June 2018

Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2017:

Updates Under Consideration for Well-Related Activity Data

In supporting documentation associated with the development of EPA's 2018 Inventory of U.S. Greenhouse Gas
Emissions and Sinks (GHGI), EPA stated plans to assess options to increase consistency and improve activity data
for a number of sources and activities related to onshore oil and gas wells.

This memo summarizes current methodologies and updates under consideration to increase consistency and
accuracy for certain emission source estimates that rely on well-related activity data.

Note, this memo references a memo under concurrent development, Inventory of U.S. Greenhouse Gas Emissions
and Sinks 1990-2017: Updates Under Consideration for Incorporating GHGRP Data1, which focuses on
incorporating GHGRP data into the 2019 GHGI and includes a dedicated section on hydraulically fractured (HF) oil
well completions and workovers.

1 Current GHGI Methodologies

Table 1 below summarizes the data sources that are currently used to develop activity data for emission sources
that directly rely on counts of wells or well-related activities. Appendix A provides a table that shows all well-
related activity data over the time series as used in the 2018 GHGI (as well as data elements from updates under
consideration, as discussed in Section 3).

Note that several existing GHGI methodologies documented in Table 1 (e.g., developing counts of active wells)
rely on EPA's analysis of Drillinglnfo's subscription-based digital Dl Desktop raw data feed2; this data set is referred
to throughout this memo as "Drillinglnfo data."

Table 1. 2018 GHGI Well-Related Activity Data Summary

Emission Source/Activity Data Element

Activity Basis

Data Source/Basis

Natural Gas Systems





Non-associated gas wells (less HF wells)

Wellheads

Drillinglnfo data analysis; active wells with GOR>100
mcf/bbl

Gas wells with hydraulic fracturing

Wellheads

Drillinglnfo data analysis; subset of non-associated gas
wells located in unconventional formation and/or
horizontally drilled

Non-HF gas well completions

Events

400 completions/year for all gas wells in 1992 (GRI/EPA
19963), scaled in future years

Non-HF gas well workovers

Events

4.35% of non-HF gas wells (GRI/EPA 1996)

HF gas well completions (four control categories)

Events

GHGRP direct counts (if higher than Drillinglnfo data
analysis; count of newly spud or newly producing gas
wells located in unconventional formation and/or
horizontally drilled)

HF gas well workovers (four control categories)

Events

1% of HF gas wells are worked-over annually

1	https://www.epa.gov/ghgemissions/stakeholder-process-natural-gas-and-petroleum-systems-1990-2017-inventory

2	https://info.drillinginfo.com/products/di-plus/

3	Methane Emissions from the Natural Gas Industry. Prepared by Harrison, M., T. Shires, J. Wessels, and R. Cowgill, eds., Radian
International LLC for National Risk Management Research Laboratory, Air Pollution Prevention and Control Division, Research Triangle Park,
NC. EPA-600/R-96-080a.

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Emission Source/Activity Data Element

Activity Basis

Data Source/Basis

Gas well drilling

Events

EIA - gas wells and fraction of dry wells drilled (data set
last updated in 2010)

Petroleum Systems





Producing oil wells

Wellheads

Drillinglnfo data analysis; active wells with GOR<100
mcf/bbl

Heavy crude wells population fraction

Fraction

7.05% of all oil wells (EPA/ICF 19994)

Non-HF oil well completions

Events

EIA crude oil wells drilled, less HF oil well completions

Oil well workovers

Events

7.5% of producing oil wells (Radian 19995)

HF oil well completions (two control categories)

Events

Drillinglnfo data analysis; count of newly spud or newly
producing oil wells located in unconventional formation
and/or horizontally drilled

Oil well drilling

Events

EIA - oil wells and fraction of dry wells drilled (data set
last updated in 2010)

2 Updates Under Consideration

EPA is considering implementing methodological updates focused on five general areas, to increase consistency
and accuracy of activity data for certain emission sources shown in Table 1:

•	Well drilling: The U.S. Department of Energy's Energy Information Administration (EIA) no longer
maintains the well drilling activity data set within its Monthly Energy Review publication that was used to
develop well drilling activity inputs in past GHGIs (most recent estimates cover through 2010), so the
GHGI requires a new data source for the entire time series, or at least 2011 forward.

