Evaluation of CO 2 -Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations
[1];
- Energy & Geoscience Institute, The University of Utah, Salt Lake City, UT 84108, USA, Department of Civil and Environmental Engineering, The University of Utah, Salt Lake City, UT 84112, USA
- Department of Geology & Geophysics, The University of Wyoming, Laramie, WY 82071, USA, School of Energy Resources, The University of Wyoming, Laramie, WY 82071, USA
Recent studies suggest that using supercritical CO 2 (scCO 2 ) instead of water as a heat transmission fluid in Enhanced Geothermal Systems (EGS) may improve energy extraction. While CO 2 -fluid-rock interactions at “typical” temperatures and pressures of subsurface reservoirs are fairly well known, such understanding for the elevated conditions of EGS is relatively unresolved. Geochemical impacts of CO 2 as a working fluid (“CO 2 -EGS”) compared to those for water as a working fluid (H 2 O-EGS) are needed. The primary objectives of this study are (1) constraining geochemical processes associated with CO 2 -fluid-rock interactions under the high pressures and temperatures of a typical CO 2 -EGS site and (2) comparing geochemical impacts of CO 2 -EGS to geochemical impacts of H 2 O-EGS. The St. John’s Dome CO 2 -EGS research site in Arizona was adopted as a case study. A 3D model of the site was developed. Net heat extraction and mass flow production rates for CO 2 -EGS were larger compared to H 2 O-EGS, suggesting that using scCO 2 as a working fluid may enhance EGS heat extraction. More aqueous CO 2 accumulates within upper- and lower-lying layers than in the injection/production layers, reducing pH values and leading to increased dissolution and precipitation of minerals in those upper and lower layers. Dissolution of oligoclase for water as a working fluid shows smaller magnitude in rates and different distributions in profile than those for scCO 2 as a working fluid. It indicates that geochemical processes of scCO 2 -rock interaction have significant effects on mineral dissolution and precipitation in magnitudes and distributions.
- Research Organization:
- Univ. of Utah, Salt Lake City, UT (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Geothermal Technologies Office; Utah Science Technology and Research Initiative (USTAR)
- Grant/Contract Number:
- EE0002766
- OSTI ID:
- 1400022
- Alternate ID(s):
- OSTI ID: 1473908
- Journal Information:
- Geofluids, Journal Name: Geofluids Vol. 2017; ISSN 1468-8115
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- Canada
- Language:
- English
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