Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2017: Other Updates Considered for 2019 and Future GHGIs


April 2019
Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2017:
Other Updates Considered for 2019 and Future GHGIs
1 Background
During development of EPA's 2019 Inventory of U.S. Greenhouse Gas Emissions and Sinks (GHGI), EPA identified
several estimates that might be improved using currently available data. EPA released draft and final memoranda
discussing considerations and final revisions to two natural gas industry segments: gathering and boosting (G&B)
and liquefied natural gas (LNG) stations and terminals. In October 2018, EPA released a draft memo discussing
background and considerations for additional revisions to implement in the 2019 GHGI or later GHGIs: Inventory
of U.S. Greenhouse Gas Emissions and Sinks 1990-2017: Other Updates Under Consideration ("Other Updates
memo")1. As an outcome to finalizing the 2019 GHGI, EPA released this updated version of the Other Updates
memo to document updates implemented in the final 2019 GHGI as well as updates still under consideration.
Table 1 below documents the topics covered in this memo and identifies whether they were implemented in the
final 2019 GHGI or are still under consideration. In addition to the specific stakeholder requests in Section 5
below, EPA continues to seek stakeholder feedback on prioritizing the outstanding revisions for incorporation into
the 2020 GHGI and future GHGIs, and on other topics to consider for future GHGI updates.
Table 1. Additional Updates Considered for 2019 and Future GHGIs
Topic
2019 GHGI Status
Memo Section
Incorporating Available GHGRP Data
2
HF oil well completions and workovers
Implemented update
2.1
Flaring N20 emissions
Implemented update
2.2
Transmission pipeline blowdowns
Implemented update
2.3
Updating Well-related Activity Data
3
Well drilling
Implemented update
3.1
Well completions and workovers
Consider for future GHGIs
3.2
Definition of oil versus gas well
Consider for future GHGIs
3.3
Heavy versus light crude equipment service
Consider for future GHGIs
3.4
Identification of HF wells
Consider for future GHGIs
3.5
Anomalous leak events
Consider for future GHGIs
4
2 Incorporating Available GHGRP Data
Subpart W of the EPA's GHGRP collects annual activity and emissions data on numerous sources from onshore
natural gas and petroleum systems that meet a reporting threshold of 25,000 metric tons of C02 equivalent (mt
C02e) emissions. Facilities that meet the subpart W reporting threshold have been reporting since reporting year
(RY) 2011; however, data elements for hydraulically fractured (HF) oil well completions and workovers and
transmission pipeline blowdowns were first required to be reported in RY2016. Subpart W activity and emissions
data have been used in recent GHGIs to calculate CH4 and C02 emissions for many production, processing, and
transmission and storage sources.
GHGRP subparts W and Y (petroleum refining) include reporting of N20 from flaring. The GHGRP calculation
methodologies specify that subpart W reporters must calculate N20 emissions from flares using an EF of 0.0001 kg
N20 per million BTU, and subpart Y reporters using an EF of 0.0003 kg N20 per million BTU. N20 emissions are
also reported to GHGRP for engine exhaust and other combustion sources, combustion emissions from which are
generally included within GHGI estimates from fuel combustion, separate from natural gas and petroleum
systems.
1 https://www.epa.gov/sites/production/files/2018-ll/documents/ghgi_2018stakeholders_other.pdf
Page 1 of 17

-------
April 2019
The GHGRP data used in the analyses discussed in this memo are those reported to the EPA as of August 19, 2018,
unless otherwise documented. Appendix A documents the subpart W calculation methodologies for certain
sources discussed in this memo. Stakeholders have suggested additional or alternate uses of GHGRP data, such as
for certain sources using measurement data only. Stakeholders have also suggested modifications to the reported
GHGRP data for use in the GHGI, such as through removal of stakeholder-identified outliers. In the current GHGI,
EPA uses the publicly available GHGRP data set without modification for the GHGI, to ensure transparency and
reproducibility of GHGI estimates. Prior to public release of the GHGRP data, the EPA has a multi-step data
verification process for the data, including automatic checks during data-entry, statistical analyses on completed
reports, and staff review of the reported data. Based on the results of the verification process, the EPA follows up
with facilities to resolve identified potential issues before public release.
2,1 Incorporating GHGRP Data for HF Oil Well Completions and Workovej
GHGI Updal
As discussed above, HF oil well completions and workovers were newly required to be reported in RY2016. EPA
analyzed the subpart W data for this source to consider updates to the existing GHGI methodology. In the 2019
GHGI, EPA used subpart W data to update the estimates for this source, as described below.
2.1.1 Overview of 20 evious) GHGI Methodology
In the 2018 GHGI methodology for HF oil well completions, controlled and uncontrolled CH4 EFs were developed
using data analyzed for the 2015 NSPS OOOOa proposal. The 2018 GHGI estimated C02 emissions using C02 EFs
developed by applying a default production segment ratio of C02-to-CH4 gas content. As such, this approach did
not fully account for C02 emissions from flaring.
