Drilling Rig Emission 

Inventory for the State of 

Texas 

Final Report 

Prepared for: 

Texas Commission on Environmental 

Quality 

Prepared by: 

Eastern Research Group, Inc. 

July 15, 2009
Drilling Rig Emission Inventory for the State of Texas 

Final Report 

Prepared for: 

Greg Lauderdale 

Texas Commission on Environmental Quality 

P. O. Box 13087 

Austin, TX 78711-3087 

Prepared by: 

Rick Baker 

Mike Pring 

Eastern Research Group, Inc. 

5608 Parkcrest Drive, Suite 100 

Austin, TX 78731 

July 8, 2009 
Table of Contents 

LIST OF ACRONYMS ................................................................................................................. iii 

1.0 Executive Summary......................................................................................................... 1-1 

2.0 Introduction...................................................................................................................... 2-1 

3.0 Review of Existing Literature.......................................................................................... 3-1 

3.1 Review of Existing Studies.................................................................................. 3-1 

3.2 Review of Existing Data ...................................................................................... 3-2 

3.3 Drilling Rig Overview ......................................................................................... 3-3 

4.0 Data Collection Plan ........................................................................................................ 4-1 

4.1 Participant Recruitment ....................................................................................... 4-1 

4.2 Phone/Email Surveys........................................................................................... 4-1 

4.3 Confidentiality ..................................................................................................... 4-2 

5.0 Data Collection Results.................................................................................................... 5-1 

5.1 Survey Findings ................................................................................................... 5-1 

5.2 Model Rig Category Development ...................................................................... 5-3 

5.3 Fracturing............................................................................................................. 5-6 

6.0 Emissions Inventory Development and Results .............................................................. 6-1 

6.1 Activity Data........................................................................................................ 6-1 

6.1.1 2008 Base Year Activity.......................................................................... 6-1 

6.1.2 2002 and 2005 Prior Years Activity ........................................................ 6-1 

6.1.3 2009 through 2021 Projected Activity..................................................... 6-3 

6.1.4 2002, 2005, and 2008 through 2021 Activity Summary..........................6-6 

6.2 Model Rig Emission Profiles............................................................................. 6-12 

6.2.1 Model Rig Engine Profiles..................................................................... 6-12 

6.2.2 Model Rig Emission Factors.................................................................. 6-14 

6.3 Emission Estimation Methodology.................................................................... 6-17 

6.4 Results................................................................................................................ 6-19 

6.4.1 Emission Summary ................................................................................ 6-19 

6.4.2 NIF 3.0 Files .......................................................................................... 6-19 

7.0 Conclusions and Recommendations................................................................................ 7-1 

8.0 References........................................................................................................................ 8-1 

Appendix A – Approved Data Collection Plan 

Appendix B – Survey Letter 

Appendix C – Drill Rig Survey Form 

Appendix D – Survey Data 

Appendix E – Total Drilling Depth by County by Model Rig Well Type Category 

Appendix F – Emission Factors 

Appendix G – Annual and OSD County-Level Emission Estimates 

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List of Tables 

Table 1.1 Drilling Rig Estimates (tons/year)............................................................................... 1-2 

Table 3.1 Existing Oil and Gas Exploration Emissions Studies.................................................. 3-1 

Table 5.1 Survey Summary Statistics .......................................................................................... 5-3 

Table 5.2 Model Rig Category Statistics..................................................................................... 5-5 

Table 6.1 2002 and 2005 Prior Year Activity Scaling Factors.................................................... 6-3 

Table 6.2 Projected Crude Oil Production 2008-2021................................................................. 6-5 

Table 6.3 Projected Natural Gas Production 2008-2021 ............................................................. 6-5 

Table 6-4 Projected Growth Factors 2009-2021.......................................................................... 6-7 

Table 6.5 2008 Total Depth by Model Rig Well Type Category (1,000 feet)............................. 6-8 

Table 6.6 Model Rig Engine Parameters................................................................................... 6-14 

Table 6.7 PM10 Speciation Factors ............................................................................................ 6-16 

Table 6.8 TOG Speciation Factors............................................................................................. 6-16 

Table 6.9 TxLED Counties........................................................................................................ 6-17 

Table 6.10 Texas Drilling Rig Estimates (tons/year)................................................................. 6-20 

Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estimates......... 6-21 

List of Figures 

Figure 5.1 Counties with Survey Data......................................................................................... 5-4 

Figure 6.1 TRC District Map....................................................................................................... 6-2 

Figure 6.2 EIA Regions ............................................................................................................... 6-4 

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iii 

LIST OF ACRONYMS

Acronym Definition

API American Petroleum Institute 

CARB California Air Resources Board 

CO Carbon Monoxide 

DOE U.S. Department of Energy 

EIA Energy Information Administration 

ERG Eastern Research Group 

HAP Hazardous Air Pollutant 

hp Horsepower 

IADC International Association of Drilling Contractors 

MMBBL Million Barrels 

NEI National Emissions Inventory 

NIF NEI Input Format 

NOx Nitrogen Oxides 

OSD Ozone Season Daily 

PM10 PM with particle diameter less than 10 micrometers 

PM2.5 PM with particle diameter less than 2.5 micrometers 

SCC Source Classification Code 

SIP State Implementation Plan 

SO2 Sulfur Dioxide 

TCEQ Texas Commission on Environmental Quality 

TexAER Texas Air Emissions Repository 

TIPRO Texas Independent Producers and Royalty Owners Association 

TOG Total Organic Gases 

TRC Texas Railroad Commission 

TxLED Texas Low Emission Diesel 

TXOGA Texas Oil and Gas Association 

US EPA United States Environmental Protection Agency 

VOC Volatile Organic Compounds 

WRAP Western Regional Air Partnership 
1.0 Executive Summary 

The purpose of this study was to develop a comprehensive emissions inventory for 

drilling rig engines associated with onshore oil and gas exploration activities occurring in Texas 

in 2008. Oil and gas exploration and production facilities are considered some of the largest 

sources of area source emissions in certain geographical areas, dictating the need for continuing 

studies and surveys to more accurately depict these activities. A 2005 base year oil and gas 

emissions inventory developed for the Texas Commission on Environmental Quality (TCEQ) by 

Eastern Research Group (ERG) in 2007 (TCEQ, 2007) was comprehensive in coverage of all 

exploration and production facility and equipment types, including drilling rig engines. However, 

that project relied on data from secondary sources with assumptions applied to represent local 

activities. The Western Regional Air Partnership (WRAP) developed a comprehensive emissions 

inventory of oil and gas exploration and production facilities for the western states that did not 

include Texas, although the previous ERG study did make use of the WRAP results in terms of 

methodology and emission factors where practicable. 

The current inventory effort built off of the previous 2007 study, focusing exclusively on 

drilling activities. The previous effort was expanded upon by improving both the activity data 

(well counts, types, and depths) used to estimate emissions, and through the development of 

updated drilling rig engine emission profiles. The improved well activity data was obtained 

through acquisition of the “Drilling Permit Master and Trailer” database from the Texas Railroad 

Commission (TRC), while the improved drilling rig emissions characterization profiles were 

obtained through a survey of oil and gas exploration and production companies. The activity data 

and emissions characterization data were then used to develop the drilling rig engine emissions 

inventory for a 2008 base year. 

In order to survey drilling rig contractors and oil and gas operators across the state, ERG 

purchased contact information for companies that were active in well drilling activities that 

occurred in Texas in 2008 through a commercial vendor (RigData®). Through phone and email 

surveys, ERG obtained 45 drilling rig profiles representative of over 1,500 wells drilled in Texas 

in 2008. 

The survey effort itself focused on collecting the following information from each 

respondent: 

• The number of engines on a rig 

• Engine make, model, model year, and size (hp) 

• Average load for each engine 

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• Engine function (draw works, mud pumps, power) 

• Actual engine hour data for each well (total hours) 

• Actual engine fuel use data for each well (total fuel use) 

• Total well drilling time (actual number of drilling days) 

• Total well completion time (number of days needed for well completion activities) 

• Well depth 

• Number of wells represented by survey 

Target pollutants for this inventory include nitrogen oxides (NOX), volatile organic 

compounds (VOC), carbon monoxide (CO), particulate matter (PM10 and PM2.5), sulfur dioxide 

(SO2), and hazardous air pollutants (HAP). Emissions were calculated for each county in Texas 

where drilling occurred in 2008 and are provided in annual tons per year and by typical ozone 

season day. For planning purposes, the 2008 base year estimates were used to develop 2002 and 

2005 prior year inventories, as well as projected inventories for 2009 through 2021. 2002 and 

2005 prior year inventories were based on TRC records of oil and gas well completions during 

those years, and U.S Department of Energy (DOE), Energy Information Administration (EIA) oil 

and gas production growth estimates were used to develop the projections for future years 2009 

through 2021. 

Emissions estimates developed from this inventory project may be used for improved 

input data to photochemical air quality dispersion modeling, emissions sensitivity analyses, State 

Implementation Plan (SIP) development, and other agency activities. The final 2002, 2005, and 

2008 base year inventory estimates are provided in National Emissions Inventory (NEI) Input 

Format (NIF) 3.0 to facilitate entry of the data into the state’s TexAER (Texas Air Emissions 

Repository) database, and for the purposes of submittal to US EPA. For purposes of NIF 

preparation, Source Classification Code (SCC) 23-10-000-220 (Industrial Processes - Oil and 

Gas Exploration and Production - All Processes - Drill Rigs) was used as provided by TCEQ 

(TCEQ, 2009). 

Table 1-1 summarizes the statewide annual emission estimates for 2002, 2005, and 2008 

through 2021. 

Table 1.1 Drilling Rig Estimates (tons/year) 

Year CO NOx PM10 PM2.5 SO2 VOC 

2002 13,305 35,828 2,552 2,475 4,776 3,631 

2005 15,878 42,854 3,036 2,945 5,977 4,337 

2008 16,721 55,238 2,543 2,467 956 4,326 

2009 16,769 55,457 2,550 2,474 961 4,340 

2010 16,336 53,123 2,417 2,344 45 4,182 

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Table 1.1 Drilling Rig Estimates (tons/year) (Continued) 

Year CO NOx PM10 PM2.5 SO2 VOC 

2011 15,117 48,462 2,319 2,249 44 3,806 

2012 14,748 46,253 2,263 2,196 43 3,665 

2013 12,008 39,793 1,378 1,337 38 3,413 

2014 11,945 39,461 1,372 1,331 38 3,392 

2015 11,755 38,837 1,350 1,310 37 3,349 

2016 11,558 36,440 1,320 1,280 37 3,320 

2017 8,915 34,771 1,118 1,085 36 2,800 

2018 6,114 31,282 811 787 35 2,227 

2019 6,073 31,127 805 781 35 2,215 

2020 6,035 30,771 800 776 35 2,205 

2021 3,299 26,063 448 435 33 1,504 
2.0 Introduction 

The purpose of this study was to develop a comprehensive emissions inventory for 

drilling rig engines associated with onshore oil and gas exploration activities occurring in Texas 

in 2008. Oil and gas exploration and production facilities are considered some of the largest 

sources of area source emissions in certain geographical areas, dictating the need for continuing 

studies and surveys to more accurately depict these activities. A previous study conducted by 

Eastern Research Group (ERG) in 2007 under TCEQ contract 582-7-84003, Work Order 01 was 

comprehensive in coverage of all the exploration and production facility and equipment types, 

including drilling rig engines, although this project relied on data from secondary sources with 

assumptions applied to represent local activities (TCEQ, 2007). The Western Air Regional 

Partnership (WRAP) developed a comprehensive emissions inventory of oil and gas exploration 

and production facilities for the western states that did not include Texas, although the previous 

ERG study did make use of the WRAP study in terms of methodology and emission factors 

where practicable. 

While drilling activities are generally short-term in duration, typically covering a few 

weeks to a few months, the associated diesel engines are usually very large, from several 

hundred to over a thousand horsepower. As such, drilling activities can generate a substantial 

amount of NOx emissions. While previous studies have focused more intently on quantifying the 

ongoing fugitive VOC emissions associated with oil and gas production, significant uncertainty 

remains regarding the shorter term NOx emission levels associated with drilling activity. 

In order to gain a more accurate understanding of emissions from drilling rig engines, 

data regarding typical rig profiles (number of engines, engine sizes, and engine load factors) 

were collected through phone and email surveys for drilling operations for the 2008 base year. 

These data were used to develop well drilling emissions profiles using US EPA’s NONROAD 

emissions model.1

 To develop the statewide emissions inventory, the drilling rig emissions 

profiles developed as a result of the survey were applied to well drilling activity data for 2008 

obtained from the Texas Railroad Commission (TRC). 

The activity and drilling rig engine emissions profiles developed under this study were 

used to develop emissions estimates of volatile organic compounds (VOC), nitrogen oxide 

(NOx), carbon monoxide (CO), particulate matter (PM10 and PM2.5), sulfur dioxide (SO2), and 

 

1

 While the NONROAD model was used to calculate drilling activity emissions (in order to more accurately capture 

emission standard phase in impacts), these emissions are actually classified as area sources emissions and reported 

as such to the TCEQ. 

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hazardous air pollutants (HAP) for drilling rig engines across the state. Emissions are calculated 

on a county-level basis and provided in annual tons per year and by typical ozone season day. 

For planning purposes, the 2008 base year estimates were used to develop 2002 and 2005 prior 

year inventories, as well as projected inventories for 2009 through 2021. 

Section 3.0 of this report provides the results of a review of existing literature as well as 

currently available data that could be used to develop the inventory. This discussion also 

provides an overview of the drilling process and identifies the types of activities and equipment 

that are commonly associated with drilling activity. Section 4.0 provides an overview of the data 

collection plan and the subsequent survey that was used to obtain the information needed to 

develop the model drilling rig emissions profiles. Section 5.0 presents the results of the survey, 

including a discussion of how the data was broken down into distinct “model” drilling rigs by 

well type and depth. Section 6.0 describes the development of the emissions inventory including 

how the activity data was compiled, how the model drilling rig emission profiles were 

developed, and how these model drilling rig emission profiles were combined with the activity 

data to develop the 2002, 2005, and 2008 through 2021 emission inventories. 
3.0 Review of Existing Literature 

At the start of this study ERG conducted a review of relevant literature, current studies, 

and available data that could be used in the development of a drilling rig engine emissions 

inventory for Texas. The results of this research are discussed below in Sections 3.1 through 3.3. 

Section 3.1 discusses the review of existing studies concerning estimating emissions from oil and 

gas drill rig operations, Section 3.2 covers the results of the review of existing Texas data 

available from government and industry websites and publications, and Section 3.3 includes a 

discussion of drilling rigs and the types of engines and activities occurring during a drilling 

operation. 

3.1 Review of Existing Studies 

Over the last several years numerous studies have been conducted in the western states to 

develop area source emission estimates for oil and gas exploration and production sources, with 

subsequent studies improving upon the data collection methodology and emission estimation 

approaches. Most of these studies addressed emissions from drilling rig engines to some degree. 

The relevant studies ERG identified are listed in Table 3-1. 

Table 3.1 Existing Oil and Gas Exploration Emissions Studies 

Report Title Geographic 

Coverage 

Publication Date 

Oil and Gas Emission Inventories for the Western 

States (Russell, et al., 2005) WRAP States December, 2005 

Ozone Precursors Emission Inventory for San 

Juan and Rio Arriba Counties, New Mexico 

(Pollack, et al., 2006) 

San Juan and 

Rio Arriba 

Counties, 

New Mexico 

August, 2006 

Emissions from Oil and Gas Production Facilities 

(TCEQ, 2007) Texas August, 2007 

WRAP Area Source Emissions Inventory 

Projections and Control Strategy Evaluation 

Phase II (Bar-Ilan, et al., 2007) 

WRAP States September, 2007 

Development of Baseline 2006 Emissions from 

Oil and Gas Activity in the Denver-Julesburg 

Basin (Bar-Ilan, et al., 2008) 

DenverJulesburg 

Basin, 

Colorado 

April, 2008 

Recommendations for Improvements to the 

CENRAP States’ Oil and Gas Emissions 

Inventories (Bar-Ilan, et al., 2008a) 

CENRAP 

States November, 2008 

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Table 3.1 Existing Oil and Gas Exploration Emissions Studies (Cont.) 

Report Title Geographic 

Coverage 

Publication Date 

Development of Baseline 2006 Emissions from 

Oil and Gas Activity in the Piceance Basin (BarIlan, et al., 2009) 

Piceance 

Basin, 

Colorado 

January, 2009 

Based on a review of these studies, ERG developed a series of survey questions to obtain 

the types of data that would be needed to develop the 2008 base year emissions inventory. The 

resultant survey was developed using example survey questions and forms from several of these 

existing studies. 

The studies identified in Table 3-1 were comprehensive in nature, inclusive of all 

emission sources found at oil and gas exploration and production locations. While drilling rig 

engines were typically included in these studies, this source category was not the primary focus 

of these efforts, as these inventories addressed emissions sources associated with both the 

exploration and production sides of the oil and gas industry. As such, many of the surveys used 

in these studies were sent to the oil and gas producers themselves, and not directly to the owners 

and operators of the drill rigs, who are typically contracted by the producers to drill the well. As 

described below in Section 5, ERG focused this survey effort on the drilling contractors 

themselves, who are most familiar with drilling equipment and activities, with less emphasis on 

the production companies. 

3.2 Review of Existing Data 

All exploratory oil and gas drilling in Texas requires a permit. These permits are 

processed and maintained through the TRC. The drilling permits are available for review through 

the TRC website, and include well-specific data such as approval date, location (county), well 

profile (vertical, horizontal, directional), well depth, start or “spud-in” date, and well completion 

date. On March 10, 2009, ERG obtained this data in electronic format through acquisition of the 

“Drilling Permit Master and Trailer” database. This database formed the basis of the activity data 

used to develop the 2008 base year emissions inventory. 

In addition to the drilling permit data obtained through the TRC, many of the larger 

drilling contractors provide information about their drilling rig fleets in their on-line websites. 

Examples of these websites are provided in the approved Data Collection Plan, which is included 

as Appendix A of this report. ERG reviewed this on-line information in an effort to gain a better 

understanding of typical drilling rig engine profiles, including the size, number, and type of 

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engines used on typical rigs. Additional information provided included make and model of the 

engines. Engine manufacturer websites were also reviewed and proved useful as a resource to 

obtain engine specifications and fuel usage data that could be used to gapfill the data obtained 

during the survey and needed to complete the emissions inventory. For example, engine fuel 

usage data could be used to determine load percentages for engines where the operator provided 

fuel use data but did not provide load estimates. 

3.3 Drilling Rig Overview 

Air pollutant emissions from oil and gas drilling operations originate from the 

combustion of diesel fuel in the drilling rig engines. The main functions of the engines on an oil 

and gas drilling rig are to provide power for hoisting pipe, circulating drilling fluid, and rotating 

the drill pipe. Of these operations, hoisting and drilling fluid circulation require the most power. 

There are two common types of rigs currently in use 

– mechanical and electrical. In general, mechanical rigs 

have three independent sets of engines. The first set of 

engines (draw works engines) are used to provide power to 

the hoisting and rotating equipment, a second set of engines 

(mud pump engines) are dedicated to circulating the drilling 

fluid which is commonly referred to as “mud”, and a third 

set of engines (generator engines) are used to provide power to auxiliary equipment found on the 

drill site such as lighting equipment and heating and air conditioning for crew quarters and office 

space. There may be one, two, or more draw works engines, depending on the input power 

required. There are typically two mud pumps for land rigs, with each mud pump independently 

powered by a separate engine. The mud pump engines are typically the largest engines used on a 

mechanical rig. Finally, there are typically two electric generator engines per mechanical rig, 

with one running continuously and the second serving as a stand by unit. 

Electrical rigs are typically comprised of two to three large, identical diesel-fired enginegenerator sets that provide electricity to a control house called a silicon controlled rectifier (SCR) 

house. Electricity from the SCR house is then used to provide power to separate motors on the 

rig. In this configuration, there are dedicated electric motors used for the draw works/hoisting 

operations, the mud pumps, and other ancillary power needs (such as lighting). The generator 

engines are loaded as required to meet fluctuating power demands, with one unit typically 

designated for standby capacity. The trend in new rig design is almost exclusively towards 

electric rigs, except perhaps for the smallest rigs. This is probably due to the relative expense of 

Draw Works engines – 

used to power hoisting and 

rotating equipment 

Mud Pump engines – used 

to circulate drilling fluid 

Generator engines – used to 

power auxiliary equipment 

3-3 
engines versus motors, both in terms of initial cost and maintenance. Today, electrical rigs are 

common, especially for larger rigs (Bommer, 2008). 

After drilling and casing a well, it must be “completed.” Completion is the process in 

which the well is enabled to produce oil or gas. Once the desired well depth is reached, the 

geological formation must be tested and evaluated to determine whether the well will be 

completed for production, or plugged and abandoned. To complete the well production, casing is 

installed and cemented and the main drilling rig is dismantled and moved to the next site. A 

smaller rig, called a completion rig (also known as a workover rig), is then moved on site to 

bring the well into production, to perforate the production casing and run production tubing to 

complete the well. Typically, the completion rig is a carrier-mounted arrangement and may be 

on-site for several days to a week or more depending on well depth and other factors. The 

completion rigs hoist smaller loads and pump at lower rates than the drilling rigs, and therefore 

require much smaller engine capacity. 

Increasingly, reservoir productivity is enhanced by the application of a stimulation 

technique called hydraulic fracturing. In this process, the reservoir rock is hydraulically 

overloaded to the point of rock fracture. The fracture is induced to propagate away from the well 

bore by pumping hydraulic fracturing fluid into the well bore under high pressure. The fracture is 

kept open after the end of the job by the introduction of a solid proppant (sand, ceramic, bauxite, 

or other material), by eroding the sides of the fracture walls and creating rubble by high injection 

rates, or for carbonate formations, by etching the walls with acid. The fracture thus created and 

held open by the proppant materials becomes a high conductivity pathway to the well bore for 

reservoir fluid. 

In vertical wells a single fracture job per reservoir is commonly done. In high angle or 

horizontal wells, it is common to perform multiple fracturing jobs (multi stage fracturing) along 

the path of the bore hole through a reservoir. Fracturing jobs are often high rate, high volume, 

and high pressure pumping operations. They are accomplished by bringing very large truckmounted diesel-powered pumps (e.g., 2,000 hp or more) to the well site to inject the fracturing 

fluids and material, and to power the support equipment such as fluid blenders. The measure of 

the power required is based on the hydraulic horsepower necessary to fracture the well. Although 

very short in duration (typically less than a day), fracturing activities may result in substantial 

NOx emissions due to the very high horsepower requirements. 

