June 12, 2014

U.S. Environmental Protection Agency

RE: State of Colorado Comments

White Papers on Methane and VOC Emissions in the Oil and Natural Gas Sector

On April 15, 2014, the United States Environmental Protection Agency (“EPA”) released 

five technical white papers on oil and gas sector emissions for external review. The 

technical papers focused on compressors, hydraulically fractured oil well completions 

and associated gas during ongoing production, leaks, liquids unloading processes, and 

pneumatic devices. EPA stated that EPA will use the white papers and input from the 

peer reviewers and the public to determine how best to pursue additional emission 

reductions from these sources. The State of Colorado Department of Public Health and 

Environment, Air Pollution Control Division (“Division”) appreciates the opportunity to 

submit the following comments on several of EPA’s oil and natural gas sector white 

papers.

Colorado recently promulgated significant air quality regulations concerning the oil and 

gas sector in Colorado relating to several of the white paper topics.1 Colorado now 

requires rod packing replacement on reciprocating compressors located at natural gas 

compressor stations, and a minimum 95% control of emissions from wet seal fluid 

degassing systems on wet seal centrifugal compressors. Colorado established a leak 

detection and repair (“LDAR”) program for well production facilities and natural gas 

compressor stations. Colorado requires operators to either route gas produced from any 

newly constructed, hydraulically fractured, or recompleted oil and gas well to a gas 

gathering line or control hydrocarbon emissions by 95%. Colorado requires operators to 

use best management practices to minimize hydrocarbon emissions and the need for well 

venting associated with liquids unloading. Colorado requires low-bleed pneumatic 

controllers and no-bleed pneumatic controllers where electric grid power is utilized. 

Colorado also requires the replacement or retrofit of high-bleed pneumatic controllers 

such that VOC emissions are equal to or less than a low-bleed pneumatic controller.

The Division estimates that the newly adopted strategies will reduce volatile organic 

compound (“VOC”) emissions in Colorado by 93,500 tons per year and methane/ethane 

1 Colorado Air Quality Control Commission, Oil and Gas Rulemaking Hearing 

http://www.colorado.gov/cs/Satellite/CDPHE-AQCC/CBON/1251647985820

Submitted electronically June 12, 2014, via

oilandgas.whitepapers@epa.gov

June 12, 2014 Page 1 of 5

 
emissions by 64,000 tons per year, while promoting greater beneficial use of natural gas. 

Colorado’s new regulations go beyond current EPA regulations and are cost-effective. 

The regulations were developed after an extensive stakeholder process, and were 

supported by significant members of the oil and gas industry, environmental community, 

and local government.

Oil and Natural Gas Sector Hydraulically Fractured Oil Well Completions and 

Associated Gas during Ongoing Production

This paper presents EPA’s understanding of emissions and available emissions mitigation 

techniques for hydraulically fractured oil well completions and associated gas during 

ongoing production. 

In defining oil well completions, EPA states that the backflow velocity during oil well 

refracturing will typically be too high for the normal wellhead equipment. The Division 

recommends that EPA further clarify that the production equipment, while possibly 

already onsite during refracturing events as EPA noted, is typically not suitable for 

flowback.

In discussing emissions estimates for associated gas from hydraulically fractured oil 

wells, EPA states that one method could be to use the gas-to-oil ratio (“GOR”) of the 

well. In further considering this option, the Division requests EPA clarify or address how 

EPA would develop this emission factor, including how gas composition would affect the 

development of the emission factor. Specifically, the Division requests that EPA clarify 

how it anticipates that GOR will influence emission factor development.

Concerning the costs of completion combustion devices, EPA states that annual costs are 

assumed to be equal to capital costs because combustion devices are purchased for that 

site’s REC events. The Division notes that owners can move combustion devices to 

different sites when the device is no longer necessary at the currently installed site, so 

costs could potentially be lower for companies with multiple well REC events. 

EPA requested comments on various approaches to estimating completion emissions 

from hydraulically fractured oil wells in Charge Question Four. The Division has found 

that the initial NSPS OOOO reporting shows flowback periods ranging from three to 

thirty days in Colorado. The Division believes EPA should use an averaging period 

consistent with the actual period of flowback (i.e. weekly or monthly), which would more 

conservatively estimate emissions from operations. Further, the Division has also 

observed through review of and communications with operators regarding NSPS OOOO 

well completions reporting that some formations may have an initial period during 

flowback with no emissions or several days where the well does not have flowback due 

to the formation characteristics. The Division believes EPA should also consider this 

potential delay when determining the average used to calculate emissions from such 

operations.

June 12, 2014 Page 2 of 5
EPA requested comments on other methodologies or data sources appropriate for 

estimating hydraulically fractured oil well completion emissions in Charge Question 

Five. The Division suggests that EPA review the Colorado Oil and Gas Conservation 

Commission’s online database of well completions and production for information 

related to estimating hydraulically fractured oil well completion emissions.2

EPA requested comment on the emission reductions that RECs and completion 

combustion devices achieve when used during hydraulically fractured oil well 

completions in Charge Question Nine. Colorado requires that combustion devices 

controlling emissions from newly constructed, hydraulically fractured, or recompleted oil 

and gas wells achieve an average hydrocarbon control efficiency of 95% and have a 

design destruction efficiency of at least 98%. While these combustion devices may have 

an average control efficiency greater than 95%, the Division established the 95% control 

efficiency to account for periods of downtime and/or combustion device performance 

issues. The Division requests EPA also consider the need to account for combustion 

device downtime and performance.

Oil and Natural Gas Sector Leaks

This paper presents EPA’s understanding of emissions and available emissions mitigation 

techniques for leaks from equipment related to oil and gas production, processing, 

transmission, and storage. For purposes of this paper, EPA did not consider emissions 

from equipment intended to vent as part of normal operations, such as natural gas-driven 

pneumatic controllers, as leaks.

