Elucidating geochemical response of shallow heterogeneous aquifers to CO2 leakage using high-performance computing: Implications for monitoring of CO2 sequestration |
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| Institution: | 1. Hydrologic Science and Engineering Program, Colorado School of Mines, United States;2. Department of Geology and Geological Engineering, Colorado School of Mines, United States;3. Pacific Northwest National Laboratory, Richland, WA, United States;4. Los Alamos National Laboratory, Los Alamos, NM, United States;1. Colorado School of Mines, Dept. of Geophysics, 1500 Illinois St., Golden, CO, 80401, United States;2. Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States;1. Geoscience Australia, GPO Box 378, Canberra, ACT, 2601, Australia;3. CSIRO Energy Transformed Flagship, GPO Box 3023, Canberra, ACT, 2601, Australia;4. Australian School of Petroleum, University of Adelaide, Adelaide, SA, 5005, Australia;5. Flinders University, PO Box 335 Salisbury South, SA 5106, Australia;6. The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia;7. National Geosequestration Laboratory, 26 Dick Perry Ave, Kensington, WA, 6151, Australia;8. CSIRO Mineral Resources Flagship, 26 Dick Perry Ave, Kensington, WA, 6151, Australia;9. CSIRO Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT, 2601, Australia;10. China Geological Survey, 1305 Qiyi Middle Road, Baoding, Hebei, China;11. CSIRO Plant Industry, Cnr Clunies Ross St and Barry Dr, Canberra, ACT, 2601, Australia |
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| Abstract: | Predicting and quantifying impacts of potential carbon dioxide (CO2) leakage into shallow aquifers that overlie geologic CO2 storage formations is an important part of developing reliable carbon storage techniques. Leakage of CO2 through fractures, faults or faulty wellbores can reduce groundwater pH, inducing geochemical reactions that release solutes into the groundwater and pose a risk of degrading groundwater quality. In order to help quantify this risk, predictions of metal concentrations are needed during geologic storage of CO2. Here, we present regional-scale reactive transport simulations, at relatively fine-scale, of CO2 leakage into shallow aquifers run on the PFLOTRAN platform using high-performance computing. Multiple realizations of heterogeneous permeability distributions were generated using standard geostatistical methods. Increased statistical anisotropy of the permeability field resulted in more lateral and vertical spreading of the plume of impacted water, leading to increased Pb2+ (lead) concentrations and lower pH at a well down gradient of the CO2 leak. Pb2+ concentrations were higher in simulations where calcite was the source of Pb2+ compared to galena. The low solubility of galena effectively buffered the Pb2+ concentrations as galena reached saturation under reducing conditions along the flow path. In all cases, Pb2+ concentrations remained below the maximum contaminant level set by the EPA. Results from this study, compared to natural variability observed in aquifers, suggest that bicarbonate (HCO3?) concentrations may be a better geochemical indicator of a CO2 leak under the conditions simulated here. |
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