Capillary Pressure鈥揝aturation Relations for Supercritical CO2 and Brine in Limestone/Dolomite Sands: Implications for Geologic Carbon Sequestration in Carbonate Reservoirs

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• 作者：Shibo Wang ; Tetsu K. Tokunaga
• 刊名：Environmental Science & Technology
• 出版年：2015
• 出版时间：June 16, 2015
• 年：2015
• 卷：49
• 期：12
• 页码：7208-7217
• 全文大小：526K
• ISSN：1520-5851

文摘

In geologic carbon sequestration, capillary pressure (P_c)鈥搒aturation (S_w) relations are needed to predict reservoir processes. Capillarity and its hysteresis have been extensively studied in oil鈥搘ater and gas鈥搘ater systems, but few measurements have been reported for supercritical (sc) CO₂鈥搘ater. Here, P_c鈥?i>S_w relations of scCO₂ displacing brine (drainage), and brine rewetting (imbibition) were studied to understand CO₂ transport and trapping behavior under reservoir conditions. Hysteretic drainage and imbibition P_c鈥?i>S_w curves were measured in limestone sands at 45 掳C under elevated pressures (8.5 and 12.0 MPa) for scCO₂鈥揵rine, and in limestone and dolomite sands at 23 掳C (0.1 MPa) for air鈥揵rine using a new computer programmed porous plate apparatus. scCO₂鈥揵rine drainage and imbibition curves shifted to lower P_c relative to predictions based on interfacial tension, and therefore deviated from capillary scaling predictions for hydrophilic interactions. Fitting universal scaled drainage and imbibition curves show that wettability alteration resulted from scCO₂ exposure over the course of months-long experiments. Residual trapping of the nonwetting phases was determined at P_c = 0 during imbibition. Amounts of trapped scCO₂ were significantly larger than for those for air, and increased with pressure (depth), initial scCO₂ saturation, and time. These results have important implications for scCO₂ distribution, trapping, and leakage potential.