Experimental Observation of Permeability Changes In Dolomite at CO2 Sequestration Conditions

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• 作者：Benjamin M. Tutolo ; Andrew J. Luhmann ; Xiang-Zhao Kong ; Martin O. Saar ; William E. Seyfried ; Jr.
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：February 18, 2014
• 年：2014
• 卷：48
• 期：4
• 页码：2445-2452
• 全文大小：424K
• ISSN：1520-5851

文摘

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^鈥?5.9 to 10^鈥?5.2 m² over the initial 216 h at 21 掳C, decreased to 10^鈥?6.2 m² over 289 h at 50 掳C, largely due to thermally driven CO₂ exsolution, and reached a final value of 10^鈥?6.4 m² after 145 h at 100 掳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 cm³ CO₂ and 1.5 cm³ dolomite per kg of water, respectively, resulting in substantial porosity and permeability redistribution.