Methane contamination of drinking water caused by hydraulic fracturing remains unproven

Abstract

Shale gas extraction involves the drilling of organic-rich, low-permeability shale and then stimulation of hydraulic fractures that allows gas to be produced. Methane in aquifers located above the shale strata, for instance, in Pennsylvania, United States, has been attributed by some to be the result of contamination caused by the hydraulic fracturing process. The work by Osborn et al. (1) described geochemical data from 68 drinking water wells in northeastern Pennsylvania and upstate New York and evaluated whether the aquifers that the water wells penetrated were contaminated with thermogenic methane sourced from the underlying Marcellus and Utica shale formations. The work by Osborn et al. (1) concluded that contamination had occurred and that the contamination accompanied gas well drilling and hydraulic fracturing. The inference from the text and title of the paper is clear—hydraulic fracturing had a role. However, the evidential basis for implicating this specific process is not sound and needs to be closely scrutinized.