•	Well completions and workovers: The non-HF gas well completion activity data methodology is based on
industry characteristics in base year 1992 (from the 1996 GRI/EPA study). An updated data source should
account for changing trends over time. Non-HF oil well completions are sometimes zero in recent time
series years, due to limitations of the current data sources and methodologies for both oil well drilling and
HF oil well completion counts. For HF gas well completions, the GHGRP reported counts are higher than
those obtained from the Drillinglnfo data analysis; due to the reporting threshold, GHGRP counts should
represent a subset of national activity, so Drillinglnfo counts should be equal to, or greater than, GHGRP
direct counts. For HF oil well completions, EPA is beginning to review newly reported GHGRP activity data
in comparison to existing activity developed from the Drillinglnfo data analysis (refer to companion memo
on incorporating GHGRP data into the 2019 GHGI). The current assumptions for workover rates have not
been updated in recent years, and there is no current estimate representing HF oil well workovers.

•	Definition of oil versus gas well: The current methodology estimates the count of active gas wells in a
given year as any well in the Drillinglnfo data set with a gas-to-oil ratio (GOR) > 100 mcf/bbl in that year,
and active oil wells as those with GOR < 100 mcf/bbl. Other industry data sets (e.g., those published by
EIA) use different thresholds for defining oil versus gas wells. A value of 6 mcf/bbl is another common
threshold. EPA reviewed available data reported under GHGRP subpart W to evaluate how reported GOR
values compare to the current GHGI methodology.

•	Heavy versus light crude equipment service: The fractions used to split counts of wellheads, headers, and
separators between heavy and light crude service were developed in the 1990s and applied for all time
series years. An updated data source should account for changing trends over time.

•	Identification of HF wells: The current methodology identifies HF gas or oil wells as those horizontally
drilled (based on Drillinglnfo data) and/or located in a shale, low permeability, or coalbed formation.

4	Estimates of Methane Emissions from the U.S. Oil Industry (Draft Report). Prepared by ICF International. Office of Air and Radiation, U.S.
Environmental Protection Agency. October 1999.

5	EPA/Radian (1999) Methane Emissions from the U.S. Petroleum Industry. Prepared by Radian International. U.S. Environmental Protection
Agency. February 1999.

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Potential GHGI updates to address these priority areas are discussed in more detail in the subsections below.
Appendix A provides a table that shows all well-related activity data over the time series as used in the 2018
GHGI, as well as data elements from updates under consideration, as discussed below. After these priority areas
are addressed, EPA might investigate updated methodology and/or data sources to potentially improve estimates
for other well-related activity data elements.

2.1 Well Drilling

As described above, EIA no longer maintains the Monthly Energy Review well drilling activity data set that was
used to develop well drilling activity inputs in past GHGIs (most recent estimates cover through 2010), so the
GHGI requires a new data source for the entire time series, or at least 2011 forward. EPA is evaluating two general
options to estimate well drilling counts over the time series:

1.	Identify another data set published by EIA.

2.	Develop methodology for querying Drillinglnfo data set.

EPA is in the process of reviewing available EIA data that could provide updated well drilling activity. EPA is
reviewing ElA's Drilling Productivity Report6 which provides counts of wells drilled, wells completed, and wells
drilled but uncompleted; but the public data are not comprehensive (covers years 2014 forward, covers seven
production regions (not all U.S. onshore), and does not include conventional wells). EPA is also reviewing data
underlying a recently published EIA analysis of HF wells on its Today in Energy website7, which includes coverage
of non-HF well drilling and completions. The Today in Energy drilling activity estimates, which are presented in
graphical form on the website, are generally lower than those published in ElA's Monthly Energy Review over
comparable time periods; this is due to exclusion of dry wells, which are included in current GHGI activity
estimates.

At the same time, EPA is developing a methodology for querying the Drillinglnfo data set to develop estimates of
wells drilled. EPA is considering the following approach:

•	Count all wells drilled in time series year N with:

o Onshore location -and-

o Spud date within year N -or- spud date not reported, but date of first production within year
N+l

•	Apportion counts between oil, gas, and dry production types

o Dry or temporarily inactive (TIA) wells drilled: spud date within year N, but no production is

reported in year N+l
o Gas wells drilled: GOR in year N+l >100 mcf/bbl
o Oil wells drilled: GOR in year N+l < 100 mcf/bbl

•	Apportion dry/TIA counts to natural gas and petroleum systems according to the year-specific split
between gas wells drilled and oil wells drilled.

