Data and Analysis in Support of “Methane Fluxes in a Region Containing Shale Gas Wells Cited with Cementing and Casing Issues”

We quantified atmospheric methane emissions from a subsurface source in the vicinity of a shale gas well that was cited for casing and cementing issues. We measured the magnitude and spatial and temporal variability of emissions in a farm field where patches of dead vegetation and methane bubbling from a nearby stream were observed. The methane emissions were quantified using an eddy covariance flux tower, chamber flux measurements, and a survey of near-surface methane mole fraction enhancements. The study area was approximately 2,500 m2 and measurements were conducted from December 2018 through May 2019. We found that the emissions are highly heterogeneous in space, but we detected no temporal trends in emissions. The site-wide emission rate is estimated to be ~6 kg CH4/day. The isotopic signature of ??13CH4 of the atmospheric CH4 source is -29‰, indicating that the methane is of thermogenic origin and similar to the source isotopic ratio of a nearby shale gas well. This source is modest in magnitude compared to large emitters identified among shale gas production sites, but large compared to estimates of emissions from abandoned wells. Since the sources of emissions to the atmosphere extend beyond our measurement site, our emissions estimate is certainly an underestimate of total emissions.