Stream measurements locate thermogenic methane fluxes in groundwater discharge in an area of shale-gas development

Victor M. Heilweil, Paul L. Grieve, Scott A. Hynek, Susan L. Brantley, D. Kip Solomon, Dennis W. Risser

Research output: Contribution to journalArticle

29 Scopus citations

Abstract

The environmental impacts of shale-gas development on water resources, including methane migration to shallow groundwater, have been difficult to assess. Monitoring around gas wells is generally limited to domestic water-supply wells, which often are not situated along predominant groundwater flow paths. A new concept is tested here: combining stream hydrocarbon and noble-gas measurements with reach mass-balance modeling to estimate thermogenic methane concentrations and fluxes in groundwater discharging to streams and to constrain methane sources. In the Marcellus Formation shale-gas play of northern Pennsylvania (U.S.A.), we sampled methane in 15 streams as a reconnaissance tool to locate methane-laden groundwater discharge: concentrations up to 69 μg L-1 were observed, with four streams ≥5 μg L-1. Geochemical analyses of water from one stream with high methane (Sugar Run, Lycoming County) were consistent with Middle Devonian gases. After sampling was completed, we learned of a state regulator investigation of stray-gas migration from a nearby Marcellus Formation gas well. Modeling indicates a groundwater thermogenic methane flux of about 0.5 kg d-1 discharging into Sugar Run, possibly from this fugitive gas source. Since flow paths often coalesce into gaining streams, stream methane monitoring provides the first watershed-scale method to assess groundwater contamination from shale-gas development.

Original languageEnglish (US)
Pages (from-to)4057-4065
Number of pages9
JournalEnvironmental Science and Technology
Volume49
Issue number7
DOIs
StatePublished - Apr 7 2015

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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