For a Drillinglnfo-based methodology, EPA seeks feedback on a few additional considerations. First, whether this
approach adequately accounts for dry wells (which are spud but do not achieve reportable production levels).
Based on preliminary analysis of results, this approach does appear to sufficiently represent dry wells at
comparable levels to the EIA data set; on average, dry wells (not including TIA wells which report production after
year N+l) contribute 10% of total wells drilled. Second, whether this approach is overly inclusive of wells that may
not be drilled for oil and gas production purposes but are present in the Drillinglnfo data set. Second, how to
account for time series coverage issues. For states without recently released data, EPA might develop a surrogate
methodology wherein an early year's data are assigned to recent years to fill state-level data gaps, similar to the
existing approach for counts of active wells. Additionally, total wells drilled in most recent time series year cannot

6	https://www.eia.gov/petroleum/drilling/

7	https://www.eia.gov/todayinenergy/detail.php?id=34732

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be fully estimated by the current approach (i.e., GOR in year N+l is not available); EPA is considering a surrogate
approach such as using the previous year's estimate.

Appendix A shows well drilling counts across the time series in the 2018 GHGI, as well as relevant publicly
available data from ElA's Monthly Energy Review publication and preliminary estimates by the Drillinglnfo data
analysis approach described above. EPA seeks stakeholder feedback on these approaches under consideration, or
other data sets or methodologies to consider for well drilling activity data in the 2019 GHGI; see Section 3 for
specific stakeholder feedback requests.

2.2 Well Completions and Workovers

As described above, the current methodology for well completion and workover event counts involves a mix of
Drill ingl nfo data analyses, GHGRP data analyses, and historical assumptions.

EPA is investigating the use of Drillinglnfo data and GHGRP data to update current activity data methodologies,
including allocation across control categories. Specifically:

•	Non-HF gas well completion counts: Currently based on industry characteristics in base year 1992 (from
the 1996 GRI/EPA study). Drill inglnfo data might offer an update to total activity across all time series
years, and GHGRP data might be used to check/supplement Drill inglnfo data and provide updated control
assumptions in recent years.

•	Non-HF oil well completion counts: Are sometimes zero in recent time series years, due to limitations of
the current data sources and methodologies for both oil well drilling and HF oil well completion counts.
Drillinglnfo data might offer an update to total activity across all time series years.

•	HF gas well completions: GHGRP reported counts are higher than those obtained from the Drillinglnfo
data analysis; due to the reporting threshold, GHGRP counts should represent a subset of national
activity, so Drillinglnfo counts should be equal to, or greater than, GHGRP direct counts. EPA is continuing
to review Drillinglnfo and GHGRP data to assess whether updates can be made to ensure that activity data
for this source represents national coverage.

•	HF oil well completions: EPA is beginning to review newly reported GHGRP activity data (refer to
companion memo on incorporating GHGRP data into the 2019 GHGI) in comparison to existing activity
developed from the Drillinglnfo data analysis.

•	Workover rates: Have not been updated in recent years, and there is no current estimate representing HF
oil well workovers. EPA is beginning to review GHGRP activity data to ensure that activity data for
workovers reflects trends overtime and represents national coverage.

EPA has conducted a preliminary analysis to assess how workover rates reflected in the subpart W data compare
to current GHGI assumptions. The subpart W data reporting structure and requirements limit the level of detail
for such an analysis, due to: (1) there is not a specific reporting element indicating whether reported wells are HF
or non-HF; and (2) non-HF oil well workovers are not reported. EPA analyzed the overall gas well workover rate, as
summarized in Table 2. For gas wells reported under subpart W, the overall workover rate is 5-6% in recent years
(compared to the current GHGI assumption of 4.35% for non-HF gas wells and 1% for HF gas wells).

Table 2. Subpart W Gas Well Workover Data and Calculated Workover Rate

Subpart W Data Element

2015

2016

# Gas wells reported (Introduction3 table AA.l.ii)

309,132

284,112

# Gas well workovers with HF reported

263

103

# Gas well workovers without HF reported

18,031

14,957

Calculated: Gas well workover rate

6%

5%

a - Reported under 40 CFR 98.236(aa). Number of producing wells at the end of the calendar year. Data element "ii" refers

to count from the "Sub-basin characterization" table.

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Appendix A shows completion and workover counts across the time series in the 2018 GHGI. EPA seeks
stakeholder feedback on improving the current methodology in the 2019 GHGI; see Section 3 for specific
stakeholder feedback requests.

