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Barnett Shale Study Finds Methane Emissions 90% Above EPA Inventory

A new study focused on the Barnett Shale in Texas shows methane emissions from oil/natural gas operations are 90% higher than data in the baseline inventory of the U.S. Environmental Protection Agency (EPA), according to the study’s sponsor, the Environmental Defense Fund (EDF).

The study was published Monday in Proceedings of the National Academy of Sciences, authored by 20 scientists, including EDF chief scientist Steven Hamburg, and researchers at several universities. Using aerial and ground-level measurements, EDF officials said they are confident the study shows that the organization's collaborative regional and national efforts are not missing any major sources of methane.

"Globally, there is now no question that emissions are larger than what people have been estimating, but also it shows there is a huge opportunity to make substantial reductions in methane emissions," said Mark Brownstein, EDF vice president for climate and energy programs. "We just need to do a better job monitoring facilities over time, and doing leak detection and repair."

Last July University of Houston (UH) research coordinated by EDF found some Barnett Shale gas wells, compressor stations and gas processing plants leak more methane than previously estimated, but many of the problems could be addressed through easy measures (see Shale Daily, July 9).

For a number of years, and particularly the last two, the Obama administration's EPA and EDF have said methane emissions from U.S. oil and natural gas onshore operations could be economically cut significantly below projected future levels (see Daily GPIMarch 3, 2014).

The latest study is a convergence of scientific methodologies, according to Hamburg, and it shows a pattern of underestimating methane emissions in locations across the nation. "One big reason is that conventional inventories fail to accurately account for very large, unpredictable emissions from leaks, malfunctions or other problems," Hamburg said.

Brownstein, during a conference call, cited the ongoing Southern California Gas Co. underground storage well leak (see Daily GPIDec. 3) as an example of "sporadic, hard-to-predict events."

The Barnett study data showed that 30% of the production sources are responsible for 70% of the emissions, Brownstein said. "This goes right to the heart of why we and others continue to believe that there is a need for increased attention to regulations requiring ongoing leak detection and repair because the emissions we are seeing in the field are the result of sporadic, hard-to-predict events that can be quite large."

EDF's study analyzed data from 12 separate papers published earlier this year as part of an extensive coordinated effort among several research teams working in coordination to quantify oil/gas methane emissions at a regional scale.

In August, EPA said methane emissions from natural gas production had fallen about 38% since 2005, but emissions from processing increased by about 38% since that year, and rose about 11% from gas transmission and storage sources (see Daily GPIApril 16).

Hamburg stressed the importance of the methodology questions that were answered by the Barnett Shale study, resolving differences between top-down and bottom-up methods. "That means scientists, policymakers and companies can now have greater certainty about methane emission rates not only in the Barnett, but also have proven methodologies that can be used to get a clear picture of emissions elsewhere," he said.

EDF on Monday said it intends to launch a global study of methane emissions drawing on the regional and national work now completed in the United States.

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