The 2018 GHGI activity data time series (counts of HF oil well completions, which is also referenced in calculating
non-HF oil well completions) was developed from analyzing Drillinglnfo data on well-level dates of completion or
first reported production. The 2018 GHGI methodology also included assumptions to develop activity factors (AFs)
for apportioning total counts into control categories. In 2008, Colorado and Wyoming adopted regulations that
require reduced emission completions (RECs); the 2018 GHGI assumed that 7% of completions are RECs with 95%
control efficiency, from 2008 forward.
For workovers, the 2018 GHGI methodology estimated emissions from all oil well workovers without
distinguishing HF from non-HF, using an EF developed for conventional wells and an assumption that 7.5% of all
oil wells are worked over in each year.
2.1.2 Analysis of Available Data
EPA analyzed RY2016 subpart W data for HF oil well completions and workovers to consider updating the 2018
GHGI methodology. The new subpart W data allow development of separate GHGI emissions estimates for HF
completions and workovers, in parallel control categories that exist for HF gas well events (reflecting
combinations of REC use, venting, and flaring).2
2 The GHGI methodology for HF gas well completions and workovers incorporates GHGRP data. For HF gas well completions and workovers,
EFs are developed from reporting year-specific GHGRP subpart W data (2011 forward), with year 2011 EFs applied for earlier time series
years. The EFs are developed for four control categories: non-REC/vented; non-REC/flared; REC/vented; and REC/flared. The total counts of
HF completions are developed from Drillinglnfo data for years prior to 2011, and GHGRP data are used for year 2011 forward (as the
directly reported counts are higher than Drillinglnfo-based estimates). The counts are apportioned into control categories based on year-
specific GHGRP data for 2011 forward; for years 1990-2000, it is assumed all events are non-REC, and 10% of events flare; interpolation is
used to develop AFs in intermediate years. For HF gas well workovers, it is assumed that 1% of the count of existing HF gas wells in a given
year (estimated from analyzing Drillinglnfo data) are worked over.
Page 2 of 17

-------
April 2019
Additionally, as summarized in Section 2.1.1, the 2018 GHGI HF oil well completion C02 EF was calculated by
applying an associated gas C02-to-CH4 content ratio, which did not account for C02 conversion during
hydrocarbon combustion. This methodological limitation would be obviated by using subpart W data to directly
calculate CH4 and C02 EFs, parallel to the current methodology for HF gas well events.
This section documents the development of EFs and activity data for HF oil well completions and workovers
consistent with the general methodology used in the existing GHGI for HF gas well completions and workovers.
Section 3 below details considerations for potentially improving the approach to estimating national total activity
data for all completions and workovers (e.g., Drillinglnfo query methodology, workover rate assumptions).
Table 2 below shows EFs calculated using RY2016 subpart W data for HF oil well completions and workovers for
each event type/control category, compared to 2018 GHGI EFs. Table 3 shows AFs for each event type/control
category.
Table 2. Emission Factors Calculated from Subpart W Compared to 2018 (Previous) GHGI, for Year 2016
Event Type
Control
Category
CH4 EF (mt/event)
CO2 EF (mt/event)
2018 GHGI
Subpart W
2018 GHGI
Subpart W
Non-REC
Vent
6.76
40.5
0.38
0.9
Flare
1.2
259.7
REC
Vent
0.34
1.2
0.02
0.1
Flare
1.3
281.5
Table 3. Activity Factors Calculated from Subpart W Compared to 2018 (Previous) GHGI, for Year 2016
Event Type
Control
Category
HF Completions
HF Workovers
Subpart W
2018 GHGIa
Subpart W
# of Events
% of total
# of Events
% of total
# of Events
% of total
Non-REC
Vent
109
3%
11,567
93%
12
4%
Flare
537
13%
16
6%
REC
Vent
1,448
35%
871
7%
159
57%
Flare
2,090
50%
93
33%
Total

4,184
100%
12,438
100%
280
100%
a - For years 2008 forward, the current GHGI assumes 7% of HF oil well completions are controlled via REC due to state-
specific regulations. The current GHGI does not include specific estimates for HF oil well workovers.
To develop national total activity data for HF oil well completions, EPA analyzed counts derived from the
Drillinglnfo data set compared to reported counts. For HF gas well completions, counts reported under GHGRP
exceed Drillinglnfo-based estimates, so are assumed to represent national coverage and used directly as national
total activity in the GHGI. For HF oil well completions, this is not the case; Drillinglnfo-based counts exceed
reported counts. Therefore, to develop the national emissions estimates presented in Section 2.1.4, Drillinglnfo-
based activity data are used.