2.3 Definition of Oil versus Gas Well

The current methodology estimates the count of active gas wells in a given year as all wells in the Drillinglnfo data
set with a gas-to-oil ratio (GOR) > 100 mcf/bbl in that year, and active oil wells as those with GOR < 100 mcf/bbl.
By this definition, oil wells include associated gas wells.

Other data sets (e.g., those published by EIA) use different GOR thresholds for defining oil versus gas wells and
might have different underlying assumptions regarding whether associated gas wells are a subset of oil wells. A
value of 6 mcf/bbl is another common definition threshold, based on the oil and gas energy equivalence factor (6
mcf gas provides roughly the same amount of energy as 1 bbl oil equivalent (BOE); BOE is commonly used in
financial statements to combine oil and gas production into a single measure).

EPA is beginning to review available data reported under GHGRP subpart W to evaluate how reported GOR values
compare to the current GHGI methodology and consider whether the current production type delineation
threshold of 100 mcf/bbl is appropriate. Reporters have been providing GOR data for oil wells under GHGRP
subpart W since 2011, as summarized below. Per subpart W, oil wells are defined as producing from an oil
formation, not defined by a specific GOR thresholds.

•	RY2011-2014, summary data (Envirofacts table W_SUB_BASIN)

o Average GOR for all oil wells operated by a company within a given sub-basin (i.e., county)
o Well counts not directly reported

•	RY2015-2016, summary data (Envirofacts table EF_W_FACILITY_OVERVIEW)

o Average GOR for all oil wells operated by a company within a given sub-basin (i.e., county)
o Associated counts of active wells as of the end of the calendar year are also reported
o Available data cover over 400,000 wells

•	RY2016, well-level data (Envirofacts table EF_W_ONSHORE_WELLS)

o Well-level GOR, but only for oil wells that use measured data for calculating emissions from HF

completions and workovers
o Available data cover less than 160 wells

Table 3 below summarizes reported GOR data based on EPA's review of subpart W RY2015-2016 summary data
(Envirofacts table EF_W_FACILITY_OVERVIEW, containing data for over 400,000 wells reported to the EPA as of
August 5, 2017). For most oil wells reported under subpart W (73%), the sub-basin level average GOR falls within
the current GHGI definition (<100 mcf/bbl); while a significant fraction (27%) have higher average GORs. At a
lower delineation threshold (e.g., 6 mcf/bbl), an even higher fraction of subpart W oil wells (roughly 50%) would
be considered gas wells. Therefore, based on this analysis, EPA finds support for the current approach to
delineating oil versus gas wells, but seeks stakeholder feedback (see Section 3 for specific requests on this topic).

Table 3. 2018 GHGI Well-Related Activity Data Summary



# Oil Wells with Specified GOR (mcf/bbl)

Reporting Year

GOR <10

10< GOR <100

100< GOR <1,000

GOR >1,000

2015

123,446

28,104

11,674

48,091

[58%]

[13%]

[6%]

[23%]

2016

117,538

33,346

21,068

32,781

[57%]

[16%]

[10%]

[16%]

Combined

240,984

61,450

32,742

80,872

[58%]

[15%]

[8%]

[19%]

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2.4 Heavy versus Light Crude Equipment Service

Heavy crude is defined as oil with lower than 20° API gravity. The GHGI uses separate EFs and activity data for
wellheads, separators, and headers in heavy versus light crude service. Currently, the total counts of wellheads
and headers are split into heavy versus light crude categories using an assumed split between heavy crude wells
(7.05% of all oil wells) and light crude wells (92.95%). As documented in the 1999 EPA/ICF report8, this
assumption, and its extension to wellhead and header activity, was developed for a 1995 base year; this split is
currently applied to calculate equipment counts in all time series years. The split between heavy and light crude
separators in base year 1995 is also documented in the 1999 EPA/ICF report: EPA assumed 90.1% of separators
are in light crude service, and 9.9% in heavy crude service, and applied this split to all time series years. EPA has
identified multiple data sources that might facilitate improvement to the current methodology by allowing
calculation of the heavy versus light crude equipment splits in recent years.

