Attachment E

Hydraulically Fractured Oil Wells

Karen Olson

Southwestern Energy
Peer-review of “Oil and Natural Gas Sector Hydraulically Fractured Oil Well 

Completions and Associated Gas during Ongoing Production”, April 2014,

U.S. EPA Office of Air Quality Planning and Standards (OAQPS)

By Karen Olson, Director, Southwestern Energy (SWN)

The Report for Oil and Natural Gas Sector Hydraulically Fractured Oil Well Completions and Associated 

Gas during Ongoing Production Report (“White Paper”) is a compendium of prior measurements and 

analysis of methane emissions and control technologies relating to the initial flowback of hydraulically 

fractured oil wells. The stated purpose of the white paper is to provide a “summary of the EPA’s 

understanding of emissions from hydraulically fractured oil well completions and associated gas during 

ongoing production, the mitigation techniques available to reduce these emissions, the efficacy of these 

techniques and prevalence of these techniques in the field.” In general, the summary developed in the 

white paper is an accurate reflection of current data. In addition to the sources that EPA refers to in the 

document, there are other technical documents that we recommend EPA consult to improve its 

understanding of the emissions profile and techniques.

Key Comments

• This paper is a compilation of emission studies that are based on uncontrolled i.e. venting of 

associated natural gas for a time period ranging from 3-7 days depending on the assumed length

of time for the completion. Many states do not allow for uncontrolled emissions. The EPA 

white paper does not include a review of state regulations that regulate flowback emissions and 

associatd gas emissions from oil wells. I would suggest a review of state regulations be a part of 

this white paper. The potential (uncontrolled) and actual (controlled) emissions can be 

estimated after appropriate consideration of the current state regulatory requirements, 

operating practices, efficiency of the Reduced Emissions Completions (green completions) and

flaring (which was mentioned on average of 95% efficiency). For example Colorado State 

Regulations related to flowbacks Rule 805 b. (3) applies to both oil and gas wells.

• Both completion and recompletions are assumed to have the same assumptions but, a typical 

recompletion is when a well is completed to a new horizon and occurs on a well that already has 

production equipment in place. On the other hand, refracturing which is usually defined as a 

workover and is a restimulation of an existing horizon. Both recompletions and refracturing 

operations occur where the well site has existing production equipment and flow lines. Hence, I 

would recommend staying focused on new well completions and maybe expand this to clearly 

discuss oil wells with associated gas and gas-condensate wells.

• The Fort Berthold Indian Reservation (FBIR) dataset discussed in the White Paper seemed to be 

discounted because it was primarily from the Bakken and Three Forks formation which limits it 

to a regional dataset. Also, the data having a high variability in oil rates and a product 

composition containing a high amount of lighter end VOC components seems to be 

considerations in discounting the FBIR data set. However, this study could be relevant for
unconventional oil plays which typically do have a high variability of oil rates and typically 

produce lighter ends due to the extreme tightness of the pore throats for the hydrocarbons to 

flow through.

• The white paper states “The national level estimates of uncontrolled methane emissions from 

hydraulically fractured oil well completions range from 44,306 tons per year (ERG/ECR) to 

247,000 tons per year (EDF/Stratus analysis)”. I recommend that the EPA also give a range of 

controlled methane emissions from hydraulically fractured oil well completions.

• The same analysis can be done for the controlled VOC emissions from hydraulically fractured oil 

well completions.

• This paper states that it cannot determine the number of oil wells that are controlled using REC 

or flaring, SWN would suggest this can be estimated by the number of wells completed in each 

state based on each state’s regulations regarding associated gas.

• The discussion with respect to the economical feasibility of gas capture technologies of oil wells 

should be expanded to show basic economics depending on the oil rate, GOR, gas price and 

investment cost. The figure below is one example based on oil rate and gas-oil ratio (GOR).

• Reference to gas technologies that are being investigated for use in completions and for control 

of associated gas emissions should also include a discussion of the emerging technology of CNG 

in a box which allows for the storage of natural gas on a wellsite location and is portable. A New 

York Times article dated December 17, 2013 by Clifford Krauss “Applying Creativity to a 

Byproduct of Oil Drilling” discusses the work GE in conjunction with Statoil is using their “C.N.G. 

in a box” to compress and store natural gas (once the NGL’s are stripped).

0

500

1000

1500

2000

2500

3000

3500

0 200 400 600 800 1000 1200 1400

GOR (SCF/BO)

BOPD

Breakeven Oil Rate

$6 MCF Case

$5 MCF Case

$4 MCF Case
Note: Below are reference rules and regulations from Colorado and Texas

Colorado Rules and Regulations

http://cogcc.state.co.us/

Workover Remedial work to the equipment within a well, the well 

pipework, or relating to attempts to increase the rate of 

flow. 