Oil and gas wells are commonly classified as vertical, directional, or horizontal wells, 

depending on the direction of the well bore. Vertical wells are the most common, and are wells 

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that are drilled straight down from the location of the drill rig on the surface. Directional wells 

are wells where the well bore has not been drilled straight down, but has been made to deviate 

from the vertical. Directional wells are drilled through the use of special tools or techniques to 

ensure that the well bore path hits a particular subsurface target, typically located away from (as 

opposed to directly under) the surface location of the well. Horizontal wells are a subset of 

directional wells in that they are not drilled straight down, but are distinguished from directional 

wells in that they typically have well bores that deviate from vertical by 80 - 90 degrees. 

Horizontal wells are commonly drilled in shale formations. Once the desired depth has been 

reached (the well bore has penetrated the target formation), lateral legs are drilled to provide a 

greater length of well bore in the reservoir.
4.0 Data Collection Plan 

ERG’s Data Collection Plan identified the proposed approach for collecting the 

information needed to develop a comprehensive emissions inventory for land-based drilling rig 

engines in the state of Texas in 2008. The primary focus of the data collection survey was to 

obtain engine operating data from rig operators who were actively drilling in Texas in 2008. The 

goal of this survey was to obtain sufficient data to allow for the development of a series of 

“model” drilling rig emission profiles for different well types and/or depths to apply to the 

corresponding subsets of the TRC well activity data. 

Details of the Data Collection Plan were subject to external peer review and approved by 

TCEQ. ERG conducted the data collection as per the approved Data Collection Plan, which is 

included as Appendix A. 

4.1 Participant Recruitment 

In order to encourage survey response rates, stakeholder support for the study was 

sought. In addition to consulting with contacts at the University of Texas, Southern Methodist 

University, and the Texas Railroad Commission for suggestions on implementing the survey and 

soliciting participants, the following trade associations were contacted to help encourage 

participation in the study: 

• International Association of Drilling Contractors (IADC) 

• Texas Independent Producers and Royalty Owners Association (TIPRO) 

• Texas Oil and Gas Association (TXOGA) 

ERG provided the trade associations with a draft copy of the survey materials and 

requested they distribute them to their membership for feedback. In addition, ERG requested 

these trade groups lend their support to the project through a letter of introduction about the 

study to be sent to their constituents. While these associations were supportive of the goals and 

appreciated the need for this study, ERG did not receive any feedback on the draft survey 

materials. However, both TIPRO and TXOGA recognized the importance of the project and 

agreed to allow ERG to reference their support in the survey transmittal letter (see Appendix B). 

4.2 Phone/Email Surveys 

Once the survey was developed, ERG obtained contact information for oil and gas well 

operators and drilling contractors in order to distribute the survey. The primary source of data 

used to identify target respondents was the commercial RigData® database. This database 

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contains information for over 24,000 drilling permits issued in Texas between January 1, 2008 

and March of 2009. For over 14,000 of these records, drilling contractor contact information was 

provided. The RigData® database used to develop the target respondent list has been provided to 

the TCEQ in electronic format 

ERG attempted to contact each of the drilling contractors included in this listing through 

phone and/or email surveys. The survey effort itself focused on collecting the following 

information from each respondent: 

• The number of engines on a rig 

• Engine make, model, model year, and size (hp) 

• Average load for each engine 

• Engine function (draw works, mud pumps, power) 

• Actual engine hour data for each well (total hours) 

• Actual engine fuel use data for each well (total fuel use) 

• Total well drilling time (actual number of drilling days) 

• Total well completion time (number of days needed for well completion activities) 

• Well depth 

• Number of wells represented by survey 

An example of the data collection form used to compile the results of the survey is 

presented in Appendix C. For those respondents who were contacted via email, an Excel file 

containing similar information was provided as an email transmittal. The results of the survey 

effort are described in Section 5.0. 

4.3 Confidentiality 

Confidentiality was stressed to survey participants, as evidenced in the survey letter. ERG 

is particularly sensitive to the privacy of individuals and businesses. Therefore all interviews and 

data collection efforts began with a guarantee of privacy, anonymity, and confidentiality. To 

ensure survey respondent’s rights to privacy, respondents were informed of the research purpose, 

the kinds of questions that would be asked, and how the TCEQ may use the results of the study. 

Confidentiality was maintained by eliminating respondent names from the study datasets before 

provision to the TCEQ. 
5.0 Data Collection Results 

5.1 Survey Findings 

Using the contact information in the RigData® dataset, ERG began implementation of the 

Data Collection Plan on April 30, 2009 and collected data through June 16, 2009. Initially, 

contacts were attempted with many of the oil and gas well operators themselves. As a rule, the 

operators were knowledgeable concerning general information about the drilling process 

including average depth, drilling days, number of engines used and gallons of fuel used per day. 

However, they typically did not have the specific information about the characteristics of the rig 

engines (model year, engine size, and load factors) needed to estimate emissions. 

During phone interviews it was discovered that several of the operators also drilled their 

own wells. Based on these interviews, the strategy for the remainder of the data collection phase 

of the project was refined. In particular, factors such as depth of the well, the engine 

configurations used, the individual preferences of drilling superintendents to idle engines or to 

turn them off, and the difficulty of estimating load and operating hours over the entire drilling 

period made it difficult to collect the data via email or fax without being able to discuss the 

needed data directly with the respondent. The complexity of the drilling process and the lack of 

response from the operators to anything other than a verbal interview informed the collection 

process for the drilling contractors. 

Therefore to obtain the information needed, a verbal interview with the actual drilling 

contractors was determined to be preferable in order to carefully walk the respondent through the 

survey questions. 

The RigData® dataset included approximately 225 unique contact profiles for drilling 

contractors. However, many of these contacts were regional contacts for the same company, 

several had gone out of business, and others had recently consolidated into a single company. As 

a result, the final number of unique contacts for the drillers was approximately 190. 

ERG attempted to contact each of the drilling companies at least four times, by phone 

and/or email. Based on the experience with contacting the operators, verbal contact was 

attempted with each respondent before distribution of the survey through email or fax. The 

strategy was designed to increase participation by explaining the purpose of the survey, to 

explain the data being requested, and thus avoid receiving incomplete or inaccurate surveys. For 

each targeted survey respondent, three attempts were made via phone to find someone to speak 

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with before a voicemail was left or an email was sent. This strategy was intended to eliminate 

dead-end contacts such as unreturned voicemails or emails. 

Because smaller companies generally had fewer administrative and management 

personnel, contact for companies with less than 50 wells generally consisted of a phone call 

answered by a receptionist who either took a message, transferred the call to a voicemail, or 

established direct contact with someone who could answer the survey questions. If there was no 

answer, a return call was scheduled. After three attempts without response, a short voice message 

was left. If no reply was received to this message, no further attempt was made to contact the 

respondent. 

For the larger drilling companies (those that drilled over 100 wells in 2008), an enhanced 

contact strategy was used. Because some of the companies are quite large and represent a 

significant percentage of the wells drilled in the state, more extensive efforts were made to 

increase their participation. For several of these companies, an effort was made to encourage 

response by providing them with tailored Excel spreadsheets identifying their wells and asking 

about specific well types and locations. In addition, attempts were made to contact the company 

through multiple avenues, either through multiple contacts provided in the RigData® dataset, or 

through contact information available on-line. In one case, ERG collected data from one of the 

top 25 drilling contractors after an initial refusal from one drilling superintendent by requesting 

data through other contacts at the company. 

Generally speaking, at least ten contacts through phone calls and emails were attempted 

for the larger companies, the medium sized companies required from 5 to 7 contacts, and the 

smaller companies required 3 to 4 contacts before identifying the appropriate person to talk to. 

At the completion of the survey effort, 45 completed surveys with sufficient data to 

estimate emissions had been obtained from 39 different drilling rig contractors and/or oil and gas 

well operators. This figure reflects approximately a 15% response rate for complete surveys from 

the attempted contacts. One additional survey was received after the submittal cutoff date, but it 

was not received in time for incorporation into the inventory. 

The surveys that were received and used in the inventory were representative of over 

1,500 wells drilled in Texas in 2008 and covered 121 counties and all of the major oil and gas 

basins in the state (Andarko, East Texas, Ft. Worth/Bend Arch, Permian, and Western Gulf). An 

additional 17 survey responses were obtained, but the respondents for these surveys did not 

provide sufficient information to be used in the final model drilling rig emission profile 

development. Typically, these incomplete responses were those received from the oil and gas 

5-2 
well operators and not the drilling contractors. Considering both the complete and incomplete 

survey responses, the overall response rate for the survey effort was approximately 21%. 

Table 5-1 presents the summary results for the survey effort. 

Table 5.1 Survey Summary Statistics 

Survey Activity/Results Number of Respondents 

Attempted Company Contacts 295 

Refusal to Participate 24 

Soft Refusal (did not return attempted contacts via 

phone calls or email) 209 

Respondent Interviewed and provided sufficient data 

for inclusion in inventory dataset 45 

Respondent Interviewed, but insufficient data 

provided for inclusion in inventory dataset 17 

Figure 5-1 provides a county-level map of Texas providing a graphical representation of 

the geographic coverage of the survey results. 

5.2 Model Rig Category Development 

Upon completion of the survey and data collection task, the survey results were compiled 

into a spreadsheet database for evaluation in order to disaggregate the survey data into subcategories for model drilling rig profile development. As each completed survey was received 

from the surveyor, identifying information for that survey was entered into a tracking 

spreadsheet, and the survey was prepared for data entry and forwarded to data entry personnel. 

Upon receipt of the survey, data entry personnel transferred the data in the survey form into the 

spreadsheet database, and updated the survey tracking spreadsheet with date of data entry and 

their initials. A QA check was then performed on the data entered into the spreadsheet database, 

and the tracking spreadsheet was updated to indicate the date of QA and the initials of the 

personnel performing the QA. 

5-3 
Figure 5.1 Counties with Survey Data 

Survey results for vertical, directional, and horizontal well types were reviewed as 

described below. 

A review of the 32 surveys completed for vertical drilling, representing 1,261 wells, 

provided a clear distinction between the engine profiles (number and size of engines) used to 

drill shallow vertical wells relative to deeper vertical wells. In particular, by separating the 

5-4 
survey results into those representing wells at 7,000 feet of depth or less, and those representing 

wells deeper than 7,000 feet, the following differences were observed: 

• The average drilling duration for the shallower wells was 8 days, with a maximum of 

14 days; 

• The average drilling duration for deeper wells was 27 days, with a maximum of 

84 days; 

• Only 1 of the 16 profiles for shallow wells was for an electrical rig, compared to 

6 electrical rig profiles out of the 16 profiles for the deeper wells; 

• The engine sizes were significantly different for the shallow and deep wells, with the 

survey results for the shallow wells containing no engines over 700 hp, while the 

engine population for surveys received for the deeper wells contained approximately 

25 engines rated at over 1,000 hp. 

For horizontal and directional wells, a total of 13 completed surveys were received 

representative of 288 wells. The average measured well depth of the wells covered under these 

surveys was approximately 11,000 feet, with a minimum of 8,000 feet and a maximum of 

17,688 feet. All of the profiles for horizontal and directional wells were either for electrical rigs 

(6 profiles) with 2 or 3 engines, or for mechanical rigs (7 profiles) with 6 engines. Due to the 

limited number of surveys received for horizontal and directional wells, and the relative 

consistency of the profiles for these types of wells, it was determined to consolidate the survey 

results for horizontal and directional wells into one model rig category. 

Table 5-2 provides a summary of the final survey statistics for each of the three model rig 

well type categories. 

Table 5.2 Model Rig Category Statistics 

Model Rig 

Well Type 

Category 

Number 

of surveys 

included 

in profile 

Number of 

respondents 

providing 

surveys 

Number of 

Wells 

Represented 

Number of 

Mechanical 

Rig Profiles 

Number of 

Electrical 

Rig Profiles 

Horizontal and 

Directional 

Wells 

13 10 288 7 6 

Vertical Wells 

<= 7,000 feet 16 16 900 15 1 

Vertical Wells > 

7,000 feet 16 13 361 10 6 

Tables D-1 through D-3 in Appendix D contain the collected survey data for each of the 

three model rig well type categories. 

5-5 
5.3 Fracturing 

During the data collection phase of this project, information was solicited from 

respondents regarding fracturing activities. While not specifically mentioned in the original work 

plan or data collection plan, a review of existing literature and studies showed fracturing activity 

to be increasing in Texas over the past several years. As part of their survey response, the drilling 

contractors and oil and gas exploration companies occasionally provided some qualitative or 

quantitative information regarding fracturing, but the responses were highly variable in content 

and format. In general, the indication was that fracturing was a short-term activity (less than one 

day in duration), and that pump trucks containing multiple, large diesel-fired engines could be 

used simultaneously to pump the fracturing fluids into the well. Specific information regarding 

the frequency of fracturing events and the total hp-hours required per event were not 

generalizable to the inventory as a whole, however. 

Further investigation regarding fracturing was made by contacting service companies that 

provide fracturing services, as well as interviewing personnel at the TRC and researching the 

availability of fracturing data on-line through the TRC website. 

Two of the three service companies contacted provided some data for the fracturing 

activities they performed in 2008, which varied from the use of five 1,250 hp pump engines for a 

total duration of 1 hour, to the use of seven 2,500 hp pump engines for a total duration of 

12 hours. The third service company contacted did not provide any data as of the time of this 

draft report. 

Unlike the drilling permit records obtained through the “Drilling Permit Master and 

Trailer” database, fracturing data is not compiled by the TRC or otherwise made readily 

available in any summarized format through any on-line queries or electronic datasets. However, 

images of individual well completion records (referred to as G-1 forms for gas well completions 

and W-2 forms for oil well completions) are available on-line through the TRC website. Using 

American Petroleum Institute (API) numbers from the TRC data, a random on-line search was 

performed to review the G-1 and W-2 records for approximately 1,200 wells. The G-1 and W-2 

forms were only found for approximately one-third of these wells. These forms are frequently 

completed by hand, with inconsistent data being reported by individual well operators, with 

much of the data being incomplete. However, based on a review of the records we were able to 

identify, it appears that approximately 80% of the wells in the sample had some kind of 

fracturing activity occurring prior to well completion. 

5-6 
5-7 

While data is not currently available under this project to provide emission estimates for 

fracturing activities, due to the large engine sizes used by the pump trucks, this is a source 

category that may be considered for inclusion in future emission inventory development projects. 
6.0 Emissions Inventory Development and Results 

The 2008 activity data from the TRC and the model rig emissions profiles developed 

using the survey results for each model rig well type category were utilized to develop emissions 

estimates for selected target years as described below. 

6.1 Activity Data 

6.1.1 2008 Base Year Activity 

Activity data for the 2008 base year was obtained from the TRC through acquisition of 

the “Drilling Permit Master and Trailer” database, which contains information on well drilling 

activities, including American Petroleum Institute (API) number, date approved, location 

(county), well profile (vertical, horizontal, directional), well depth, spud-in date, and well 

completion date. The TRC data was combined with data from the RigData® dataset used to 

identify survey respondents as discussed previously. This combined database was used to 

compile an initial list of all oil and gas wells that were either completed in 2008 (based on 

completion date), or that were started in 2008 (based on spud-in date). 

As many of the wells completed in 2008 were started in 2007, and many of the wells 

started in 2008 were not completed until 2009, an adjustment was needed to the initial list of 

wells to determine a representative dataset for 2008. This adjustment was accomplished by 

including only those wells with spud dates of December 1, 2007 or later (and that were 

completed in 2008), and only those wells with completion dates of January 31, 2009 or earlier 

(and that had spud-in dates in 2008). In all, 16,964 oil and gas wells are included in the final 

2008 dataset which compares favorably with the 16,569 oil and gas well completions reported by 

the TRC in 2008 (TRC, 2009c). The slight discrepancy with the total wells included in the 2008 

dataset compared to the completion figure from the TRC is due to the fact that the TRC data only 

includes 2008 completions and does not account for wells started in 2008 that were not 

completed until 2009. 

The final 2008 activity dataset contains drilling activity data for 210 of the 254 counties 

in Texas. 

6.1.2 2002 and 2005 Prior Years Activity 

Once the final 2008 activity dataset was established, activity data scaling factors for 2002 

and 2005 were developed based on the ratio of the oil and gas well completions for those years 

relative to the number of oil and gas well completions in 2008 as reported by the TRC (TRC 

6-1 
2009a, TRC 2009b, TRC 2009c). This analysis was performed at the TRC district level, which 

allowed geographic variation in drilling trends across the state from 2002 through 2008 to be 

reflected in the 2002 and 2005 prior year datasets. Figure 6-1 provides a county-level map of 

Texas showing the location and coverage of each of the TRC districts. 

Figure 6.1 TRC District Map 

6-2 
For example, in 2008 there were 512 total oil/gas well completions in TRC District 1, and 

in 2002 there were 165 total oil/gas well completions in District 1. Therefore, the scaling factor 

from 2002 to 2008 is: 

2002 to 2008 scaling factor = 165 wells / 512 wells = 0.32 

Table 6-1 shows the 2002, 2005, and 2008 oil and gas well completion records and the 

resultant 2002 and 2005 scaling factors that were developed for each district for this analysis. 

Table 6.1 2002 and 2005 Prior Year Activity Scaling Factors 

TRC District 

2008 Total 

Oil/Gas 

Completions 

2002 Total 

Oil/Gas 

Completions 

2002 Scaling 

Factor 

2005 Total 

Oil/Gas 

Completions 

2005 Scaling 

Factor 

1 512 165 0.32 389 0.76 

2 687 513 0.75 672 0.98 

3 699 724 1.04 712 1.02 

4 1,351 1,266 0.94 1,123 0.83 

5 738 618 0.84 714 0.97 

6 1,973 717 0.36 1,556 0.79 

7B 746 298 0.40 501 0.67 

7C 2,082 887 0.43 1,389 0.67 

8 2,641 1,281 0.49 927 0.35 

8A 559 756 1.35 626 1.12 

9 3,484 1,096 0.31 1,185 0.34 

10 1,095 419 0.38 856 0.78 

As can be seen in Table 6-1, certain areas of the state experienced significant growth in 

drilling activity in 2008 relative to 2002, while other areas remained relatively stable. The most 

dramatic example of this change in activity can be seen in TRC District 9, which contains the 

Barnett Shale, an area that has experienced significant growth in drilling activity over the last 

6 years. For this District, drilling activity approximately tripled between 2002 and 2008. 

The scaling factors presented in Table 6-1 were applied to the 2008 base year well depth 

totals by county for each of the three model rig well types to determine county-level well depth 

for each model rig type for 2002 and 2005. 

6.1.3 2009 through 2021 Projected Activity 

2009 through 2021 projected activity data were developed using the 2008 base year 

activity data from the TRC and forecasting future activity based on US DOE Energy Information 

Administration (EIA) projections of oil and gas production for the Southwest and Gulf Coast 

6-3 
6-4 

regions from the Annual Energy Outlook 2009, Updated Reference Case with ARRA (EIA, 

2009). The EIA data tables (specifically Tables 113 and 114) present estimated crude oil and 

natural gas production estimates for the years 2006-2030. The geographic level of the projected 

data is by EIA Region. 

Portions of Texas fall into three EIA Regions: Gulf Coast (Region 2); Southwest (Region 

4); and Midcontinent (Region 3). The majority of the State is in the Gulf Coast and Southwest 

EIA Regions. Only a small portion (area to the west of Oklahoma) is in the Midcontinent 

Region. In addition, because the Midcontinent EIA Region contains six other states, any 

projections data for the Midcontinent EIA Region may not be reflective of Texas operations. 

Thus, it was assumed that the Southwest and Gulf Coast EIA Regions are representative of Texas 

and each region was weighted equally to determine the statewide projections. Figure 6-2 shows 

the EIA regions and their coverage in Texas. 

Figure 6.2 EIA Regions 

Tables 6-2 and 6-3 show projected crude oil and natural gas production for the Gulf 

Coast and Southwest EIA Regions, as well as the combined total for both regions, from 2008 

through 2021. The total percentage change for each year from 2009 through 2021 is presented 

relative to the base year of 2008. 

This data was then used to calculate a projected growth factor (%) for each year from 

2009 through 2021 by weighing the oil and gas percentage growth figures relative to the number 

of oil and gas wells completed in Texas 2008. For example, the projected growth factor for 2009 

is calculated as follows:
Table 6.2 Projected Crude Oil Production 2008-2021 

Crude Oil Production (MMBBL/day) 

EIA Region 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2018 

Gulf Coast 0.503 0.505 0.503 0.483 0.465 0.450 0.438 0.401 0.374 0.347 0.320 

Southwest 0.919 0.920 0.904 0.892 0.890 0.915 0.956 1.000 1.043 1.082 1.117 

Total 1.422 1.425 1.407 1.375 1.355 1.365 1.393 1.402 1.416 1.429 1.436 

% change from 2008 0.21% -1.05% -3.29% -4.71% -4.01% -2.02% -1.42% -0.39% 0.50% 1.02% 

Table 6.3 Projected Natural Gas Production 2008-2021 

Natural Gas Production (trillion cubic feet) 

EIA Region 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2018 

Gulf Coast 5.412 5.165 4.792 4.606 4.415 4.326 4.233 4.162 4.086 4.020 3.959 

Southwest 2.170 2.474 2.623 2.716 2.713 2.679 2.659 2.645 2.627 2.609 2.603 

Total 7.582 7.639 7.415 7.321 7.128 7.005 6.892 6.807 6.713 6.629 6.563 

% change from 2008 0.76% -2.20% -3.44% -5.99% -7.61% -9.09% -10.2% -11.5% -12.6% -13.4% 

6-5 
2009 growth factor = ((% change from 2008 to 2009 in Crude Oil Production x number of oil 

well completions in 2008) + (% change from 2008 to 2009 in Natural Gas 

Production x number of gas well completions in 2008)) / (total number of 

oil and gas well completions in 2008) 

Using the data in Tables 6-2 through 6-4, the projected growth factor for 2009 is: 

2009 growth factor = ((0.21% x 6,208) + (0.76% x 10,361)) / (6,208 + 10,361) = 0.55% 

Table 6-4 shows the growth factors that were developed for each projected year as a 

result of this analysis. These factors were then applied to the 2008 base year well depth totals by 

county for each of the three model rig profile well types to determine activity data for 2009 

through 2021. It is worth noting that through the first five months of 2009, the number of well 

completions in Texas has exceeded the number of well completions for the same period in 2008. 

However, during the second half of 2008, there was a dramatic increase in drilling activity in 

Texas which dropped off significantly by the end of the year due to commodity prices and the 

effects of the economic recession. Therefore, while Table 6-4 presents projected production data 

based on the current DOE EIA data, the volatility in drilling activity during 2008, coupled with 

the rapidly changing economic climate over the last year, results in a high level of uncertainty 

regarding these (or any) projections for drilling activity in 2009 and beyond. These projections 

are based on the best data currently available, but should be revisited once the economic climate 

and oil and gas prices stabilize in order to more accurately assess future year projected 

emissions. 