GHGRP subpart W collects API gravity data associated with production in all oil sub-basins. Based on an analysis of
RY2015 and RY2016 data, 19% and 18%, respectively, of oil wells reporting to GHGRP produce heavy crude. This
value is higher than the current assumption of 7.05% of wells producing heavy crude (and subsequent assumption
that 7.05% of wellheads and headers are in heavy crude service). To follow the existing methodology which
assumes that per well equipment counts are the same for heavy crude and light crude wells (with the exception of
separators, where on average over the time series each heavy crude well has 0.47 separators while each light
crude well has 0.32 separators), EPA might analyze subpart W data specifically for facilities that produce heavy
crude versus light crude. For this approach, however, only a subset of onshore production facility data can be
analyzed—those with either all heavy crude sub-basin formation types or all light crude sub-basin formation
types—since equipment counts (e.g., separators) are reported at a basin level. Table 4 summarizes the data
availability and preliminary estimates of separator activity factors based on this approach. EPA might use subpart
W data to update the equipment count splits in recent years and reflect updated industry trends.

Table 4. Subpart W Equipment Counts3



Count of





Separators/

Number of Data





Separators

Count of Wellheads

Wellhead

Points (Facilities)



Data Set

2015

2016

2015

2016

2015

2016

2015

2016

Notes/Methodology

All onshore
oil prod

















Counts from records classified

76,690

86,890

213,380

221,326

0.36

0.39

319

315

in Table R.4 as "Crude oil

















production equipment"15



















Counts from records in Table

Heavy

















R.4 - from facilities that

crude-only

1,818

345

40,894

40,063

0.04

0.01

14

14

produce only heavy crude (all

facilities

















sub-basins are oil with API
gravity <20 in Table AA.l.ii)



















Counts from records in Table

Light crude-

















R.4 - from facilities that

only

22,153

23,048

54,098

51,428

0.41

0.45

102

103

produce only light crude (all

facilities

















sub-basins are oil with API
gravity >20 in Table AA.l.ii)

a - Data reported as of August 5, 2017.

b - For this approach, data from all facilities reporting presence of crude oil production equipment for equipment leak
calculations can be used (ignoring the reported sub-basin formation type(s)).

Alternatively, EPA might use the methodology documented in the 1999 Radian report which was the basis for the
1999 EPA/ICF report estimates. The 1999 Radian report methodology analyzed state-level reported heavy oil

8 Estimates of Methane Emissions from the U.S. Oil Industry (Draft Report). Prepared by ICF International. Office of Air and Radiation, U.S.
Environmental Protection Agency. October 1999.

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production as a fraction of total oil production, then applied that fraction to state-level oil well counts to estimate
heavy oil well counts in each state, and finally summed heavy oil well counts to estimate the national population
fraction. The EIA data set described above provides oil production data by API gravity range for many states in
years 2015 and 2016; EPA might pair this data set with state-level well counts from Drillinglnfo to estimate the
current national fraction of heavy oil wells in recent years. This approach would not facilitate development of a
heavy versus light split for equipment other than wellheads (e.g., a specific split for separators as in the current
methodology).

EPA seeks stakeholder feedback on the data sources and approaches described above, or other methodologies to
consider for improving this aspect of the oil production segment major equipment activity estimates; see Section
3 for specific stakeholder feedback requests on this topic.

2.5 Identification of HF Wells

Appendix A shows current GHGI estimates of HF gas and oil well counts. There are limited public data estimating
national total counts comparable to the GHGI; Appendix A shows year 2016 estimates from ElA's Today in Energy
website.

EPA seeks stakeholder feedback on data sources and methodologies that might be used to update the current
approach for identifying HF gas and oil wells within the Drillinglnfo data set. EPA might retain the current
assumption that all horizontally drilled wells are hydraulically fractured but update the methodology for
identifying wells that do not report horizontal drill type but would be expected to be hydraulically fractured based
on location in an unconventional formation. EPA is considering reviewing subpart W sub-basin-level (county-level)
data to assess whether a crosswalk of location and HF indication might be constructed from or verified using
reporting data, in order to estimate total national HF well counts (at least for recent time series years).

3 Requests for Stakeholder Feedback

Well Drilling (Section 2.1)

1.	EPA seeks stakeholder feedback on data available to improve annual national activity estimates for well
drilling across the time series. EPA seeks feedback on the most appropriate data source for updating the
GHGI, whether it is highlighted in Section 2.1 (i.e., EIA or Drillinglnfo) or another source that should be
considered.

