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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 annuall y (as previously

assumed in Subpart W’s Technical Supporting Document3). MSC understands that this 10% re - fracture frequency per ye ar was originally

developed based on a single paper which evaluated the post re - stimulation perform ance of five (5) wells in the Barnett shale area which was then incorrectl y applied to unconventional wells across the country. MSC requests that EPA fully and completel y explain the derivation of the 10% re - stimulation frequency per ye ar, rather than simp ly

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 an y credibility to EPA’s anal ys is. 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 signi ficantly 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 Year2

In the TSD, EPA states that “10 percent of the w ells being re - fractured annually (as previousl y 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 underl yi ng the National Inventory

and was developed based on one paper which evaluated the post re stimulation 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 ye ar rather than simpl y 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 anal ys is. According to a 1996 study b y the Gas Research In stitute (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 onl y 15% of the well populations are potentiall y high potential restimulation candidates which should be subjected to additional analy sis. Another study done in 1999 that was pr esented in a paper at a Societ y 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 anal ys is must be done to determine whether these 15% would actually benefit from restimulation. This paper presented an anal ysis 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, onl y a small number (~2% of the total wells) of the top 15% candidate wells would actuall y be economic to restimulate an yt ime in their life. Other developing information suggests the percentage of wells refractured annually is less than 1%. Appl yi ng a 1% restimulation rate per y ear 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, befo re doing so it should reevaluate its assumption for the frequency of recompletions. A preliminary review of data collected b y3

industry suggests that the actual frequency of recompletions is significantly lower than the 10 percent assumed b y 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 - H Q - 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 re completion frequency

estimate.