Workover data are not contained within EPA's Drillinglnfo analysis data set, so an assumption of 1% annual
workover rate is applied for HF gas wells in the current GHGI. In each year of the time series, 1% of existing HF
wells (estimated from the Drillinglnfo data set) are assumed to undergo workovers. For HF gas wells, this
approach results in national total activity data that exceed HF workover counts reported under subpart W. For the
national emissions estimates presented in Section 2.1.4, EPA applies the same assumption to HF oil wells to
calculate national total workover activity. Similar to HF gas wells, this approach results in national total activity
data that exceed HF oil well workover counts reported under subpart W.
Page 3 of 17

-------
April 2019
As stated above, Section 3 details considerations for potentially improving the approach to estimating national
total activity data for all completions and workovers in the GHGI, which might include refining the Drillinglnfo
query methodology and/or further incorporating subpart W data. For example, a preliminary analysis discussed in
Section 3.2 showed that within the RY2015-2016 subpart W data for gas wells, an 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).
2.1.3	Regional Variability and Time Series Considerations
For HF oil well completions and workovers, the updates considered for the 2019 GHGI were developed to parallel
the 2018 GHGI methodology to develop estimates for HF gas well events; EFs and AFs are calculated at the
national level. EPA requested stakeholder feedback on whether a region-specific approach should be considered
for these sources.
To develop the time series AFs for HF oil well completions and workovers based generally on the 2018 GHGI
methodology for gas well events, and incorporating current control assumptions for HF oil well events, the
following assumptions were applied:
•	For years 1990-2007, all completions and workovers are non-REC, and 10% of events flare.
•	For the first year in which subpart W data are available, 2016, control fractions across the four categories
are developed directly from reported subpart W data.
•	For intermediate years, 2008-2015, control fractions are developed through linear interpolation.
This produces AFs across the time series that are generally consistent with the 2018 GHGI assumption that oil well
RECs are introduced beginning in year 2008, during which 7% of completions and workovers are REC, and 10% of
both REC and non-REC events flare.
To apply EFs across the time series in the 2019 GHGI, EPA applied year-specific EFs for GHGRP years, and EFs from
the earliest GHGRP year to all prior years, consistent with the approach for HF gas well events. For the 2019 GHGI,
this approach means that EFs calculated from RY2016 data are applied for years 1990-2016, and RY2017 data are
used to develop EFs for year 2017.
2.1.4	Updated Methodology and National Emissions in the 2019 GHGI
Stakeholder feedback generally supported incorporating GHGRP data for this source, using an approach
consistent with that currently used for HF gas well events. Stakeholders expressed interest in developing separate
EFs for completions versus workovers (in the current approach for both gas and oil well events, both types of
events are combined). EPA reviewed available data and notes that due to the approach wherein year-specific EFs
are calculated for each of four control categories, the number of data points in some categories is relatively small.
Therefore, EPA determined it was appropriate to implement the existing approach in the 2019 GHGI, wherein HF
oil well completions and workovers data are combined to calculate EFs (while activity for each event type is
separately estimated).
EPA implemented the following updates to the methodology for HF oil well completions and workovers in the
2019 GHGI, using the latest subpart W data (reported to EPA as of August 19, 2018):
•	To develop national total activity data for HF oil well completions, analyze Drillinglnfo data set.
•	To develop national total activity data for HF oil well workovers, apply the assumption used for HF gas
wells, that 1% of total national HF wells are worked over annually.
•	To develop the time series AFs (split among four control categories) assume:
o For years 1990-2007, all completions and workovers are non-REC, and 10% of events flare,
o For years in which subpart W data are available, 2016 forward, control fractions across the four
categories are developed directly from reported subpart W data,
o For intermediate years, 2008-2015, control fractions are developed through linear interpolation.
Page 4 of 17

-------
April 2019
• Apply year-specific EFs for GHGRP years (2016 forward), and EFs from the earliest GHGRP year to all prior
years, consistent with the approach for HF gas well events.
Table 4 below shows resulting national total activity data, CH4 and C02 emission factors, and CH4 and C02
emissions for select time series years.
