtained from EPA’s official SCC list (US EPA, 2004a).

13All exploratory oil and gas drilling in Te xas requires a permit. On the Texas Railroad Commission (TRC) website, a listing of year 2005 approved drilling permits was available, with the assumption being made that this would be typical for actual drilling activities that occurred in 2005. It is possible that drilling permits approved in 2005, did not have actual drilling commen ce until 2006. Conversely, actual drilling may have taken place in 2005 under permit approvals made in 2004. An additional parameter retrieved for each approved permit is well depth.

For most of the drilling perm it data, the “spud date”, or the date in which drilling commenced, and the completed drilling date are included. Thus, actual number of drilling days can be calculated for each perm it. Unfortunately, the effort required for obtaining this information for over 11,000 permits was time and resource prohibitive. As an alternative, representa tive drilling profiles were developed for each county and wellbore type (vertical, horizontal, directi onal, etc.) by obtaining the number of days drilled (from spud date and completed dri lling date) for the permit with the maximum well depth. A total of 430 county-wellbore dr illing profiles were developed and applied to over 11,000 permits. As expected, wellbore pr ofiles that were “horizontal” took longer to drill significant depths when compared to “vertical” wellbores. Approximately 85% of identified drilling permits indicated the use of wellbore drilling. Using industry guidance, average horsepower ratings can be assigned for lightweight, intermediate, or heavyweight drilling operations (Engeser, 2004) . These classifications are based on well depth. For example, lightwei ght rigs are generally used for well depths between 1,500 to 2,000 meters (4,900 – 6,500 feet). The average horsepower for lightweight rigs is 650 hp. Similar factors are available for interm ediate and heavy wei ght rigs. Drilling operations are assumed to be 24-hours a da y during the drilling period. Thus, total engine power output in terms of horsepowe r-hours (hp-hr) can be calculated for each permitted drilling operation, which in turn allows for the estimation of emissions.

143.0 SUMMARY OF 2005 BASE YEAR EMISSIONS

This section of the project report presents summarized results of the Texas area source oil and gas emission inventory developm ent effort. Emission inventory estimates are presented on both statewide and county-spec ific bases according to the previously identified groupings of onshore explorat ion sources, onshore production sources, and offshore production sources (Section 3.1). In ad dition to presenting the inventory results, discussion is provided on the strengths a nd weaknesses of the inventory, inventory uncertainties, and possible improvements that can be made to the emission estimates.

Section 3.2 describes how the various indivi dual source categories compare and rank

relative to each other for each of the estimated pollutants. Section 3.3 provides input on the level of emissions per county and what counties represent the largest share of statewide emissions. In Section 3.4, emissions are examined in terms of county attainment/nonatta inment designations. The distribution of emissions by designation is presented.

3.1 Oil and Gas Emissions Summary

For the 2005 base year, emission estimate s were prepared on both an annual and ozone season daily (OSD) basis. The speci fic details on how each category’s emissions were calculated can be found in Appendix A (f or onshore exploration sources), Appendix B (for onshore production sources ), and Appendix C (for offshore production sources). Any required derivations of activity or emissi on factor data are explained, and all data

used for the derivations are shown. All a pplied equations are pr esented and discussed, and every variable, constant, and conversion factor used is defined and documented. Each source appendix section presents emi ssion estimates (in tabular form) on an SCC basis for every applicable county in the state. All of these individual emissions data are summed to provide the tables in Section 3.0. Electronic Excel ® spreadsheet files are provided along with this hard copy report th at mimic all of the information in the documentation appendices.

Table 3-1 presents a summary of annual statewide criteria pollutant emissions from individual area source oil and gas categorie s. Table 3-2 presents the same statewide information, but for emissions on an OSD ba sis as opposed to annual. The emissions data in Tables 3-1 and 3-2 are organized by the exploration, production, and offshore (divided into state and federal waters) groupi ngs. As shown in Table 3-1, the largest amount of CO emissions (70.6 %) comes from onshore produ ction sources (primarily from natural gas compressor engines). Emissions of NO

x are dominated by onshore exploration (54.2%) and onshore production so urces (41.6%). Drill rig engines are the most significant NO

x exploration category, while compressor engines are the major production-related NO

x source.