Fracturing A method of breaking down a formation by pumping fluid 

at very high pressures. The objective is to increase 

production rates from a reservoir

 
800 Series AESTHETIC AND NOISE CONTROL REGULATIONS

Rule 805 b. (3)

Green completion practices shall include, but not be limited to, the following emission reduction 

measures: 

i. The operator shall employ sand traps, surge vessels, separators, and tanks as soon as practicable 

during flowback and cleanout operations to safely maximize resource recovery and minimize releases to 

the environment. 

ii. Well effluent during flowback and cleanout operations prior to encountering hydrocarbon gas of salable 

quality or significant volumes of condensate may be directed to tanks or pits (where permitted) such that 

oil or condensate volumes shall not be allowed to accumulate in excess of twenty (20) barrels and must 

be removed within twenty-four (24) hours. The gaseous phase of non-flammable effluent may be directed 

to a flare pit or vented from tanks for safety purposes until flammable gas is encountered. 

iii. Well effluent containing more than ten (10) barrels per day of condensate or within two (2) hours after 

first encountering hydrocarbon gas of salable quality shall be directed to a combination of sand traps, 

separators, surge vessels, and tanks or other equipment as needed to ensure safe separation of sand, 

hydrocarbon liquids, water, and gas and to ensure salable products are efficiently recovered for sale or 

conserved and that non-salable products are disposed of in a safe and environmentally responsible 

manner. 

iv. If it is safe and technically feasible, closed-top tanks shall utilize backpressure systems that exert a 

minimum of four (4) ounces of backpressure and a maximum that does not exceed the pressure rating of 

the tank to facilitate gathering and combustion of tank vapors. Vent/backpressure values, the combustor, 

lines to the combustor, and knock-outs shall be sized and maintained so as to safely accommodate any 

surges the system may encounter. 

v. All salable quality gas shall be directed to the sales line as soon as practicable or shut in and 

conserved. Temporary flaring or venting shall be permitted as a safety measure during upset conditions 

and in accordance with all other applicable laws, rules, and regulations. 

C. An operator may request a variance from the Director if it believes that using green completion 

practices is infeasible due to well or field conditions, or would endanger the safety of wellsite personnel or 

the public. 

D. In instances where green completion practices are not technically feasible, operators shall employ Best 

Management Practices (BMPs) to reduce emissions. Such BMPs shall consider safety and shall include measures or 

actions to minimize the time period during which gases are emitted directly to the atmosphere, and monitoring 

and recording the volume and time period of such emissions.

900 Series Exploration and Production Waste Management

912. VENTING OR FLARING NATURAL GAS 

a. The unnecessary or excessive venting or flaring of natural gas produced from a well is prohibited. 

b. Except for gas flared or vented during an upset condition, well maintenance, well stimulation flowback, purging 

operations, or a productivity test, gas from a well shall be flared or vented only after notice has been given and 

approval obtained from the Director on a Sundry Notice, Form 4, stating the estimated volume and content of the 

gas. The notice shall indicate whether the gas contains more than one (1) ppm of hydrogen sulfide. If necessary to 

protect the public health, safety or welfare, the Director may require the flaring of gas.
Texas

Texas Administrative Code Title 16 Part 1 Chapter 3 Rule 3.32 Gas Well Gas and 

Casinghead Gas Shall Be Utilized for Legal Purposes

Texas Railroad Commission

• Fugitive emissions--Releases of gas from lease production, gathering, 

compression, or gas plant equipment components, including emissions from 

valve stems, pressure relief valves, flanges and connections, gas-operated 

valves, compressor and pump seals, pumping well stuffing boxes, casing-tocasing bradenheads subject to the provisions of §3.17 of this title (relating to 

Pressure on Bradenhead), pits, and sumps, that cannot reasonably be captured 

and sold or routed to a vent or flare.

(1) Releases of gas that are not readily measured by devices routinely used in the 

operation of oil wells, gas wells, gas gathering systems, or gas plants, such as 

meters, are not required by the commission to be reported or charged against lease 

allowable production and are not subject to the remaining requirements of this 

section. Releases of gas exempt from the requirements of this section under this 

paragraph include, but are not limited to, the following:

 (A) tank vapors from crude oil storage tanks, gas well condensate storage tanks, 

or salt water storage tanks, including makeup gas for gas blanket maintenance; 

 (B) fugitive emissions of gas; 

 (C) amine treater, glycol dehydrator flash tank and/or reboiler emissions; 

 (D) blowdown gas from flow lines, gathering lines, meter runs, pressurized 

vessels, compressors, or other gas handling equipment for construction, 

maintenance or repair; 

 (E) gas purged from compressor cylinders or other gas handling equipment for 

startup; 

 (F) gas released at a wellsite during drilling operations and prior to the completion 

date of the well, including gas produced during air or gas drilling operations or gas 

which must be separated from drilling fluids using a mud-gas separator, or muddegasser; or 

 (G) gas released at a wellsite during initial completion, recompletion in another 

field, or workover operations in the same field, including but not limited to 

perforating, stimulating, deepening, cleanout, well maintenance or repair operations. 
 (2) Notwithstanding the foregoing, the commission or the commission's delegate 

may require the flaring of releases of gas not readily measured by devices routinely 

used in the operation of oil wells, gas wells, gas gathering systems, or gas plants, 

such as meters, if the commission or the commission's delegate determines that 

flaring is required for safety reasons.