2.	EPA seeks feedback on how to ensure time series consistency, given the current EIA data source provides
annual activity through 2010. Should a new data source cover only recent years, or be used to entirely
replace current estimates?

3.	As EPA further considers developing annual well drilling activity estimates from Drillinglnfo data, feedback
is sought on the specific methodology and other considerations outlined in Section 2.1. Specifically:

a.	Whether this approach adequately accounts for dry wells (which are spud but do not achieve
reportable production levels). Based on preliminary analysis of results, this approach does appear
to sufficiently represent dry wells at comparable levels to the EIA data set; on average, dry wells
(not including TIA wells which report production after year N+l) contribute 10% of total wells
drilled.

b.	Whether this approach is overly inclusive of wells that may not be drilled for oil and gas
production purposes but are present in the Drillinglnfo data set (e.g., wells drilled specifically for
injection). EPA expects a minor contribution from such wells, since estimates developed from the
Drillinglnfo approach under consideration are comparable with EIA estimates for the overlapping
time frame (1990-2010), as shown in Appendix A. EPA estimates that that injection wells might
contribute approximately 2-4% to total counts; it is difficult to identify such wells in the

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Drillinglnfo data set due to the presence of hundreds of reported production types. EPA seeks
feedback on how the Drillinglnfo-based methodology might take this issue into account.

c. How to account for time series coverage issues (due to states with lagging reporting and therefore
not fully represented in the Drillinglnfo data set in recent years).

Well Completions and Workovers (Section 2.2)

4.	EPA seeks stakeholder feedback on how to use available data to improve national activity estimates for
well completion and workover events—specifically, how Drillinglnfo and subpart W data sets might be
used in conjunction, or if one data set should be used to develop estimates and the other to verify
estimates.

Definition of Oil vs. Gas Well (Section 2.3)

5.	EPA seeks stakeholder feedback on whether the current methodology for counting and allocating active
well counts between oil and gas should be updated, and if so, how.

Heavy vs. Light Crude Equipment Service (Section 2.4)

6.	Based on RY2015 and RY2016 subpart W data, 19% and 18%, respectively, of oil wells in that data set
produce heavy crude (API gravity less than 20), compared to the current GHGI basis of 7.05%. This
updated heavy crude fraction is based on reported data for approximately 210,000 active oil wells (out of
approximately 580,000 active oil wells nationwide). EPA seeks stakeholder feedback on incorporating this
updated fraction into the GHGI time series.

a.	Should EPA consider developing geographic-specific (e.g., NEMS region-level) estimates of heavy
crude well fractions?

b.	Should EPA retain the estimate of 7.05% of oil wells producing heavy crude (developed for base
year 1995) for early years of the time series, and interpolate to the updated fraction based on
subpart W data? Or is a different approach more appropriate—for example, where the heavy
crude fraction is more tailored to the specific time period, rather than a set or linearly increasing
value? EPA seeks information on data sources that might offer information to implement a more
tailored approach.

7.	How should EPA use API gravity data in conjunction with equipment count data reported under subpart W
to improve oil production segment major equipment activity estimates? For example, Table 4 above
presents activity factors for separators per oil well developed specifically for heavy and light crude
populations.

a.	Should EPA retain the current approach of extending the heavy/light crude well count split to
wellhead and header activity data (for example, 19% of oil wells produce heavy crude, therefore
19% of headers are in heavy crude service)?

b.	Should EPA retain the current approach of developing specific activity factors for separators in
heavy versus light crude service, as shown in Table 4?

Identification of HF Wells (Section 2.5)

8.	EPA seeks stakeholder feedback on whether it is reasonable to retain the current assumption that all wells
with horizontal drill type according to the Drillinglnfo data set are hydraulically fractured, or if there are
recommendations for improving this assumption.

9.	EPA seeks input on publicly available data sources and methodologies that might be used to identify wells
that do not report horizontal drill type in the Drillinglnfo data set but would be expected to be
hydraulically fractured based on location in an unconventional formation (i.e., used to create a new
formation type crosswalk).

a. EPA specifically seeks feedback on how GHGRP subpart W data might be used in this step to
construct or verify such a crosswalk.