6.1.4 2002, 2005, and 2008 through 2021 Activity Summary 

Once the final activity dataset for 2008 was determined, total county-level well depth for 

each of the three model rig well type categories was calculated by summing the individual well 

depths in each county by model rig well type category. The total county-level well depth for 

2002, 2005, and 2009 through 2021 for each model rig well type category was then calculated 

based on the 2008 summary data using the methodology described above. Table 6-5 shows the 

total depth by model rig well type category for 2008 (blank cells indicate there was no activity in 

that county for that well type).

6-6 
Table 6-4 Projected Growth Factors 2009-2021 

Production % change from 2008 

2008 Well Completions 2009 2010 2011 2012 2103 2014 2015 2016 2017 2018 

Oil 6,208 0.21% -1.05% -3.29% -4.71% -4.01% -2.02% -1.42% -0.39% 0.50% 1.02% 

Natural Gas 10,361 0.76% -2.20% -3.44% -5.99% -7.61% -9.09% -10.2% -11.5% -12.6% -13.4% 

Projected Growth Factor 0.55% -1.77% -3.38% -5.51% -6.26% -6.44% -6.92% -7.31% -7.67% -8.02% 

6-7 
Table 6.5 2008 Total Depth by Model Rig Well Type Category (1,000 feet) 

County Vertical <= 7,000 feet Vertical > 7,000 feet Directional/Horizontal 

Anderson 52.20 113.70 20.33 

Andrews 1,969.19 1,115.41 46.30 

Angelina 1.32 394.74 101.70 

Aransas 6.00 45.45 23.30 

Archer 221.32 15.50 

Atascosa 39.80 38.50 

Austin 67.19 28.70 15.02 

Bastrop 6.40 74.60 71.70 

Baylor 45.54 5.50 

Bee 239.20 204.49 240.25 

Bell 4.50 

Bexar 0.80 

Borden 11.45 166.10 42.85 

Bosque 10.00 15.80 

Bowie 9.00 

Brazoria 15.90 252.90 103.39 

Brazos 33.14 214.89 

Briscoe 6.50 8.50 

Brooks 17.16 582.32 103.96 

Brown 41.00 

Burleson 208.41 172.77 

Caldwell 29.86 8.15 

Calhoun 15.60 112.60 82.83 

Callahan 81.68 

Cameron 9.50 

Carson 6.50 10.10 

Cass 7.00 

Chambers 78.60 153.46 

Cherokee 9.40 886.08 243.05 

Childress 9.30 

Clay 116.15 23.00 52.50 

Cochran 229.30 25.00 

Coke 121.70 15.70 

Coleman 97.69 

Colorado 122.71 149.88 25.42 

Comanche 3.00 

Concho 167.15 

Cooke 161.00 228.84 17.90 

Coryell 4.00 

Cottle 39.20 106.70 8.00 

Crane 602.54 175.75 43.26 

Crockett 881.48 1,822.74 131.17 

Crosby 91.69 

Culberson 216.89 44.00 

Dallas 99.50 

6-8 
Table 6.5 2008 Total Depth by Model Rig Well Type Category (1,000 feet) (Cont.) 

County Vertical <= 7,000 feet Vertical > 7,000 feet Directional/Horizontal 

Dawson 42.70 359.69 17.50 

Denton 11.10 79.50 2,491.72 

DeWitt 57.40 392.08 568.84 

Dickens 174.02 123.70 

Dimmit 270.51 178.14 125.64 

Duval 68.80 479.83 71.95 

Eastland 48.09 

Ector 501.36 1,619.73 73.30 

Edwards 119.55 206.10 67.50 

Ellis 1.50 269.00 

Erath 29.95 97.10 

Falls 1.80 

Fannin 19.00 

Fayette 15.08 22.10 93.80 

Fisher 162.58 68.30 

Foard 25.10 

Fort Bend 159.90 74.65 125.04 

Franklin 10.90 94.55 

Freestone 11.40 2,650.39 484.37 

Frio 153.73 62.80 61.74 

Gaines 407.24 633.81 56.99 

Galveston 4.40 51.15 53.37 

Garza 189.30 52.00 3.20 

Glasscock 900.20 19.20 

Goliad 231.61 377.49 76.04 

Gonzales 15.53 21.26 21.50 

Gray 12.15 13.00 

Grayson 12.99 49.00 37.60 

Gregg 503.10 263.25 

Grimes 3.90 169.64 

Guadalupe 9.20 7.79 

Hale 65.00 15.00 

Hansford 62.41 263.33 50.20 

Hardeman 12.59 96.23 28.60 

Hardin 81.95 284.12 180.35 

Harris 19.20 34.20 85.40 

Harrison 60.61 2,900.41 1,836.28 

Hartley 17.95 

Haskell 63.70 

Hemphill 6.50 3,936.45 685.47 

Henderson 233.25 53.60 

Hidalgo 37.54 1,324.96 347.92 

Hill 7.00 1,161.12 

Hockley 208.43 123.40 87.44 

Hood 1,011.19 

6-9 
Table 6.5 2008 Total Depth by Model Rig Well Type Category (1,000 feet) (Cont.) 

County Vertical <= 7,000 feet Vertical > 7,000 feet Directional/Horizontal 

Hopkins 4.50 21.80 

Houston 8.30 161.85 56.50 

Howard 81.64 779.85 

Hudspeth 26.00 22.00 

Hutchinson 313.77 17.10 39.00 

Irion 196.70 1,513.07 

Jack 197.69 137.50 

Jackson 205.63 319.66 32.99 

Jasper 8.10 44.50 194.33 

Jefferson 24.80 166.30 300.61 

Jim Hogg 9.40 194.13 14.38 

Jim Wells 84.07 52.75 6.11 

Johnson 52.00 8,421.16 

Jones 221.93 

Karnes 21.40 100.90 179.60 

Kenedy 7.00 382.44 92.50 

Kent 120.99 109.80 36.00 

King 203.90 7.40 

Kleberg 54.50 150.10 

Knox 54.20 7.20 

La Salle 52.36 691.44 24.00 

Lamb 32.80 7.50 

Lavaca 107.69 552.74 216.53 

Lee 35.30 24.48 83.01 

Leon 68.91 524.00 310.50 

Liberty 34.00 330.85 145.10 

Limestone 6.30 1,876.14 451.40 

Lipscomb 214.88 1,447.13 

Live Oak 132.03 342.83 129.60 

Loving 149.10 620.83 33.00 

Lubbock 60.30 

Lynn 46.25 

Madison 36.31 66.20 

Marion 104.73 66.50 

Martin 3,643.04 

Matagorda 25.97 590.09 100.27 

Maverick 333.88 27.00 241.35 

McCulloch 1.00 

McLennan 1.23 9.50 9.50 

McMullen 128.79 749.60 49.50 

Medina 30.11 

Menard 70.50 

Midland 8.60 2,637.28 75.30 

Milam 19.29 10.00 

Mitchell 640.83 

6-10 
Table 6.5 2008 Total Depth by Model Rig Well Type Category (1,000 feet) (Cont.) 

County Vertical <= 7,000 feet Vertical > 7,000 feet Directional/Horizontal 

Montague 107.08 475.44 365.20 

Montgomery 6.00 51.95 24.52 

Moore 126.48 6.30 

Motley 5.00 9.00 

Nacogdoches 1.00 2,210.41 761.92 

Navarro 36.15 102.10 6.60 

Newton 30.55 68.50 

Nolan 332.89 37.70 

Nueces 66.84 339.36 64.62 

Ochiltree 16.50 309.88 427.67 

Oldham 45.90 

Orange 7.00 17.00 101.32 

Palo Pinto 212.17 135.05 

Panola 92.08 2,693.70 1,652.45 

Parker 6.45 880.85 

Pecos 224.68 2,667.60 840.55 

Polk 60.63 90.83 218.65 

Potter 21.20 

Reagan 34.05 2,509.42 

Real 3.00 

Red River 5.80 8.20 5.80 

Reeves 88.15 310.70 374.12 

Refugio 588.28 335.65 

Roberts 17.80 1,337.30 361.71 

Robertson 2,317.69 438.50 

Runnels 375.57 4.80 

Rusk 27.00 3,697.44 508.05 

Sabine 8.00 

San Augustine 52.50 286.91 

San Jacinto 3.70 127.95 24.00 

San Patricio 29.80 94.07 89.11 

Schleicher 117.95 416.02 

Scurry 155.28 224.80 96.96 

Shackelford 206.38 

Shelby 546.60 881.58 

Sherman 274.40 80.60 

Smith 6.50 108.75 185.85 

Somervell 144.00 

Starr 69.53 1,406.17 178.30 

Stephens 469.77 14.40 

Sterling 40.42 294.86 9.25 

Stonewall 221.08 

Sutton 740.80 1,866.84 7.20 

Tarrant 37.45 18.00 7,630.70 

Taylor 69.30 4.00 

6-11 
Table 6.5 2008 Total Depth by Model Rig Well Type Category (1,000 feet) (Cont.) 

County Vertical <= 7,000 feet Vertical > 7,000 feet Directional/Horizontal 

Terrell 79.85 295.70 92.95 

Terry 26.89 86.20 55.20 

Throckmorton 90.84 

Titus 4.60 

Tom Green 123.60 16.00 

Trinity 4.10 

Tyler 23.11 70.20 329.95 

Upshur 11.77 260.21 96.80 

Upton 78.50 4,699.94 288.60 

Val Verde 3.10 73.30 

Van Zandt 8.20 35.20 

Victoria 296.15 207.20 33.03 

Walker 4.90 

Waller 82.71 61.80 10.00 

Ward 460.51 161.91 482.33 

Washington 6.00 42.00 

Webb 262.53 1,689.96 305.77 

Wharton 239.83 586.42 114.77 

Wheeler 3,839.70 482.40 

Wichita 366.76 9.00 

Wilbarger 126.99 

Willacy 301.75 25.50 

Wilson 4.45 

Winkler 20.50 294.95 148.92 

Wise 93.50 121.00 2,032.78 

Wood 17.70 37.86 32.00 

Yoakum 462.25 195.22 171.10 

Young 259.30 

Zapata 6.00 2,031.18 500.35 

Zavala 16.05 60.20 

Statewide Total 20,746 82,337 48,121 

Appendix E contains a summary of the total well depth by county and year for each 

model rig well type category. 

6.2 Model Rig Emission Profiles 

6.2.1 Model Rig Engine Profiles 

As described in Section 5.2, the survey data was disaggregated into three model rig 

categories for the following well types and depths based on the results of the data collection 

survey: 

• Vertical wells less than or equal to 7,000 feet; 

6-12 
• Vertical wells greater than 7,000 feet; and 

• Horizontal/Directional wells. 

For each of these rig categories, a model rig engine profile was developed. In order for 

the model rig engine profile data to be applied consistently to the TRC activity data, the survey 

results were normalized to a 1,000 foot drilling depth. This was accomplished by dividing the 

total drilling hours for each engine included in each survey by the well depth for that survey to 

obtain the hours of operation per engine per 1,000 feet of drilling depth. 

As the engine profiles and functions for engines used on mechanical rigs and electrical 

rigs are distinctly different as described in Section 3.3, separate engine profiles for mechanical 

and electrical rigs were developed for each model rig well type category. 

The following average engine parameters were calculated for each model rig well type 

category using a weighted average for each parameter based on the number of wells associated 

with each survey: 

• Number of engines by rig type (i.e., mechanical draw works, mud pumps, and 

generators; electrical rig engines; and completion engines). 

• Engine age 

• Engine size (hp) 

• Engine on-time (hours/1,000 feet drilled) 

• Overall average load (%) 

Surveys with missing data parameters were excluded from the weighted average 

calculation. The weighted averaged engine parameters developed for each model rig category by 

rig type are summarized in Table 6-6. 

6-13 
Table 6.6 Model Rig Engine Parameters 

Model Rig 

Category 

Rig Type Engine 

Type 

# of 

Engines 

Average 

Age (yrs) 

Engine 

Size (hp) 

Hours/1,000 

ft drilled 

Average 

Load (%) 

Draw Works 1.60 7 442 30.8 51.8 

Mud Pumps 1.69 6 428 29.4 45.9 

Vertical <= 

7,000 ft1

Mechanical 

Generator 0.97 4 330 28.3 70.4 

Draw Works 2.01 25 455 35.9 47.4 

Mud Pumps 1.62 18 761 33.2 46.0 

Mechanical 

Generator 2.00 10 407 19.3 78.7 

Vertical 

> 7,000 ft 

Electrical 2.15 2 1,381 62.6 48.5 

Draw Works 2.00 15 483 50.1 41.1 

Mud Pumps 2.00 6 1,075 36.4 42.6 

Mechanical 

Generator 2.00 10 390 26.8 69.0 

Horizontal/ 

Directional 

Electrical 2.03 2 1,346 47.3 52.5 

All All Completion 1.00 Default 350 10.0 43.0 1

 The one electrical rig surveyed for vertical wells <= 7,000 feet represents less than 0.5% of the total wells in this 

model rig well type category and was considered to have a negligible contribution to the emissions profile.

As can be seen in Table 6-6, the expected trend toward larger engine sizes and more 

hours required per 1,000 feet for the deeper vertical wells and the horizontal/directional wells is 

verified. The older engine ages for the mechanical rigs used on the deeper vertical wells and the 

horizontal/directional wells are based on several surveys received for these well types that 

covered a large number of wells drilled by rigs with older engines. However, as noted in Section 

3.3, the future trend for these types of wells is towards the use of electrical rigs, and the average 

age of the engines used on the electrical rigs for these well types is only two years. 

6.2.2 Model Rig Emission Factors 

Once the final mechanical and electrical rig engine profiles were established for each 

model rig well type category, US EPA’s NONROAD model was used to develop criteria 

pollutant emission factors for each rig type for each year of the inventory (2002, 2005, and 

2008 – 2021). Use of the NONROAD model allowed for expected reductions in emissions over 

time due to the phasing in of EPA’s emissions standards for nonroad diesel engines. 

Using the engine parameters summarized in Table 6-6, NONROAD model input files 

were developed (U.S. EPA, 2005). In particular, the NONROAD Activity file was modified 

using the hours per 1,000 feet drilled and average load, while the Population files were modified 

using the engine size. In addition, the population for a particular engine type was adjusted to a 

unit value of 1 for ease in calculation. The modified NONROAD files used in the emission factor 

calculation have been provided to the TCEQ in electronic format. 

6-14 
A total of 16 years were modeled – the base year of 2008, the prior years of 2002 and 

2005, and 13 projected years from 2009 to 2021. For each year modeled, the engine model age 

was kept constant. For instance, the 7 year old mechanical draw works engine for vertical wells < 

7,000 feet was modeled as a 2001 model year engine for the 2008 base year, as a 1995 model 

year engine for 2002, and as a 2014 model year engine for the future year of 2021. 

The model year-specific emissions output from the NONROAD model (i.e., based on the 

model year fraction of the unit engine population specified by the NONROAD population file) 

was then ratioed up to the number of engines in each rig type.2 For mechanical rigs, the draw 

works, mud pump, and generator engine emissions were aggregated together. For both 

mechanical and electrical rig types, a single completion engine of 350 hp running 10 hours per 

1,000 feet drilled was also included to model completion activities. A composite model rig 

emissions profile was developed by aggregating the mechanical and electrical rig types together 

based upon the percentage of wells associated with each rig type. For example, for the 

horizontal/directional model rig well type, approximately two-thirds of the wells were 

represented by electrical rigs, so the resultant emission factors are weighted two-thirds by the 

NONROAD electrical rig emission factors, and one-third by the mechanical rig emission factors. 

SO2 emissions are based on fuel sulfur content profiles for Texas obtained from historical 

fuel sampling data performed for the TCEQ. The average diesel sulfur content (% weight) for a 

particular analysis year was developed using the county-level fuel parameter data contained in 

TCEQ’s TexN model, weighted by the number of wells in each county. The statewide average 

diesel sulfur content values calculated were 0.2995% for 2002 and 2005, 0.0316% for 2008 and 

2009, and 0.0015% for 2010 through 2021, reflecting the reduced sulfur requirements over time. 

Total hydrocarbon (THC) exhaust emissions from the NONROAD model were converted 

to VOC and TOG using ratios of 1.053 and 1.070, respectively (U.S. EPA, 2005a). Crankcase 

THC emissions were assumed to be equivalent to both VOC and TOG (U.S. EPA, 2005b). For 

diesel nonroad engines, PM10 is assumed to be equivalent to PM, while the PM2.5 fraction of 

PM10 is estimated to be 0.97 (U.S. EPA, 2005a). 

Hazardous air pollutant (HAP) emission factors were then developed by applying 

speciated HAP emissions profiles for PM10 and TOG from the California Air Resources Board’s 

 

2

 The NONROAD model allocates the total equipment population across a distribution of model years and estimates 

the emissions associated with each model year. For a given calendar year this analysis is interested in just one 

engine age/model year representing the average age for each model profile. Therefore the emissions for the model 

year of interest were scaled back up as if the entire engine population specified in NONROAD were allocated to just 

this one model year. 

6-15 
(CARB) Speciation Profile Database for diesel combustion to the PM and TOG emissions 

factors obtained from the NONROAD model (ARB, 2001). ARB profile #425 was used to 

speciate PM10, and ARB profile #818 was used to speciate TOG. Tables 6-7 and 6-8 present the 

speciation profiles for PM10 and TOG, respectively. 

Table 6.7 PM10 Speciation Factors 

HAP HAP CAS # 

Weight 

Fraction of 

PM10 

Antimony 7440360 0.000036 

Arsenic 7440382 0.000005 

Cadmium 7440439 0.000040 

Cobalt 7440484 0.000011 

Chlorine 7782505 0.000344 

Lead 7439921 0.000042 

Manganese 7439965 0.000040 

Nickel 7440020 0.000019 

Mercury 7439976 0.000030 

Phosphorous 7723140 0.000127 

Selenium 7782492 0.000010 

Table 6.8 TOG Speciation Factors 

HAP HAP CAS # 

Weight 

Fraction of 

TOG 

1,3-butadiene 106990 0.002 

2,2,4-trimethylpentane 540841 0.003 

Acetaldehyde 75070 0.074 

Benzene 71432 0.02 

Cumene 98828 2E-04 

Ethylbenzene 100414 0.003 

Formaldehyde 50000 0.147 

Methanol 67561 3E-04 

m-xylene 108383 0.006 

Naphthalene 91203 9E-04 

n-hexane 110543 0.002 

o-xylene 95476 0.003 

Propionaldehyde 123386 0.01 

p-xylene 106423 0.001 

Styrene 100425 6E-04 

Toluene 108883 0.015 

The final emissions profile for each of the three model rig well type categories was 

developed by weighing the emission profiles for each rig type (mechanical and electrical) by the 

6-16 
percentage of wells of each rig type in each model rig well type category. Appendix F presents 

the emission factors developed for each of the model rig well type categories for 2002, 2005, and 

2008 through 2021. 

6.3 Emission Estimation Methodology 

Using the model rig well type category emission profiles, county-level emission estimates 

were calculated using the activity data from the TRC dataset. County-level well activity data in 

terms of total depth (1,000 feet) drilled was obtained by summing the depth of each individual 

well drilled for each of the three model rig well type categories for each county as described in 

Section 6.1. Once the total depth drilled by model rig well type category was known and the 

emission factor profile for each model rig well type category was developed, annual county level 

emissions for each model rig well type category were estimated by multiplying the total depth 

drilled (in terms of 1,000 feet) by the emission factors obtained through use of the survey data 

and the NONROAD model as follows: 

 Epoll-type = (Depth (1,000 feet/yr)) x (EFpoll (tons/1,000 feet)) 

Where: 

 Epoll-type = Emissions of pollutant for county by model rig well type 

category (tons/yr) 

 Depth = Total depth drilled in model rig well type category by county 

(1,000 feet/yr) 

 EFpoll = Emission factor of pollutant (tons/1,000 feet) 

For 2008 through 2021, NOx emission estimates for the 110 counties subject to the Texas 

Low Emission Diesel (TxLED) program were adjusted downward by 6.2% to account for the 

effect of the rule.3

 Table 6-9 identifies the counties where this adjustment was made. 

Table 6.9 TxLED Counties 

Anderson Denton Johnson Robertson 

Angelina Ellis Karnes Rockwall 

Aransas Falls Kaufman Rusk 

Atascosa Fannin Lamar Sabine 

Austin Fayette Lavaca San Jacinto 

Bastrop Franklin Lee San Patricio 

Bee Freestone Leon San Augustine 

 

3

 The TxLED program requirements initiated in February 2006, so these adjustments were not applied to the 2002 

and 2005 modeling scenarios. 

6-17 
Table 6.9 TxLED Counties (Cont.) 

Bell Fort Bend Liberty Shelby 

Bexar Galveston Limestone Smith 

Bosque Goliad Live Oak Somervell 

Bowie Gonzales Madison Tarrant 

Brazoria Grayson Marion Titus 

Brazos Gregg Matagorda Travis 

Burleson Grimes McLennan Trinity 

Caldwell Guadalupe Milam Tyler 

Calhoun Hardin Montgomery Upshur 

Camp Harris Morris Van Zandt 

Cass Harrison Nacogdoches Victoria 

Chambers Hays Navarro Walker 

Cherokee Henderson Newton Waller 

Collin Hill Nueces Washington 

Colorado Hood Orange Wharton 

Comal Hopkins Panola Williamson 

Cooke Houston Parker Wilson 

Coryell Hunt Polk Wise 

Dallas Jackson Rains 

De Witt Jasper Red River 

Delta Jefferson Refugio 

For counties subject to TxLED requirements, NOx emissions were estimated as follows: 

ENOx-type = (Depth (1,000 feet/yr)) x (EFNOx (tons/1,000 feet)) x (0.938) 

Where: 

 ENOx-type = Emissions of NOx for each county by model rig well type 

category (tons/yr) 

 Depth = Total depth drilled in model rig well type category by county 

(1,000 feet/yr) 

 EFNOx = NOx emission factor (tons/1,000 feet) 

 (0.938) = Adjustment Factor to account for 6.2% TxLED reduction 

Total county level annual emissions were then obtained by summing the total emissions 

for each of the three model rig well type categories for each county. Ozone season daily (OSD) 

emissions were calculated by dividing the annual emissions by 365 (days/year). 

6-18 
6.4 Results 

6.4.1 Emission Summary 

Table 6-10 summarizes the statewide annual criteria pollutant emission estimates for 

2002, 2005, and 2008 through 2021. Table 6-11 summarizes both annual and OSD criteria 

pollutant emissions by county for the 2008 base year. Appendix G contains detailed tables 

showing statewide annual emission estimates for each year for all criteria pollutants and HAPs 

(Appendix G, Table 1), as well as county-level annual and OSD emission estimates for each year 

for all criteria pollutants and HAPs (Appendix G, Tables 2 and 3, respectively). The decreasing 

emissions after 2009 reflecting the falling oil and gas production projections from the EIA 

dataset for the areas including Texas.

