HR: 12:05h
AN: GC12A-08    [Abstracts]
TI: Gas-Water-Rock Interactions in Saline Aquifers Following CO₂ Injection: Results From Frio Formation, Texas, USA
AU: * Kharaka, Y K
EM: ykharaka@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd. Mail Stop 417, Menlo Park, CA 94025 United States
AU: Cole, D R
EM: coledr@ornl.gov
AF: Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831 United States
AU: Gunter, W D
EM: gunter@arc.ab.ca
AF: Alberta Research Council, 250 Karl Clark Rd., Edmonton, AB T6N 1E4 Canada
AU: Thordsen, J J
EM: jthordsn@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd. Mail Stop 417, Menlo Park, CA 94025 United States
AU: Kakouros, E
EM: kakouros@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd. Mail Stop 417, Menlo Park, CA 94025 United States
AB: To investigate the potential for the geologic storage of CO₂ in saline sedimentary aquifers, ~16 million kg of CO₂ were injected at ~1,500-m depth into a 24-m sandstone section of the Frio Formation - a regional brine and oil reservoir in the U. S. Gulf Coast. Fluid samples obtained from the injection and observation wells before, during and post CO₂ injection, show a Na-Ca-Cl type brine with 93,000 mg/L TDS and near saturation of CH₄ at reservoir conditions. As injected CO₂ became the dominant gas at the observation well, results showed sharp drops in pH (6.5 to 5.7), pronounced increases in alkalinity (100 to 3,000 mg/L as HCO₃) and Fe (30 to 1,100 mg/L), and significant shifts in the isotopic compositions of H₂O, DIC and CH₄. Geochemical modeling indicates that brine pH would have dropped lower, but for the buffering by dissolution of carbonate and iron oxyhydroxides. The low pH values resulting from CO₂ injection could cause rapid dissolution of carbonate and other minerals creating pathways for CO2 and brine leakage. Dissolution of some minerals, especially iron oxyhdroxides could mobilize trace metals and other toxic components. Also, where residual oil and other organics are present, the injected CO₂ may mobilize organic compounds, some may be environmentally toxic. The δ¹⁸O values for brine and CO₂ samples indicate that supercritical CO₂ comprises ~45% of fluid volume in Frio sandstone near injection well ~6 months after end of injection. Post-injection sampling, coupled with geochemical modeling, indicate the brine gradually returning to its pre-injection composition.
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1630 Impacts of global change (1225)
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1832 Groundwater transport
SC: Global Climate Change [GC]
MN: Fall Meeting 2005