Methane in groundwater before, during, and after hydraulic fracturing of the Marcellus Shale

Abstract

Significance This study incorporates time series sampling of groundwater before, during, and after drilling, hydraulic fracturing, and initiation of shale gas production. Using monitoring wells installed next to gas well pads and above gas well laterals, previously undocumented responses to drilling and a gas well casing breach were observed, although groundwater impacts arising from the process of hydraulic fracturing were not detected. We discover considerable temporal variability in methane concentrations in deeper horizons of freshwater aquifers and attribute this to persistent shifts in aquifer recharge that influence mixing between shallow freshwater and comparatively saline and methane-rich deep groundwater. These results have implications for attribution of groundwater contamination to specific stages of shale gas development or natural processes and improving regulatory monitoring.