Table 4. National EFs, Activity, and Emissions Estimates for HF Oil Well Completions and Workovers, Select
Years
Data Element
1990
2000
2005
2010
2015
2016
2017
CH4 emission factors (mt/event)
Non-REC/Vent
40.5
40.5
40.5
40.5
40.5
40.5
14.4
Non-REC/Flare
1.2
1.2
1.2
1.2
1.2
1.2
1.5
REC/Vent
1.2
1.2
1.2
1.2
1.2
1.2
0.6
REC/Flare
1.3
1.3
1.3
1.3
1.3
1.3
1.6
CO2 emission factors (mt/event)
Non-REC/Vent
0.9
0.9
0.9
0.9
0.9
0.9
1.3
Non-REC/Flare
259.7
259.7
259.7
259.7
259.7
259.7
350.2
REC/Vent
0.1
0.1
0.1
0.1
0.1
0.1
0.0
REC/Flare
281.5
281.5
281.5
281.5
281.5
281.5
307.5
HF oil well completions (#)
3,029
2,241
4,719
8,203
12,136
6,680
8,866
Non-REC/Vent (%)
90%
90%
90%
61%
12%
3%
2%
Non-REC/Flare (%)
10%
10%
10%
11%
13%
13%
13%
REC/Vent(%)
0%
0%
0%
12%
31%
35%
41%
REC/Flare (%)
0%
0%
0%
17%
44%
50%
44%
HF oil well workovers (#)
854
859
961
1,250
1,934
1,913
1,929
Non-REC/Vent (%)
90%
90%
90%
61%
14%
4%
0%
Non-REC/Flare (%)
10%
10%
10%
9%
6%
6%
4%
REC/Vent(%)
0%
0%
0%
19%
50%
57%
57%
REC/Flare (%)
0%
0%
0%
11%
30%
33%
39%
2019 GHGI CH4 emissions (kt)
142
113
208
238
87
21
15
2018 GHGI CHa emissions (kt)a
21
15
31
52
79
79
n/a
2019 GHGI CO2 emissions (kt)
104
83
152
690
2,105
1,370
1,877
2018 GHGI CO2 emissions (kt)a
1
1
2
3
4
4
n/a
a - Does not include estimate for workovers. The 2018 GHGI does not specifically estimate emissions from HF oil well workovers; the
estimate for all (non-HF and HF) oil well workovers is negligible compared to the magnitude of other estimates shown in this table (<0.1 kt
across the time series).
2.2 Incorporating GHGRP Data for Flaring N2O Emissions (2019 GHGI Update)
The 2018 GHGI did not estimate N20 emissions for natural gas and petroleum systems. However, with recent
updates that use GHGRP data to estimate CH4 and C02 flaring emissions, EPA sought stakeholder feedback on
implementing updates in the 2019 GHGI to incorporate N20 emissions for the same flaring sources. Based on
stakeholder feedback supporting the update, EPA applied the existing source-specific methodologies for using
GHGRP CH4 data to develop N20 EFs.
Table 5 presents newly calculated N20 flaring emissions by source in the 2019 GHGI.
Page 5 of 17

-------
April 2019
Table 5. National N20 Emissions Estimates (mt) for Flaring Sources in Natural Gas and Petroleum Systems,
Select Years
Emission Source
1990
2000
2005
2010
2015
2016
2017
Natural Gas & Petroleum Production
Tank Flaring
0.4
4.7
6.2
8.6
18.0
13.7
9.6
NG: Large Condensate Tanks w/Flares
0.4
0.4
0.5
0.9
1.5
1.1
0.5
NG: Small Condensate Tanks w/Flares
NO
+
0.1
0.1
0.2
0.0
0.1
Petro: Large Oil Tanks w/Flares
NO
3.6
4.9
6.5
14.0
12.5
8.4
Petro: Small Oil Tanks w/Flares
NO
0.6
0.8
1.1
2.3
+
0.6
Associated Gas
14.8
11.1
11.0
14.1
35.5
25.9
28.2
Petro: Associated Gas Flaring
14.8
11.1
11.0
14.1
35.5
25.9
28.2
NG: Flared Gas Well Completions and
Workovers
0.9
1.6
3.7
3.2
11.4
0.5
1.7
HF Completions - Non-REC with Flaring
0.8
1.4
2.5
1.7
0.4
+
0.2
HF Completions - REC with Flaring
NO
NO
0.7
1.0
7.8
0.3
0.7
Non-HF Completions - flared
+
+
+
+
0.9
+
+
HF Workovers - Non-REC with Flaring
0.1
0.2
0.4
0.5
0.1
+
0.2
HF Workovers - REC with Flaring
NO
NO
+
+
2.1
0.1
0.5
Non-HF Workovers - flared
NO
+
+
+
0.0
NO
NO
Petro: Flared Oil Well HF Completions
and Workovers
0.2
0.1
0.3
1.2
3.6
2.4
2.9
HF Completions - Non-REC with Flaring
0.1
0.1
0.2
0.4
0.7
0.4
0.6
HF Completions - REC with Flaring
NO
NO
NO
0.7
2.6
1.6
1.8
HF Workovers - Non-REC with Flaring
+
+
+
+
0.1
0.1
+
HF Workovers - REC with Flaring
NO
NO
NO
0.1
0.3
0.3
0.3
Miscellaneous Production Flaring
NO
2.1
3.3
4.8
11.7
6.1
6.7
Natural Gas Systems
NO
1.3
2.1
3.1
5.3
2.2
1.8
Petroleum Systems
NO
0.8
1.2
1.8
6.3
4.0
4.9
Well Testing
1.2
1.4
1.8
2.1
2.2
0.1
0.1
Natural Gas Systems
0.8
1.1
1.4
1.7
1.7
NO
+
Petroleum Systems
0.4
0.4
0.4
0.4
0.5
0.1
0.1
Natural Gas Processing
Flare Stacks
NO
7.2
11.2
16.1
19.4
12.8
10.2
Transmission and Storage
Transmission Station Flare Stacks
0.1
0.1
0.1
0.1
0.1
0.0
0.1
Storage Station Flare Stacks
+
+
+
+
+
0.1
+
LNG Storage Station Flare Stacks
0.7
0.8
0.8
0.8
0.8
0.8
0.8
LNG Import/Export Station Flare Stacks
+
+
0.1
0.2
0.2
0.4
0.6
Petroleum Refining
Flare Stacks
30.7
34.6
34.8
35.6
39.1
38.8
36.4
NO - Not occurring
+ Does not exceed 0.05 mt
2.3 Incorporating GHGRP Data for Transmission Pipeline Blowdowns (2019 GHGI
Update)
As discussed above, transmission pipeline blowdowns were newly required reporting elements in GHGRP RY2016.
