Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 48, Issue 4, Pages 2445-2452Publisher
AMER CHEMICAL SOC
DOI: 10.1021/es4036946
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Funding
- Department of Energy (DOE) Geothermal Technologies Program [EE0002764]
- National Science Foundation (NSF) [CHE-1230691]
- Institute on the Environment (IonE) at the University of Minnesota (UMN) through its Initiative for Renewable Energy and the Environment (IREE)
- George and Orpha Gibson Foundation
- Division Of Earth Sciences
- Directorate For Geosciences [1230691] Funding Source: National Science Foundation
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Injection of cool CO2 into geothermally warm carbonate reservoirs for storage or geothermal energy production may lower near-well temperature and lead to mass transfer along flow paths leading away from the well. To investigate this process, a dolomite core was subjected to a 650 h, high pressure, CO2 saturated, flow-through experiment. Permeability increased from 10(-15.9) to 10(-15.2) m(2) over the initial 216 h at 21 degrees C, decreased to 10(-16.2) m(2) over 289 h at 50 degrees C, largely due to thermally driven CO2 exsolution, and reached a final value of 10(-16.4) m(2) after 145 h at 100 degrees C due to continued exsolution and the onset of dolomite precipitation. Theoretical calculations show that CO2 exsolution results in a maximum pore space CO2 saturation of 0.5, and steady state relative permeabilities of CO2 and water on the order of 0.0065 and 0.1, respectively. Post-experiment imagery reveals matrix dissolution at low temperatures, and subsequent filling-in of flow passages at elevated temperature. Geochemical calculations indicate that reservoir fluids subjected to a thermal gradient may exsolve and precipitate up to 200 cm(3) CO2 and 1.5 cm(3) dolomite per kg of water, respectively, resulting in substantial porosity and permeability redistribution.
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