(e) Gas Releases to be Burned in a Flare. 

Except as otherwise provided in subsections (d), (f)(1)(B) and (C), (g)(2), or an 

exception granted under subsection (h) of this section, all gas releases of greater 

than 24 hours duration authorized under the provisions of this section shall be 

burned in a flare if the gas can be burned safely. All gas releases of 24 hours' 

duration or less authorized under the provisions of this section may be vented to the 

air if flaring is not required for safety reasons or by other regulation and the gas can 

be safely vented. 

Gas releases authorized under this section must be managed in accordance with the 

provisions of §3.36 of this title (relating to Oil, Gas, or Geothermal Resource 

Operation in Hydrogen Sulfide Areas) when applicable. 

An exception to the requirements of this subsection may be granted under 

subsection (h) by the commission or the commission's delegate to allow the venting 

of gas to the air for releases of greater than 24 hours' duration if the operator 

presents information that shows the gas cannot be both safely and continuously 

burned in a flare, and the gas can be safely vented.

 (4) Notwithstanding the provisions of paragraph (1) of this subsection or an 

exception granted under subsection (h), the commission or the commission's 

delegate may require that the gas be flared if flaring is required for safety reasons.

RULE §3.49 Gas-Oil Ratio

Any oil well producing with a gas-oil ratio in excess of 2,000 cubic feet of gas per 

barrel of oil produced shall be allowed to produce daily only that volume of gas 

obtained by multiplying its maximum daily oil allowable, as determined by the 

allocation formula applicable to the well, by 2,000. The gas volume thus obtained 

shall be known as the daily gas limit of the well. The daily oil allowable of the well 

shall then be determined by dividing its daily gas limit, obtained as provided in this 

section, by its producing gas-oil ratio in cubic feet per barrel of oil produced. 

(b) Any gas well producing from the same reservoir in which oil wells are completed 

and producing shall be allowed to produce daily only that amount of gas which is the 

volumetric equivalent in reservoir displacement of the gas and oil produced from the 

oil well in the reservoir that withdraws the maximum amount of gas in the production 

of its daily oil allowable. 
 (1) The following formula shall be used in the determination of the allowable of a 

gas well producing with a gas-oil ratio of 100,000 or more.

Attached Graphic

 (2) The following formula shall be used in the determination of the allowable of a 

gas well producing with a gas-oil ratio of less than 100,000 under the provisions of 

the rule stated. 

Attached Graphic

 (3) The allowable for an associated gas well as determined by this subsection shall 

be limited to the lesser of: 

 (A) the gas well allowable as calculated by paragraph (1) or (2) of this subsection; 

 (B) the well's capability as determined by §3.31(e) of this title (relating to Gas 

Reservoirs and Gas Well Allowable) (Statewide Rule 31); or 

 (C) the highest monthly production during those months averaged to a daily 

amount for wells that reported production during any of the three most recently 

reported production months. 

(c) The necessary reservoir data shall be obtained from the file of the most recent 

MER hearing or shall be estimated by the commission unless more recent 

information is submitted by the operators. 

(d) If the gas produced from an oil reservoir is returned to the same reservoir from 

which it was produced, only the volume of gas not returned to the reservoir shall be 

considered in applying the rule stated. 

(e) Associated gas wells. 

 (1) Subsection (b) of this section will not be applicable to associated gas wells in 

reservoirs for which unlimited net gas-oil ratio authority has been granted for oil 

wells, where such net gas is defined as total gas produced less gas diverted to legal 

uses; however, this subsection does not apply to reservoirs where net gas is defined 

as total gas produced less gas returned to the reservoir from which it was produced, 

or where special field rules have been adopted for associated gas wells, or where a 

total gas volume limitation is placed upon the oil well producing under a net ratio, 

except that each associated gas well in such a reservoir shall be entitled to an 

additional gas voidage not to exceed the limitation placed upon the net ratio 

authority granted and the facts are shown on the current oil proration schedule for 

the field. 
 (2) Allowables for associated gas wells producing from reservoirs that are subject 

to an unlimited net gas-oil ratio authority will be dropped from the associated gas 

well schedule, effective that date such an unlimited net gas-oil ratio is authorized for 

any oil well in such reservoir. 

(f) All gas-oil ratios determined by test or allocation shall be reported on the oil well 

status report form in accordance with instructions thereon and the provisions of 

§3.53(a) of this title (relating to Annual Well Tests and Well Status Reports 

Required). 

(g) Allowables. 

 (1) No well shall have its allowable curtailed below the allowable fixed by the 

applicable field rules and the general statewide market demand order, unless such 

well is incapable of producing this allowable on a calendar day basis. 

 (2) Any well that has a gas-oil ratio in excess of the prescribed ratio for the field in 

which it is located will have its schedule daily allowable penalized due to such ratio.

Hydraulic fracturing treatment--A completion process involving treatment of a well by 

the application of hydraulic fracturing fluid under pressure for the express purpose of 

initiating or propagating fractures in a target geologic formation to enhance 

production of oil and/or natural gas. The term does not include acid treatment, 

perforation, or other non-fracture treatment completion activities.