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COMMENTS RELATING TO THE REFRACTURE FREQUENCY

Comment Number: EPA-HQ-OAR-2010-0505-4246-54

Organization: Marcellus Shale Coalition (MSC)

Commenter: Kath Z. Klaber

Comment Excerpt Text:

Issue 13. In the TSD, EPA states that “10 percent of the wells being re-fractured annually (as 

previously assumed in Subpart W’s Technical Supporting Document3). MSC understands that 

this 10% re-fracture frequency per year was originally developed based on a single paper which 

evaluated the post re-stimulation performance of five (5) wells in the Barnett shale area which 

was then incorrectly applied to unconventional wells across the country. MSC requests that EPA 

fully and completely explain the derivation of the 10% re-stimulation frequency per year, rather 

than simply referencing the technical support document for Subpart W which simply makes the 

10% assumption with no explanation or backup information. As the largest single reduction 

category in the proposed rule this explanation is necessary to add any credibility to EPA’s 

analysis. It is the contention of MSC members that the re-stimulation rate more realistically falls 

somewhere between 1 and 2 percent.

Comment Number: EPA-HQ-OAR-2010-0505-4251-24

Organization: Pioneer Natural Resources USA, Inc.

Commenter: Gretchen C. Kern

Comment Excerpt Text:

If EPA proceeds with regulating recompletions, it should reevaluate its assumption for the 

frequency of recompletions. In 2010, Pioneer refractured less than one-percent of its gas wells. 

This percentage varies significantly from EPA's ten-percent refrac figure. If EPA proceeds with 

the regulation of recompletions, it should recalculate the cost-effectiveness using updated 

estimates of emissions and VOC content, as discussed above, as well as recompletion frequency.

Comment Number: EPA-HQ-OAR-2010-0505-4266-218

Organization: American Petroleum Institute (API)

Commenter: Howard J. Feldman

Comment Excerpt Text:

15.11. Over Estimate of Number Recompletions per Year 
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In the TSD, EPA states that “10 percent of the wells being re-fractured annually (as previously 

assumed in Subpart W’s Technical Supporting Document3). From anecdotal information, API

understands that this 10% re-fracture frequency per year was originally from work underlying 

the National Inventory and was developed based on one paper which evaluated the post restimulation performance of five (5) wells in the Barnett shale area which was then extrapolated 

to the population of unconventional wells nationwide. Obviously relying on extrapolation of 

somewhat unrelated information on five (5) wells in one area and one formation to the 

nationwide population of unconventional wells is completely unsupportable. API requests that 

EPA fully and completely explain the derivation of the 10% re-stimulation frequency per year 

rather than simply referencing the technical support document for Subpart W which simply

makes the 10% assumption with no explanation or backup information. As the largest single 

reduction category in the proposed rule, this explanation is necessary to reasonably support 

EPA’s analysis. 

According to a 1996 study by the Gas Research Institute (GRI) [Footnote O: Reeves, S.R.: 

“Assessment of Technology Barriers and Potential Benefits of Restimulation R&D for Natural 

Gas Wells”, Final Report, GRI- 96/0267, July, 1996.], only 2-3% of wells are refractured. This 

study found that only 15% of the well populations are potentially high potential restimulation 

candidates which should be subjected to additional analysis. Another study done in 1999 that 

was presented in a paper at a Society of Petroleum Engineers conference [Footnote P: Reeves, 

S.R., Hill, D.G., Tiner, R.L, Bastian, P.A, Conway, M.W. and Mohaghegh, S.: “Restimulation of 

Tight Gas Sand Wells in the Rocky Mountain Region”, SPE 55627, Proceedings of the SPE 

Rocky Mountain Regional Meeting, Gillette, May 15-19, 1999.], showed that further analysis 

must be done to determine whether these 15% would actually benefit from restimulation. This 

paper presented an analysis of some 300 tight sand wells which had originally been hydraulic 

fracture stimulated, high-graded the top 15% of candidate wells for further evaluation and 

ultimately reduced the wells recommended for restimulation to five (5) of which 2 had been 

restimulated at the time the paper was written. In other words, only a small number (~2% of the 

total wells) of the top 15% candidate wells would actually be economic to restimulate anytime in 

their life. Other developing information suggests the percentage of wells refractured annually is 

less than 1%. Applying a 1% restimulation rate per year rather than a 10% would reduce the 

projected number of affected units to ~1,205 rather than 12,050 (90% reduction) and reduce the 

emissions reductions by the same magnitude.

Comment Number: EPA-HQ-OAR-2010-0505-4241-15

Organization: America?s Natural Gas Alliance (ANGA), American Exploration and 

Petroleum Council (AXPC)

Commenter: Amy Farrell

Comment Excerpt Text:

G. Recompletions

If EPA proceeds with the regulation of recompletions, before doing so it should reevaluate its 

assumption for the frequency of recompletions. A preliminary review of data collected by 
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industry suggests that the actual frequency of recompletions is significantly lower than the 10 

percent assumed by EPA. ANGA and AXPC would like to work with EPA to develop a more 

appropriate estimate. Before we can do this, however, we need to resolve a discrepancy with the 

domestic well inventory used by EPA. The data made available by EPA through the rulemaking 

docket[FN 32: EPA-HQ-OAR-2011-0512-0020.] has significantly fewer wells than EIA’s 

estimate of the number of producing gas wells in the U.S. [FN 33:Energy Information Agency, 

Number of Producing Gas Wells. September 29, 2011 Release. Available at: 

http://www.eia.gov/dnav/ng/ng_prod_wells_s1_a.htm.] EPA has indicated that it will not be able 

to address this discrepancy until after the close of the comment period. We would welcome the 

opportunity to work with EPA to resolve the discrepancy and develop a more appropriate well 

recompletion frequency estimate.