Understanding methane emissions from natural gas production has become increasingly important because of its increase role in the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern Pennsylvania in June 2012. A large regional flux was quantified for a ∼2,800-km2 area, which did not differ statistically from a bottom-up inventory. Large emissions averaging 34 g CH4/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than U.S. Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ∼1% of the total number of wells, account for 4–30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts.
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