hf-report20121214

Study of the Potential Impacts of Hydraulic Fracturing
on Drinking Water Resources: Progress Report December 2012
much of this information in an organized file, which cumulatively represents the history of the well.
The EPA refers to this file as a “well file.” Some of the information in a well file may be required by
law to be reported to state oil and gas agencies, and some of the information may be considered CBI
by the operator.
For this project, the EPA is scrutinizing actual well files from hydraulic fracturing operations in
different geographic areas that are operated by companies of various sizes. These wells include
vertical, horizontal, and deviated wells that produce oil, gas, or both from differing geological
environments. This review is providing information that can be used to identify practices that may
impact drinking water resources.
3.4.3. Research Approach
While a portion of the data needed for this project is reported to state oil and gas agencies, the
complete dataset is available only in the well files compiled by oil and gas operators. 30 Further,
different states have different reporting requirements. As a result, the EPA selected 350 well
identifiers believed to represent oil and gas production wells hydraulically fractured by the nine
hydraulic fracturing service companies and requested the corresponding well files from operators
associated with those wells. 31 This section describes the process used by the EPA to select well files
for review, the information requested, and the planned analyses.
Well File Selection. The EPA used a list of hydraulically fractured oil and gas wells provided to the
agency by the nine hydraulic fracturing service companies (referred to hereafter as the “service
company well list”) to select 350 specific well identifiers associated with nine oil and gas
operators. 32 The service company well list obtained by the EPA contains 24,925 well identifiers
associated with wells that were reported to have been hydraulically fractured between September
2009 and October 2010 (Figure 10) and identifies 1,146 oil and gas operators. This compiled list
includes, for each well, a well identifier, the operator’s name, and the well’s state and county
location.
Counties containing the 24,925 well identifiers were grouped into four geographic regions
according to a May 9, 2011, map of current and prospective shale gas plays within the lower 48
states (US EIA, 2011c). 33 If any portion of a county was within one of the shale gas plays defined on
the map, the entire county was assigned to that shale play and the corresponding geographic
region. The four regions—East, South, West, and Other—are shown in Figure 11 with the
corresponding number of wells in each region. Counties outside the shale gas plays were grouped
30 The EPA analyzed several state oil and gas agency websites and estimated that it would find less than 15% of the
necessary data from websites to answer the research questions.
31 Oil and gas production wells are generally assigned API numbers by state oil and gas agencies, a unique 10-digit
number. Wells may also be commonly identified by a well name that is designated by the operator. The EPA considers
both of these to be well identifiers.
32 The EPA used the service company well list because it is unaware of the existence of a single list showing all oil and gas
production wells in the United States, their operators, and whether each well has been hydraulically fractured.
33 Wells within a designated shale play on the map are not guaranteed to be producing from that shale; they could be
producing from rock formations within the same stratigraphic column.
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