EPA analyzed the subpart W data for this source to consider updates to the existing GHGI methodology. In the
2019 GHGI, EPA used subpart W data to update the estimates for this source, as described below.
Page 6 of 17

-------
April 2019
2.3.1	2018 (Previous) GHGI Methodology
The 2018 GHGI showed emissions from transmission pipeline blowdowns as "pipeline venting for routine
maintenance and upsets." Emissions were calculated using a "potential" CH4 EF from GRI/EPA 1996 and annual
transmission pipeline miles from the U.S. Department of Transportation's Pipeline and Hazardous Materials Safety
Administration (PHMSA). Reported voluntary reductions (Gas STAR data) were taken into account to calculate
"net" CH4 emissions across the time series. C02 emissions were calculated from the CH4 EF and a default
downstream gas profile of 93.4% CH4 and 1.0% C02.
2.3.2	Analysis of Available Data
A subpart W transmission pipeline facility must report blowdown emissions from natural gas transmission
pipelines (as defined at 40 CFR 98.238) that it owns and operates. EPA calculated transmission pipeline blowdown
EFs from the subpart W data by summing the reported emissions and dividing by the reported transmission
pipeline miles. Table 6 shows the calculated subpart W EFs for RY2016 and RY2017 compared to the 2018 GHGI
EFs. Note, the subpart W RY2016 data reflect approximately 50% of the total transmission pipeline mileage
estimated in the 2018 GHGI for year 2016 (147,000 of 300,000 miles).
Table 6. Preliminary Emission Factors (mt/pipeline mile) Calculated from Subpart W Compared to 2018
(Previous) GHGI, for Years 2016 and 2017
Data Source
CH4
C02
2018 GHGI
0.6
0.01
Subpart W RY2016
0.8
0.02
Subpart W RY2017
0.6
0.02
EPA also compared subpart W RY2016 reporters of this source to a PHMSA data set that includes transmission
pipeline mileage by company, state, and type (i.e., interstate or intrastate). Based on a preliminary analysis,
approximately 71% of the national total interstate transmission pipeline miles and 11% of intrastate transmission
pipeline miles were reported to subpart W in RY2016. EPA may further consider this distinction and calculate
unique EFs for interstate and intrastate pipelines in future GHGIs, which would be paired with activity data
specific to each type.
2.3.3 Time Series Considerations
EPA sought stakeholder feedback as to whether the EFs used in the 2018 GHGI (based on the 1996 GRI/EPA study)
or the newly calculated subpart W-based EFs best represent emissions over the time series. EPA considered
various approaches for developing EFs to apply over the time series, including: (1) applying the 1996 GRI/EPA EFs
to early years of the time series (1990-1992) and linearly interpolating to the year 2016 subpart W EFs, (2)
applying the 2018 GHGI EFs for 1990-2015 and year-specific subpart W EFs for 2016 forward, and (3) applying
subpart W-based EFs (average EFs or year-specific EFs) to all years of the time series. Based on currently available
data (see Table 6), there is not an obvious difference in EFs calculated from historic data compared to more recent
subpart W data.
Stakeholder feedback suggested that companies are making concerted efforts to reduce blowdown emissions,
which may lead to a downward trend over time that would be reflected in the future subpart W data. Stakeholder
feedback also suggested that the reported subpart W data for this source might not be representative of national
emissions in recent years (e.g., facilities meeting the reporting threshold might generally have larger-diameter
pipelines leading to higher emissions per mile). As discussed above, EPA considered and sought additional
stakeholder feedback regarding whether sufficient data are available to develop separate EFs and accompanying
activity data for interstate versus intrastate pipelines as a potential means to recognize differences in the
reporting versus nonreporting population. Establishing subcategories might offer improved representativeness,
but is dependent on identifying an accurate method for categorizing subpart W data (interstate versus instrastate
Page 7 of 17

-------
April 2019
designation is not directly reported but might be inferred through analysis of external data sets such as published
by PHMSA) and the statistical characterization of reported data points in each category (e.g., whether the data set
size and variance support establishing separate EFs).
2.3.4 Updated Methodology and National Emissions Estimates
Table 7 below shows national total emissions for select time series years based on the approach that EPA
implemented in the 2019 GHGI based on stakeholder feedback:
•	Use existing GHGI activity (pipeline miles) for all years.
