GRADY COUNTY —
Fracked natural gas wells leak much less methane — a potent climate change-driving greenhouse gas — at certain points during the production process than previous studies and the Environmental Protection Agency have estimated, according to a University of Texas study released Monday.
Methane is one of the chief components of natural gas locked up in underground shale formations — the target of a natural gas drilling boom stretching from Pennsylvania to the Rockies and beyond. Energy companies tap the formations using a method called hydraulic fracturing, or “ fracking,” a well completion process that requires large volumes of water, sand and chemicals to be injected into the shale at high pressure, cracking the rock and allowing the trapped gas to flow into the well and to the surface.
The natural gas wells and the fracking process are hardly leak-free, however. The EPA estimated in 2011 that natural gas drilling accounts for at least about 1,200 gigagrams — about 2.6 billion pounds — of methane emissions each year from well completions, equipment leaks and pneumatic controllers. The EPA estimated that “flowback,” one of the final stages in the well completion process during which fracking fluids and other materials flow out of the well, emits an average of 81 megagrams of methane per operation.
The study, led by University of Texas chemical engineering professor David T. Allen and sponsored by the Environmental Defense Fund and nine oil and gas companies, found that methane emissions from the natural gas production sites were overall about the same as EPA estimates with some notable exceptions. But if emissions control technology is used, emissions can be drastically reduced during some parts of the gas production process. The study was published Monday in the Proceedings of the National Academy of Sciences.
The study found that emissions control equipment companies installed at the natural gas production sites they selected reduced emissions during the well completion process by 97 percent. The team found that emissions from fracking flowback operations alone ranged from between 0.01 megagrams to 17 megagrams, averaging only 1.7 megagrams per flowback operation at the sites included in the study — much less than the average 81 megagrams the EPA had estimated.