As compared to the previous oil and gas study prepared by TCEQ in 2007 (for a 2005 

base year), the emission estimates presented in this study reflect a significant decrease in the 

statewide NOx emission estimate from drilling rig engines for 2005 (42,854 tons per year in this 

study compared to 119,647 tons per year in the 2007 study). While not as pronounced, there 

were also significant decreases in the SO2 and CO emission estimates based on this study. For 

VOC, PM10, and PM2.5, the estimates contained in this study show slightly higher estimates than 

in the previous study. These differences in the estimates between the two studies can be 

attributed to the emissions estimation methodologies used in each study. While the previous 

study was done using a top-down approach, conservative emission estimation assumptions, and 

the use of AP-42 emission factors, the current study used 2008 survey data on the actual engine 

parameters (engine size, hours of operation, and engine load) used in drilling oil and gas wells in 

2008, as well as utilizing the NONROAD model to develop emission factors. 

6.4.2 NIF 3.0 Files 

Once the emissions inventory was completed, NIF 3.0 area source text-formatted input 

files were prepared for base years 2002, 2005, and 2008. The NIF 3.0 files were created using 

information provided by TCEQ regarding the correct format and valid code listings for submittal 

to TexAER (TCEQ 2009a). Prior to submittal to TCEQ, the NIF 3.0 files were pre-processed 

using EPA’s NIF Basic Format and Content Checker to check for errors and inconsistencies. 

Additionally, ERG performed a test upload to TexAER to ensure the files were complete and 

accurate and in a format consistent with the TexAER area source file data requirements. 

6-19 
6-20 

Table 6.10 Texas Drilling Rig Estimates (tons/year) 

Year CO NOx PM10 PM2.5 SO2 VOC 

2002 13,305 35,828 2,552 2,475 4,776 3,631 

2005 15,878 42,854 3,036 2,945 5,977 4,337 

2008 16,721 55,238 2,543 2,467 956 4,326 

2009 16,769 55,457 2,550 2,474 961 4,340 

2010 16,336 53,123 2,417 2,344 45 4,182 

2011 15,117 48,462 2,319 2,249 44 3,806 

2012 14,748 46,253 2,263 2,196 43 3,665 

2013 12,008 39,793 1,378 1,337 38 3,413 

2014 11,945 39,461 1,372 1,331 38 3,392 

2015 11,755 38,837 1,350 1,310 37 3,349 

2016 11,558 36,440 1,320 1,280 37 3,320 

2017 8,915 34,771 1,118 1,085 36 2,800 

2018 6,114 31,282 811 787 35 2,227 

2019 6,073 31,127 805 781 35 2,215 

2020 6,035 30,771 800 776 35 2,205 

2021 3,299 26,063 448 435 33 1,504 
Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Est

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Anderson 2.03E+01 5.53E-02 5.94E+01 1.62E-01 3.10E+00 8.47E-03 3.01E+00 8.21E-03 1.04E+00 Andrews 2.33E+02 6.36E-01 7.75E+02 2.12E+00 3.52E+01 9.61E-02 3.41E+01 9.33E-02 1.37E+01 Angelina 6.70E+01 1.83E-01 1.93E+02 5.27E-01 1.03E+01 2.82E-02 1.00E+01 2.73E-02 3.26E+00 Aransas 8.80E+00 2.41E-02 2.75E+01 7.51E-02 1.34E+00 3.67E-03 1.30E+00 3.56E-03 4.85E-01 Archer 9.32E+00 2.55E-02 3.94E+01 1.08E-01 1.35E+00 3.68E-03 1.31E+00 3.57E-03 8.11E-01 Atascosa 7.02E+00 1.92E-02 2.05E+01 5.61E-02 1.07E+00 2.93E-03 1.04E+00 2.84E-03 3.69E-01 Austin 7.59E+00 2.07E-02 2.63E+01 7.20E-02 1.13E+00 3.10E-03 1.10E+00 3.01E-03 5.13E-01 Bastrop 1.69E+01 4.63E-02 5.76E+01 1.57E-01 2.56E+00 7.01E-03 2.49E+00 6.80E-03 1.04E+00 Baylor 1.87E+00 5.10E-03 9.04E+00 2.47E-02 2.65E-01 7.24E-04 2.57E-01 7.02E-04 1.90E-01 Bee 5.68E+01 1.55E-01 2.06E+02 5.62E-01 8.51E+00 2.32E-02 8.25E+00 2.25E-02 3.92E+00 Bell 1.42E-01 3.89E-04 6.28E-01 1.72E-03 2.01E-02 5.49E-05 1.95E-02 5.32E-05 1.45E-02 Bexar 2.53E-02 6.92E-05 1.12E-01 3.05E-04 3.57E-03 9.76E-06 3.46E-03 9.47E-06 2.58E-03 Borden 2.86E+01 7.80E-02 8.82E+01 2.41E-01 4.39E+00 1.20E-02 4.25E+00 1.16E-02 1.41E+00 Bosque 2.72E+00 7.44E-03 9.98E+00 2.73E-02 4.09E-01 1.12E-03 3.97E-01 1.08E-03 1.85E-01 Bowie 1.35E+00 3.68E-03 3.50E+00 9.57E-03 2.09E-01 5.70E-04 2.03E-01 5.53E-04 5.63E-02 Brazoria 4.64E+01 1.27E-01 1.40E+02 3.84E-01 7.10E+00 1.94E-02 6.89E+00 1.88E-02 2.44E+00 Brazos 2.17E+01 5.92E-02 9.57E+01 2.62E-01 3.18E+00 8.69E-03 3.09E+00 8.43E-03 1.88E+00 Briscoe 1.48E+00 4.04E-03 4.49E+00 1.23E-02 2.26E-01 6.18E-04 2.19E-01 6.00E-04 7.41E-02 Brooks 9.58E+01 2.62E-01 2.87E+02 7.84E-01 1.48E+01 4.03E-02 1.43E+01 3.91E-02 4.50E+00 Brown 1.30E+00 3.54E-03 6.10E+00 1.67E-02 1.83E-01 5.00E-04 1.78E-01 4.85E-04 1.32E-01 Burleson 4.46E+01 1.22E-01 1.48E+02 4.04E-01 6.77E+00 1.85E-02 6.57E+00 1.80E-02 2.65E+00 Caldwell 1.58E+00 4.31E-03 7.31E+00 2.00E-02 2.25E-01 6.14E-04 2.18E-01 5.96E-04 1.60E-01 Calhoun 2.38E+01 6.50E-02 7.79E+01 2.13E-01 3.61E+00 9.87E-03 3.50E+00 9.57E-03 1.40E+00 Callahan 2.58E+00 7.06E-03 1.22E+01 3.32E-02 3.65E-01 9.96E-04 3.54E-01 9.67E-04 2.64E-01 Cameron 1.42E+00 3.89E-03 3.94E+00 1.08E-02 2.20E-01 6.02E-04 2.14E-01 5.84E-04 5.94E-02 Carson 9.90E-01 2.71E-03 5.12E+00 1.40E-02 1.42E-01 3.89E-04 1.38E-01 3.77E-04 9.95E-02 Cass 2.22E-01 6.05E-04 9.77E-01 2.67E-03 3.13E-02 8.54E-05 3.03E-02 8.28E-05 2.26E-02 Chambers 2.37E+01 6.47E-02 8.97E+01 2.45E-01 3.55E+00 9.69E-03 3.44E+00 9.40E-03 1.68E+00 Cherokee 1.52E+02 4.15E-01 4.40E+02 1.20E+00 2.33E+01 6.37E-02 2.26E+01 6.18E-02 7.46E+00 Childress 2.94E-01 8.04E-04 1.38E+00 3.78E-03 4.15E-02 1.13E-04 4.03E-02 1.10E-04 3.00E-02 

6-21 
Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estima

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Clay 1.12E+01 3.06E-02 4.84E+01 1.32E-01 1.64E+00 4.48E-03 1.59E+00 4.35E-03 9.27E-01 Cochran 1.10E+01 3.01E-02 4.45E+01 1.22E-01 1.60E+00 4.38E-03 1.56E+00 4.25E-03 8.97E-01 Coke 6.20E+00 1.69E-02 2.46E+01 6.73E-02 9.08E-01 2.48E-03 8.80E-01 2.41E-03 4.91E-01 Coleman 3.09E+00 8.45E-03 1.45E+01 3.97E-02 4.36E-01 1.19E-03 4.23E-01 1.16E-03 3.15E-01 Colorado 2.83E+01 7.73E-02 8.52E+01 2.33E-01 4.31E+00 1.18E-02 4.18E+00 1.14E-02 1.53E+00 Comanche 9.49E-02 2.59E-04 4.46E-01 1.22E-03 1.34E-02 3.66E-05 1.30E-02 3.55E-05 9.69E-03 Concho 5.29E+00 1.45E-02 2.49E+01 6.80E-02 7.46E-01 2.04E-03 7.24E-01 1.98E-03 5.40E-01 Cooke 4.07E+01 1.11E-01 1.18E+02 3.24E-01 6.23E+00 1.70E-02 6.04E+00 1.65E-02 2.09E+00 Coryell 1.27E-01 3.46E-04 5.58E-01 1.53E-03 1.79E-02 4.88E-05 1.73E-02 4.73E-05 1.29E-02 Cottle 1.78E+01 4.87E-02 5.34E+01 1.46E-01 2.74E+00 7.49E-03 2.66E+00 7.26E-03 8.56E-01 Crane 4.87E+01 1.33E-01 1.80E+02 4.93E-01 7.25E+00 1.98E-02 7.04E+00 1.92E-02 3.38E+00 Crockett 3.11E+02 8.50E-01 9.41E+02 2.57E+00 4.77E+01 1.30E-01 4.63E+01 1.26E-01 1.53E+01 Crosby 2.90E+00 7.93E-03 1.36E+01 3.73E-02 4.09E-01 1.12E-03 3.97E-01 1.08E-03 2.96E-01 Culberson 3.59E+01 9.80E-02 1.08E+02 2.95E-01 5.53E+00 1.51E-02 5.36E+00 1.46E-02 1.70E+00 Dallas 7.73E+00 2.11E-02 3.84E+01 1.05E-01 1.12E+00 3.05E-03 1.08E+00 2.96E-03 7.73E-01 Dawson 5.66E+01 1.55E-01 1.63E+02 4.45E-01 8.73E+00 2.39E-02 8.47E+00 2.31E-02 2.52E+00 Denton 2.06E+02 5.62E-01 9.93E+02 2.71E+00 2.99E+01 8.16E-02 2.90E+01 7.91E-02 1.99E+01 DeWitt 1.05E+02 2.86E-01 3.80E+02 1.04E+00 1.57E+01 4.30E-02 1.53E+01 4.17E-02 7.06E+00 Dickens 2.40E+01 6.56E-02 7.72E+01 2.11E-01 3.65E+00 9.96E-03 3.54E+00 9.66E-03 1.34E+00 Dimmit 4.50E+01 1.23E-01 1.66E+02 4.53E-01 6.75E+00 1.84E-02 6.55E+00 1.79E-02 2.96E+00 Duval 7.96E+01 2.17E-01 2.39E+02 6.53E-01 1.22E+01 3.35E-02 1.19E+01 3.25E-02 3.78E+00 Eastland 1.52E+00 4.16E-03 7.16E+00 1.96E-02 2.15E-01 5.87E-04 2.08E-01 5.69E-04 1.55E-01 Ector 2.64E+02 7.21E-01 7.77E+02 2.12E+00 4.06E+01 1.11E-01 3.94E+01 1.08E-01 1.23E+01 Edwards 3.99E+01 1.09E-01 1.31E+02 3.58E-01 6.07E+00 1.66E-02 5.89E+00 1.61E-02 2.20E+00 Ellis 2.09E+01 5.72E-02 1.04E+02 2.84E-01 3.03E+00 8.27E-03 2.94E+00 8.02E-03 2.10E+00 Erath 8.49E+00 2.32E-02 4.44E+01 1.21E-01 1.22E+00 3.34E-03 1.19E+00 3.24E-03 8.51E-01 Falls 5.70E-02 1.56E-04 2.51E-01 6.87E-04 8.04E-03 2.20E-05 7.80E-03 2.13E-05 5.81E-03 Fannin 2.84E+00 7.77E-03 7.39E+00 2.02E-02 4.41E-01 1.20E-03 4.28E-01 1.17E-03 1.19E-01 Fayette 1.11E+01 3.03E-02 4.69E+01 1.28E-01 1.63E+00 4.46E-03 1.58E+00 4.33E-03 9.16E-01 Fisher 1.54E+01 4.20E-02 5.25E+01 1.44E-01 2.31E+00 6.31E-03 2.24E+00 6.12E-03 9.52E-01 

6-22 
Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estima

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Foard 7.94E-01 2.17E-03 3.74E+00 1.02E-02 1.12E-01 3.06E-04 1.09E-01 2.97E-04 8.10E-02 Fort Bend 2.60E+01 7.09E-02 9.96E+01 2.72E-01 3.85E+00 1.05E-02 3.73E+00 1.02E-02 1.95E+00 Franklin 1.45E+01 3.96E-02 3.83E+01 1.05E-01 2.24E+00 6.13E-03 2.17E+00 5.94E-03 6.26E-01 Freestone 4.35E+02 1.19E+00 1.22E+03 3.33E+00 6.70E+01 1.83E-01 6.50E+01 1.77E-01 2.04E+01 Frio 1.91E+01 5.21E-02 7.43E+01 2.03E-01 2.84E+00 7.75E-03 2.75E+00 7.52E-03 1.37E+00 Gaines 1.12E+02 3.07E-01 3.47E+02 9.48E-01 1.72E+01 4.69E-02 1.66E+01 4.55E-02 5.72E+00 Galveston 1.19E+01 3.26E-02 4.11E+01 1.12E-01 1.81E+00 4.93E-03 1.75E+00 4.78E-03 7.49E-01 Garza 1.40E+01 3.83E-02 5.11E+01 1.39E-01 2.09E+00 5.70E-03 2.02E+00 5.53E-03 9.61E-01 Glasscock 1.36E+02 3.72E-01 3.81E+02 1.04E+00 2.11E+01 5.76E-02 2.05E+01 5.59E-02 5.78E+00 Goliad 6.97E+01 1.91E-01 2.09E+02 5.70E-01 1.06E+01 2.91E-02 1.03E+01 2.82E-02 3.70E+00 Gonzales 5.35E+00 1.46E-02 1.87E+01 5.12E-02 8.04E-01 2.20E-03 7.80E-01 2.13E-03 3.50E-01 Gray 2.33E+00 6.37E-03 7.20E+00 1.97E-02 3.56E-01 9.72E-04 3.45E-01 9.43E-04 1.20E-01 Grayson 1.07E+01 2.91E-02 3.54E+01 9.66E-02 1.62E+00 4.42E-03 1.57E+00 4.28E-03 6.40E-01 Gregg 9.58E+01 2.62E-01 2.97E+02 8.12E-01 1.46E+01 4.00E-02 1.42E+01 3.88E-02 5.19E+00 Grimes 1.33E+01 3.64E-02 6.59E+01 1.80E-01 1.92E+00 5.25E-03 1.86E+00 5.09E-03 1.33E+00 Guadalupe 8.96E-01 2.45E-03 4.29E+00 1.17E-02 1.29E-01 3.51E-04 1.25E-01 3.41E-04 9.02E-02 Hale 3.22E+00 8.80E-03 1.58E+01 4.33E-02 4.59E-01 1.25E-03 4.45E-01 1.22E-03 3.26E-01 Hansford 4.53E+01 1.24E-01 1.39E+02 3.80E-01 6.95E+00 1.90E-02 6.74E+00 1.84E-02 2.24E+00 Hardeman 1.70E+01 4.65E-02 5.35E+01 1.46E-01 2.61E+00 7.13E-03 2.53E+00 6.92E-03 8.64E-01 Hardin 5.91E+01 1.62E-01 1.92E+02 5.23E-01 8.98E+00 2.45E-02 8.71E+00 2.38E-02 3.44E+00 Harris 1.24E+01 3.38E-02 4.89E+01 1.34E-01 1.84E+00 5.02E-03 1.78E+00 4.87E-03 9.40E-01 Harrison 5.79E+02 1.58E+00 1.84E+03 5.04E+00 8.82E+01 2.41E-01 8.55E+01 2.34E-01 3.26E+01 Hartley 5.68E-01 1.55E-03 2.67E+00 7.30E-03 8.01E-02 2.19E-04 7.77E-02 2.12E-04 5.80E-02 Haskell 2.02E+00 5.51E-03 9.48E+00 2.59E-02 2.84E-01 7.77E-04 2.76E-01 7.54E-04 2.06E-01 Hemphill 6.43E+02 1.76E+00 1.92E+03 5.23E+00 9.90E+01 2.71E-01 9.61E+01 2.62E-01 3.00E+01 Henderson 3.91E+01 1.07E-01 1.11E+02 3.04E-01 6.01E+00 1.64E-02 5.83E+00 1.59E-02 1.87E+00 Hidalgo 2.27E+02 6.19E-01 6.98E+02 1.91E+00 3.48E+01 9.51E-02 3.38E+01 9.23E-02 1.11E+01 Hill 9.04E+01 2.47E-01 4.49E+02 1.23E+00 1.31E+01 3.57E-02 1.27E+01 3.46E-02 9.05E+00 Hockley 3.19E+01 8.71E-02 1.18E+02 3.23E-01 4.77E+00 1.30E-02 4.63E+00 1.27E-02 2.12E+00 Hood 7.86E+01 2.15E-01 3.90E+02 1.07E+00 1.13E+01 3.10E-02 1.10E+01 3.01E-02 7.86E+00 

6-23 
Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estima

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Hopkins 3.41E+00 9.31E-03 9.11E+00 2.49E-02 5.26E-01 1.44E-03 5.10E-01 1.39E-03 1.51E-01 Houston 2.89E+01 7.89E-02 8.59E+01 2.35E-01 4.43E+00 1.21E-02 4.29E+00 1.17E-02 1.48E+00 Howard 1.19E+02 3.26E-01 3.36E+02 9.17E-01 1.85E+01 5.04E-02 1.79E+01 4.89E-02 5.14E+00 Hudspeth 4.12E+00 1.12E-02 1.30E+01 3.55E-02 6.26E-01 1.71E-03 6.08E-01 1.66E-03 2.21E-01 Hutchinson 1.55E+01 4.24E-02 6.98E+01 1.91E-01 2.24E+00 6.11E-03 2.17E+00 5.92E-03 1.42E+00 Irion 2.33E+02 6.36E-01 6.57E+02 1.79E+00 3.60E+01 9.83E-02 3.49E+01 9.54E-02 1.01E+01 Jack 1.69E+01 4.63E-02 8.59E+01 2.35E-01 2.43E+00 6.63E-03 2.35E+00 6.43E-03 1.71E+00 Jackson 5.69E+01 1.56E-01 1.66E+02 4.53E-01 8.70E+00 2.38E-02 8.44E+00 2.31E-02 2.92E+00 Jasper 2.20E+01 6.02E-02 9.34E+01 2.55E-01 3.25E+00 8.88E-03 3.15E+00 8.61E-03 1.81E+00 Jefferson 4.90E+01 1.34E-01 1.84E+02 5.03E-01 7.34E+00 2.01E-02 7.12E+00 1.95E-02 3.46E+00 Jim Hogg 3.05E+01 8.33E-02 8.78E+01 2.40E-01 4.71E+00 1.29E-02 4.57E+00 1.25E-02 1.36E+00 Jim Wells 1.10E+01 3.01E-02 3.69E+01 1.01E-01 1.67E+00 4.56E-03 1.62E+00 4.42E-03 6.49E-01 Johnson 6.62E+02 1.81E+00 3.27E+03 8.93E+00 9.57E+01 2.62E-01 9.28E+01 2.54E-01 6.58E+01 Jones 7.02E+00 1.92E-02 3.30E+01 9.02E-02 9.91E-01 2.71E-03 9.61E-01 2.63E-03 7.17E-01 Karnes 2.97E+01 8.12E-02 1.11E+02 3.05E-01 4.45E+00 1.22E-02 4.32E+00 1.18E-02 2.10E+00 Kenedy 6.47E+01 1.77E-01 1.98E+02 5.40E-01 9.94E+00 2.72E-02 9.64E+00 2.63E-02 3.13E+00 Kent 2.31E+01 6.30E-02 7.83E+01 2.14E-01 3.49E+00 9.54E-03 3.39E+00 9.25E-03 1.36E+00 King 7.56E+00 2.07E-02 3.34E+01 9.13E-02 1.08E+00 2.96E-03 1.05E+00 2.87E-03 7.05E-01 Kleberg 1.98E+01 5.42E-02 8.43E+01 2.30E-01 2.95E+00 8.06E-03 2.86E+00 7.82E-03 1.51E+00 Knox 2.79E+00 7.63E-03 1.11E+01 3.02E-02 4.09E-01 1.12E-03 3.97E-01 1.08E-03 2.20E-01 La Salle 1.07E+02 2.92E-01 3.04E+02 8.32E-01 1.65E+01 4.52E-02 1.60E+01 4.38E-02 4.68E+00 Lamb 1.62E+00 4.43E-03 7.96E+00 2.18E-02 2.31E-01 6.30E-04 2.24E-01 6.11E-04 1.64E-01 Lavaca 1.03E+02 2.81E-01 3.14E+02 8.57E-01 1.57E+01 4.30E-02 1.53E+01 4.17E-02 5.49E+00 Lee 1.12E+01 3.07E-02 4.65E+01 1.27E-01 1.66E+00 4.53E-03 1.61E+00 4.39E-03 9.12E-01 Leon 1.05E+02 2.86E-01 3.33E+02 9.10E-01 1.59E+01 4.36E-02 1.55E+01 4.23E-02 5.91E+00 Liberty 6.19E+01 1.69E-01 1.89E+02 5.18E-01 9.46E+00 2.58E-02 9.17E+00 2.51E-02 3.31E+00 Limestone 3.16E+02 8.64E-01 9.05E+02 2.47E+00 4.86E+01 1.33E-01 4.72E+01 1.29E-01 1.53E+01 Lipscomb 1.45E+02 3.95E-01 6.84E+02 1.87E+00 2.12E+01 5.80E-02 2.06E+01 5.63E-02 1.26E+01 Live Oak 6.56E+01 1.79E-01 2.02E+02 5.51E-01 1.00E+01 2.73E-02 9.70E+00 2.65E-02 3.58E+00 Loving 1.00E+02 2.74E-01 2.93E+02 8.01E-01 1.54E+01 4.22E-02 1.50E+01 4.09E-02 4.62E+00 