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Appendix A. Well-Related Activity Data



1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Well counts

2018 GHGI

Non-HF gas wells

135,552

141,052

139,823

140,834

142,127

142,245

144,501

144,082

148,078

148,112

144,545

156,621

157,696

162,506

167,595

168,855

175,567

178,970

187,366

186,667

187,098

187,153

182,776

179,300

179,305

173,544

168,151

HF gas wells

62,074

78,538

76,875

82,527

88,242

90,423

99,399

103,820

108,880

113,260

122,364

135,526

142,815

154,003

162,832

179,615

195,683

207,348

227,138

234,576

242,301

248,162

250,614

248,528

252,141

252,107

248,730

Total active gas wells

197,626

219,590

216,698

223,361

230,369

232,668

243,900

247,902

256,958

261,372

266,909

292,147

300,511

316,509

330,427

348,470

371,250

386,318

414,504

421,243

429,399

435,315

433,390

427,828

431,446

425,651

416,881

Non-HF oil wells *

469,317

467,760

454,605

446,499

432,774

423,199

418,579

419,582

401,394

381,938

382,314

379,071

375,274

372,953

372,994

374,960

379,859

380,541

391,513

387,949

389,226

393,598

401,244

404,373

405,284

398,424

373,608

HF oil wells*

84,582

88,843

86,070

87,745

87,088

84,442

86,754

87,650

84,935

82,132

84,785

86,243

86,547

88,223

91,457

94,672

98,627

97,217

112,992

113,657

123,494

135,121

151,260

165,297

184,166

191,593

188,356

Total active oil wells

553,899

556,603

540,675

534,244

519,862

507,641

505,333

507,232

486,329

464,070

467,099

465,314

461,821

461,176

464,451

469,632

478,486

477,758

504,505

501,606

512,720

528,719

552,504

569,670

589,450

590,017

561,964

Total HF wells *

146,656

167,381

162,945

170,272

175,330

174,865

186,153

191,470

193,815

195,392

207,149

221,769

229,362

242,226

254,289

274,287

294,310

304,565

340,130

348,233

365,795

383,283

401,874

413,825

436,307

443,700

437,086

Total active wells

751,525

776,193

757,373

757,605

750,231

740,309

749,233

755,134

743,287

725,442

734,008

757,461

762,332

777,685

794,878

818,102

849,736

864,076

919,009

922,849

942,119

964,034

985,894

997,498

1,020,896

1,015,668

978,845

EIA Today in Energy

Total HF wells

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

670,000

Total active wells

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

NPA

977,000

Drilling event counts

2018 GHGI

Gas wells drilled (incl. fraction
of dry)

15,096

13,066

10,887

13,047

12,232

10,465

11,498

14,473

14,507

14,564

19,863

25,350

20,041

23,582

27,180

31,969

36,536

36,255

35,824

20,266

18,837

18,837

18,837

18,837

18,837

18,837

18,837

Oil wells drilled (incl. fraction
of dry)

17,234

16,796

12,540

11,744

9,587

10,679

11,255

14,105

9,575

5,818

9,424

10,208

7,830

9,251

9,877

12,053

14,893

14,816

18,478

12,537

17,774

17,774

17,774

17,774

17,774

17,774

17,774

Total wells drilled

32,330

29,862

23,427

24,791

21,819

21,144

22,753

28,578

24,082

20,382

29,287

35,558

27,871

32,833

37,057

44,022

51,429

51,071

54,302

32,803

36,611

36,611

36,611

36,611

36,611

36,611

36,611

EIA Monthly Energy Review (basis of 2018 GHGI)

Gas (EIA)

11,246

9,793

8,163

9,839

9,375

8,082

9,027

11,498

11,639

12,027

17,051

22,072

17,342

20,722

24,186

28,590

32,838

32,719

32,246

18,088

16,696

NE

NE

NE

NE

NE

NE

Oil (EIA)

12,839

12,588

9,402

8,856

7,348

8,248

8,836

11,206

7,682

4,805

8,090

8,888

6,775

8,129

8,789

10,779

13,385

13,371

16,633

11,190

15,753

NE

NE

NE

NE

NE

NE

Dry (EIA)

