Experimental observation of permeability changes in dolomite at CO2 sequestration conditions.
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 °C, decreased to 10(-16.2) m(2) over 289 h at 50 °C, largely due to thermally driven CO2 exsolution, and reached a final value of 10(-16.4) m(2) after 145 h at 100 °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.
Department of Earth Sciences, University of Minnesota , Minneapolis, Minnesota, 55455, United States.
Benjamin M
BM
Tutolo
Andrew J
AJ
Luhmann
Xiang-Zhao
XZ
Kong
Martin O
MO
Saar
William E
WE
Seyfried
D002119:Calcium Carbonate / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D011232:Chemical Precipitation; D019015:Geologic Sediments / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry*; D008854:Microscopy, Electron; D010539:Permeability; D012995:Solubility; D013696:Temperature; D013997:Time Factors; D014057:Tomography, X-Ray Computed
D002245:Carbon Dioxide; D002119:Calcium Carbonate; D008274:Magnesium; C028042:calcium magnesium carbonate