Stable Isotope and Radiocarbon Evidence for Biogenic Coalbed Methane in Groundwater Wells in Utica Shale

Townsend-Small, Amy

Stable Isotope and Radiocarbon Evidence for Biogenic Coalbed Methane in Groundwater Wells in Utica Shale

Tuesday, April 25, 2017: 1:30 p.m.

Amy Townsend-Small , Departments of Geology and Geography, University of Cincinnati, Cincinnati, OH

Previous studies have shown that natural gas methane (CH₄) was present in groundwater near shale gas wells, but did not have pre-development baseline measurements. We present a time series of groundwater CH₄ concentration and isotopic composition through a period of increasing shale gas extraction in the Utica Shale of Ohio. Dissolved CH₄ ranged from 0.2 μg L^-1 to 25 mg L^-1, and stable isotopic measurements indicated a biogenic CH₄source. Radiocarbon dating of CH₄ in three samples indicated a fossil biogenic coalbed CH₄ source, with one ¹⁴C date indicative of modern biogenic CH₄. We found no relationship between CH₄ concentration in groundwater and proximity to active gas well sites and no significant change in CH₄ concentration or isotopic composition in water wells during the study period. Continuous monitoring of private drinking water wells is critical to ensuring residents are not exposed to harmful levels of natural gas or fracking contaminants.

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Amy Townsend-Small, Departments of Geology and Geography, University of Cincinnati, Cincinnati, OH

Dr. Townsend-Small has a BA from Skidmore College and a PhD from the University of Texas at Austin and is currently an Associate Professor at the University of Cincinnati. In addition to her work on using stable isotopes to assess sources of methane in groundwater, she also has ongoing research assessing methane emissions from the natural gas supply chain as well as determining whether climate warming and changing hydrology will result in increasing emissions of methane from Arctic ecosystems and lakes and reservoirs.