8,245

7,481

5,862

6,096

5,096

4,814

4,890

5,874

4,761

3,550

4,146

4,598

3,754

3,982

4,082

4,653

5,206

4,981

5,423

3,525

4,162

NE

NE

NE

NE

NE

NE

Total wells drilled

32,330

29,862

23,427

24,791

21,819

21,144

22,753

28,578

24,082

20,382

29,287

35,558

27,871

32,833

37,057

44,022

51,429

51,071

54,302

32,803

36,611

NE

NE

NE

NE

NE

NE

Preliminary Drillinglnfo Data Analysis (described in Section 2.1)a

Gas

13,417

6,719

7,464

6,794

7,208

7,648

16,608

9,557

9,089

10,507

14,449

17,131

14,390

17,237

20,018

23,060

24,733

24,964

23,600

11,636

12,172

9,206

5,512

4,725

4,385

2,580

1,550

Oil

15,013

11,030

11,854

10,720

9,145

10,210

18,925

12,636

7,746

8,447

10,981

11,232

9,558

11,570

13,498

15,553

16,951

18,820

18,633

12,566

20,697

25,874

29,953

30,422

30,209

14,049

8,246

Dry/TIA

7,971

5,650

5,220

4,641

4,249

3,909

4,228

4,601

3,898

3,601

5,095

6,782

4,875

5,549

6,477

6,872

9,190

7,631

9,232

4,773

5,614

6,271

5,781

5,304

7,037

3,861

1,964

Gas wells drilled (incl. fraction
of dry/TIA)

17,179

8,858

9,481

8,594

9,081

9,322

18,584

11,538

11,193

12,503

17,344

21,227

17,319

20,557

23,886

27,164

30,186

29,315

28,759

13,931

14,251

10,852

6,410

5,438

5,277

3,179

1,861

Oil wells drilled (incl. fraction
of dry/TIA)

19,222

14,541

15,057

13,561

11,521

12,445

21,177

15,256

9,540

10,052

13,181

13,918

11,504

13,799

16,107

18,321

20,688

22,100

22,706

15,044

24,232

30,499

34,836

35,013

36,354

17,311

9,899

Total wells drilled

36,401

23,399

24,538

22,155

20,602

21,767

39,761

26,794

20,733

22,555

30,525

35,145

28,823

34,356

39,993

45,485

50,874

51,415

51,465

28,975

38,483

41,351

41,246

40,451

41,631

20,490

11,760

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June 2018



1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

Completion event counts























































2018 GHGI

Gas well non-HF completions

365

405

400

412

425

429

450

458

474

482

493

539

555

584

610

643

685

713

765

778

793

804

800

790

796

786

770

Gas well HF completions

3,769

3,630

2,630

3,425

3,322

3,034

4,057

5,352

4,785

4,583

6,881

8,675

7,536

8,911

10,459

12,866

14,176

14,206

15,223

8,811

8,691

9,749

7,665

7,382

7,141

5,272

3,105

Oil well non-HF completions

9,764

9,644

6,395

5,916

4,742

5,855

6,203

7,671

5,359

3,476

5,844

5,791

4,285

4,618

5,046

6,185

7,369

7,142

8,305

6,117

7,565

3,252

0

0

0

3,315

3,315

Oil well HF completions

3,075

2,944

3,007

2,940

2,606

2,393

2,633

3,535

2,323

1,329

2,246

3,097

2,490

3,511

3,743

4,594

6,016

6,229

8,328

5,073

8,188

12,501

16,335

17,332

19,154

12,438

12,438

Workover event counts

2018 GHGI

Gas well non-HF workovers

5,897

6,136

6,082

6,126

6,183

6,188

6,286

6,268

6,441

6,443

6,288

6,813

6,860

7,069

7,290

7,345

7,637

7,785

8,150

8,120

8,139

8,141

7,951

7,800

7,800

7,549

7,315

Gas well HF workovers

621

785

769

825

882

904

994

1,038

1,089

1,133

1,224

1,355

1,428

1,540

1,628

1,796

1,957

2,073

2,271

2,346

2,423

2,482

2,506

2,485

2,521

2,521

2,487

Oil well workovers

41,542

41,745

40,551

40,068

38,990

38,073

37,900

38,042

36,475

34,805

35,032

34,899

34,637

34,588

34,834

35,222

35,886

35,832

37,838

37,620

38,454

39,654

41,438

42,725

44,209

44,251

42,147

* Values not published in the 2018 GHGI, but underlie the current estimates of HF oil well completion event counts
N/A - Not applicable
NPA - Not publicly available
NE - Not estimated

a - Results of preliminary approach discussed in Section 2.1. This does not include state-level adjustments to account for lagging reporting that EPA implements for other well-related data elements that are based on Drillinglnfo data. After
adjustments that would be implemented in a final methodology, estimates in recent years (e.g., 2015 forward) will likely increase.

Page 10 of 10

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