•	Use existing EFs for years 1990 through 2015.
•	Use newly calculated year-specific EFs from subpart W data starting in year 2016.
•	Do not take into account historical voluntary reductions (Gas STAR data).
Table 7. National Emissions Estimates for Transmission Pipeline Blowdowns, Select Years
Data Element
1990
2000
2005
2010
2015
2016
2017
2018 GHGI
# Pipeline miles
291,925
298,957
300,468
304,803
300,376
300,645
n/a
Cm EF (mt/mile)
0.61
0.61
0.61
0.61
0.61
0.61
n/a
CO2 EF (mt/mile)
0.018
0.018
0.018
0.018
0.018
0.018
n/a
Total CH4 emissions (kt)
178
182
183
186
184
183
n/a
Total CO2 emissions (kt)
5
5
5
5
5
5
n/a
2019 GHGI
CH4 EF (mt/mile)
0.61
0.61
0.61
0.61
0.61
0.83
0.61
CO2 EF (mt/mile)
0.02
0.02
0.02
0.02
0.02
0.02
0.02
Total CH4 emissions (kt)
178
182
183
186
184
250
184
Total CO2 emissions (kt)
5
5
5
5
5
7
5
n/a - Not applicable
3 Updating Well-related Activity Data
Appendix B 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 considered for and implemented in the 2019 GHGI, as discussed
below. Note that several of the existing and updated GHGI methodologies (e.g., developing counts of active wells)
rely on EPA's analysis of Drillinglnfo's subscription-based digital Dl Desktop raw data feed3; this data set is referred
to throughout this memo as "Drillinglnfo data."
3.1 Well Drilling (2019 GHGI Update)
The U.S. Department of Energy's Energy Information Administration (DOE/EIA) no longer maintains the Monthly
Energy Review well drilling activity data set that was used to develop well drilling activity inputs in the 2018 and
earlier GHGIs (most recent estimates cover through 2010), so the 2019 GHGI required a new data source for the
entire time series, or at least from 2011 forward.
EPA did not identify another data set published by EIA that provides complete well drilling activity over the GHGI
time series. EPA developed a methodology for querying the Drillinglnfo data set to develop estimates of wells
drilled and presented preliminary results to solicit stakeholder feedback. The Drillinglnfo-based approach is:
• 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
3 https://info.drillinginfo.com/products/di-plus/
Page 8 of 17

-------
April 2019
• 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.
Stakeholder feedback on the Drillinglnfo-based approach noted that preliminary estimates appeared reasonable
for incorporation into the GHGI.
For a Drillinglnfo-based methodology, EPA also sought 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. EPA has not received
stakeholder feedback on this topic nor quantified this potential population, but it is expected to be minimal. Third,
how to account for time series coverage issues. For states without recently released data, EPA developed 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 be fully estimated by the current approach (i.e., GOR in year N+l is not available); EPA
developed a surrogate approach of using the previous year's estimate.
In the 2019 GHGI, EPA implemented the Drillinglnfo-based approach to develop well drilling activity across the
time series, for both Natural Gas and Petroleum Systems. Appendix B shows well drilling counts across the time
series in the 2018 GHGI and updated estimates that appear in the 2019 GHGI based on the Drillinglnfo data
analysis approach described above.
* •• •"*, •• : V npletions and Workove.- • Ider for Future GHGIs)
As described above, the current methodology for well completion and workover event counts involves a mix of
Drillinglnfo data analyses, GHGRP data analyses, and historical assumptions.
EPA has conducted a preliminary analysis to assess how completion counts and workover rates reflected in the
subpart W data compare to current GHGI assumptions. Regarding workover rates, 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 therefore analyzed the number of completion and workover events and the overall gas well workover rate
using historical RY2015 and RY2016 data (reported as of August 5, 2017), as summarized in Table 8.
In response to stakeholder feedback, EPA developed the following considerations based on this analysis and the
estimation that approximately 70% of gas wells in the U.S. are covered by subpart W reporting:
• Non-HF gas well completion counts might be over-estimated in recent years of the GHGI.
• Non-HF gas well workover counts might be under-estimated in recent years of the GHGI.
• HF gas well workover counts might be over-estimated in recent years of the GHGI.
Page 9 of 17

-------
April 2019
Table 8. Comparison of Gas Well Event Activity Data and Calculated Workover Rate
Activity Data Element
Current GHGI
GHGRP As-reported
Basis
2015
2016
2015
2016
# Non-HF gas well completions
Scaled from 400 events/year in 1992
786
770
108
88
# Non-HF gas well workovers
4.35% of active non-HF gas wells
7,549
7,315
18,031
14,957
# HF gas well workovers
1% of active HF gas wells
2,521
2,487
263
103
Overall gas well workover rate
4.35% of active non-HF gas wells;
1% of active HF gas wells
6%a
5%a
a - Calculated using number of reported gas well workover events (with and without HF) divided by the number of producing wells
at the end of the calendar year (reported under 40 CFR 98.236(aa), found in the "sub-basin characterization" table).
