Recently there has been good news about fugitive methane emissions from natural gas systems: emission rates are going down–in 2013 the Environmental Protection Agency (EPA) reported that U.S. emissions decreased by 1.6 percent from 2010 to 2011.
Also, in 2013 the EPA revised its previous estimates of methane emissions from natural gas systems to reflect that certain emissions-reducing technologies, specifically a process known as green completions, are far more widely used than previously understood. The use of green completions is expected to rapidly rise as industry works to improve its image and green completions become mandatory starting in 2015.
Perhaps, most important–a long-awaited study by the University of Texas has been released. The report in the Proceedings of the National Academy of Science details measured methane emissions at 190 US onshore natural gas sites (150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers), and reported that methane emissions from oil and gas production were 0.42% of gross gas production. These numbers are very close to the most recent EPA estimates.
One area where more study is needed is gas well unloading–the process in which the well’s separator is bypassed in order to increase gas flow to purge the well of accumulated liquids that slow production. This study sampled few well unloadings, and the sampling showed great variation in the frequency and emissions of unloading events, with some events generating significant volumes of fugitive methane. Additional data will be needed to reconcile the differences between this study and the industry inventory provided to EPA by the American Petroleum Institute and America’s Natural Gas Alliance.