6-24 
Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estima

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Lubbock 1.91E+00 5.21E-03 8.97E+00 2.45E-02 2.69E-01 7.36E-04 2.61E-01 7.14E-04 1.95E-01 Lynn 6.92E+00 1.89E-02 1.92E+01 5.24E-02 1.07E+00 2.93E-03 1.04E+00 2.84E-03 2.89E-01 Madison 1.06E+01 2.89E-02 3.96E+01 1.08E-01 1.59E+00 4.33E-03 1.54E+00 4.20E-03 7.41E-01 Marion 2.08E+01 5.70E-02 6.64E+01 1.81E-01 3.18E+00 8.68E-03 3.08E+00 8.42E-03 1.17E+00 Martin 5.45E+02 1.49E+00 1.51E+03 4.13E+00 8.45E+01 2.31E-01 8.20E+01 2.24E-01 2.28E+01 Matagorda 9.69E+01 2.65E-01 2.72E+02 7.43E-01 1.49E+01 4.08E-02 1.45E+01 3.96E-02 4.55E+00 Maverick 3.34E+01 9.11E-02 1.60E+02 4.37E-01 4.83E+00 1.32E-02 4.68E+00 1.28E-02 3.12E+00 McCulloch 3.16E-02 8.65E-05 1.49E-01 4.07E-04 4.46E-03 1.22E-05 4.33E-03 1.18E-05 3.23E-03 McLennan 2.20E+00 6.01E-03 7.53E+00 2.06E-02 3.33E-01 9.08E-04 3.23E-01 8.81E-04 1.37E-01 McMullen 1.20E+02 3.28E-01 3.50E+02 9.58E-01 1.85E+01 5.06E-02 1.80E+01 4.91E-02 5.49E+00 Medina 9.53E-01 2.60E-03 4.48E+00 1.22E-02 1.34E-01 3.67E-04 1.30E-01 3.56E-04 9.72E-02 Menard 2.23E+00 6.10E-03 1.05E+01 2.87E-02 3.15E-01 8.60E-04 3.05E-01 8.34E-04 2.28E-01 Midland 4.01E+02 1.10E+00 1.13E+03 3.08E+00 6.21E+01 1.70E-01 6.02E+01 1.64E-01 1.71E+01 Milam 2.11E+00 5.76E-03 6.58E+00 1.80E-02 3.18E-01 8.69E-04 3.09E-01 8.43E-04 1.25E-01 Mitchell 2.03E+01 5.54E-02 9.54E+01 2.61E-01 2.86E+00 7.82E-03 2.78E+00 7.58E-03 2.07E+00 Montague 1.03E+02 2.81E-01 3.63E+02 9.92E-01 1.56E+01 4.26E-02 1.51E+01 4.14E-02 6.16E+00 Montgomery 9.87E+00 2.70E-02 3.05E+01 8.33E-02 1.51E+00 4.12E-03 1.46E+00 3.99E-03 5.35E-01 Moore 4.49E+00 1.23E-02 2.14E+01 5.85E-02 6.35E-01 1.74E-03 6.16E-01 1.68E-03 4.57E-01 Motley 1.51E+00 4.11E-03 4.48E+00 1.22E-02 2.31E-01 6.31E-04 2.24E-01 6.13E-04 7.24E-02 Nacogdoches 3.90E+02 1.07E+00 1.15E+03 3.15E+00 5.98E+01 1.63E-01 5.80E+01 1.59E-01 1.97E+01 Navarro 1.69E+01 4.63E-02 4.73E+01 1.29E-01 2.60E+00 7.11E-03 2.53E+00 6.90E-03 8.06E-01 Newton 9.90E+00 2.70E-02 3.83E+01 1.05E-01 1.48E+00 4.04E-03 1.43E+00 3.92E-03 7.23E-01 Nolan 1.62E+01 4.42E-02 6.52E+01 1.78E-01 2.36E+00 6.45E-03 2.29E+00 6.26E-03 1.31E+00 Nueces 5.79E+01 1.58E-01 1.66E+02 4.54E-01 8.90E+00 2.43E-02 8.63E+00 2.36E-02 2.84E+00 Ochiltree 8.01E+01 2.19E-01 3.07E+02 8.38E-01 1.21E+01 3.30E-02 1.17E+01 3.20E-02 5.31E+00 Oldham 6.87E+00 1.88E-02 1.90E+01 5.20E-02 1.06E+00 2.91E-03 1.03E+00 2.82E-03 2.87E-01 Orange 1.06E+01 2.91E-02 4.67E+01 1.27E-01 1.56E+00 4.27E-03 1.52E+00 4.14E-03 9.16E-01 Palo Pinto 1.72E+01 4.70E-02 8.71E+01 2.38E-01 2.46E+00 6.73E-03 2.39E+00 6.53E-03 1.73E+00 Panola 5.35E+02 1.46E+00 1.70E+03 4.64E+00 8.14E+01 2.23E-01 7.90E+01 2.16E-01 3.00E+01 Parker 6.86E+01 1.88E-01 3.40E+02 9.30E-01 9.91E+00 2.71E-02 9.62E+00 2.63E-02 6.87E+00 

6-25 
Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estima

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Pecos 4.72E+02 1.29E+00 1.49E+03 4.06E+00 7.23E+01 1.98E-01 7.02E+01 1.92E-01 2.39E+01 Polk 3.25E+01 8.88E-02 1.28E+02 3.50E-01 4.83E+00 1.32E-02 4.69E+00 1.28E-02 2.46E+00 Potter 6.71E-01 1.83E-03 3.16E+00 8.62E-03 9.47E-02 2.59E-04 9.18E-02 2.51E-04 6.84E-02 Reagan 3.77E+02 1.03E+00 1.05E+03 2.86E+00 5.84E+01 1.59E-01 5.66E+01 1.55E-01 1.58E+01 Real 9.49E-02 2.59E-04 4.46E-01 1.22E-03 1.34E-02 3.66E-05 1.30E-02 3.55E-05 9.69E-03 Red River 1.86E+00 5.09E-03 6.24E+00 1.70E-02 2.81E-01 7.68E-04 2.73E-01 7.45E-04 1.15E-01 Reeves 7.84E+01 2.14E-01 2.96E+02 8.08E-01 1.18E+01 3.22E-02 1.14E+01 3.13E-02 5.13E+00 Refugio 6.89E+01 1.88E-01 2.13E+02 5.81E-01 1.04E+01 2.85E-02 1.01E+01 2.76E-02 4.00E+00 Roberts 2.29E+02 6.25E-01 7.06E+02 1.93E+00 3.52E+01 9.61E-02 3.41E+01 9.32E-02 1.12E+01 Robertson 3.81E+02 1.04E+00 1.07E+03 2.93E+00 5.87E+01 1.60E-01 5.69E+01 1.56E-01 1.79E+01 Runnels 1.23E+01 3.35E-02 5.79E+01 1.58E-01 1.73E+00 4.73E-03 1.68E+00 4.59E-03 1.25E+00 Rusk 5.94E+02 1.62E+00 1.64E+03 4.48E+00 9.16E+01 2.50E-01 8.88E+01 2.43E-01 2.71E+01 Sabine 1.20E+00 3.27E-03 3.11E+00 8.50E-03 1.86E-01 5.07E-04 1.80E-01 4.92E-04 5.00E-02 San Augustine 3.02E+01 8.24E-02 1.31E+02 3.58E-01 4.44E+00 1.21E-02 4.30E+00 1.18E-02 2.56E+00 San Jacinto 2.11E+01 5.77E-02 5.96E+01 1.63E-01 3.25E+00 8.89E-03 3.16E+00 8.62E-03 9.98E-01 San Patricio 2.19E+01 6.00E-02 7.51E+01 2.05E-01 3.32E+00 9.06E-03 3.22E+00 8.79E-03 1.38E+00 Schleicher 6.60E+01 1.80E-01 1.90E+02 5.19E-01 1.02E+01 2.78E-02 9.87E+00 2.70E-02 2.98E+00 Scurry 4.61E+01 1.26E-01 1.56E+02 4.27E-01 7.00E+00 1.91E-02 6.79E+00 1.85E-02 2.66E+00 Shackelford 6.53E+00 1.78E-02 3.07E+01 8.39E-02 9.21E-01 2.52E-03 8.94E-01 2.44E-03 6.66E-01 Shelby 1.50E+02 4.11E-01 5.53E+02 1.51E+00 2.26E+01 6.17E-02 2.19E+01 5.98E-02 1.03E+01 Sherman 2.07E+01 5.67E-02 7.43E+01 2.03E-01 3.09E+00 8.46E-03 3.00E+00 8.20E-03 1.39E+00 Smith 3.09E+01 8.45E-02 1.15E+02 3.14E-01 4.64E+00 1.27E-02 4.50E+00 1.23E-02 2.15E+00 Somervell 1.12E+01 3.06E-02 5.55E+01 1.52E-01 1.62E+00 4.42E-03 1.57E+00 4.28E-03 1.12E+00 Starr 2.27E+02 6.19E-01 6.67E+02 1.82E+00 3.49E+01 9.54E-02 3.39E+01 9.26E-02 1.04E+01 Stephens 1.60E+01 4.37E-02 7.58E+01 2.07E-01 2.26E+00 6.17E-03 2.19E+00 5.99E-03 1.63E+00 Sterling 4.61E+01 1.26E-01 1.32E+02 3.61E-01 7.12E+00 1.95E-02 6.91E+00 1.89E-02 2.05E+00 Stonewall 7.00E+00 1.91E-02 3.29E+01 8.99E-02 9.87E-01 2.70E-03 9.57E-01 2.62E-03 7.14E-01 Sutton 3.03E+02 8.29E-01 8.88E+02 2.43E+00 4.67E+01 1.28E-01 4.53E+01 1.24E-01 1.41E+01 Tarrant 5.97E+02 1.63E+00 2.95E+03 8.07E+00 8.62E+01 2.36E-01 8.36E+01 2.29E-01 5.95E+01 Taylor 2.50E+00 6.84E-03 1.20E+01 3.27E-02 3.54E-01 9.68E-04 3.44E-01 9.39E-04 2.55E-01 

6-26 
6-27 

Table 6.11 2008 Annual and OSD County-Level Criteria Pollutant Emission Estima

CO-ANN CO-OSD 

NOXANN NOX- OSD PM10- ANN PM10- OSD PM2.5- ANN PM2.5- OSD SO2-ANN 

County tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr tons/day tons/yr 

Terrell 5.40E+01 1.48E-01 1.73E+02 4.72E-01 8.26E+00 2.26E-02 8.01E+00 2.19E-02 2.83E+00 Terry 1.80E+01 4.93E-02 6.24E+01 1.71E-01 2.74E+00 7.48E-03 2.66E+00 7.26E-03 1.05E+00 Throckmorton 2.87E+00 7.85E-03 1.35E+01 3.69E-02 4.06E-01 1.11E-03 3.93E-01 1.07E-03 2.93E-01 Titus 1.46E-01 3.98E-04 6.42E-01 1.75E-03 2.05E-02 5.61E-05 1.99E-02 5.44E-05 1.49E-02 Tom Green 6.31E+00 1.72E-02 2.50E+01 6.84E-02 9.23E-01 2.52E-03 8.95E-01 2.45E-03 4.99E-01 Trinity 1.30E-01 3.54E-04 5.72E-01 1.56E-03 1.83E-02 5.00E-05 1.78E-02 4.85E-05 1.32E-02 Tyler 3.69E+01 1.01E-01 1.58E+02 4.31E-01 5.43E+00 1.48E-02 5.27E+00 1.44E-02 3.08E+00 Upshur 4.68E+01 1.28E-01 1.40E+02 3.83E-01 7.18E+00 1.96E-02 6.96E+00 1.90E-02 2.42E+00 Upton 7.28E+02 1.99E+00 2.08E+03 5.68E+00 1.13E+02 3.08E-01 1.09E+02 2.98E-01 3.19E+01 Val Verde 1.11E+01 3.02E-02 3.09E+01 8.43E-02 1.71E+00 4.68E-03 1.66E+00 4.54E-03 4.68E-01 Van Zandt 5.53E+00 1.51E-02 1.48E+01 4.05E-02 8.53E-01 2.33E-03 8.28E-01 2.26E-03 2.46E-01 Victoria 4.30E+01 1.17E-01 1.35E+02 3.68E-01 6.50E+00 1.78E-02 6.30E+00 1.72E-02 2.51E+00 Walker 1.55E-01 4.24E-04 6.84E-01 1.87E-03 2.19E-02 5.98E-05 2.12E-02 5.80E-05 1.58E-02 Waller 1.26E+01 3.46E-02 3.94E+01 1.08E-01 1.92E+00 5.23E-03 1.86E+00 5.08E-03 7.31E-01 Ward 7.63E+01 2.08E-01 3.34E+02 9.12E-01 1.12E+01 3.07E-02 1.09E+01 2.98E-02 6.25E+00 Washington 3.45E+00 9.43E-03 1.70E+01 4.65E-02 4.98E-01 1.36E-03 4.83E-01 1.32E-03 3.46E-01 Webb 2.85E+02 7.79E-01 8.66E+02 2.37E+00 4.38E+01 1.20E-01 4.25E+01 1.16E-01 1.38E+01 Wharton 1.04E+02 2.85E-01 3.06E+02 8.36E-01 1.60E+01 4.36E-02 1.55E+01 4.23E-02 5.33E+00 Wheeler 6.12E+02 1.67E+00 1.79E+03 4.89E+00 9.45E+01 2.58E-01 9.17E+01 2.50E-01 2.77E+01 Wichita 1.30E+01 3.54E-02 5.83E+01 1.59E-01 1.85E+00 5.04E-03 1.79E+00 4.89E-03 1.24E+00 Wilbarger 4.02E+00 1.10E-02 1.89E+01 5.16E-02 5.67E-01 1.55E-03 5.50E-01 1.50E-03 4.10E-01 Willacy 4.72E+01 1.29E-01 1.36E+02 3.71E-01 7.29E+00 1.99E-02 7.07E+00 1.93E-02 2.08E+00 Wilson 3.46E-01 9.45E-04 1.72E+00 4.69E-03 4.99E-02 1.36E-04 4.84E-02 1.32E-04 3.46E-02 Winkler 5.64E+01 1.54E-01 1.87E+02 5.10E-01 8.61E+00 2.35E-02 8.35E+00 2.28E-02 3.07E+00 Wise 1.79E+02 4.89E-01 8.44E+02 2.31E+00 2.60E+01 7.11E-02 2.53E+01 6.90E-02 1.69E+01 Wood 8.71E+00 2.38E-02 2.95E+01 8.07E-02 1.32E+00 3.60E-03 1.28E+00 3.49E-03 5.42E-01 Yoakum 5.71E+01 1.56E-01 2.20E+02 6.01E-01 8.51E+00 2.33E-02 8.26E+00 2.26E-02 4.04E+00 Young 8.21E+00 2.24E-02 3.86E+01 1.05E-01 1.16E+00 3.16E-03 1.12E+00 3.07E-03 8.37E-01 Zapata 3.43E+02 9.38E-01 1.05E+03 2.87E+00 5.28E+01 1.44E-01 5.12E+01 1.40E-01 1.66E+01 Zavala 5.19E+00 1.42E-02 2.71E+01 7.41E-02 7.47E-01 2.04E-03 7.25E-01 1.98E-03 5.20E-01 
7.0 Conclusions and Recommendations 

This study presents a comprehensive, statewide 2008 emissions inventory for Texas for 

drilling rig engines. This inventory was prepared using well drilling activity data obtained 

through permit records from the TRC, combined with emissions data derived through detailed 

drilling rig engine data collected through a bottom-up survey effort. 

Survey data was collected through a phone and email survey which resulted in the 

collection of 45 completed surveys obtained from 39 different drilling rig contractors and/or oil 

and gas well operators. These surveys were representative of over 1,500 wells drilled in Texas in 

2008, or about 10% of all wells drilled in that year, and covered all of the major oil and gas 

basins in the state (Andarko, East Texas, Ft. Worth/Bend Arch, Permian, and Western Gulf). The 

data collected included drilling rig engine sizes (hp), ages, hours of operation, and model year. 

The 2008 inventory was used as the basis for developing 2002 and 2005 year inventories, 

as well as projected inventories for 2009 through 2021. As compared to the previous oil and gas 

study prepared by TCEQ in 2007 (for a 2005 base year), the emission estimates presented in this 

study reflect a significant decrease in the statewide NOx emission estimate for 2005 (42,854 tons 

per year in this study compared to 119,647 tons per year in the 2007 study). While not as 

pronounced, there were also significant decreases in the SO2 and CO emission estimates based 

on this study. For VOC, PM10, and PM2.5, the estimates contained in this study show slightly 

higher estimates than in the previous study. 

Further improvements to this inventory could be made through the addition of emission 

estimates for fracturing operations, as well as additional refinement of the activity data used for 

projected years 2009 through 2021. 

7-1 
8.0 References 

ARB, 2001. Speciation Profile Database. Internet address: 

http://www.arb.ca.gov/ei/speciate/interopt01.htm 

Bar-Ilan, Amnon; Friesen, Ron; Pollack, Alison; and Hoats, Abigail, 2007. WRAP Area Source 

Emissions Inventory Projections and Control Strategy Evaluation Phase II. Prepared for the 

Western Governor’s Association. September, 2007. 

Bar-Ilan, Amnon; Grant, John; Parikh, Rajashi; Pollack, Alison; Henderer, Doug; Pring, Daniel; 

and Sgamma, Kathleen, 2008. Development of Baseline 2006 Emissions from Oil and Gas 

Activity in the Denver-Julesburg Basin. Prepared for Colorado Department of Public Health and 

Environment Air Pollution Control Division. April, 2008. 

Bar-Ilan, Amnon; Parikh, Rajashi; Grant, John; Shah, Tejas; and Pollack, Alison, 2008a. 

Recommendations for Improvements to the CENRAP States’ Oil and Gas Emissions Inventories. 

Prepared for Central States Regional air Partnership. November, 2008 

Bar-Ilan, Amnon; Grant, John; Friesen, Ron and Pollack, Alison, 2009. Development of Baseline 

2006 Emissions from Oil and Gas Activity in the Piceance Basin. Prepared for the Western 

Governor’s Association and the Independent Petroleum Association of Mountain States. January, 

2009. 

Bommer, P, 2008. A Primer of Oilwell Drilling, A Basic Text of Oil and Gas Drilling, Seventh 

Edition. The University of Texas at Austin, Petroleum Extension Service. 2008. 

Energy Information Administration (EIA), 2009. Supplemental Tables to the Annual Energy 

Outlook 2009, Updated Reference Case with ARRA, Data Tables 113 and 114. Data released 

April 2009. Washington, D.C. Internet address: 

http://www.eia.doe.gov/oiaf/aeo/supplement/stimulus/regionalarra.html

Pollack, Alison; Russell, James; Grant, John; Friesen, Ron; Fields, Paula; and Wolf, Marty, 

2006. Ozone Precursors Emission Inventory for San Juan and Rio Arriba Counties, New Mexico. 

Prepared for New Mexico Environment Department. August, 2006. 

Russell, James and Pollack, Alison, 2005. Oil and Gas Emissions Inventories for the Western 

States. Prepared for Western Governor’s Association. December, 2005. 

Texas Commission on Environmental Quality (TCEQ), 2007. Emissions from Oil and Gas 

Production Facilities, 2007. Prepared by Eastern Research Group, Inc. August 31, 2007. 

Texas Commission on Environmental Quality (TCEQ), 2009. New Oil and Gas SCCs. Data 

provided by Greg Lauderdale, TCEQ. June 2, 2009. Email communication from Greg 

Lauderdale, TCEQ to Mike Pring, Eastern Research Group, Inc. 

8-1 
8-2 

Texas Commission on Environmental Quality (TCEQ), 2009a. NIF 3.0 Formatting for 

TEXAER. Data provided by Greg Lauderdale, TCEQ. June 24, 2009. Email communication 

from Greg Lauderdale, TCEQ to Mike Pring, Eastern Research Group, Inc. 

Texas Railroad Commission (TRC), 2009a. Summary of Drilling, Completion and Plugging 

Reports Processed for 2002. Accessed June 5, 2009. Internet address: 

http://www.rrc.state.tx.us/data/drilling/drillingsummary/2002/ogdc02an.pdf

Texas Railroad Commission (TRC), 2009b. Summary of Drilling, Completion and Plugging 

Reports Processed for 2005. Accessed June 5, 2009. Internet address: 

http://www.rrc.state.tx.us/data/drilling/drillingsummary/2005/ogdc05an.pdf

Texas Railroad Commission (TRC), 2009c. Summary of Drilling, Completion and Plugging 

Reports Processed for 2008. Accessed June 5, 2009. Internet address: 

http://www.rrc.state.tx.us/data/drilling/drillingsummary/2008/annual2008.pdf

U.S. EPA, 2005. User’s Guide for the Final NONROAD2005 Model. EPA-420-R-05-013. U.S. 

Environmental Protection Agency, Office of Air and Radiation. December. 

U.S. EPA, 2005a. Conversion Factors for Hydrocarbon Emission Components. EPA-420-R-05-

015. U.S. Environmental Protection Agency, Office of Air and Radiation. December. 
Appendix A – Approved Data Collection Plan 
5608 Parkcrest Drive, Suite 100 

Austin, TX 78731 

MEMORANDUM 

TO: Greg Lauderdale (TCEQ) 

FROM: Rick Baker, Mike Pring (ERG) 

DATE: April 3, 2009 

SUBJECT: Work Order # 582-7-83985-FY09-01, Deliverable 2b- Final Data Collection Plan

This document serves as the final deliverable for Task 2 of the Work Order, and includes the 

results of ERG’s review of existing activity and emissions data, and presents a Data Collection 

Plan which identifies the proposed approach for collecting the information needed to develop a 

comprehensive emissions inventory for land-based drilling rig engines in the state of Texas in 

2008. In addition, as described in the Work Plan, we have included our recommendations on how 

to proceed with the Texas oil and gas drilling activity emissions estimation project. 

The methodology used to develop the 2008 emissions inventory will be based on the 2005 

emissions inventory ERG completed for TCEQ in 2007, but will expand on that effort by 

improving the analysis and data collection of both activity data and emissions data. ERG will 

conduct the data collection survey as per the proposed Data Collection Plan and as approved by 

TCEQ. 

1.0 Review of Existing Studies, Data, and Industry Websites

Under Task 2, ERG has conducted a literature review and evaluated existing information and 

studies pertinent to the development of a comprehensive oil and gas drilling activity emissions 

inventory for the state of Texas for the year 2008. The results of this research is discussed below 

in two parts, the first being a review of existing studies that address estimating emissions from 

oil and gas drill rig operations, and the second being the results of our review of existing Texas 

data available from government and industry websites and publications. 