For VOC emissions, onshore production sour ces make up 85.1% of the total VOC and onshore exploration sources at 14.3%. The chief produc tion sources contributing to VOC are glycol dehydrators (26.9%), conde nsate storage tanks (22.9%), and gas

1516 wellheads (12.6%). The onshore explorati on grouping, namely drill rig engines,

constitute 98.4% of SO 2 emissions. Drill rig engines (onshore exploration) and compressor engines (onshore production) togeth er are responsible for roughly 96.4% of PM (PM 10 and PM 2.5 ) emissions. The source category contributions are summarized by pollutant in Table 3-3.

Table 3-1. Summary of Annual Statew ide Criteria Pollutant Emissions

Annual Emissions (tons/yr)

Oil and Gas Emission Sources CO NO X PM 10 PM 2.5 SO 2 VOC Onshore Exploration Drilling Rig Engines 27,442 119, 647 1,998 1,954 13,697 3,183 Mud Degassing

-- -- -- -- -- 10,674 Pneumatic Pumps-Gas Wells

-- -- -- -- -- 73,474 Pneumatic Pumps-Oil Wells

-- -- -- -- -- 19,764 Well Completions: Gas Wells 2,180 401

-- -- -- 19,764 Well Completions: Oil Wells 74 14

-- -- 138 13,145 Onshore Exploration Total 29,695 120,061 1,998 1,954 13,835 120,240

Table 3-2. Summary of Ozone Season Daily (OSD) Statewide Criteria Pollutant

Emissions

Ozone Season Daily (tons/day)

Oil and Gas Emission Sources CO NO X PM 10 PM 2.5 SO 2 VOC Onshore Exploration Drilling Rig Engines 74.82 326.21 5.45 5.33 37.34 8.68 Mud Degassing

-- -- -- -- -- 29.10 Pneumatic Pumps-Gas Wells

-- -- -- -- -- 200.21 Pneumatic Pumps-Oil Wells

-- -- -- -- -- 182.12 Well Completions: Gas Wells 5.94 1.09

-- -- -- 53.88 Well Completions: Oil Wells 0.20 0.04

-- -- 0.38 35.81 Onshore Exploration Total 80.96 327.33 5.45 5.33 37.72 327.88Table 3-3. Summary of Oil and Gas Category Emission Contribution Rankings by PollutantCO EmissionsContributionsNOxEmissionsContributionsVOC EmissionsContributionsPM10EmissionsContributionsPM2.5EmissionsContributionsSO2EmissionsContributionsCompressor Engines(OP) – 70.5%Drill Rig Engines(OE) – 54.1%Glycol Dehydrators (OP)– 26.9%Drill Rig Engines(OE) - 53.8%Drill Rig Engines(OE) - 53.3%Drill Rig Engines(OE) – 97.4%Drill Rig Engines (OE) –21.8%Compressor Engines(OP) – 41.2%Condensate StorageTanks (OP) – 22.9%Compressor Engines(OP) – 42.5%Compressor Engines(OP) – 43%Oil WellCompletions (OE)– 1.0%Gas Well Completions(OE) – 1.7%Natural Gas Turbines(OSW) – 1.5%Gas Wellheads (OP) –12.6%Diesel Engines(OSW) – 1.9%Diesel Engines(OSW) – 1.9%All others - <1%eachAll others - <1% eachCompressor Engines(OFW) – 1.5%Crude Oil Storage Tanks(OP) – 9.1%All others - <1% eachAll others - <1% eachAll others - <1% eachGas & Oil WellPneumatic Devices (OE)– 8.7%Pump & Piping Fugitives(OP) – 5.1%Oil Wellheads (OP) –4.1%Oil Loading (OP) – 3.2%Gas Well Completions(OE) – 2.4%Oil Well Completions(OE) – 1.6%Mud Degassing (OE) –1.3%All others - <1% each173.2 Source Category Contributions by Pollutant

