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Memorandum: Summary of Revisions to Oil
and Gas National Emissions Estimation Tool -
Version 2
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EPA-454/B-20-026
March 2014
Memorandum: Summary of Revisions to Oil and Gas National Emissions Estimation Tool -
Version 2
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Assessment Division
Research Triangle Park, NC
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MEMORANDUM
TO: Roy Huntley, US EPA
Jennifer Snyder, US EPA
FROM: Mike Pring, Eastern Research Group, Inc. (ERG)
Regi Oommen, ERG
Stephen Treimel, ERG
DATE: March 31, 2014
SUBJECT: Summary of Revisions to Oil and Gas National Emissions Estimation Tool -
Version 2
The purpose of this memo is to summarize the changes that have been made to the oil and gas
area source emissions estimation tool since Draft Version 1.4 was submitted on September 12,
2013.
Activitv/Basin/Emission Factor Data Updates
1) Updated the tool to include WRAP basin factors for the following basins:
a. Powder River (Wyoming, Montana);
b. South San Juan (New Mexico, Utah);
c. Uinta (Utah);
d. Southwest Wyoming (Wyoming, Utah);
e. Wind River (Wyoming);
f. Denver-Julesburg (CO); and
g. Piceance (CO).
(Note: "hybrid" data previously used for the South San Juan and Uinta basins has been
replaced using discrete data for coalbed methane wells separate from all other wells.)
2) Applied surrogate data for several counties in New Mexico as follows:
a. For Chavez, Eddy, Lea, and Roosevelt counties, applied data from Andrews
County in Texas as being representative of Permian Basin characteristics in New
Mexico; and
b. For Colfax County (Raton Basin), applied WRAP data from the South San Juan
Basin. Engine emissions have been zeroed out for this county as the engines are
all electric.
3) Updated the methodology to determine well completion counts to consider "Date of 1st
Production" if no well completion date is available.
4) Updated the methodology to identify unconventional wells to consider both the
DOE/EIA Crosswalk identifiers and all horizontal wells.
5) Corrected an error in the CO2 percentage used in the calculation for gas-actuated
pumps.
6) Updated the N>0 emission factor for engines to use an emission factor from the API
Compendium.
7) Updated the emission factors for Benzene, Toluene, Ethylbenzene, and Xylene for 4-
stroke lean burn lateral compressor engines.
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Emission Estimation Algorithm Updates
1) Modified the algorithm used to estimate emissions from mud degassing and condensate
tank emissions to reflect CBM activity.
2) Updated the methodology used to estimate fugitive (equipment leak) emissions to
reflect that all wells have components in light oil service AND in gas service.
Previously, only oil wells were assumed to have components in light oil service and
only gas wells were assumed to have components in gas service. The default
component count profile for oil and gas wells is now the same, as follows:
('ompoiH'iil Type
Service Tv pc-
('ompoiH'iil ( (unit
Valves
Gas
13.83
Valves
Light Oil
19.01
Connectors
Gas
39.07
Connectors
Light Oil
82.71
Flanges
Gas
21.69
Flanges
Light Oil
3.46
Open-ended Lines
Gas
5.23
Open-ended Lines
Light Oil
2.61
3) Modified the algorithm to estimate emissions from wellhead compressor seals to
remove the "24" factor in the denominator as the factor Vvented is in terms of
(S CF/compres sor/hour).
Tool Updates
1) Modified the tool to include discrete emissions estimation algorithms for coalbed
methane wells. At this time, coalbed methane-specific basin factors are included in the
tool for the following basins:
a. Powder River (Wyoming, Montana);
b. South San Juan (New Mexico, Utah);
c. Uinta (Utah)
2) Added a reference field for "OIL_TANK_AVG_LOSSES".
3) Revised field names in the Liquids Unloading Basin Factor table to reflect that controls
may include technologies other than flaring. Specifically, revised
"LIQ_UNL_FRACTION_WITH_FLARING'' to
'LIQ_UNL_FRACTION_WITH_CONT'' and "LIQ_UNL_FLARE_CONT_EFF" to
"LIQ_UNL_CONT_EFF".
4) Updated the "GLOSSARY_BASIN_FACTORS" table to reflect the new coalbed
methane fields.
Report Updates
1) Added pictures to the report illustrative of each source category type (with the
exceptions of gas-actuated pumps, loading, and mud degassing).
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2) Updated the tool instructions included as Appendix A.
3) Added "default" values (and default value references) to each of the basin factors
included in the Data Element Dictionary (Appendix C).
4) Removed the "24" factor in the denominator of equation 25 as the emission factor
(Vvented) is in terms of (SCF/compressor/hour).
5) Updated the Data Element Dictionary (Appendix C) to reflect the new coalbed methane
fields.
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United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-20-026
Environmental Protection Air Quality Assessment Division March 2014
Agency Research Triangle Park, NC
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