The US Environmental Protection Agency has overestimated methane emissions from unconventional natural gas well operations, including well completions and hydraulic fracturing, in its latest greenhouse gases emissions inventory, two trade associations said.

The American Petroleum Institute and America's Natural Gas Alliance surveyed members about methane emissions from wells and commissioned URS Corp. and the Levon Group to analyze survey results and write a 48-page report, released in June (OGJ, June 11, 2012, p. 23).

The ANGA-API report estimated methane emissions from gas wells at 4.42 million tonnes compared with the EPA's estimate of 8.79 million tonnes (see table).

EPA responded, saying it would consider the API-ANGA report. "We are always open to reviewing relevant information that may help inform the science around important standards," EPA said.

"Methane emissions have become a very important and controversial issue given their potency as a greenhouse gas," said Mary Barcella, IHS CERA director of North American natural gas. "Unfortunately, such emissions are not being measured. Estimates are being used that are not supported by data, do not reflect current industry practice, and would be unreliable to use as a base for decision-making." [Emphasis and underscoring added.]

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