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Evidence of sulfate-dependent anaerobic methane oxidation within an area impacted by coalbed methane-related gas migration
Citation:
Wolfe, A. AND Rick Wilkin. Evidence of sulfate-dependent anaerobic methane oxidation within an area impacted by coalbed methane-related gas migration. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 51(3):1901-1909, (2017).
Impact/Purpose:
This study examines secondary water quality impacts related to the degradation of methane in groundwater. Methane migration into aquifers used for drinking water may occur during development of natural gas resources. The findings indicate that methane degradation in sulfate-rich aquifers can lead to the production and buildup of hydrogen sulfide, an undesirable secondary water quality impact.
Description:
The rapid development of unconventional gas resources has been accompanied by an increase in public awareness regarding the potential effects of drilling operations on drinking water sources. Incidents have been reported involving blowouts (e.g., Converse County, WY; Lawrence Township, PA; Aliso Canyon, CA) and home/property explosions (e.g., Bainbridge Township, OH; Dimock, PA; Huerfano County, CO) caused by methane migration in the subsurface within areas of natural gas development. We evaluated water quality characteristics in the northern Raton Basin of Colorado and documented the response of the Poison Canyon aquifer system several years after upward migration of methane gas occurred from the deeper Vermejo Formation coalbed production zone. Results show persistent secondary water quality impacts related to the biodegradation of methane. We identify four distinct characteristics of groundwater methane attenuation in the Poison Canyon aquifer: (i) consumption of methane and sulfate and production of sulfide and bicarbonate, (ii) methane loss coupled to production of higher-molecular-weight (C2+) gaseous hydrocarbons, (iii) patterns of 13C enrichment and depletion in methane and dissolved inorganic carbon, and (iv) a systematic shift in sulfur and oxygen isotope ratios of sulfate, indicative of microbial sulfate reduction. We also show that the biogeochemical response of the aquifer system has not mobilized naturally occurring trace metals, including arsenic, chromium, cobalt, nickel, and lead, likely due to the microbial production of hydrogen sulfide which favors stabilization of metals in aquifer solids.
