The level of methane emissions from the development and production of natural gas in the United States are down from previous studies.
A recent field study conducted by the University of Texas at Austin and sponsored by the Environmental Defense Fund and natural gas producers has found that methane emissions now represent .38 percent of production, 10 percent lower than the findings of a September 2013 study conducted by the same research team.
Researchers found that the majority of hydraulically fractured well completions sampled in the study had equipment in place that reduces methane emissions by 99 percent.
“Because of this equipment, methane emissions from well completions are 97 percent lower than calendar year 2011 national emission estimates, which were released by the U.S. Environmental Protection Agency (EPA) in April 2013,” UT said in a statement.
While the level of methane emissions are lower from hydraulically fractured well completions, the study found that emissions from certain types of pneumatic devices are 30 percent to several times higher than current EPA estimates for this equipment. Together, emissions from pneumatics and equipment leaks account for about 40 percent of estimated national emissions of methane from gas production, according to a press statement from UT.
The total methane emissions from gas production, from all sources measured by researchers, were comparable to the most recent EPA estimates. EPA reported in late September that methane emissions from hydraulic fracturing have declined by 73 percent since 2011, the American Petroleum Institute (API) noted in a statement.
David Allen, professor of chemical engineering at UT’s Cockrell School of Engineering and principal investigator for the study, said that the way in which wells are drilled and brought into production has been evolving.
“The overall goal was to measure methane emissions during production at a large number of recently developed sites, and to assess the national implication for methane emissions. The team performed the first-ever direct measurements of methane emissions from some of these sources.”
Two-thirds of the well completion flowbacks measured in the study either captured or combusted emissions, resulting in emission measurements 99 percent lower than what would have occurred without capture and combustion. The remaining one-third of completion flowbacks vented methane, but these were low emitting wells, so in total, emissions from completion flowbacks were 97 percent lower than current EPA estimates.
The study’s findings indicate that, when producers use practices to capture or control emissions, such as green completions, methane can be dramatically reduced, said Mark Brownstein, associate vice president and chief counsel of the U.S. Climate and Energy Program for the Environmental Defense Fund.
However, the study also demonstrated that certain methane emissions are larger than previously thought, showing that many further opportunities exist to reduce emissions, Brownstein noted.
“Study after study shows that industry-lead efforts to reduce emissions through investments in new technologies and equipment are paying off,” said Howard Feldman, director of regulatory and scientific affairs for API, in a Dec. 9 press statement.
Feldman noted that the oil and gas industry will continue to make substantial progress to reduce emissions voluntarily and in compliance with EPA regulations that will be fully implemented next month.
A spokesperson for America’s Natural Gas Alliance (ANGA) said the group was still reviewing the study, it provides further support for the findings of other credible researchers – that greater use of natural gas reduces greenhouse gas emissions.
“Natural gas producers have reduced methane emissions by 25 percent since 1990, even as production has grown 37 percent,” said Erica Bowman, vice president of research and policy analysis for ANGA, in a Dec. 9 press statement. “We remain committed to working with stakeholders to ensure that, as an industry, we continue the substantial progress we have made through ongoing innovation.”
The year-long study was conducted by researchers from UT’s Cockrell School of Engineering and environmental testing firms URS and Aerodyne Research, who took measurements at 190 U.S. gas production sites with 489 wells, 27 well completion flowbacks, nine well unloadings, and four well workovers. The types of sources measured account for two-thirds of methane emissions that occur in gas production, as estimated in the most recent national greenhouse gas inventory.
Nine energy firms provided researchers access to these sites, which were located in the Gulf Coast, Mid-Continent, Rocky Mountain and Appalachian regions. These companies include Anadarko Petroleum Corporation; BP Group Plc; Chevron Corp.; EnCana Oil & Gas (USA) Inc.; Pioneer Natural Resources Company; SWEPI LP (Shell), Southwestern Energy; Talisman Energy USA; and ExxonMobil subsidiary XTO Energy.
The study is part of a larger research effort led by the Environmental Defense Fund to measure methane emissions through the gas supply chain. Results for the studies addressing other parts of the supply chain will be reported over the next 12 to 18 months.