Strontium isotope quantification of siderite,brine and acid mine drainage contributions to abandoned gas well discharges in the Appalachian Plateau |
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| Institution: | 1. Laboratory of Stem Cell and Cancer Epigenetic Research, UCLA School of Dentistry, Los Angeles, CA, USA;2. Department of Biostatistics, UCLA School of Public Health, Los Angeles, CA, USA;3. Center for Oral and Head/Neck Oncology Research Center, Los Angeles, CA, USA;4. Division of Oral Biology and Medicine, UCLA School of Dentistry, Los Angeles, CA, USA;5. UCLA''s Jonsson Comprehensive Cancer Center, Los Angeles, CA, USA;6. UCLA Broad Stem Cell Research Center, Los Angeles, CA, USA;1. National Energy Technology Laboratory, U.S. Department of Energy, Pittsburgh, PA 15236, United States;2. Department of Geology and Environmental Science, University of Pittsburgh, Pittsburgh, PA 15260, United States;3. Geology Department, California State University, Sacramento, Sacramento, CA 95819, United States;1. School of Earth Sciences, The Ohio State University, USA;2. Department of Earth Sciences, University of Delaware, USA |
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| Abstract: | Unplugged abandoned oil and gas wells in the Appalachian region can serve as conduits for the movement of waters impacted by fossil fuel extraction. Strontium isotope and geochemical analysis indicate that artesian discharges of water with high total dissolved solids (TDS) from a series of gas wells in western Pennsylvania result from the infiltration of acidic, low Fe (Fe < 10 mg/L) coal mine drainage (AMD) into shallow, siderite (iron carbonate)-cemented sandstone aquifers. The acidity from the AMD promotes dissolution of the carbonate, and metal- and sulfate-contaminated waters rise to the surface through compromised abandoned gas well casings. Strontium isotope mixing models suggest that neither upward migration of oil and gas brines from Devonian reservoirs associated with the wells nor dissolution of abundant nodular siderite present in the mine spoil through which recharge water percolates contribute significantly to the artesian gas well discharges. Natural Sr isotope composition can be a sensitive tool in the characterization of complex groundwater interactions and can be used to distinguish between inputs from deep and shallow contamination sources, as well as between groundwater and mineralogically similar but stratigraphically distinct rock units. This is of particular relevance to regions such as the Appalachian Basin, where a legacy of coal, oil and gas exploration is coupled with ongoing and future natural gas drilling into deep reservoirs. |
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