Appendix B shows all categories of completion and workover counts across the entire time series in the 2018
GHGI. EPA did not make updates for this data element in the 2019 GHGI and continues to seek stakeholder
feedback on improving the current methodology in future GHGIs; see Section 5 for specific stakeholder feedback
requests.
3.3 Definition of Oil versus Gas Well (Consider for Future GHGIs)
The current methodology estimates the count of active gas wells in a given year as all wells in the Drillinglnfo data
set with a 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 reviewed 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. Per subpart W, oil wells are defined as producing from an oil formation, not defined by a
specific GOR threshold.
Table 9 below summarizes reported GOR data based on EPA's review of historic 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.
Table 9. 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%]
Page 10 of 17

-------
April 2019
In response to recent stakeholder feedback, EPA calculated oil and gas well counts across the time series by two
different GOR delineation thresholds (100 mcf/bbl and 6 mcf/bbl). The results of this sensitivity analysis are
shown in Figure 1.
700,000
100 mcf/bbl: Active - Gas
100 mcf/bbl: Active - Oil
—	— — 6 mcf/bbl: Active - Gas
—	— — 6 mcf/bbl: Active - Oil
600,000
534,302
	J
500,000
462,218
400,000
300,000
200,000
100,000
0
o*Ho<-i(Nro,!tfLnu3
cncncncrtc^cncr>cna^CTioooooooooo*-iT-i<-iT-iT-iT-i<-i
cncnaiaiaicnaicncncnooooooooooooooooo
t-H *H t-H *—I *H CM fN fN fN fN fN 
-------
April 2019
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 10 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 10. Subpart W Equipment Counts3
Data Set
Count of
Separators
Count of Wellheads
Separators/
Wellhead
Number of Data
Points (Facilities)
Notes/Methodology
2015
2016
2015
2016
2015
2016
2015
2016
All onshore
oil prod
76,690
86,890
213,380
221,326
0.36
0.39
319
315
Counts from records classified
in Table R.4 as "Crude oil
production equipment"15
Heavy
crude-only
facilities
1,818
345
40,894
40,063
0.04
0.01
14
14
Counts from records in Table
R.4 - from facilities that
produce only heavy crude (all
sub-basins are oil with API
gravity <20 in Table AA.l.ii)
Light crude-
only
facilities
22,153
23,048
54,098
51,428
0.41
0.45
102
103
Counts from records in Table
R.4 - from facilities that
produce only light crude (all
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)).
EPA also reviewed 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
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. This approach does 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); additionally, inherent in this
approach is an assumption that heavy and light crude wellheads have the same average production rates. EPA
recently reviewed EIA state-level production and API gravity data and estimated that 4-5% of crude produced in
the lower 48 states in recent years is heavy crude. Due to the assumptions and limitations of this analysis (i.e.,
using production split between heavy and light as surrogate for wellhead split), EPA is focusing further efforts
toward how subpart W data, such as that summarized in Table 10, might be used to update the GHGI for recent
time series years.
EPA did not make updates for this data element in the 2019 GHGI and continues to seek 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 5 for specific stakeholder feedback
requests on this topic.
Page 12 of 17
-------
April 2019
3,5 Identification of HF Wells (Consider for Future GHGIs)
Appendix B shows 2018 GHGI estimates of HF gas and oil well counts. There are limited public data estimating
national total counts comparable to the GHGI; Appendix B shows year 2016 estimates from ElA's Today in Energy
website.
EPA did not make updates for this data element in the 2019 GHGI and continues to seek 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; see Section 5. 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).
4	Anomalous Leak Events (Consider for Future GHGIs)
In recent GHGIs, EPA incorporated an emissions estimate for the Aliso Canyon gas leak during years 2015 and
2016 in the storage well category. EPA used the California Air Resources Board (CARB) published estimate of the
methane release from the leak.5
EPA did not make updates for this type of source in the 2019 GHGI and continues to seek stakeholder feedback on
existing data sources or suggested methodologies for identifying similar events across natural gas and petroleum
systems, with emissions beyond what is likely accounted for in GHGI EFs; see Section 5.
5	Requests for Stakeholder Feedback
The following questions may be considered for the stakeholder process for the 2020 or future GHGIs.
Well Completions and Workovers (Section 3.2)
1.	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 3.3)
2.	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 3.4)
3.	Based on historical 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
5 https://www.epa.gov/sites/production/files/2017-04/documents/2017_aliso_canyon_estimate.pdf
Page 13 of 17
-------
April 2019
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.
4.	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 10 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 10?
Identification of HF Wells (Section 3.5)
5.	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.
6.	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.
Anomalous Leak Events (Section 4)
7.	EPA seeks stakeholder feedback on existing data sources or suggested methodologies for identifying
similar events across natural gas and petroleum systems, with emissions beyond what is likely accounted
for in GHGI EFs.
