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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 2O-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 2O-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 2O-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 precipitationmore » 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. Univ. of Utah, Salt Lake City, UT (United States). Energy & Geoscience Inst. Dept. of Civil and Environmental Engineering
  2. Univ. of Wyoming, Laramie, WY (United States). Dept. of Geology & Geophysics. School of Energy Resources
Publication Date:
Grant/Contract Number:
EE0002766
Type:
Published Article
Journal Name:
Geofluids
Additional Journal Information:
Journal Volume: 2017; Journal ID: ISSN 1468-8115
Publisher:
Wiley
Research Org:
Univ. of Utah, Salt Lake City, UT (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G); Utah Science Technology and Research Initiative (USTAR)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES
OSTI Identifier:
1400022
Alternate Identifier(s):
OSTI ID: 1473908

Pan, Feng, McPherson, Brian J., and Kaszuba, John. Evaluation of CO2-Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations. United States: N. p., Web. doi:10.1155/2017/5675370.
Pan, Feng, McPherson, Brian J., & Kaszuba, John. Evaluation of CO2-Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations. United States. doi:10.1155/2017/5675370.
Pan, Feng, McPherson, Brian J., and Kaszuba, John. 2017. "Evaluation of CO2-Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations". United States. doi:10.1155/2017/5675370.
@article{osti_1400022,
title = {Evaluation of CO2-Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations},
author = {Pan, Feng and McPherson, Brian J. and Kaszuba, John},
abstractNote = {Recent studies suggest that using supercritical CO2 (scCO2) instead of water as a heat transmission fluid in Enhanced Geothermal Systems (EGS) may improve energy extraction. While CO2-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 CO2 as a working fluid (“CO2-EGS”) compared to those for water as a working fluid (H2O-EGS) are needed. The primary objectives of this study are (1) constraining geochemical processes associated with CO2-fluid-rock interactions under the high pressures and temperatures of a typical CO2-EGS site and (2) comparing geochemical impacts of CO2-EGS to geochemical impacts of H2O-EGS. The St. John’s Dome CO2-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 CO2-EGS were larger compared to H2O-EGS, suggesting that using scCO2 as a working fluid may enhance EGS heat extraction. More aqueous CO2 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 scCO2 as a working fluid. It indicates that geochemical processes of scCO2-rock interaction have significant effects on mineral dissolution and precipitation in magnitudes and distributions.},
doi = {10.1155/2017/5675370},
journal = {Geofluids},
number = ,
volume = 2017,
place = {United States},
year = {2017},
month = {10}
}