Page 1 of 7 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

OFFICE OF AIR AND RADIATION

Petroleum and Natural Gas Systems (Subpart W) of the Greenhouse Gas Reporting Rule Docket: EPA-HQ-OAR-2009-0923

Title: Equipment-Level Population Emissi on Factors for Onshore Production

Summary: This memo discusses the developm ent of major equipment-level population component counts and emission factors for the onshore petroleum and natural gas production industry segment, as outlined in the Subpart W – Petroleum and Natural Gas Systems - Final Rule, 40 CFR Part 98.Page 2 of 7 Equipment-Level Population Emission Factors for Onshore Production

This memo discusses the deve lopment of major equipment-le vel population component counts and emission factors for the onshore petroleum a nd natural gas production industry segment, as outlined in the Subpart W – Petroleum and Natu ral Gas Systems - Final Rule, 40 CFR Part 98. This is a response to comments requesting EPA to significantly reduce reporting burden. The alternative proposed in today’s final rule doe s reduce burden significantly while sustaining an appropriate quality of data to inform future policy.

Background

C omments received on the April 2010 proposed rule identified the burden to count individual equipment leak components (flanges, connectors, valves, etc) at well-sites would be a major burden, given wells are geographi cally dispersed over many square miles in a single basin. Commenters also proposed the alternative approach whereby each owner-operator could perform a limited count of a selected numbe r of wellheads, and create their own emission factors for component count per major piece of equipment.

Alternative Methodologies

EPA considered the commenters’ proposal, and decided that a method wherein each company selects their count, could not be described in a rule in terms th at would be consistent across different reporters or be validated by EPA. First, EPA evaluated the component count data in the EPA/GRI 5 study titled Methane Emissions from the Natural Gas Industry , June 1996, to determine how well it was documented, how using it for the rule would reduce burden and how it might affect emissions estimation quality.

EPA also reviewed API #4615 1 , titled Emission Factors for Oil and Gas Production Operations

, 2009 API Compendium 2 , the U.S. GHG Inventory 3 , EPA/Radian 4 , and EPA/GRI 5 for average equipment component counts and emissions fact ors. The 2009 API Compendium provides the necessary data to estimate these elements; how ever, in onshore petroleum and natural gas production cases, it references the EPA/GRI st udy. The U.S. GHG Inventory uses the EPA/GRI study for its base year (1992), then extrapolates the equipment activities for future years using EIA well counts and production ra tes. API #4615 provides component emissions factors for components in light crude oil ( ≥ 20  ̊ API) and heavy crude oil (< 20  ̊ API) service, which are referenced in the 2009 API Compendium; howev er, it does not provide average component counts per common oil production equipment (taken from U.S. GHG Inventory, but originally an API publication). The 2009 API Compendium a nd U.S. GHG Inventory both point to the 1999 EPA/Radian study for the component c ounts per oil production equipment.

1 API. Publication #4615, Emission Factors for Oil and Gas Production Operations . January 1995.

2 API. Compendium of Greenhouse Gas Emissions Methodologies for the Oil and Natural Gas Industry . August 2009.
3 EPA. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 – 2008. U.S. EPA #430-R-10-006. April 2010.

4 EPA/Radian. Methane Emissions from the Petroleum Industry . 1999.

5 EPA/GRI. Methane Emissions from the Natural Gas Industry . June 1996.Page 3 of 7 EPA concluded that major equipment component counts with population em ission factors satisfy the objective of the reporting ru le by providing sufficient activity data on actual count of major equipment at onshore production we llheads, and with that, emissions information sufficient to inform policies while minimizing the cost burden to reporters.

EPA determined that most sources use EPA/ GRI as the basis for natural gas production equipment component leak emission factors, and so me variation of the information gathered in API#4615 for crude oil production equipment compone nt leak emission factors. Therefore the source for gas service emission factors was EPA/ GRI, and the source for crude oil service emission factors was API#4615.

Basis of Development of Population Emissi on Factors and Population Counts Tables

As outlined above, today’s final rule allows onshore production reporters to count the major equipment by type (e.g., dehydrators, compressors , heaters, wellheads, separators) and apply default average component counts based on the primary equipment count. This will provide EPA with valuable activity data for equipment counts and will result in significantly less burden to reporters than counting each component (valve , flange, open-ended line, connector, pressure relief valve, etc.) while ensuring a necessary quality of data to in form future policy.

