Written Answers to Follow-Up Questions from the Senate Committee on the Environment and Public Works Submitted May 17, 2011

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David Neslin

Director, Colorado Oil & Gas Conservation Commission

Written Answers to Follow-Up Questions from the

Senate Committee on the Environment and Public Works

Submitted May 17, 2011

Questions from Senator Barbara Boxer:

1. During your testimony before the Committee, you stated that nearly all of the natural gas

wells drilled in Colorado involve horizontal drilling and hydraulic fracturing. In your

written testimony, you state the COGCC has investigated hundreds of allegations of

groundwater contamination from natural gas drilling operations in Colorado, but that

“[t]o date, we have found no verified instance of hydraulic fracturing harming

groundwater.” During the hearing, you indicated that your agency has found instances

where groundwater has been contaminated from a spill, leak or failure of a cement job.

Question. Do you agree that the use of hydraulic fracturing greatly increases the pressures

on a gas well, including the casing, the cementing, and the blowout preventer?

Answer. Hydraulic fracturing involves injection pressures that exceed those of the

geologic formation. In practice, however, the well casing, cementing, and blowout

preventer are all designed to manage these pressures. In Colorado, regulations adopted by

the Oil & Gas Conservation Commission (“COGCC”) further require that the well

components manage these pressures. COGCC Rule 317.a states that the “working

pressure of any [blowout preventer] shall exceed the anticipated surface pressure to

which it may be subjected.” Rule 317.d mandates that well casings be “planned and

maintained” to “prevent the migration of oil, gas or water from one (1) horizon to

another.” Rules 317.g and 317.h set forth specific cementing requirements. And Rule

317.j requires production casing to be “adequately pressure tested for conditions

anticipated to be encountered during completion and production operations.”

I would also like to clarify that to date relatively few natural gas wells drilled in Colorado

have involved horizontal drilling.

Question. Do you agree that hydraulic fracturing greatly increases the volumes of liquids

which must be properly managed?

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        DEPARTMENT OF NATURAL RESOURCES

        John W. Hickenlooper, Governor

        1120 Lincoln St. Suite 801

        Denver, CO 80203

        Phone: (303) 894-2100

        FAX: (303) 894-2109

        www.colorado.gov/cogcc