Horizontal drilling and hydraulic fracturing have enhanced energy production but raised concerns about drinking-water contamination and other environmental impacts associated with unconventional energy development. The occurrence of fugitive gas contamination in drinking-water wells near unconventional natural gas development has been central to the debate about the environmental impacts of hydraulic fracturing, but still has a controversial origin that has variably been attributed to natural geogenic occurrences, poor well bore integrity, and crustal-scale migration of natural gas along natural deformation features. Differentiating amongst these possibilities is critical to ongoing efforts to understand the environmental implications of the presence of elevated methane and aliphatic hydrocarbons (ethane, propane, etc.) in drinking-water and a necessary step toward the development of implementable solutions that limit the occurrence of future fugitive gas events. Here we will expand upon our recent work in the Marcellus and Barnett gas fields (Jackson et al., 2013; Darrah et al., 2014; 2015) that developed noble gas techniques for distinguishing natural and anthropogenic mechanisms of natural gas migration by integrating the molecular and isotopic composition of non-hydrocarbon molecules (N2, H2S, CO2) in addition to compound specific isotopes of hydrocarbons (d2H of CH4 and C2H6 and d13C of CH4, C2H6, and C3H8) and non-hydrocarbon compounds (d15N-N2). The expanded data sets validate our initial study and support the hypothesis that a subset of drinking-water wells experience natural gas contamination following faulty well construction or poor well integrity amid a background of naturally occurring gas and salt-rich groundwater.

Using noble gas geochemistry to determine the source and mechanism of natural gas leakage into shallow aquifers near unconventional drilling

251st National Meeting (2016)

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