Onshore reporters may as an al ternative count components individually fo r a facility and apply the appropriate population emission factors; however , if they choose to do so, it must be done for the entire onshore petroleum and natural ga s production facility. For counting components individually, it was determined that tubing system s that are equal to or less than 0.5 inch in diameter do not need to be reported.

The EPA/GRI study notes that regional differe nces exist in onshore production operations between those of the Eastern U.S. (comprising th e Atlantic and the Great Lakes region) and the Western U.S. (comprising the re st of the country, excluding th e Atlantic and the Great Lakes region). Equipment differences exis t by way of differences in the se rvice, number, type, age, and leak detection and repair characteristics in th e equipment typically loca ted at production sites that are distinct in the two ge ographical regions. Further, pr oduced gas characteristics differ between the two regions. EPA/GR I notes that natural gas produ ced from wells in the Eastern U.S. region has a very low hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) content, making it sweeter than produced natural gas from wells in the Western U.S. region. Further, natural gas produced from wells in the Easter U.S. region have relatively low moisture content, and low production rates per well compared to gas produced inthe other regions of the U.S. Thus, few inline heaters and glycol dehydrators exist fo r gas production in the Eastern region. Thus, EPA/GRI performed separate emissions measur ement programs for these geographical regions and developed separate component counts for major equipment types and emission factors characteristic to each of thes e two distinct geographical regi ons. Therefore, population emission factors and major equipment component counts have been segregated into region-specific values for the Eastern and the Western U.S. geographical areas, and are cited in Tables W – 1A thru W1D of the Final Rule.Page 4 of 7 EPA/GRI defines the Eastern U.S. as “Atlantic a nd Great Lakes region” and the Western U.S. as the “rest of the country, excluding the Atlantic and Great Lakes region.” For the purposes of the GHG Reporting Rule, EPA will define the regions as shown in Table 1 . The average component counts for major natural gas production equipment that were identified, for both the Eastern and the Western U.S. regions, are listed in Table 2A and Table 2B.

In the EPA/GRI study, component counts for ons hore petroleum and natural gas production in the Eastern U.S. region were collected based on the Eastern U.S. production fugitives study, with the assumption that the component counts for the in-line heaters and glycol dehydrators in the Eastern region are identical to those derived for the Western U. S. Component emission factors for onshore petroleum and natural gas production in the Eastern U.S. were obtained from a measurement program using a combination of sc reening to identify leaking components and the GRI Hi-Flow device to quantify emission rates fr om leaking components, wherein a total of 192 individual well-sites were screened using EPA Method 21 at 12 eastern gas production facilities. The EPA/GRI data reports that component emission factors we re adjusted for an average methane content in the produced gas of 78.8% by volume.

For the Western U.S. region, component emissi on factors for onshore gas production were based on an API/GRO measurement program that made use of the EPA Method 21 protocol, where screening and bagging data were co llected from 83 gas wells at 4 production sites in the Pacific, Mountain, Central and Gulf regi ons. Component emissi on factors were adjusted for an average methane content in the produced gas of 78.8% by volume.

For light crude and heavy crude services, Subpa rt W final rule uses the population emissions factors from API Publication No. 4615. The AP I report developed average emission factors using screening data covering over 200,000 compone nts from 24 facilities including light crude production, heavy crude producti on, gas production, gas proce ssing and offshore production. Portable devices were used to screen compone nts and mass emission rates were recorded using “bagged” methods. The data compiled and the anal ysis conducted represen ts the best existing measurement study and analysis av ailable publicly for which the emission factors are used in subpart W in the onshore production sector.

EPA used the reported component leak emissions factors from these stud ies and converted them to hourly whole gas leak rates using average meth ane contents. The default whole gas emission factors for the onshore petroleum and natural gas production sector as reported in Subpart W are presented in Table 3

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Concluding Remarks

EPA evaluated industry comments regarding the burden and alternative methods to estimate equipment leaks. EPA evaluated an alternat ive methodology documented in publicly available sources which will result in significant re ductions to subpart W compliance burden while sustaining an appropriate quality of data to inform future policy.Page 5 of 7 Table 1. Table of Eastern and Western U.S. Designation

