Higher odds of produced-water-like chemistry in groundwater vulnerable to shale gas spills

Abstract Unconventional oil and gas development (UOGD), the extraction of hydrocarbons from shale and other low-permeability formations through horizontal drilling and hydraulic fracturing, has bolstered the USA’s domestic energy production and economy. These benefits have been accompanied by public concerns about the industry’s impacts on drinking-water resources, the environment and human health. Here we explore the association between observed groundwater chemistry and documented surface spills from UOGD in the northern Appalachian Basin. Using published data from over 16,000 groundwater samples and high-resolution, physically based groundwater flow and transport modelling, we find that areas with high hydrologic vulnerability to surface spills exhibit a threefold increase in the odds of detecting chemical signatures resembling produced water or deep formation brines in domestic well water, even when accounting for other factors that may explain such chemical imprints. Across our study region, we estimate that over 120,000 people served by domestic wells reside in locations where groundwater is vulnerable to contamination from UOGD activities.