A-1 
1.1 Review of Existing Studies

As mentioned above, the goal of this project is to improve upon the 2005 emissions inventory 

ERG completed for TCEQ in 2007 for drill rig engines by obtaining more highly resolved 

activity data, as well as more accurate emissions information. Over the last several years, 

numerous studies have been conducted in the western states to develop area source emission 

estimates for oil and gas sources, with subsequent studies improving upon the data collection 

methodology and emission estimation approaches in prior studies. The relevant studies ERG has 

identified are provided in Table 1. 

Table 1. Existing Drill Rig Engine Studies 

Report Geographic Coverage Publication Date 

Oil and Gas Emission Inventories for the Western 

States (WRAP Phase I) 

WRAP States December, 2005 

Ozone Precursors Emission Inventory for San Juan 

and Rio Arriba Counties, New Mexico 

San Juan and Rio 

Arriba Counties, New 

Mexico 

August, 2006 

Emissions from Oil and Gas Production Facilities Texas August, 2007 

WRAP Area Source Emissions Inventory 

Projections and Control Strategy Evaluation Phase 

II 

WRAP States September, 2007 

Development of Baseline 2006 Emissions from Oil 

and Gas Activity in the Denver-Julesburg Basin 

Denver-Julesburg 

Basin, Colorado 

April, 2008 

Recommendations for Improvements to the 

CENRAP States’ Oil and Gas Emissions 

Inventories 

CENRAP States November, 2008 

Development of Baseline 2006 Emissions from Oil 

and Gas Activity in the Piceance Basin 

Piceance Basin, 

Colorado 

January, 2009 

A-2 
As a result of a review of the existing literature, ERG has been able to develop a firm 

understanding of the types of equipment currently used by industry for different drilling 

activities, as well as basic approaches to surveying and compiling emissions estimates. Based on 

this review, ERG anticipates organizing our survey based on rig type (drilling rigs vs. 

completion/workover rigs), rig engine application (draw works engines, mud pump engines, and 

engines for general rig power), whether the rig is mechanical or electrical, well depth, and 

wellbore type (vertical, horizontal). Engine size (hp) will also be critical in our analysis, but the 

parameters listed above will dictate the various engine sizes we anticipate seeing. For example, 

many workover and completion rigs may be powered by a single engine at less than 600 hp, 

while rigs used on deep (over 15,000 feet) horizontal wells may require four or five engines, 

ranging in size from 500 to 1,000 hp each. 

In addition to process information, example surveys and survey questions were included in 

several studies, and ERG anticipates formulating the survey used for this project utilizing 

examples provided in these reports. 

It should be noted that these existing studies were comprehensive in nature, inclusive of all 

emission sources found at oil and gas exploration and production locations. While well drilling 

was included as an emission source, this source category was not a major focus of these efforts. 

As such, many of the surveys used in these studies were sent to the oil and gas producers 

themselves, and not directly to the owners and operators of the drill rigs, who are typically 

contracted by the producers to drill the well. Once a given well is completed, the drilling 

contractor will move on to the next well. Therefore, ERG anticipates focusing our survey efforts 

on the drilling contractors themselves, with less emphasis on the production companies as has 

been done previously. 

A-3 
Of the reports listed in Table 1, the CENRAP report appears to be the most relevant for this 

study as Texas is one of the CENRAP states covered under the report, and the report also 

provides “default” activity data and emission factors for the five major oil and gas basins in 

Texas (Andarko, East Texas, Fort Worth, Permian, and Western Gulf). While ERG anticipates 

developing specific activity data and emissions data from our survey efforts as part of this 

project, the CENRAP report may be useful for gap-filling and/or validation depending upon the 

results of our survey activities. 

1.2 Review of Existing Activity Data 

The primary source of activity data to be used to compile the 2008 drill rig emissions inventory 

will come from the Texas Railroad Commission (RRC). ERG has contacted the RRC and 

obtained a copy of the “Drilling Permit Master and Trailer” database, which contains information 

on every application to drill for an oil or gas well in Texas since 1976, including American 

Petroleum Institute (API) number, date approved, location (county), wellbore profile, well depth, 

spud-in date, and well completion date. ERG is currently in the process of translating this 

database into Access for ease of use in estimating emissions. This data will allow us to allocate 

emissions spatially (aggregated at the county level), as well as temporally (based on spud-in date 

and well completion date for each individual well). Use of this database will result in a more 

highly refined dataset than was used in development of the 2005 emissions inventory, which was 

based on total depth drilled by county by wellbore type, with drilling times estimated from the 

“worst case” well for each county/wellbore-type combination. 

In addition, by obtaining the complete dataset, ERG will be able to analyze activity data for 

multiple years. As described in the work plan, ERG has concerns regarding the 

representativeness of activity data for 2008 given the extreme volatility in the market that year. 

Once the data has been properly compiled, ERG will consult with TCEQ and make a final 

recommendation as to the base year for this inventory effort. Regardless of which base year is 

chosen, the RRC data will be used to backcast the base year inventory to develop the 2002 and 

2005 prior year inventories based on drilling permit records for those years. ERG anticipates 

developing 2009 through 2021 projected inventories using the base year inventory and 

forecasting future activity based on US DOE Energy Information Administration projections of 

A-4 
oil and gas production for the Southwest and Gulf Coast regions from the Annual Energy 

Outlook 2009.

1.3 Review of Industry Websites 

Using information available on the International Association of Drilling Contractors (IADC) 

website, we were able to identify many of the larger drilling contractors in Texas (while there 

may be non-IADC members with significant drilling activities in Texas, we did not identify any 

during our review). A review of the websites for these larger contractors provided useful 

information regarding the drilling rig fleets in use in Texas, and we were able to easily assimilate 

a dataset with specific equipment information on over 225 drill rigs. A few examples of this type 

of information can be found at the following drill rig operator websites: 

a) http://www.gwdrilling.com/services/riglist.htm

b) http://www.pioneerdrlg.com/HTML/RigFleet.html

c) http://www.rowancompanies.com/fw/main/Land-Rig-Fleet-61.html

This effort was not exhaustive, and if additional information is needed to gap-fill or supplement 

our survey findings, there is additional information that can be obtained online. For example, 

Appendix A contains an example “spec sheet” for a specific rig used by Pioneer Drilling, 

including specific makes and models of both the draw works engines and mud pump engines. 

ERG will compile this information to the extent possible prior to conducting the survey in order 

to familiarize ourselves with the engine makes and models we are likely to encounter through the 

survey. 

2.0 Data Collection Plan

By obtaining and translating the RRC “Drilling Permit Master and Trailer” database, we will 

have highly resolved data on all drilling activity that occurred in Texas during the base year. In 

addition to wells that were started and finished during the base year, we will also have data on 

drilling activities that commenced during the year preceding the base year (but finalized during 

the base year), as well as data on wells that were started during the base year but were not 

A-5 
completed until the following year. Therefore, we feel we have obtained the best activity data 

available to use as the basis for the base year inventory. 

As we will have obtained the activity data needed to estimate emissions from the RRC database, 

the primary focus of our data collection and survey activities will be on obtaining real data from 

rig operators who were actively drilling in Texas in 2008. The goal of this survey will be to 

develop a series of “model rig profiles” for different rig types, well depths, and geographic 

locations (basin-specific profiles are preferred). 

Our proposed survey methodology for obtaining this information is provided below. 

2.1 Participant Recruitment 

In order to encourage survey response, stakeholder support for the study will be sought. At the 

current time, ERG has consulted with contacts at the University of Texas, Southern Methodist 

University, the Texas Railroad Commission, and the IADC in an effort to obtain an 

understanding of well drilling practices, and to assist us in encouraging stakeholder participation. 

The IADC provided helpful information on industry practices, but their organization does not 

endorse or participate in any survey activities, so further contribution from them may be limited 

to feedback on our draft survey materials and/or survey approach. 

In addition to those sources we have already contacted, ERG anticipates encouraging additional 

stakeholder participation by contacting the following trade associations and local organizations: 

a) Texas Oil and Gas Association (TxOGA) 

b) Texas Independent Producers and Royalty Owners Association (TIPRO) 

c) Independent Petroleum Association of America (IPAA) 

d) Petroleum Equipment Suppliers Association (PESA) 

e) The Barnett Shale Energy Education Council (BSEEC) 

If possible, ERG will attempt to provide information regarding the study and survey to trade 

associations before administering the survey to promote cooperation with the study and to 

A-6 
identify potential survey participants. We will prepare a draft survey for peer review by members 

of the Petroleum Engineering Department at the University of Texas to obtain feedback prior to 

implementation. ERG will also request trade associations and stakeholders help distribute a letter 

of introduction about the project on TCEQ letterhead to the owners and operators of drill rigs. 

2.2 Mail and Phone Surveys 

At this point we do not have a specific list of target respondents, but in general, will seek to find 

willing participants through our planned communication with the trade groups as described 

above, as well as searches through business listings and directories obtained from such sources 

as USA Data. Once we have identified a comprehensive listing of likely drilling rig operators, 

ERG will obtain the services of a survey contractor to execute this portion of the Data Collection 

Plan. ERG will train the survey contractor staff in conducting phone surveys of drill rig 

operators, providing background in the purpose of the study and familiarizing staff with industry 

terminology they may encounter. Once trained, the survey contractor will initiate the survey, first 

by phone calls to targeted respondents, then potentially by follow-up with phone, mail or fax 

surveys (as needed). Respondents will be asked to specify their preferred survey response mode, 

although phone surveys will be encouraged in order to reduce incomplete responses and errors. 

Upon completion of the first week of phone surveys (and at regular intervals thereafter), ERG 

will review and audit the results of the phone surveys to confirm that we are contacting 

participants willing to provide us the needed information over the phone (or willing to continue 

with the mail survey), and determine if adjustments need to be made to the survey or survey 

method in order to ensure sufficient response for proper stratification of our model rig profiles. 

The survey itself will focus on collecting the following information for representative, or average 

(based on a particular basin or drilling depth), drilling operations: 

a) The number of engines on a rig 

b) Engine make, model, model year, and size (hp) 

c) Average load for each engine 

d) Engine function (draw works, mud pumps, power) 

A-7 
e) Actual engine hour data for well completion (total hours) 

f) Actual engine fuel use data for well completion (total fuel use) 

g) Engine fuel type (and sulfur content for diesel fuel) 

h) Engine-specific emission factors (based on manufacturers’ or vendor data) or actual test 

data if available 

i) Well location (county, API #) 

j) Total well drilling time (actual number of drilling days) 

k) Total well completion time (number of days needed for well completion activities) 

l) Well depth 

Depending on how responsive the survey participant are to the phone survey, and what level of 

aggregation they have data available, we may request “average” data for their rigs, or specific 

examples based on actual data for specific wells drilled in the base year. ERG will first attempt 

to obtain all the required information via the phone survey, but it is expected that specific 

information may more readily be obtained by following up with a mail survey. 

Appendix B presents an example cover letter that will be included with the mail survey, and 

Appendix C provides an example of the types of information that will be requested. ERG will 

periodically review the mail survey responses to see if adjustments are needed in order to obtain 

a sufficient response rate by checking that all fields/basins are being covered, ensure all wellbore 

types are included, and check that the survey adequately covers the range of well depths included 

in the RRC drilling permit dataset. 

2.3 Field Observations 

Once ERG has obtained initial responses to our phone and/or mail surveys and with approval 

from the TCEQ project manager, ERG will attempt to obtain permission for site visits to active 

drilling sites through survey participation and stakeholder contacts. ERG’s protocol for 

conducting on-site visits includes a standardized data collection form, such as that presented in 

Appendix D. This form essentially requests the same information as requested during the 

phone/mail survey, but adds additional contact information and site visit date. On-site 

observations of drill rig engine operation and specifications will be used to verify the data 

A-8 
collected in the mail and phone surveys, and to attempt to establish equipment load factors and 

any other adjustment factors deemed necessary. 

Site visits will be coordinated in advance, obtaining the site location, name of contact, and 

date/time for each visit. Site contacts will be called one business day in advance to confirm the 

time and location for the visit, as well as to determine any site-specific safety or operation 

requirements. For example, it is expected that active drilling sites will require steel-toed boots, 

hard hat, and safety glasses before entry. ERG representatives will adhere to all company 

requirements while on site. If necessary, the TCEQ Project Representative shall obtain an official 

letter on TCEQ letterhead explaining the purpose of the study to be presented to site foremen or 

other company representatives as requested. 

Once on site, each engine will be assigned a unique identifier, and data collection will involve an 

inspection of each engine located on site to collect the following information: 

a) Make and model, model year, and size 

b) A description of how each unit is used (obtained from the site foreman) 

c) Typical Fuel usage information (gallons per day over the course of the drilling activity) 

d) Typical operating schedule (hours per day over the course of the drilling activity) 

e) Typical operating load if available 

The on-site data collected will be recorded using the standard reporting form such as that 

provided in Appendix D. 

ERG will attempt to arrange for visits to multiple locations/fleets for field observations, and will 

seek to arrange visits to different types and sizes of rigs, with a preference for a geographical 

distribution reflective of the well drilling data obtained from the RRC (as feasible given the 

project resources). Preference will be given to companies operating multiple drill rigs in order to 

improve data collection efficiency. 

A-9 
2.4 Confidentiality 

Confidentiality will be stressed to participants participating in the study, and will be addressed in 

the survey cover letters and/or phone questionnaire scripts. ERG is particularly sensitive to the 

privacy of individuals and businesses. Therefore all interviews and data collection efforts will 

begin with a guarantee of privacy, anonymity, and confidentiality. To ensure survey respondent’s 

rights to privacy, respondents will be informed of the research purpose, the kinds of questions 

that will be asked, and how TCEQ may use the results of the study. Confidentiality will be 

maintained by eliminating names from interview records, stripping all respondent-identifying 

characteristics from study datasets. In addition, all project staff will be given explicit training 

regarding confidentiality protocols and commitments. 

3.0 Emissions Calculation Methodology

Once the Data Collection survey is complete, ERG will develop emission estimates for model rig 

fleets which we will then apply to the population of wells from the RRC dataset. It is anticipated 

that model rig fleets will be stratified according to: 

a) Well location (basin, as identified by County) 

b) Well depth (based on RRC data) 

c) Well type (vertical, horizontal) 

While these parameters are provided in the RRC dataset, and based on our review of available 

literature and operator interviews appear to be the most critical parameters in terms of 

differentiating wells for emission estimation purposes, we may encounter other variables that 

provide additional distinction between our model rig fleets based on our survey results. For 

example, we anticipate the total hp of each rig profile to vary by well depth, and although rig 

power information is not provided in the RRC data, it will be critical in estimating emissions. 

Once we have compiled the survey data into model rig fleets, an average emissions profile will 

be developed for an average well in that fleet. The emissions profile will be developed for each 

model rig fleet using a combination of emission and deterioration factors obtained through our 

survey, EPA’s NONROAD model, and/or AP-42 emission factors. For HAPs, emission factors 

will be obtained from the SPECIATE database, and/or AP-42. 

A-10 
Each well in the RRC dataset will then be assigned to a specific model fleet, and emissions will 

be calculated for each well base on scaling emissions from the model fleet to each individual 

well based on the ratio of the actual well depth for that well to the model fleet average well 

depth. For calculating daily emission estimates (for purposes of ozone-season daily estimates), 

the total emissions for each wellbore will be evenly divided by the total number of days between 

spud date and completion date, as obtained by the RRC dataset. The end result will be an 

estimate of the actual emissions for each well for each day of the drilling period. 

4.0 Recommendations

ERG recommends that TCEQ proceed with the drill rig engine emission estimation project as 

described above. By obtaining the RRC well permit database in electronic format, the activity 

data we now have available provides us with a much greater level of geographical and spatial 

resolution for emission estimates than was available when ERG compiled the 2005 oil and gas 

emissions inventory. In addition, our literature review has indicated that the “state of the art” 

emissions estimation approaches and methodology have continued to be refined over the last few 

years as regional, state, and local agencies have become increasingly aware of the magnitude of 

emissions from the sources associated with oil and gas exploration and production. Subsequent 

studies of emissions from these sources make use of previous studies, and build upon those with 

further refinement of the activity and emission factor data used in the estimates. ERG anticipates 

being able to continue this evolution for estimating emissions from drill rig engines in Texas. 

The next challenge in this process will be to continue to solicit support from stakeholders, 

namely, the trade associations representing oil and gas drill rig operators, as well as the operators 

themselves. Through data available on the IADC website, we have obtained contact information 

for many of the major drill rig owners and operators in Texas. While we could proceed to contact 

them directly at this point, we feel it will be beneficial to the ultimate success of this project to 

obtain the endorsement and support from the industry as a whole through the trade associations if 

possible. 

A-11 
APPENDIX A 

EXAMPLE OF DRILLING RIG INFORMATION AVAILABLE ONLINE 

A-12 
APPENDIX B 

ADVANCED LETTER TO DRILL RIG OWNERS/OPERATORS --- on TCEQ letter head 

(distributed via fax &/or trade associations) 

Dear Drill Rig Manager OR <Mr./Ms. LAST NAME>: 

The Texas Commission on Environmental Quality (TCEQ) requests your help. We are 

asking for your voluntary participation in a study about engines used in the drilling of new and/or 

recompleted oil and gas wells in Texas during 2008. The study will involve rig owners sharing 

information regarding the operating practices (such as hours of operation) and rig configuration 

(such as the number and size of engines) in their fleet. This information will provide a better 

understanding of how drilling rig operations are conducted under real-world practices. 

TCEQ contracted with Eastern Research Group (ERG), an independent research organization, to 

administer this study. We urge you to participate – the results will improve the accuracy of 

TCEQ’s emissions estimates for drilling rigs across the state. 

Prominent trade associations are supporting this study, encouraging their members to participate, 

including the [TxOGA, IPAA, etc...] These organizations represent the interests of oil and gas 

exploration and production companies at the local, state, and national levels and recognize the 

value of the study to industry as well as to government. 

Your participation is both voluntary and completely confidential. ERG guarantees the 

confidentiality of all participants in this study. This means the information your company 

provides will be used for statistical purposes only. Responses will be kept confidential and will 

not be disclosed in identifiable form to anyone other than ERG employees or agents without your 

consent. Every ERG employee with access to identifying information will sign a confidentiality 

agreement. This agreement guarantees that we will not disclose any information that may 

identify you, such as your address, contact information or worksite locations, unless required by 

law. 

The study involves 3 easy steps. 

1. First, the person most knowledgeable about your business’ drilling rig operations will be 

asked to participate in a short phone survey about the typical rig configurations and 

engine numbers and types used to drill wells in Texas in 2008. In most cases, this survey 

will take ten to fifteen minutes. 

2. Second, after completion of the phone survey, ERG may send you a written survey 

requesting more detailed information about operating practices you employed in drilling 

wells in Texas during 2008. In order to minimize the amount of data we are requesting 

from any one participant, we would request data for a select number of drilling 

operations, most likely requesting information on 2-3 examples for a particular welldepth, oil field or basin, and well type. However, we would be willing to accept as much 

data as made available to us, and can also accept existing data and query it to meet our 

A-13 
needs if you have existing data that would be helpful, but is not currently in a format 

consistent with our survey. 

3. Third, after completion of the surveys, ERG may ask for permission to visit one of your 

active drilling sites. Pending your approval, an ERG representative will travel to an active 

well site and collect information on each engine found on-site. This data includes make, 

model, year, load, and engine clock hour readings and fuel usage. Only a small 

percentage of companies will be asked to participate in on-site field data collection. 

Again, we appreciate your assistance in this important study. If you have any questions, please 

call Greg Lauderdale in the Air Quality Division of TCEQ at 512-239-1433. To contact the 

independent research firm conducting the study, call the survey project manager, Rick Baker at 

512-407-1823, or email him at rick.baker@erg.com. 

Thank you in advance, 

{TCEQ Signature authority} 

A-14 
APPENDIX C 

DRILL RIG SURVEY QUESTIONS 

Part 1. General Site Information 

1. Name of Company: 

2. Well API #: 

3. Contact Name: 

4. Number of engines on site: 

5. Well Type (Vertical, Horizontal): 

6. Well Depth: 

7. Total Well Drilling Duration (days): 

8. Fuel Type (and sulfur content for diesel 

fuel) 

Part 2. Engine-Specific Information (for each engine) 

Engine 

ID 

Engine Use 

(Drawworks, 

Mud Pump, 

Power) 

Make/

Model 

Model 

Year 

Engine 

HP 

Average 

Fuel Use 

(gallons) 

Average 

Operating 

Schedule 

(hours) 

Average 

Engine 

Load (%)

A-15 
A-16 

APPENDIX D 

FIELD DATA COLLECTION FORM 

Part 1. General Site Information 

1. Name of Company: 

2. Company ID: 

3. Well API #: 

4. Site Personnel Contact Name: 

5. Site Personnel Title: 

6. Site Personnel Phone #: 

7. Number of engines on site: 

8. Well Type (Vertical, Horizontal) 

9. Well Depth: 

10. Total Well Drilling Duration (days): 

11. Fuel Type (and sulfur content for diesel 

fuel) 

12. Date of site visit: 

Part 2. Engine-Specific Information (for each engine) 

Engine 

ID 

Engine Use 

(Draw works, 

Mud Pump, 

Power) 

Make/

Model 

Model 

Year Engine HP 

Average 

Fuel Use 

(gallons) 

Average 

Operating 

Schedule 

(hours) 

Average 

Engine 

Load 

(%) 
Appendix B – Survey Letter 
Dear Owner/Operator: 

Eastern Research Group (ERG), an independent research organization, is conducting a study on 

drilling rig engine emissions for the State of Texas for calendar year 2008. ERG is conducting 

this study with the support of the Texas Independent Producers and Royalty Owners Association 

(TIPRO) and the Texas Oil & Gas Association (TXOGA). These organizations represent the 

interests of oil and gas exploration and production companies in Texas and recognize the value 

of the study to industry as well as to government. 

We are asking for your voluntary participation in this study of oil and gas wells that were drilled 

in Texas during 2008. The study will involve sharing information regarding the operating 

practices (such as the hours of operation) and rig configuration (such as the number and size of 

engines) used during well drilling. 

Your participation is voluntary and completely confidential, individual wells do not need to be 

identified. The information your company provides will be used for statistical purposes only in 

order to develop county-level estimates and will not be republished or disseminated for other 

purposes. Responses will not be disclosed in identifiable form to anyone other than ERG 

employees or agents. 

The attached Excel workbook contains our study questions. We are seeking basin specific rig 

profiles to complete a typical well in the Andarko, Bend Arch-Fort Worth, East Texas, Permian, 

and Western Gulf basins. For each basin, we would like one profile for a vertical well, and a 

second profile for a horizontal/directional well. If you operate in multiple basins in Texas, please 

complete one worksheet for each basin and well type that you are familiar with. For your 

convenience, the county/basin assignments are included in the workbook in the “Counties by 

Basin” worksheet. An example of a completed worksheet is also provided. Your expertise is 

valued; please include comments or clarifications! 

