In geologic carbon sequestration, capillary pressure (Pc) - saturation (Sw) relations are needed to predict reservoir processes. Very few measurements on capillarity and its hysteresis have been reported for supercritical (sc) CO2-brine. Here, Pc-Sw 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 Pc-Sw curves were measured in limestone sands at 45 ˚C under elevated pressures (8.5 and 12.0 MPa) for scCO2-brine, and in limestone and dolomite sands at 23 ˚C (0.1 MPa) for air-brine using a computer programmed porous plate apparatus. scCO2-brine drainage and imbibition curves shifted to lower Pc relative to predictions based on interfacial tension, and therefore deviated from capillary scaling predictions for hydrophilic interactions. Fitting universal scaled drainage and imbibition curves by adjusting contact angles shows that wettability alteration resulted from scCO2 exposure. Residual trapping of the nonwetting phases was determined at Pc = 0 during imbibition. Amounts of trapped scCO2 were significantly larger than for air, and increased with pressure (depth), initial scCO2 saturation, and time. These results have important implications for CO2 injectivity, distribution, trapping, and leakage potential.

Capillary pressure - saturation relations for supercritical CO2 and brine in limestone/dolomite sands: Implications for geologic carbon sequestration in carbonate reservoirs

250th National Meeting (2015)

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