This study examined aquifers overlying the Marcellus and Utica shale formations of northeastern Pennsylvania and upstate New York. In active gas-extraction areas (one or more gas wells within 1 km), average and maximum methane concentrations in drinking-water wells increased with proximity to the nearest gas well and were 19.2 and 64 mg CH4 /L, a potential explosion hazard; in contrast, dissolved methane samples in neighboring nonextraction sites (no gas wells within 1 km) within similar geologic formations and hydrogeologic regimes averaged only 1.1 mg/L. δ13C-CH4 data, and ratios of methane-to-higher-chain hydrocarbons were consistent with deeper thermogenic methane sources at the active sites and matched gas geochemistry from gas wells nearby. Lower-concentration samples from shallow groundwater at nonactive sites had isotopic signatures reflecting a more biogenic or mixed biogenic/thermogenic methane source. No evidence was found for contamination of drinking-water samples with deep saline brines or fracturing fluids.
Methane gas migration into water wells located over gas-ladened shale formations is not new and can occur regardless of whether hydraulic fracturing is practiced nearby. Look here for one of many videos showing flammable water caused by methane release.