Your response is requested by June 5, 2009. Completed forms may be submitted via email to Len 

Boatman at llboatman@gmail.com, or via fax to 512-579-0315. For further information or 

assistance in completing this form, please call Len Boatman at 512-579-0315. 

We appreciate your assistance in this important study. If you have any questions on the study, 

please feel free to contact me at (919) 468-7840, or via email at mike.pring@erg.com. 

Sincerely, 

Mike Pring 

Senior Environmental Engineer 

Eastern Research Group, Inc. 

B-1 
Appendix C – Drill Rig Survey Form 
DRILL RIG SURVEY QUESTIONS 

Part 1. General Site Information 

Owner/Operator: 

Owner/Operator Contact Name: 

Owner/Operator Contact Phone: 

Please use county or basin averages for each question. 

1. Well Locations (county or basin) 

2. Well Type (vertical, horizontal, directional) 

3. Typical Well Measurement Depth (feet) 

4. Typical Well Drilling Duration (days) 

5. Typical Number of engines on site 

6. Typical Rig Fuel Use (gal/day) 

7. Typical Workover/Completion (hours) 

8. Typical Workover/Completion Engine Size (HP) 

9. Fracing; Yes/No; Duration (days) 

 

Part 2. Drill Rig Engine-Specific Information (for each engine on a typical rig). 

Engine Function 

(Draw works, Mud 

Pump, Power) 

Typical 

Make and 

Model 

Typical 

Model 

Year 

Typical 

Engine 

Size (HP) 

Typical Engine 

On-time 

(hr/day) 

Typical Engine 

time under load 

(hr/day) 

Typical Engine 

Load (%) 

C-1 
Appendix D – Survey Data 
Table D.1 Survey Data – Horizontal and Directional Wells 

Survey 

ID 

# of 

wells 

covered 

by 

survey Well Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D200a 5 Directional 10,150 1

(All) Electric Rig Cat 3512 2006 1192.5 40 

D200a 5 Directional 10,150 2

(All) Electric Rig Cat 3512 2006 1192.5 40 

D200a 5 Directional 10,150 3

(All) Electric Rig Cat 3512 2006 1192.5 40 

D180 5 Horizontal 8,000 1 Drawworks Cat 3406 1985 400 22.5 D180 5 Horizontal 8,000 2 Drawworks Cat 3406 1985 400 22.5 D180 5 Horizontal 8,000 3 Mud Pump Cat 399 1985 1260 22.5 D180 5 Horizontal 8,000 4 Mud Pump Cat 399 1985 1260 22.5 D180 5 Horizontal 8,000 5 Generator Cat 3406 400 22.5 D180 5 Horizontal 8,000 6 Generator Cat 3406 400 22.5 D81 33 Horizontal 9,500 1 Drawworks 

Cat 3412B 1985 475 13.5 

D81 33 Horizontal 9,500 2 Drawworks 

Cat 3412B 1985 475 13.5 

D81 33 Horizontal 9,500 3 Mud Pump 

Cat 3508B 2005 950 13.5 

D81 33 Horizontal 9,500 4 Mud Pump 

Cat 3508B 2005 950 13.5 

D81 33 Horizontal 9,500 5 Generator Cat 3306 1985 270 13.5 

D-1 
Table D.1 Survey Data – Horizontal and Directional Wells (Cont.) 

Survey 

ID 

# of 

wells 

covered 

by 

survey Well Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D81 33 Horizontal 9,500 6 Generator Cat 3306 1985 270 13.5 D50a 34 Horizontal 10,109 1

(All) Electric Rig Cat 3508 2006 950 16 

D50a 34 Horizontal 10,109 2

(All) Electric Rig Cat 3508 2006 950 16 

D119 20 Horizontal 11,500 1

(All) Electric Rig Cat 3512 2006 1192.5 19 

D119 20 Horizontal 11,500 2

(All) Electric Rig Cat 3512 2006 1192.5 19 

D97 9 Horizontal 13,000 1 Drawworks Cat 379 1984 550 45 1D97 9 Horizontal 13,000 2 Drawworks Cat 379 1984 550 45 1D97 9 Horizontal 13,000 3 Mud Pump Cat 3508 1995 900 45 1D97 9 Horizontal 13,000 4 Mud Pump Cat 399 1989 1250 45 D97 9 Horizontal 13,000 5 Generator 

Detroit Series 60 2002 400 45 

D97 9 Horizontal 13,000 6 Generator 

Detroit Series 60 2002 400 45 

D50c 3 Horizontal 14,900 1

(All) Electric Rig 

Cat 3512C 2006 1478 67 1

D50c 3 Horizontal 14,900 2

(All) Electric Rig 

Cat 3512C 2006 1478 67 1

D50f 11 Horizontal 17,668 1

(All) Electric Rig 

Cat 3512C 2006 1478 72 1

D-2 
Table D.1 Survey Data – Horizontal and Directional Wells (Cont.) 

Survey 

ID 

# of 

wells 

covered 

by 

survey Well Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D50f 11 Horizontal 17,668 2

(All) Electric Rig 

Cat 3512C 2006 1478 72 1

D1a 14 

Horizontal/Directional 10,000 1 Drawworks 

Detroit Series 60 2008 470 21 

D1a 14 

Horizontal/Directional 10,000 2

Mud Pump # 1 

Detroit 16V2000 2008 1,205 21 

D1a 14 

Horizontal/Directional 10,000 3

Mud Pump # 2 

Detroit 16V2000 2008 1,205 21 

D1a 14 

Horizontal/Directional 10,000 4

Drawworks/ Swivel Motor 

Detroit Series 60 2008 470 21 

D1a 14 

Horizontal/Directional 10,000 5 Generator # 1 

Detroit Series 60 2008 470 21 

D1a 14 

Horizontal/Directional 10,000 6 Generator # 2 

Detroit Series 60 2008 470 21 

D1b 18 

Horizontal/Directional 10,000 1 Drawworks 

Detroit Series 60 2008 470 21 

D1b 18 

Horizontal/Directional 10,000 2

Mud Pump # 1 

Detroit 16V2000 2008 1,205 21 

D1b 18 

Horizontal/Directional 10,000 3

Mud Pump # 2 

Detroit 16V2000 2008 1,205 21 

D1b 18 

Horizontal/Directional 10,000 4

Drawworks/ Swivel Motor 

Detroit Series 60 2008 470 21 

D1b 18 

Horizontal/Directional 10,000 5 Generator # 1 

Detroit Series 60 2008 470 21 

D1b 18 

Horizontal/Directional 10,000 6 Generator # 2 

Detroit Series 60 2008 470 21 

D162a 7 

Horizontal/Directional 11,335 1 Drawworks Cat C-18 2005 600 34 

D-3 
Table D.1 Survey Data – Horizontal and Directional Wells (Cont.) 

Survey 

ID 

# of 

wells 

covered 

by 

survey Well Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D162a 7 

Horizontal/Directional 11,335 2 Drawworks Cat C-18 2005 600 34 

D162a 7 

Horizontal/Directional 11,335 3 Mud Pump Cat 3508 2005 1300 34 

D162a 7 

Horizontal/Directional 11,335 4 Mud Pump Cat 3508 2005 1300 34 

D162a 7 

Horizontal/Directional 11,335 5 Generator Cat C-15 2005 485 34 

D162a 7 

Horizontal/Directional 11,335 6 Generator Cat C-15 2005 485 34 

S51 10 Horizontal 8,692 1 Drawworks 

Cat D353 1975 450 17.5 

S51 10 Horizontal 8,692 2 Drawworks 

Cat D353 1975 450 17.5 

S51 10 Horizontal 8,692 3 Mud Pump 

Cat D 398 1984 825 17.5 

S51 10 Horizontal 8,692 4 Mud Pump 

Cat D 398 1984 825 17.5 

S51 10 Horizontal 8,692 5 Generator 

Cat D 3412 1998 450 17.5 

S51 10 Horizontal 8,692 6 Generator 

Cat D 3412 1998 450 17.5 

D11 119 Horizontal 10,570 1

(All) Electric Rig Cat 3512 2006 1476 19 

D11 119 Horizontal 10,570 2

(All) Electric Rig Cat 3512 2006 1476 19 

D-4 
Table D.2 Survey Data – Vertical Wells <= 7,000 feet 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D80 37 Vertical 1,000 1 Drawworks Cummins 1990 450 3 D80 37 Vertical 1,000 2 Mud Pump Cat 343 1985 400 3 D150 10 Vertical 1,850 1

Drawworks and Mud Pump 

Cummins KT450 1980 500 2.5 

D150 10 Vertical 1,850 2 Generator Deutz 1980 50 2.5 D74 48 Vertical 2,200 1

Draw 

Cat 3406 1990 470 2 

D74 48 Vertical 2,200 2

Mud pump 

Cat 3408 1990 470 2 

D74 48 Vertical 2,200 3

Generator 

25 2 

D51 72 Vertical 2,500 1

Draw 

Cat 3406 1992 425 2 

D51 72 Vertical 2,500 2

Mud pump 

Cat 3406 1992 425 2 

D51 72 Vertical 2,500 3

Generator John 

Deere 2000 80 2 

D172 6 Vertical 3,300 1 Drawworks 

Cummins 400 1985 400 6.5 

D172 6 Vertical 3,300 2 Mud Pump 

Cummins 400 1985 400 6.5 

D172 6 Vertical 3,300 3 Generator 

Perkins 4 Cylinder 1995 48 6.5 

D72 41 Vertical 3,700 1

Draw 

Detroit 60 2006 470 10 

D-5 
Table D.2 Survey Data – Vertical Wells <= 7,000 feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D72 41 Vertical 3,700 2

Mud Pump Cummins 

350 2002 350 10 

D72 41 Vertical 3,700 3

Mud pump Cummins 

350 2002 350 10 

D72 41 Vertical 3,700 4

Generator 

Cat 3404 2006 280 10 

D113 23 Vertical 4,200 1 Drawworks Cat 3408 1982 489 6 D113 23 Vertical 4,200 2 Mud Pump JD 600 2008 600 6 D113 23 Vertical 4,200 3 Generator Cat 3304 1985 97 6 S23 13 Vertical 4,500 1 Mud Pump 1 Cat 353 350 11 S23 13 Vertical 4,500 2 Drawworks 

Detroit Series 60 400 11 

S23 13 Vertical 4,500 3 Mud Pump 2 

Detroit Series 60 330 11 

S23 13 Vertical 4,500 4 Generator 

John Deere 80 11 

S3 16 Vertical 4,900 1 Generator Cat 3406 2002 475 11 S3 16 Vertical 4,900 2 Drawworks Cat 3406 2002 475 11 S3 16 Vertical 4,900 3 Mud Pump 

Detroit Series 60 2000 500 11 

S3 16 Vertical 4,900 4 Mud Pump 

Detroit Series 60 2000 500 11 

D-6 
Table D.2 Survey Data – Vertical Wells <= 7,000 feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D141 14 Vertical 5,000 1 Drawworks Cat 3406 1988 425 10 D141 14 Vertical 5,000 2 Mud Pump Cat 3503 1988 375 10 D141 14 Vertical 5,000 3 Mud Pump Cat 3406 1992 425 10 D141 14 Vertical 5,000 4 Generator 

Detroit Diesel 1990 250 10 

D1 519 Vertical 5,000 1 Drawworks Cat C-15 2007 425 5 D1 519 Vertical 5,000 2

Mud Pump # 1 Cat C-15 2007 425 5 

D1 519 Vertical 5,000 3

Mud Pump # 2 Cat C-15 2007 425 5 

D1 519 Vertical 5,000 4

Drawworks/ Swivel Motor Cat C-15 2007 425 5 

D1 519 Vertical 5,000 5 Generator 

Detroit Series 60 2007 470 5 

D118 25 Vertical 5,000 1 Drawworks Cat 3408 2005 550 12 D118 25 Vertical 5,000 2 Mud Pump 

Detroit Series 60 2007 550 12 

D118 25 Vertical 5,000 3 Generator 

Detroit Series 60 2007 350 12 

D139 14 Vertical 5,200 1 Drawworks Cat 3406B 1993 400 8 D139 14 Vertical 5,200 2 Drawworks Cat 3406B 1993 400 8 

D-7 
Table D.2 Survey Data – Vertical Wells <= 7,000 feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D139 14 Vertical 5,200 3 Mud Pump Cat 353E 1985 435 8 D139 14 Vertical 5,200 4 Mud Pump Cat 353E 1985 435 8 D139 14 Vertical 5,200 5 Generator Cat 3306B 1993 400 8 D139 14 Vertical 5,200 6 Generator Cat 3306B 1993 400 8 D163 8 Vertical 6,000 1 Drawworks Cat V71 1965 700 10 D163 8 Vertical 6,000 2 Drawworks Cat V71 1965 700 10 D163 8 Vertical 6,000 3 Mud Pump Cat V379 1975 600 10 D163 8 Vertical 6,000 4 Mud Pump Cat V379 1975 600 10 D163 8 Vertical 6,000 5 Generator Cat 3306 1975 175 10 D152 4 Vertical 6,500 1

(All) Electric Rig 

Detroit Series 60 2008 425 14 

D152 4 Vertical 6,500 2

(All) Electric Rig 

Detroit Series 60 2008 425 14 

D70 50 Vertical 3,000 1 Drawworks 

Detroit 8V-92 1989 475 8.5 

D70 50 Vertical 3,000 2 Mud Pump Cat 3406 1989 425 8.5 D70 50 Vertical 3,000 3 Generator 

John Deer 4 cylinder 1989 50 8.5 

D-8 
Table D.3 Survey Data – Vertical Wells > 7,000 Feet 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D142 19 Vertical 7,500 1 Drawworks Cat 3406 2005 400 20 D142 19 Vertical 7,500 2 Drawworks Cat 3406 2005 400 20 D142 19 Vertical 7,500 3 Mud Pump Cat 3412 2006 650 20 D142 19 Vertical 7,500 4 Mud Pump Cat C-18 2006 600 20 D142 19 Vertical 7,500 5 Generator Cat 3406 2000 400 20 D142 19 Vertical 7,500 6 Generator Cat 3406 2000 400 20 D35 114 Vertical 8,300 1 Drawworks Cat 353 1970 450 12 D35 114 Vertical 8,300 2 Drawworks Cat 353 1970 450 12 D35 114 Vertical 8,300 3 Mud Pump Cat 398 1997 800 12 D35 114 Vertical 8,300 4 Generator Cat 3408 2000 350 12 D35 114 Vertical 8,300 5 Generator Cat 3408 2000 350 12 D200 9 Vertical 9,550 1

(All) Electric Rig Cat 3512 2006 1192.5 30.5 

D200 9 Vertical 9,550 2

(All) Electric Rig Cat 3512 2006 1192.5 30.5 

D-9 
Table D.3 Survey Data – Vertical Wells > 7,000 Feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D200 9 Vertical 9,550 3

(All) Electric Rig Cat 3512 2006 1192.5 30.5 

D83 36 Vertical 9,750 1 Drawworks Cat C-15 2004 475 15.5 D83 36 Vertical 9,750 2 Drawworks Cat C-15 2004 475 15.5 D83 36 Vertical 9,750 3 Mud Pump Cat 398 1975 970 15.5 D83 36 Vertical 9,750 4 Mud Pump Cat 398 1975 970 15.5 D83 36 Vertical 9,750 5 Generator Cat 3406 1995 435 15.5 D83 36 Vertical 9,750 6 Generator Cat 3406 1995 435 15.5 S12 12 Vertical 10,000 1

(All) Electric Rig Cat 3512 1192.5 17 

S12 12 Vertical 10,000 2

(All) Electric Rig Cat 3512 1192.5 17 

D206 2 Vertical 10,000 1 Drawworks 

Cat 3408 DITA 475 17.5 

D206 2 Vertical 10,000 2 Drawworks 

Cat 3408 DITA 475 17.5 

D206 2 Vertical 10,000 3 Mud Pump 

Cat D399PC 1200 17.5 

D206 2 Vertical 10,000 4 Mud Pump 

Cat D399PC 1200 17.5 

D-10 
Table D.3 Survey Data – Vertical Wells > 7,000 Feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D206 2 Vertical 10,000 5 Generator Cat 3406 425 17.5 D206 2 Vertical 10,000 6 Generator Cat 3406 425 17.5 D191 3 Vertical 10,000 1 Drawworks Cat C-13 2006 410 15 D191 3 Vertical 10,000 2 Drawworks Cat C-13 2006 410 15 D191 3 Vertical 10,000 3 Mud Pump Cat C-15 2006 500 15 D191 3 Vertical 10,000 4 Mud Pump Cat C-15 2006 500 15 D191 3 Vertical 10,000 5 Generator Cat C-15 2006 500 15 D191 3 Vertical 10,000 6 Generator Cat C-15 2006 500 15 D37 101 Vertical 10,300 1 Drawworks Cat 353 1981 450 13.5 D37 101 Vertical 10,300 2 Drawworks Cat 353 1981 450 13.5 D37 101 Vertical 10,300 3 Mud Pump Cat 379 1981 550 13.5 D37 101 Vertical 10,300 4 Mud Pump Cat 379 1981 550 13.5 D37 101 Vertical 10,300 5 Generator Cat 3406 1995 425 13.5 D37 101 Vertical 10,300 6 Generator Cat 3406 1995 425 13.5 

D-11 
Table D.3 Survey Data – Vertical Wells > 7,000 Feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D190 3 Vertical 10,500 1 Drawworks Cat C-15 2005 475 30 D190 3 Vertical 10,500 2 Drawworks Cat C-15 2005 475 30 D190 3 Vertical 10,500 3 Drawworks Cat C-15 2005 475 30 D190 3 Vertical 10,500 4 Mud Pump Cat 399 1200 30 D190 3 Vertical 10,500 5 Mud Pump Cat 399 1200 30 D190 3 Vertical 10,500 6 Generator Cat 3412 1000 30 D190 3 Vertical 10,500 7 Generator Cat 3412 1000 30 D121 12 Vertical 10,800 1 Drawworks Cat C-15 2004 485 32.5 D121 12 Vertical 10,800 2 Drawworks Cat C-15 2004 485 32.5 D121 12 Vertical 10,800 3 Mud Pump 

Cat D399TA 2004 1200 32.5 

D121 12 Vertical 10,800 4 Mud Pump 

Cat D399TA 2004 1200 32.5 

D121 12 Vertical 10,800 5 Generator Cat C-15 2004 485 32.5 D121 12 Vertical 10,800 6 Generator Cat C-15 2004 485 32.5 D162 8 Vertical 11,500 1 Drawworks Cat C-18 2005 600 25 

D-12 
Table D.3 Survey Data – Vertical Wells > 7,000 Feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D162 8 Vertical 11,500 2 Drawworks Cat C-18 2005 600 25 D162 8 Vertical 11,500 3 Mud Pump Cat 3508 2005 1300 25 D162 8 Vertical 11,500 4 Mud Pump Cat 3508 2005 1300 25 D162 8 Vertical 11,500 5 Generator Cat C-15 2005 485 25 D162 8 Vertical 11,500 6 Generator Cat C-15 2005 485 25 D215 1 Vertical 12,200 1 Mud Pump 

Detroit 2000 2008 1205 16 

D215 1 Vertical 12,200 2 Mud Pump 

Detroit 2000 2008 1205 16 

D215 1 Vertical 12,200 3 Drawworks 

Detroit Series 60 2008 470 16 

D215 1 Vertical 12,200 4 Drawworks 

Detroit Series 60 2008 470 16 

D215 1 Vertical 12,200 5 Generator 

Detroit Series 60 2008 470 16 

D215 1 Vertical 12,200 6 Generator 

Detroit Series 60 2008 470 16 

D50b 16 Vertical 12,211 1

(All) Electric Rig 

Cat 3512C 2006 1478 21 

D50b 16 Vertical 12,211 2

(All) Electric Rig 

Cat 3512C 2006 1478 21 

D-13 
D-14 

Table D.3 Survey Data – Vertical Wells > 7,000 Feet (Cont.) 

