United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-92/083 June 1992
EPA Project Summary
Oil and Gas Field
Emissions Survey
C.E. Burklin, M.A. Zarate, R. K. Smith, J.W. Sullivan, L. N. Gerald,
and I.D. Shaw
This report presents available infor-
mation that may be used for defining
emission estimate methodologies for
oil and gas production emission
sources. From this information, EPA
will define additional studies to fill in
data gaps and develop emission esti-
mation methodologies.
The production segment of the oil
and gas industry has been identified
as a source category that requires the
development of more reliable emissions
inventory methodologies. The overall
purpose of this project was to deter-
mine available activity and emission
factor data that may be used to de-
velop methodologies for states to use
in estimating emissions inventories for
oil and gas field operations at the
county level.
There were four objectives of this
project: (1)To gather and compile avail-
able activity factors on oil and gas field
operations; (2)To gather and compile
available emission data for total and
speciated volatile organic compounds
(VOCs) from all emission sources as-
sociated with oil and gas field produc-
tion activities; (3)To identify ongoing
studies for the development of emis-
sions data; and (4)To identify activity
and emission data gaps and to recom-
mend future studies to develop neces-
sary data and estimate methodologies.
Activity and emission factors for oil
and gas production facilities, natural
gas processing plants, and ports and
marine terminals are presented, data
limitations are identified, and recom-
mendations for future studies are made.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Background
The EPA is engaged in developing im-
proved methodologies for calculating emis-
sion estimates for various emission source
categories. The production segment of
the oil and gas industry has been identi-
fied as a source category that requires
the development of more reliable emis-
sions inventory methodologies. The cur-
rent version of the EPA report "Compila-
tion of Air Pollutant Emission Factors, Vol-
ume I, AP-42" does not identify proce-
dures for estimating VOC emissions from
oil and gas field operations. Examples of
emission sources from these operations
are wellheads, gathering tanks, and field
separation and gas processing equipment.
Because some of these emission sources
are often uncontrolled and are not identi-
fied by the current AP-42 procedures, they
may represent a significant missing source
in emissions inventories.
This report presents available informa-
tion on data for oil and gas production
emissions and activities that may be used
for defining specific emission estimate
methodologies for oil and gas production
emission sources. From this information,
EPA will define additional studies to fill in
data gaps and develop emission estima-
tion methodologies.
Printed on Recycled Paper
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Project Description
The overall purpose of this project was
to determine available activity and emis-
sion factor data that may be used to de-
velop methodologies for states to use in
estimating emissions inventories for oil and
gas field operations at the county level.
Activity factor data include any data that
characterizes a particular operation of
emission source. Typical activity data for
oil and gas field production include the
number of drilling and producing wells,
the amount of oil and gas produced, and
typical types and numbers of oil field equip-
ment. Emissions data include emission
factors and total emissions released from
specific emission sources. An emission
factor is an average value relating the
quantity of a pollutant released to the at-
mosphere with the activity associated with
the pollutant release.
There were four objectives in this project.
The first was to gather and compile all
available activity factors on oil and gas
field operations, including data for domes-
tic U.S. ports and transhipment facilities.
The second objective was to gather and
compile all available emission data for to-
tal and speciated VOCs from all emission
sources associated with oil and gas field
production activities, including data for
marine terminals at U.S. ports. Emissions
data for oxides of nitrogen (NOX) from
combustion sources were also gathered.
The third objective was to identify ongoing
studies for the development of emissions
data. The fourth objective was to identify
activity and emissions data gaps and to
recommend future studies to develop ac-
tivity and emissions data and emission
estimates methodologies.
The study focused on developing an
Industry characterization for the field pro-
duction operations using activity factors
and an emissions characterization using
emissions data. The technical approach
for industry characterization was to gather
information on all possible sources of ac-
tivity factor data at the county level. This
information gathering process included re-
views of published literature and existing
and planned databases. The primary fo-
cus of this review was to identify viable
sources of data. Information was obtained
from 23 different sources, including state
and federal agencies, trade associations,
private oil and gas consulting firms, and
oil and gas equipment manufacturers.
In searching for activity factor data, in-
formation on petroleum production opera-
tions was divided into eight major areas:
(1) oil and gas drilling activity, (2) oil and
gas well count data, (3) oil and gas pro-
duction data, (4) oil assay information, (5)
typical oil and gas field equipment, (6)
gathering systems (storage tanks), (7) gas
processing plants, and (8) ports and ma-
rine terminals. When relevant activity fac-
tor databases were identified, their con-
tent, format, resolution, and limitations
were noted.
The five top oil- and gas-producing
states (Texas, California, Louisiana, Okla-
homa, and Pennsylvania) were contacted
by phone to obtain activity factor data as
well as emissions data.
The technical approach for the emis-
sions characterization was to gather all
available emissions data from previous
studies on oil and gas production emis-
sion sources. Particular efforts were made
to gather emissions data from state regu-
latory agencies. Trade associations, oil
and gas consulting firms, and state agen-
cies were contacted to obtain information
about relevant ongoing studies.
Finally, the gathered information was
analyzed to determine data gaps and rec-
ommendations were made for future stud-
ies.
Discussion of Results
Oil and Gas Production
Facilities
Activity Factors. Activity factor data are
available at the county level primarily for
well drilling and development and for oil
and gas production wells. Count and pro-
duction data for oil and gas wells are
generally tracked by states with large oil
or gas production. In some cases, the
data are not organized on a county level;
so, in order to obtain county level totals,
additional time may be needed to sort the
data. Only the larger producer states
were contacted in this study. States not
contacted in this study should be sur-
veyed to support the statement that "most"
states track oil and gas production and
well count data. If it is found that most
states do not track well count information,
a comprehensive (national) production and
well count database is available from a
private consulting firm.
