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Methodology

Free Pass for Oil and Gas: Methodology

March 26, 2009

EWG purchased from IHS, an Englewood, Colorado-based energy data company, records of oil and natural gas wells drilled in Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington and Wyoming. We plotted the wells using latitude and longitude coordinates in IHS data dated January 1, 2009. Wells were classified by year according to their spud dates, the date in which a drill bit penetrates the ground. IHS obtains its data from state governments, oil and gas companies and internal scouts. There is typically a delay of several weeks between the time a well is drilled and the time when the data is entered in IHS’ CD database. Therefore, the total number of wells drilled between 2000 and 2008 likely does not reflect some wells drilled toward the end of 2008.

The IHS data lacked information for four New Mexico counties, Chaves, Eddy, Lea and Roosevelt, all part of the Permian Basin database sold separately by IHS. EWG obtained the data for these four counties from the New Mexico Oil Conservation Division (NMOCD). According to the NMOCD, the records have complete spud dates beginning in the early 1990s. For wells drilled prior to the early 1990s, state officials added spud dates to the database only when they had another reason to research a previously drilled well. Therefore, the data from the 1980s and 1990s likely undercounts the number of wells drilled in Chaves, Eddy, Lea and Roosevelt counties.