Survey 

ID 

# of wells 

covered 

by survey 

Well 

Type 

Well 

Depth 

Engine 

ID 

Engine 

Function 

Make 

and 

Model 

Model 

Year 

Engine 

Size 

(HP) 

Total 

Well 

Drilling 

Days 

Tot

Engi

On-ti

(hou

D50d 6 Vertical 12,483 1

(All) Electric Rig 

Cat 3512C 2006 1478 22 

D50d 6 Vertical 12,483 2

(All) Electric Rig 

Cat 3512C 2006 1478 22 

D50g 9 Vertical 17,778 1

(All) Electric Rig 

Cat 3512C 2006 1478 55 1

D50g 9 Vertical 17,778 2

(All) Electric Rig 

Cat 3512C 2006 1478 55 1

D50e 10 Vertical 17,970 1

(All) Electric Rig 

Cat 3512C 2006 1478 84 2

D50e 10 Vertical 17,970 2

(All) Electric Rig 

Cat 3512C 2006 1478 84 2
Appendix E – Total Drilling Depth by County by Model Rig Well Type 

Category

(see file “TCEQ Drilling Rig Engine Report_Appendices.xls”)
Appendix F – Emission Factors 
Table F.1 Emission Factors for Vertical Wells > 7,000 Feet 

Emission Factor (ton/1,000 feet) 

Pollutant 2002 2005 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2

CO 2.07E-01 2.06E-01 1.50E-01 1.49E-01 1.49E-01 1.45E-01 1.45E-01 1.11E-01 1.11E-01 1.11E-01 1.10E-01 9.82E-02 6.4NOx 4.61E-01 4.60E-01 4.15E-01 4.14E-01 4.11E-01 3.88E-01 3.88E-01 3.62E-01 3.62E-01 3.61E-01 3.42E-01 3.38E-01 2.9PM10 4.03E-02 4.02E-02 2.32E-02 2.32E-02 2.27E-02 2.27E-02 2.27E-02 1.31E-02 1.30E-02 1.30E-02 1.27E-02 1.20E-02 8.2PM2.5 3.91E-02 3.90E-02 2.25E-02 2.25E-02 2.20E-02 2.20E-02 2.20E-02 1.27E-02 1.26E-02 1.26E-02 1.24E-02 1.16E-02 8.0SO2 5.92E-02 5.92E-02 6.25E-03 6.25E-03 2.97E-04 2.97E-04 2.97E-04 2.73E-04 2.73E-04 2.73E-04 2.73E-04 2.73E-04 2.7TOG 5.61E-02 5.59E-02 3.85E-02 3.85E-02 3.82E-02 3.74E-02 3.73E-02 3.11E-02 3.11E-02 3.11E-02 3.10E-02 2.82E-02 2.0VOC 5.52E-02 5.50E-02 3.79E-02 3.79E-02 3.76E-02 3.68E-02 3.67E-02 3.07E-02 3.06E-02 3.06E-02 3.05E-02 2.78E-02 2.0Formaldehyde 8.25E-03 8.22E-03 5.67E-03 5.66E-03 5.62E-03 5.50E-03 5.49E-03 4.58E-03 4.58E-03 4.57E-03 4.56E-03 4.15E-03 3.0Methanol 1.68E-05 1.68E-05 1.16E-05 1.15E-05 1.15E-05 1.12E-05 1.12E-05 9.34E-06 9.33E-06 9.32E-06 9.31E-06 8.47E-06 6.2Benzene 1.12E-03 1.12E-03 7.70E-04 7.69E-04 7.63E-04 7.48E-04 7.46E-04 6.23E-04 6.22E-04 6.21E-04 6.20E-04 5.65E-04 4.1Acetaldehyde 4.12E-03 4.11E-03 2.83E-03 2.83E-03 2.81E-03 2.75E-03 2.74E-03 2.29E-03 2.29E-03 2.28E-03 2.28E-03 2.08E-03 1.5Naphthalene 5.05E-05 5.03E-05 3.47E-05 3.46E-05 3.44E-05 3.36E-05 3.36E-05 2.80E-05 2.80E-05 2.80E-05 2.79E-05 2.54E-05 1.8o-xylene 1.91E-04 1.90E-04 1.31E-04 1.31E-04 1.30E-04 1.27E-04 1.27E-04 1.06E-04 1.06E-04 1.06E-04 1.05E-04 9.60E-05 7.1Cumene 1.12E-05 1.12E-05 7.70E-06 7.69E-06 7.63E-06 7.48E-06 7.46E-06 6.23E-06 6.22E-06 6.21E-06 6.20E-06 5.65E-06 4.1Ethylbenzene 1.74E-04 1.73E-04 1.19E-04 1.19E-04 1.18E-04 1.16E-04 1.16E-04 9.66E-05 9.64E-05 9.63E-05 9.62E-05 8.75E-05 6.4Styrene 3.36E-05 3.35E-05 2.31E-05 2.31E-05 2.29E-05 2.24E-05 2.24E-05 1.87E-05 1.87E-05 1.86E-05 1.86E-05 1.69E-05 1.2p-xylene 5.61E-05 5.59E-05 3.85E-05 3.85E-05 3.82E-05 3.74E-05 3.73E-05 3.11E-05 3.11E-05 3.11E-05 3.10E-05 2.82E-05 2.01,3-butadiene 1.07E-04 1.06E-04 7.32E-05 7.31E-05 7.25E-05 7.10E-05 7.09E-05 5.92E-05 5.91E-05 5.90E-05 5.89E-05 5.36E-05 3.9m-xylene 3.42E-04 3.41E-04 2.35E-04 2.35E-04 2.33E-04 2.28E-04 2.28E-04 1.90E-04 1.90E-04 1.89E-04 1.89E-04 1.72E-04 1.2Toluene 8.24E-04 8.21E-04 5.66E-04 5.65E-04 5.61E-04 5.49E-04 5.49E-04 4.58E-04 4.57E-04 4.57E-04 4.56E-04 4.15E-04 3.0n-hexane 8.97E-05 8.94E-05 6.16E-05 6.15E-05 6.11E-05 5.98E-05 5.97E-05 4.98E-05 4.98E-05 4.97E-05 4.96E-05 4.52E-05 3.3Propionaldehyde 5.44E-04 5.42E-04 3.74E-04 3.73E-04 3.70E-04 3.63E-04 3.62E-04 3.02E-04 3.02E-04 3.01E-04 3.01E-04 2.74E-04 2.02,2,4-trimethylpentane 1.68E-04 1.68E-04 1.16E-04 1.15E-04 1.15E-04 1.12E-04 1.12E-04 9.34E-05 9.33E-05 9.32E-05 9.31E-05 8.47E-05 6.2Lead 1.69E-06 1.69E-06 9.74E-07 9.73E-07 9.52E-07 9.55E-07 9.53E-07 5.49E-07 5.47E-07 5.46E-07 5.35E-07 5.04E-07 3.4Manganese 1.61E-06 1.61E-06 9.28E-07 9.26E-07 9.06E-07 9.09E-07 9.07E-07 5.22E-07 5.21E-07 5.20E-07 5.10E-07 4.80E-07 3.3Mercury 1.21E-06 1.21E-06 6.96E-07 6.95E-07 6.80E-07 6.82E-07 6.81E-07 3.92E-07 3.91E-07 3.90E-07 3.82E-07 3.60E-07 2.4Nickel 7.66E-07 7.64E-07 4.41E-07 4.40E-07 4.31E-07 4.32E-07 4.31E-07 2.48E-07 2.48E-07 2.47E-07 2.42E-07 2.28E-07 1.5Antimony 1.45E-06 1.45E-06 8.35E-07 8.34E-07 8.16E-07 8.18E-07 8.17E-07 4.70E-07 4.69E-07 4.68E-07 4.59E-07 4.32E-07 2.9Arsenic 2.02E-07 2.01E-07 1.16E-07 1.16E-07 1.13E-07 1.14E-07 1.13E-07 6.53E-08 6.52E-08 6.50E-08 6.37E-08 6.00E-08 4.1Cadmium 1.61E-06 1.61E-06 9.28E-07 9.26E-07 9.06E-07 9.09E-07 9.07E-07 5.22E-07 5.21E-07 5.20E-07 5.10E-07 4.80E-07 3.3

F-1 
Table F.1 Emission Factors for Vertical Wells > 7,000 Feet (Cont.) 

Emission Factor (ton/1,000 feet) 

Pollutant 2002 2005 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2

Cobalt 4.44E-07 4.42E-07 2.55E-07 2.55E-07 2.49E-07 2.50E-07 2.50E-07 1.44E-07 1.43E-07 1.43E-07 1.40E-07 1.32E-07 9.1Phosphorous 5.12E-06 5.10E-06 2.95E-06 2.94E-06 2.88E-06 2.89E-06 2.88E-06 1.66E-06 1.65E-06 1.65E-06 1.62E-06 1.52E-06 1.0Selenium 4.03E-07 4.02E-07 2.32E-07 2.32E-07 2.27E-07 2.27E-07 2.27E-07 1.31E-07 1.30E-07 1.30E-07 1.27E-07 1.20E-07 8.2Chlorine 1.39E-05 1.38E-05 7.98E-06 7.97E-06 7.80E-06 7.82E-06 7.80E-06 4.49E-06 4.48E-06 4.47E-06 4.38E-06 4.13E-06 2.8

Table F.2 Emission Factors for Vertical Wells > 7,000 Feet 

Emission Factor (ton/1,000 feet) 

Pollutant 2002 2005 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2

CO 6.17E-02 4.13E-02 3.16E-02 3.09E-02 3.01E-02 2.95E-02 2.93E-02 2.86E-02 2.78E-02 2.23E-02 2.21E-02 1.39E-02 4.3NOx 2.21E-01 1.82E-01 1.49E-01 1.47E-01 1.33E-01 1.30E-01 1.12E-01 8.76E-02 8.28E-02 7.46E-02 7.41E-02 6.20E-02 4.0PM10 9.25E-03 6.68E-03 4.46E-03 4.43E-03 4.00E-03 3.94E-03 3.68E-03 3.37E-03 3.32E-03 2.66E-03 2.64E-03 1.67E-03 5.3PM2.5 8.97E-03 6.48E-03 4.33E-03 4.30E-03 3.88E-03 3.83E-03 3.57E-03 3.27E-03 3.22E-03 2.58E-03 2.56E-03 1.62E-03 5.2SO2 3.06E-02 3.06E-02 3.23E-03 3.23E-03 1.53E-04 1.53E-04 1.53E-04 1.53E-04 1.53E-04 1.43E-04 1.43E-04 1.28E-04 1.1TOG 1.43E-02 7.54E-03 6.72E-03 6.63E-03 6.53E-03 6.44E-03 6.39E-03 6.30E-03 6.21E-03 5.85E-03 5.81E-03 5.28E-03 4.6VOC 1.41E-02 7.42E-03 6.62E-03 6.53E-03 6.43E-03 6.34E-03 6.29E-03 6.20E-03 6.12E-03 5.76E-03 5.72E-03 5.20E-03 4.6Formaldehyde 2.11E-03 1.11E-03 9.89E-04 9.75E-04 9.60E-04 9.48E-04 9.39E-04 9.26E-04 9.14E-04 8.60E-04 8.54E-04 7.77E-04 6.8Methanol 4.30E-06 2.26E-06 2.02E-06 1.99E-06 1.96E-06 1.93E-06 1.92E-06 1.89E-06 1.86E-06 1.75E-06 1.74E-06 1.58E-06 1.4Benzene 2.87E-04 1.51E-04 1.34E-04 1.33E-04 1.31E-04 1.29E-04 1.28E-04 1.26E-04 1.24E-04 1.17E-04 1.16E-04 1.06E-04 9.3Acetaldehyde 1.05E-03 5.54E-04 4.94E-04 4.87E-04 4.80E-04 4.74E-04 4.69E-04 4.63E-04 4.57E-04 4.30E-04 4.27E-04 3.88E-04 3.4Naphthalene 1.29E-05 6.78E-06 6.05E-06 5.97E-06 5.88E-06 5.80E-06 5.75E-06 5.67E-06 5.59E-06 5.26E-06 5.23E-06 4.75E-06 4.2o-xylene 4.87E-05 2.56E-05 2.29E-05 2.25E-05 2.22E-05 2.19E-05 2.17E-05 2.14E-05 2.11E-05 1.99E-05 1.97E-05 1.80E-05 1.5Cumene 2.87E-06 1.51E-06 1.34E-06 1.33E-06 1.31E-06 1.29E-06 1.28E-06 1.26E-06 1.24E-06 1.17E-06 1.16E-06 1.06E-06 9.3Ethylbenzene 4.44E-05 2.34E-05 2.08E-05 2.05E-05 2.02E-05 2.00E-05 1.98E-05 1.95E-05 1.93E-05 1.81E-05 1.80E-05 1.64E-05 1.4Styrene 8.60E-06 4.52E-06 4.03E-06 3.98E-06 3.92E-06 3.87E-06 3.83E-06 3.78E-06 3.73E-06 3.51E-06 3.48E-06 3.17E-06 2.8p-xylene 1.43E-05 7.54E-06 6.72E-06 6.63E-06 6.53E-06 6.44E-06 6.39E-06 6.30E-06 6.21E-06 5.85E-06 5.81E-06 5.28E-06 4.61,3-butadiene 2.72E-05 1.43E-05 1.28E-05 1.26E-05 1.24E-05 1.22E-05 1.21E-05 1.20E-05 1.18E-05 1.11E-05 1.10E-05 1.00E-05 8.8m-xylene 8.74E-05 4.60E-05 4.10E-05 4.04E-05 3.98E-05 3.93E-05 3.89E-05 3.84E-05 3.79E-05 3.57E-05 3.54E-05 3.22E-05 2.8Toluene 2.11E-04 1.11E-04 9.89E-05 9.74E-05 9.60E-05 9.47E-05 9.39E-05 9.26E-05 9.13E-05 8.60E-05 8.54E-05 7.76E-05 6.8n-hexane 2.29E-05 1.21E-05 1.08E-05 1.06E-05 1.04E-05 1.03E-05 1.02E-05 1.01E-05 9.94E-06 9.36E-06 9.29E-06 8.45E-06 7.4

F-2 
Table F.2 Emission Factors for Vertical Wells > 7,000 Feet (Cont.) 

Emission Factor (ton/1,000 feet) 

Pollutant 2002 2005 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2

Propionaldehyde 1.39E-04 7.31E-05 6.52E-05 6.43E-05 6.33E-05 6.25E-05 6.19E-05 6.11E-05 6.03E-05 5.67E-05 5.63E-05 5.12E-05 4.52,2,4-trimethylpentane 4.30E-05 2.26E-05 2.02E-05 1.99E-05 1.96E-05 1.93E-05 1.92E-05 1.89E-05 1.86E-05 1.75E-05 1.74E-05 1.58E-05 1.4Lead 3.89E-07 2.81E-07 1.88E-07 1.86E-07 1.68E-07 1.66E-07 1.55E-07 1.42E-07 1.39E-07 1.12E-07 1.11E-07 7.00E-08 2.2Manganese 3.70E-07 2.67E-07 1.79E-07 1.77E-07 1.60E-07 1.58E-07 1.47E-07 1.35E-07 1.33E-07 1.07E-07 1.06E-07 6.66E-08 2.1Mercury 2.78E-07 2.00E-07 1.34E-07 1.33E-07 1.20E-07 1.18E-07 1.10E-07 1.01E-07 9.96E-08 7.99E-08 7.91E-08 5.00E-08 1.6Nickel 1.76E-07 1.27E-07 8.48E-08 8.41E-08 7.60E-08 7.49E-08 6.99E-08 6.41E-08 6.31E-08 5.06E-08 5.01E-08 3.16E-08 1.0Antimony 3.33E-07 2.40E-07 1.61E-07 1.59E-07 1.44E-07 1.42E-07 1.32E-07 1.21E-07 1.20E-07 9.59E-08 9.50E-08 6.00E-08 1.9Arsenic 4.63E-08 3.34E-08 2.23E-08 2.21E-08 2.00E-08 1.97E-08 1.84E-08 1.69E-08 1.66E-08 1.33E-08 1.32E-08 8.33E-09 2.6Cadmium 3.70E-07 2.67E-07 1.79E-07 1.77E-07 1.60E-07 1.58E-07 1.47E-07 1.35E-07 1.33E-07 1.07E-07 1.06E-07 6.66E-08 2.1Cobalt 1.02E-07 7.35E-08 4.91E-08 4.87E-08 4.40E-08 4.34E-08 4.05E-08 3.71E-08 3.65E-08 2.93E-08 2.90E-08 1.83E-08 5.9Phosphorous 1.17E-06 8.48E-07 5.67E-07 5.62E-07 5.08E-07 5.01E-07 4.67E-07 4.28E-07 4.22E-07 3.38E-07 3.35E-07 2.12E-07 6.8Selenium 9.25E-08 6.68E-08 4.46E-08 4.43E-08 4.00E-08 3.94E-08 3.68E-08 3.37E-08 3.32E-08 2.66E-08 2.64E-08 1.67E-08 5.3Chlorine 3.18E-06 2.30E-06 1.54E-06 1.52E-06 1.38E-06 1.36E-06 1.27E-06 1.16E-06 1.14E-06 9.17E-07 9.07E-07 5.73E-07 1.8

Table F.3 Emission Factors for Directional/Horizontal Wells 

Emission Factor (ton/1,000 feet) 

Pollutant 2002 2005 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2

CO 1.27E-01 1.09E-01 7.77E-02 7.75E-02 7.72E-02 6.47E-02 6.45E-02 6.40E-02 6.38E-02 6.36E-02 6.07E-02 2.66E-02 2.6NOx 5.20E-01 5.22E-01 4.11E-01 4.11E-01 4.00E-01 3.55E-01 3.37E-01 2.52E-01 2.49E-01 2.43E-01 2.24E-01 2.01E-01 2.0PM10 2.43E-02 1.97E-02 1.12E-02 1.12E-02 1.06E-02 9.28E-03 9.38E-03 6.75E-03 6.74E-03 6.75E-03 6.65E-03 3.92E-03 3.9PM2.5 2.36E-02 1.91E-02 1.09E-02 1.08E-02 1.03E-02 9.00E-03 9.10E-03 6.55E-03 6.54E-03 6.55E-03 6.45E-03 3.81E-03 3.7SO2 7.36E-02 7.36E-02 7.77E-03 7.77E-03 3.69E-04 3.69E-04 3.69E-04 3.00E-04 3.00E-04 3.00E-04 3.00E-04 2.83E-04 2.8TOG 3.95E-02 3.51E-02 2.25E-02 2.25E-02 2.17E-02 1.64E-02 1.53E-02 2.08E-02 2.06E-02 2.03E-02 2.00E-02 1.34E-02 1.3VOC 3.89E-02 3.46E-02 2.22E-02 2.21E-02 2.14E-02 1.62E-02 1.50E-02 2.05E-02 2.03E-02 2.00E-02 1.97E-02 1.32E-02 1.3Formaldehyde 5.81E-03 5.17E-03 3.31E-03 3.30E-03 3.20E-03 2.42E-03 2.25E-03 3.07E-03 3.04E-03 2.98E-03 2.95E-03 1.98E-03 1.9Methanol 1.18E-05 1.05E-05 6.75E-06 6.74E-06 6.52E-06 4.93E-06 4.58E-06 6.25E-06 6.19E-06 6.08E-06 6.01E-06 4.03E-06 4.0Benzene 7.90E-04 7.03E-04 4.50E-04 4.49E-04 4.35E-04 3.29E-04 3.05E-04 4.17E-04 4.13E-04 4.06E-04 4.01E-04 2.69E-04 2.6Acetaldehyde 2.90E-03 2.58E-03 1.65E-03 1.65E-03 1.60E-03 1.21E-03 1.12E-03 1.53E-03 1.52E-03 1.49E-03 1.47E-03 9.88E-04 9.8Naphthalene 3.55E-05 3.16E-05 2.03E-05 2.02E-05 1.96E-05 1.48E-05 1.37E-05 1.88E-05 1.86E-05 1.83E-05 1.80E-05 1.21E-05 1.2

F-3 
F-4 

Table F.3 Emission Factors for Directional/Horizontal Wells (Cont.) 

Emission Factor (ton/1,000 feet) 

Pollutant 2002 2005 2008 2009 2010 2011 2012 2103 2014 2015 2016 2017 2

o-xylene 1.34E-04 1.19E-04 7.66E-05 7.63E-05 7.39E-05 5.59E-05 5.19E-05 7.09E-05 7.02E-05 6.90E-05 6.82E-05 4.57E-05 4.5Cumene 7.90E-06 7.03E-06 4.50E-06 4.49E-06 4.35E-06 3.29E-06 3.05E-06 4.17E-06 4.13E-06 4.06E-06 4.01E-06 2.69E-06 2.6Ethylbenzene 1.22E-04 1.09E-04 6.98E-05 6.96E-05 6.74E-05 5.09E-05 4.73E-05 6.46E-05 6.40E-05 6.29E-05 6.22E-05 4.17E-05 4.1Styrene 2.37E-05 2.11E-05 1.35E-05 1.35E-05 1.30E-05 9.86E-06 9.16E-06 1.25E-05 1.24E-05 1.22E-05 1.20E-05 8.07E-06 8.0p-xylene 3.95E-05 3.51E-05 2.25E-05 2.25E-05 2.17E-05 1.64E-05 1.53E-05 2.08E-05 2.06E-05 2.03E-05 2.00E-05 1.34E-05 1.31,3-butadiene 7.50E-05 6.68E-05 4.28E-05 4.27E-05 4.13E-05 3.12E-05 2.90E-05 3.96E-05 3.92E-05 3.85E-05 3.81E-05 2.55E-05 2.5m-xylene 2.41E-04 2.14E-04 1.37E-04 1.37E-04 1.33E-04 1.00E-04 9.31E-05 1.27E-04 1.26E-04 1.24E-04 1.22E-04 8.20E-05 8.1Toluene 5.80E-04 5.17E-04 3.31E-04 3.30E-04 3.20E-04 2.42E-04 2.24E-04 3.06E-04 3.03E-04 2.98E-04 2.95E-04 1.98E-04 1.9n-hexane 6.32E-05 5.62E-05 3.60E-05 3.59E-05 3.48E-05 2.63E-05 2.44E-05 3.33E-05 3.30E-05 3.25E-05 3.21E-05 2.15E-05 2.1Propionaldehyde 3.83E-04 3.41E-04 2.18E-04 2.18E-04 2.11E-04 1.59E-04 1.48E-04 2.02E-04 2.00E-04 1.97E-04 1.94E-04 1.30E-04 1.32,2,4-trimethylpentane 1.18E-04 1.05E-04 6.75E-05 6.74E-05 6.52E-05 4.93E-05 4.58E-05 6.25E-05 6.19E-05 6.08E-05 6.01E-05 4.03E-05 4.0Lead 1.02E-06 8.28E-07 4.71E-07 4.70E-07 4.46E-07 3.90E-07 3.94E-07 2.84E-07 2.83E-07 2.84E-07 2.79E-07 1.65E-07 1.6Manganese 9.73E-07 7.89E-07 4.49E-07 4.47E-07 4.25E-07 3.71E-07 3.75E-07 2.70E-07 2.70E-07 2.70E-07 2.66E-07 1.57E-07 1.5Mercury 7.30E-07 5.91E-07 3.37E-07 3.35E-07 3.19E-07 2.78E-07 2.81E-07 2.03E-07 2.02E-07 2.03E-07 1.99E-07 1.18E-07 1.1Nickel 4.62E-07 3.75E-07 2.13E-07 2.12E-07 2.02E-07 1.76E-07 1.78E-07 1.28E-07 1.28E-07 1.28E-07 1.26E-07 7.45E-08 7.4Antimony 8.76E-07 7.10E-07 4.04E-07 4.02E-07 3.82E-07 3.34E-07 3.38E-07 2.43E-07 2.43E-07 2.43E-07 2.39E-07 1.41E-07 1.4Arsenic 1.22E-07 9.86E-08 5.61E-08 5.59E-08 5.31E-08 4.64E-08 4.69E-08 3.38E-08 3.37E-08 3.38E-08 3.32E-08 1.96E-08 1.9Cadmium 9.73E-07 7.89E-07 4.49E-07 4.47E-07 4.25E-07 3.71E-07 3.75E-07 2.70E-07 2.70E-07 2.70E-07 2.66E-07 1.57E-07 1.5Cobalt 2.68E-07 2.17E-07 1.23E-07 1.23E-07 1.17E-07 1.02E-07 1.03E-07 7.43E-08 7.41E-08 7.43E-08 7.31E-08 4.32E-08 4.2Phosphorous 3.09E-06 2.50E-06 1.43E-06 1.42E-06 1.35E-06 1.18E-06 1.19E-06 8.57E-07 8.56E-07 8.58E-07 8.44E-07 4.98E-07 4.9Selenium 2.43E-07 1.97E-07 1.12E-07 1.12E-07 1.06E-07 9.28E-08 9.38E-08 6.75E-08 6.74E-08 6.75E-08 6.65E-08 3.92E-08 3.9Chlorine 8.37E-06 6.78E-06 3.86E-06 3.85E-06 3.65E-06 3.19E-06 3.23E-06 2.32E-06 2.32E-06 2.32E-06 2.29E-06 1.35E-06 1.3
Appendix G – Annual and OSD County-Level Emission Estimates 

(Criteria Pollutants and HAPs, 2002, 2005, 2008-2021)

(see file “TCEQ Drilling Rig Engine Report_Appendices.xls”)