Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales

TLDR

Hydrocarbon production from unconventional sources is rapidly expanding, raising concerns about drinking‑water contamination and other environmental risks. The study uses noble gas and hydrocarbon tracers to distinguish natural methane from anthropogenic contamination, identify mechanisms driving elevated hydrocarbon levels in drinking water, and thereby improve shale‑gas safety and economics. The authors documented fugitive gases in eight clusters of domestic wells overlying the Marcellus and Barnett Shales, noting declining water quality over time in the Barnett cluster. Gas geochemistry indicates leaks through annulus cement, production casings, and underground well failure, rather than deep‑hydraulic‑fracturing‑induced migration.

Abstract

Significance Hydrocarbon production from unconventional sources is growing rapidly, accompanied by concerns about drinking-water contamination and other environmental risks. Using noble gas and hydrocarbon tracers, we distinguish natural sources of methane from anthropogenic contamination and evaluate the mechanisms that cause elevated hydrocarbon concentrations in drinking water near natural-gas wells. We document fugitive gases in eight clusters of domestic water wells overlying the Marcellus and Barnett Shales, including declining water quality through time over the Barnett. Gas geochemistry data implicate leaks through annulus cement (four cases), production casings (three cases), and underground well failure (one case) rather than gas migration induced by hydraulic fracturing deep underground. Determining the mechanisms of contamination will improve the safety and economics of shale-gas extraction.