Reid vapor pressure data are available
for crude types that are exported from the
U.S. Domestic Reid vapor pressure data
are available for some of the domestic
crude types — generally, those that are
exported from the U.S. An expanded data
gathering process would be necessary to
compile all domestic Reid vapor pressure
values into a single source.
Oil and gas field equipment and gather-
ing tank data are the most meager in
terms of available information. Equipment
count information for the U.S. is not avail-
able. The California Air Resources Board
is the only state agency that has an es-
tablished method for estimating and track-
ing equipment, and this is done at the
district level. A definition of typical equip-
ment at field production facilities is needed.
In addition, a survey of oil companies,
field operators, or equipment manufactur-
ers is also necessary to obtain field equip-
ment count data and information on out-
field activities (venting and flaring).
Information on the typical number of
storage tanks associated with field pro-
duction gathering systems is not readily
tracked or available.
Emission Factors. Emission factors for
the large diesel and natural gas engines
used in exploratory and development drill-
ing activities are available from AP-42.
The EPA emission factor rating is C (on
an A-E scale, with A the best). Little
information is available on drilling support
equipment type and size that could be
used to develop emission factors.
A main source of data for fugitive emis-
sion factors from oil and gas field opera-
tions, including wellheads, is the 1980
study for American Petroleum Institute
(API). Several ongoing studies should
eventually provide additional emission fac-
tor data for wellheads. While fugitive emis-
sion factors for wellheads are available
and ongojng studies exist, reliable com-
ponent co'unts are not available.
The API fugitive emission factors apply
to components associated with field sepa-
ration equipment. The 1980 study also
includes factors for pits, open-top tanks,
and sumps. Typical component counts
for field separation equipment were not
readily available from the literature that
was reviewed or from any of the oil- and
gas-producing states. Emission factors
for gas/liquid separators, glycol regenera-
tors, and heater treaters in field produc-
tion facilities were not available; however,
these emission sources are within the
scope of the Air Toxics Multi-Year Study
(ATMYS) being conducted by API. Vent-
ing and flaring emissions data are very
limited. While the combined quantities of
vented and flared gas is tracked state by
state, states do not have much informa-
tion about the emission sources or the
reason for the release; therefore, it is diffi-
cult to assess the amount of gas vented
and flared for particular emission sources.
Limited information was available re-
garding emissions from gathering tanks.
The AP-42 equations for storage tanks
are generally used to estimate emissions.
In some cases, AP-42 equations had been
modified by state agencies to estimate
their emissions. The AP-42 emission fac-
tors for transfer operations are generally
used; however, they were not specifically
developed for gathering system operations.
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No comprehensive field testing programs
have been performed for these sources.
Natural Gas Processing Plants
Activity Factors. The population of natu-
ral gas processing plants is well docu-
mented in the Oil and Gas Journal's yearly
gas processing survey. Data included are
company and plant name, location
(county), gas capacity, gas throughput,
process method, and annual production.
Emission Factors. While fugitive emis-
sion factors for components at gas pro-
cessing plants had been developed and
continue to be studied, component count
inventories of equipment at these plants
are not available. Little is known about
the amount of gas vented and flared for
particular emission sources at gas pro-
cessing plants. Emission factors for heavy-
duty natural gas-fired pipeline compressor
engines applicable to power compressors
used at gas processing plants are reported
in AP-42.
Ports and Marine Terminals
Activity Factors. The number of U.S.
ports and marine terminals are available
through the Waterborne Commerce of the
United States database maintained by the
Army Corps of Engineers. The EPA may
access these data to track the volume of
domestic and imported crude oil through-
out the U.S., but the Corps database does
not track terminal holding or storage tank
data. The number of storage tanks at
marine terminals is not readily tracked or
available. Additional information gather-
ing, coupled with field equipment surveys,
would be needed to obtain this informa-
tion.
Emission Factors. Using the AP-42
equations for storage tanks is generally
accepted for estimating emissions from
crude oil storage tanks at marine termi-
nals. The AP-42 emission factors for trans-
fer operations are also generally used for
marine terminals.
Recommendations
Several areas with data gaps and that
merit further investigation have been iden-
tified. However, a more detailed analysis
would help prioritize the areas that require
future study in the short term. The
prioritization of research areas would con-
sider the number of emission sources na-
tionwide and their estimated emissions,
as well as the data needs of the individual
major producer states. An emissions esti-
mation plan would address: (1) coordina-
tion with ongoing projects, (2) implemen-
tation of testing programs, (3) data gath-
ering through surveys, and (4) methodol-
ogy development for estimating emissions
using identified reliable activity and emis-
sion factors.
Furthermore, more specific information
on the ongoing studies would define limi-
tations within their scope and the possi-
bilities of program expansion with EPA
support.
A program for providing a Quality As-
surance Project Plan (QAPP) protocols
review should be established for the dif-
ferent testing programs being conducted
by industry and trade associations.
EPA's role could ensure the genera-
tion of accurate and reliable emission data.
Early involvement and prompt review of
QAPPs could be a key factor in the
implementating the program. Reviewing
and modifying QAPP protocols becomes
difficult after a test program is initiated.
•U.S. Government Printing Office: 1992— 648-080/60030
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C. Burklin, M. Zarate, R. Smith, J. Sullivan, L Gerald, and I. Shaw are with Radian
Corp., Research Triangle Park, NC 27709.
Charles C. Masaer is the EPA Project Officer (see below).
The complete report, entitled "Oil and Gas Field Emissions Survey," (Order No.
PB92-184 977/AS; Cost: $43.00; subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: (703) 487-4650
The EPA Project Off her can be contacted at:
Air and EnergyEngineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental
Research Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
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PERMIT No. G-35
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Penalty for Private Use $300
EPA/600/SR-92/083
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