3.2.1 Carbon Monoxide Emissions

Total statewide emissions of CO for ons hore exploration and production and offshore production sources are estimated to be 125,968 tons pe r year. The top contributor to this amount is natural gas compressor engines used fo r onshore production. Compressor engines were responsible for 70.5% of total CO emissions in th e inventory. The next largest source after compressors was drill rig engines used in expl oration, constituting 21.8% of the CO emissions. The next four largest CO contributors are offs hore platforms-federal waters compressor engines (3.6%), gas well completions (1.7%), offshore platforms-state waters compressor engines (0.68%), and offshore platforms-state waters natu ral gas turbines (0.68%) . These six categories generate nearly 99% of the CO statewide esti mate from oil and gas area sources.

3.2.2 Nitrogen Oxide Emissions

Similar to CO emissions, oil and gas area source NO

x emissions are also dominated by onshore exploration drill rig engines and onshore production co mpressor engines. Total

estimated NO

x emissions for all oil and gas area s ources included in this inventory are 221,357 tons per year. Onshore explor ation drill rig engines make up 54.1% of this amount, while onshore production compressor engi nes are responsible for 41.1%. The two categories combined generate over 95% of all estimated NO

x emissions. The most significant of the remaining sources include offshore platforms-state waters natural gas turbines (1.5%), offshore platformsfederal waters compressor engines (1.5%), offs hore platforms-state wa ters diesel engines (0.45%), onshore production heat er treaters (0.44%), and o ffshore platforms-state waters compressor engines (0.38%). These seve n categories constitute 99.4% of the NO

x emissions estimated for oil and gas area sources statewide (including offshore sources).

3.2.3 Volatile Organic Compound Emissions

Practically every source in the inventory emits VOC, some less than 1 ton a year, while

others are estimated to release several hundred thousand tons per year. Total statewide VOC

from the sources included in the inventory have been estimated at 841,295 tons per year. Five categories dominate this emissions total ( 80.2% of all VOC) – onshore production glycol dehydrators (26.9%), onshore produ ction condensate storage tanks (22.9%), onshore production gas wellheads (12.6%), onshore production crude oil storage tanks (9.1%), and pneumatic

devices associated with onshore production gas and oil wells ( 8.7%). Of the remaining VOC emissions sources, six are responsible for 17.5% of VOC emissions, making these 11 categories the source of nearly 98% of all oil and gas area sources VOC emissions. The six categories comprising the 17.5% of emissions consists of onshore production pump and piping fugitives (5.1%), onshore production oil wellheads (4.1%), onshore pro duction oil loading (3.2%), onshore exploration gas well completions (2.4%), exploration oil well completions (1.6%), and onshore exploration mud degassing (1.3%).

3.2.4 Sulfur Dioxide Emissions

4-14-2 Estimated emissions of SO 2 are clearly dominated by one source category – onshore exploration drill rig engines. This category is estimated to releas e 97.4% of the total SO 2 emissions from oil and gas area sour ces. The next la rgest source of SO 2 is onshore exploration oil well completions at 138 tons per year or 0.98 % of total emissions. Diesel engines and drill rig engines on offshore platforms-state waters are responsible for 0.56% and 0.44%, respectively,

of total SO 2 emissions. The remaining categories are estimated to be very minor SO 2 emitters.

3.2.5 Particulate Matter Emissions

Contributions to PM 10 and PM 2.5 emissions track very cons istently. Two categories dominate (over 96% of emissions) both PM 10 and PM 2.5 emissions – onshore exploration drill rig engines and onshore production natu ral gas compressor engines. Th e contributions to emissions

are summarized as follows.

PM 10

Drill Rig Engines – 53.8% of emissions Compressor Engines – 42.5% of emissions

PM 2.5

Drill Rig Engines – 53.3% of emissions Compressor Engines – 43.0% of emissions

The only other PM emissions category that is esti mated to contribute at least 1% to total PM 10 or
PM 2.5 emissions is diesel engines at offshore state waters platforms. This source category is responsible for approximately 1.9% of PM 10 and PM 2.5 emissions. All remaining PM 10 and PM 2.5 categories are less than 1% contributors.5.0 REFERENCES

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