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Title: Evaluation of CO 2 -Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations

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/productionmore » 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.« less
Authors:
ORCiD logo [1] ;  [1] ;  [2]
  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
  2. Department of Geology & Geophysics, The University of Wyoming, Laramie, WY 82071, USA, School of Energy Resources, The University of Wyoming, Laramie, WY 82071, USA
Publication Date:
Grant/Contract Number:
DE – EE0002766
Type:
Published Article
Journal Name:
Geofluids
Additional Journal Information:
Journal Volume: 2017; Related Information: CHORUS Timestamp: 2017-10-18 19:32:45; Journal ID: ISSN 1468-8115
Publisher:
Hindawi Publishing Corporation
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G)
Country of Publication:
Canada
Language:
English
OSTI Identifier:
1400022