As mentioned above, Colorado recently promulgated significant air quality regulations 

establishing a LDAR program for new and existing well production facilities and natural 

gas compressor stations.3 The inspection frequencies under Colorado’s LDAR program 

are based on the facility’s VOC emissions and begin on January 1, 2015, for natural gas 

compressor stations, October 15, 2014, for new well production facilities, and between 

January 1, 2015, and January 1, 2016, for existing well production facilities. Colorado’s 

LDAR program requires both audio, visual, and olfactory (“AVO”) inspections and 

approved instrument monitoring method (“AIMM”) inspections, which includes infrared 

cameras, EPA Method 21, and other Division approved methods.

Concerning the white paper summary of leaks emissions data and emissions estimates, 

the Division currently uses the emission factors in EPA’s 1995 Protocol for Equipment 

Leak Emission Estimate. However, the Division believes that all air regulators would 

benefit from additional studies that would help calculate site specific emission factors,

rather than just estimate emissions from the total oil and gas sector, which would better 

quantify emissions from leaks. 

Concerning the white paper summary of emissions mitigation techniques and leak repair 

programs, the Division suggests that EPA compile the complete costs of a LDAR 

2 Colorado Oil and Gas Conservation Commission, www.cogcc.state.co.us

3 Colorado Air Quality Control Commission Regulation 7, Section XVII.F.

June 12, 2014 Page 3 of 5

 
program when evaluating EPA’s range of options related to leak detection and repair. For 

example, the Division considered the costs of the equipment as well as the time spent 

surveying for leaks in order to develop a cost-effective LDAR program.

Oil and Natural Gas Sector Liquids Unloading Processes

This paper presents EPA’s understanding of emissions and available emissions mitigation 

techniques for natural gas production liquids unloading events, which occur when the 

accumulation of liquids in the well impede or halt gas production and the removal of the 

fluids is required to maintain production. 

Colorado recently promulgated regulations requiring the use of best management 

practices to prevent a well from initially loading up and to address a well once it has been 

loaded up with hydrocarbon liquids.4 The Division believes that many of the practices 

identified in the liquids unloading white paper have utility in Colorado. The Division also 

appreciates that the unique characteristics of any given well may mean that there is not a 

“one size fits all” approach. Thus, the Division is encouraged by the potential innovation 

that can be driven from Colorado’s less-prescriptive rules at this time. To that end, the 

Division met with Colorado oil and gas operators to assist the Division in developing 

guidelines for implementing Colorado’s new well unloading regulations. Through this 

meeting, the Division gained valuable insight into the reasons for and variations of well 

unloading events. 

Concerning EPA’s request in Charge Question Three for comments on the type of wells 

with the highest tendency to develop liquids unloading, vertical wells are the primary 

well type prone to liquid loading problems, although liquid loading problems are also

anticipated as horizontal wells age. Concerning EPA’s request in Charge Question Six for 

comments on the ability of plunger lift systems to perform liquids unloading without air 

emissions, plunger lifts must vent when they do not complete a cycle as anticipated by 

the operator, which resets the plunger lift and allows cycling and production to continue. 

Finally, concerning EPA’s request in Charge Question Nine for comments on the pros 

and cons of a smart automation system as part of a plunger lift system, automated plunger 

lift systems are widely used in the field and cycle multiple times a day depending on the 

software programming. If a cycle does not complete within a specified amount of time, 

the operator assumes the plunger has encountered a problem and will vent the well to 

reset the plunger lift. If the plunger lift again does not cycle as anticipated, the operator 

may elect to shut-in the well.

Oil and Natural Gas Sector Pneumatic Devices

This paper presents EPA’s understanding of emissions and available emissions mitigation 

techniques for natural gas-driven pneumatic controllers and natural gas-drive pneumatic 

pumps. 

4 Colorado Air Quality Control Commission Regulation 7, Section XVII.H.

June 12, 2014 Page 4 of 5

 
In defining pneumatic controllers and pumps, EPA includes devices driven by gases other 

than natural gas, which EPA states do not emit methane or VOCs. EPA further defines 

non-natural gas-driven pneumatic controllers to include power examples of solar, electric, 

and instrument air. The Division requests that EPA clarify what, if any besides 

instrument air, other gases EPA intends to include in “driven by gases other than natural 

gas” to avoid reader assumptions that other, unidentified gases may drive pneumatic 

controllers and pumps.

Other Comments

Additionally, the Division suggests EPA also consider reviewing the emissions and 

mitigation techniques for pipeline cleanout and inspection activities (i.e. pigging).

The Division believes it is very important that state and federal regulations work together 

and do not create duplicative or contradictory requirements. To that end, Colorado 

believes that the States, EPA, the Bureau of Land Management (“BLM”), and Federal 

Land Managers must work together to create complementary regulatory programs that 

address oil and gas emissions in a cost-effective manner. The Division notes that BLM is 

currently investigating issues similar to those under consideration by EPA.5 The Division 

encourages the federal agencies to work together to craft programs that recognize state 

expertise and rules, and avoid unduly burdensome, confusing, or redundant requirements

at the federal level.

Thank you for the opportunity to submit these comments on the White Papers on 

Methane and VOC Emissions in the Oil and Natural Gas Sector.

Sincerely,

William C. Allison V

Director, Air Pollution Control Division

Colorado Department of Public Health and Environment

cc: Martha Rudolph, CDPHE

Mike Silverstein, AQCC

5 BLM Forums on Venting & Flaring from Oil and Gas Operations on Public and Indian Trust Lands, 

http://www.blm.gov/wo/st/en/prog/energy/public_events_on_oil.html

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