Eastern U.S. Western U.S. Connecticut Alabama Delaware Alaska Florida Arizona Georgia Arkansas Illinois California Indiana Colorado Kentucky Hawaii Maine Idaho Maryland Iowa Massachusetts Kansas Michigan Louisiana New Hampshire Minnesota New Jersey Mississippi New York Missouri North Carolina Montana Ohio Nebraska Pennsylvania Nevada Rhode Island New Mexico South Carolina North Dakota Tennessee Oklahoma Vermont Oregon Virginia South Dakota West Virginia Texas Wisconsin Utah Washington Wyoming

Table 2A. Subpart W–Default Average Component Counts For Major Natural Gas Production Equipment

**Major Equipment Valves**  **Connectors Open-ended**  **Lines Pressure**  **relief valves** 
**Eastern U.S.** Wellheads 8 38 0.5 0 Separators 1 6 0 0 meters/piping 12 45 0 0 Compressors 12 57 0 0 In-line heaters 14 65 2 1 Dehydrators 24 90 2 2
**Western U.S.** Wellheads 11 36 1 0 Separators 34 106 6 2 meters/piping 14 51 1 1 Compressors 73 179 3 4 In-line heaters 14 65 2 1 Dehydrators 24 90 2 2Page 6 of 7 Table 2B. Subpart W–Default Average Compon ent Counts For Major Crude Oil Production Equipment

**Equipment Valves**  **Flanges Connecto** 

**rs O**  **pen**   ** ended** **Lines Other** 

**Eastern U.S. Wellhea**  **d 5**  **1 0**  **4 0**  **1 Separator 6**  **1 2**  **1 0**  **0 0**  **Heater-treater 8 1**  **2 2**  **0 0**  **0 Header 5**  **1 0**  **4 0**  **0**
**Western U.S. Wellhea**  **d 5**  **1 0**  **4 0**  **1 Separator 6**  **1 2**  **1 0**  **0 0**  **Heater-treater 8 1**  **2 2**  **0 0**  **0 Header 5**  **1 0**  **4 0**  **0**

Table 3 Subpart W–Default Whole Gas Emissi on Factors For Onshore Production

Onshore petroleum and natural gas production Emission Factor (scf/hour/component)

Eastern U.S. Population Emission Factors - All Components, Gas Service 1
Valve 0.027
Connector 0.004 Open-ended Line 0.062 Pressure Relief Valve 0.041 Low Continuous Bleed Pneumatic Device Vents 2 1.80 High Continuous Bleed Pneumatic Device Vents 2 48.1
Intermittent Bleed Pneumatic Device Vents 2 17.4 Pneumatic Pumps 3 10.5 Population Emission Factors - All Components, Light Crude Service 4
Valve 0.04 Flange 0.002
Connector 0.005 Open-ended Line 0.04 Pump 0.01 Other 5 0.23 Population Emission Factors - All Components, Heavy Crude Service 6
Valve 0.0004 Flange 0.0007 Connector (other) 0.0002 Open-ended Line 0.004 Other 5 0.002 Western U.S. Population Emission Factors - All Components, Gas Service 1
Valve 0.123Page 7 of 7 Connector 0.017 Open-ended Line 0.032 Pressure Relief Valve 0.196 Low Continuous Bleed Pneumatic Device Vents 2 1.80 High Continuous Bleed Pneumatic Device Vents 2 48.1 Intermittent Bleed Pneumatic Device Vents 2 17.4
Pneumatic Pumps 3 10.5 Population Emission Factors - All Components, Light Crude Service 4
Valve 0.04 Flange 0.002 Connector (other) 0.005 Open-ended Line 0.04 Pump 0.01 Other 5 0.23 Population Emission Factors - All Components, Heavy Crude Service 6
Valve 0.0004 Flange 0.0007 Connector (other) 0.0002 Open-ended Line 0.004 Other 5 0.002

1 For multi-phase flow that includes gas, use the gas service emissions factors

2 Emission Factor is in units of "scf/hour/device"

3 Emission Factor is in units of "scf/hour/pump"

4 Hydrocarbon liquids greater than or equal to 20  ̊ API are considered "light crude"

5 ”Others” category includes instruments, loading arms, pressure relief valves, stuffing boxes, compressor seals, dump lever arms, and vents.

6 Hydrocarbon liquids less than 20  ̊ API are considered "heavy crude"