EPA's Study of Hydraulic Fracturing and Its Potential Impact on Drinking Water Resources

Analysis of Existing Data

Information Requests

August 2011 Information Request

On August 11, 2011 EPA sent letters to nine oil and gas companies requesting their participation in EPA's hydraulic fracturing study. EPA requested data on well construction, design, and well operation practices for 350 oil and gas wells that were hydraulically fractured from 2009-2010. EPA made this request as part of its national study to examine the potential impacts of hydraulic fracturing on drinking water resources. The wells were selected using a stratified random method and reflect the diversity in both geography and size of the oil and gas operator. This account of well performance together with a literature review, assessment of data and information from states and communities, case studies, laboratory work, and computer modeling will allow EPA to do a more thorough assessment of the potential impacts of hydraulic fracturing on drinking water resources.

All nine oil and gas companies said that they planned to assist EPA. By sharing information about specific well construction design and operations, these companies will help EPA and the public better understand technologies and practices associated with hydraulic fracturing.

  • Letter sent by EPA to the nine oil and gas companies (PDF)
  • Companies that received the request:
    • Clayton Williams Energy
    • ConocoPhillips
    • EQT Production
    • Hogback Exploration
    • Laramie Energy II
    • MDS Energy
    • Noble Energy
    • Sand Ridge Operating
    • Williams Production
  • How were these wells selected?

    In response to EPA's September 2010 request to nine hydraulic fracturing service companies, we received a list of approximately 25,000 oil and gas production wells that were hydraulically fractured between 2009 and 2010 and the names of the oil and gas operator for each well.

    To identify the wells for this request, we first sorted the list of operators by those with the most wells to those with the fewest wells. We defined operators to be "large" if their combined number of wells accounted for the top 50% of wells on the list, "medium" if their combined wells accounted for the next 25% of wells on the list, or "small" if their wells were among the last 25% of wells on the list, and removed all operators with 10 wells or less.

    Then, using a map from the U.S. Energy Information Administration showing all shale gas plays, EPA classified four different areas of the nation: East, South, Rocky Mountain (including California) and Other. To choose the nine companies that received the request, EPA randomly selected one "large" operator from each from the geographic areas, for a total of four "large" operators, and then randomly, and without geographic consideration, selected two "medium" and three "small" operators.

    Once the nine companies were identified, we used a computer algorithm that balanced geographic diversity and random selection within an operator's list to select wells until we had a total of 350 wells.

September 2010 Information Request

On September 9, 2010, EPA issued information requests to nine hydraulic fracturing service providers. The data requested, which is integral to the hydraulic fracturing study, included:

  • the chemical composition of fluids used in the hydraulic fracturing process,
  • data on the impacts of the chemicals on human health and the environment,
  • standard operating procedures used at hydraulic fracturing sites, and
  • the locations of sites where fracturing has been conducted.

All nine companies provided access this crucial information that will help us carry out our Congressionally-mandated study on the potential impacts of hydraulic fracturing on drinking water resources.

Three of the nine hydraulic fracturing service companies also provided non-confidential information related to their hydraulic fracturing services. This information is available at Docket Number EPA-HQ-ORD-2010-0674.

News Releases

Communications between EPA and Hydraulic Fracturing Service Providers

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