8.	EPA seeks information from stakeholders on any anomalous leak events that have occurred during the
GHGI time series or more recent years that should be included in future GHGIs, in addition to the Aliso
Canyon leak in years 2015 and 2016.
Page 14 of 17
-------
April 2019
Appendix A. GHGRP Measurement Methodologies
Emission Source
Measurement and/or Calculation Type
# Sources
Location & Representativeness
EF Calculation Method
Oil Well HF Completions and
Workovers
Emissions calculated for each event, based
on (1) measured actual flowback gas
volumes from the well or (2) calculated
flowback gas volume based on well
parameters (e.g., pressure differentials,
temps).
If flared, then flare control efficiency is
applied.
Emissions data (for 2016) are
available for 4,059 completions and
330 workover events at HF oil wells
Facilities in the U.S. that exceed
25,000 mt C02e reporting
threshold.
For this memo, the EPA used
reported data to calculate,
event/control category specific
(e.g., REC, flare), average EFs
Flare Stacks
CH4 and C02 emissions calculated using: (1)
gas volume sent to the flare, (2)
combustion efficiency (from manufacturer
or assume 98%), fraction of feed gas sent to
an un-lit flare, and (3) gas composition for
C02, CH4, and hydrocarbon constituents.
N20 emissions calculated using amount of
fuel combusted, fuel heating value, and
prescribed EF of 1.0 x 10-4 kg N20/mmBtu
Varies by industry segment
Facilities in the U.S. that exceed
25,000 mt C02e reporting
threshold.
For this memo, to estimate
emissions for each source, EPA
calculated a ratio of the GHGRP
reported N20 emissions to C02
emissions and then multiplied the
N20-to-C02 ratio by the 2018 GHGI
C02 emissions
Transmission Blowdown Vent
Stack
Emissions calculated using:
•	Blowdown volumes, number of
blowdowns, and the ideal gas low
modified for compressibility; or
•	Flow meter to measure emissions for all
equipment associated with a blowdown
event.
Blowdown volumes <50 scf are exempt.
Emissions data (for 2016) are
available from 9,093 blowdowns
(which occurred over 147,187
miles).
Facilities in the U.S. that exceed
25,000 mt C02e reporting
threshold.
For this memo, EPA calculated EFs
as a straight average of all available
data.
Page 15 of 17
-------
April 2019
Appendix B. 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
2017
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
n/a
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
n/a
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
n/a
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
n/a
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
n/a
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
n/a
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
n/a
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
n/a
EIA Today in Energy (May 5, 2016)
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
n/a
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
n/a
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
n/a
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
n/a
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
n/a
2019 GHGI (update described in Section 3.1)
Gas
13,903
7,194
7,945
7,298
7,685
8,130
8,920
9,261
8,871
10,330
14,346
16,970
14,216
17,094
19,924
22,711
24,640
24,735
23,536
11,622
11,939
9,205
5,343
4,671
4,484
2,567
1,709
1,709
Oil
15,390
11,434
12,047
11,105
9,558
10,598
15,228
12,477
7,528
7,922
10,755
11,125
9,542
11,429
13,418
15,502
16,961
19,004
18,688
12,520
20,627
25,961
30,023
30,368
30,342
14,071
8,706
8,706
Dry/TIA
8,431
6,062
5,618
5,017
4,630
4,299
4,678
4,935
4,078
3,795
5,492
7,256
5,384
5,839
7,056
7,571
9,735
8,582
10,529
5,369
6,226
6,899
6,496
6,313
7,955
4,306
2,091
2,091
Gas wells drilled (incl. fraction
of dry/TIA)
17,805
9,780
10,463
9,379
10,011
10,155
10,823
11,709
11,238
12,804
17,764
21,767
17,720
20,848
24,417
27,568
30,902
29,725
29,556
14,235
14,388
11,337
6,585
5,681
5,871
3,585
2,264
2,264
Oil wells drilled (incl. fraction
of dry/TIA)
19,919
14,910
15,147
14,041
11,862
12,872
18,003
14,964
9,239
9,243
12,829
13,584
11,422
13,514
15,981
18,216
20,434
22,596
23,197
15,276
24,404
30,728
35,277
35,671
36,910
17,359
10,242
10,242
Total wells drilled
37,724
24,690
25,610
23,420
21,873
23,027
28,826
26,673
20,477
22,047
30,593
35,351
29,142
34,362
40,398
45,784
51,336
52,321
52,753
29,511
38,792
42,065
41,862
41,352
42,781
20,944
12,506
12,506
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
n/a
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
n/a
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
n/a
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
n/a
Page 16 of 17
-------
April 2019

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
2017
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
n/a
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
n/a
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
n/a
* Values not published in the GHGI, but underlie the current estimates of HF oil well completion event counts
N/A - Not applicable
NPA - Not publicly available
Page 17 of 17
-------