Groundwater Methane in Northeastern Pennsylvania Attributable to Thermogenic Sources and Hydrogeomorphologic Migration Pathways

Yunpo Li, Nathalie A. Thelemaque, Helen G. Siegel, Cassandra J. Clark, Emma C. Ryan, Rebecca J. Brenneis, Kristina M. Gutchess, Mario A. Soriano, Boya Xiong, Nicole C. Deziel, James E. Saiers, Desiree L. Plata

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Conflicting evidence exists as to whether or not unconventional oil and gas (UOG) development has enhanced methane transport into groundwater aquifers over the past 15 years. In this study, recent groundwater samples were collected from 90 domestic wells and 4 springs in Northeastern Pennsylvania located above the Marcellus Shale after more than a decade of UOG development. No statistically significant correlations were observed between the groundwater methane level and various UOG geospatial metrics, including proximity to UOG wells and well violations, as well as the number of UOG wells and violations within particular radii. The δ13C and methane-to-higher chain hydrocarbon signatures suggested that the elevated methane levels were not attributable to UOG development nor could they be explained by using simple biogenic–thermogenic end-member mixing models. Instead, groundwater methane levels were significantly correlated with geochemical water type and topographical location. Comparing a subset of contemporary methane measurements to their co-located pre-drilling records (n = 64 at 49 distinct locations) did not indicate systematic increases in methane concentration but did reveal several cases of elevated concentration (n = 12) across a spectrum of topographies. Multiple lines of evidence suggested that the high-concentration groundwater methane could have originated from shallow thermogenic methane that migrated upward into groundwater aquifers with Appalachian Basin brine.

Original languageEnglish (US)
Pages (from-to)16413-16422
Number of pages10
JournalEnvironmental Science and Technology
Issue number24
StatePublished - Dec 21 2021

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© 2021 American Chemical Society


  • geochemistry
  • groundwater
  • hydraulic fracturing
  • methane
  • unconventional oil and gas


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