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

Abstract

In geologic carbon sequestration, capillary pressure (Pc)-saturation (Sw) relations are needed to predict reservoir processes. Capillarity and its hysteresis have been extensively studied in oil-water and gas-water systems, but few measurements have been reported for supercritical (sc) CO2-water. 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 new 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 show that wettability alteration resulted from scCO2 exposure over the course of months-long experiments. Residual trapping of the nonwetting phases was determined at Pc = 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.

Capillarity and wetting of carbon dioxide and brine during drainage in Berea sandstone at reservoir conditions

“…This suggests that the sensitivity of the wetting state observed in sessile and pendant drop contact angle measurements [ Chiquet et al ., ; Espinoza and Santamarina , ; Jung and Wan , ; Wang et al ., ; Kim et al ., ; Broseta et al ., ] and in unconsolidated sand [ Plug and Bruining , ; Tokunaga et al ., ; Wang and Tokunaga , ] has little impact during drainage in consolidated sandstone. This observation was also supported by the results of the drainage and imbibition relative permeability tests, discussed below, which showed little variation between test conditions.…”

Enhancing residual trapping of supercritical CO2 via cyclic injections

“…Time-dependent surface chemistry reactions (e.g., heterogeneous wettability alteration to a more CO 2 -wet surface, clay mineral dissolution and redistribution, or adhesion of scCO 2 to the solid surface as proposed by Wang and Tokunaga [2015]) occurred upon prolonged exposure to scCO 2 , which rendered the scCO 2 phase to become increasingly more stable in the pore spaces over time. Time-dependent surface chemistry reactions (e.g., heterogeneous wettability alteration to a more CO 2 -wet surface, clay mineral dissolution and redistribution, or adhesion of scCO 2 to the solid surface as proposed by Wang and Tokunaga [2015]) occurred upon prolonged exposure to scCO 2 , which rendered the scCO 2 phase to become increasingly more stable in the pore spaces over time.…”

“…Time-dependent surface chemistry reactions (e.g., heterogeneous wettability alteration to a more CO 2 -wet surface, clay mineral dissolution and redistribution, or adhesion of scCO 2 to the solid surface as proposed by Wang and Tokunaga [2015]) occurred upon prolonged exposure to scCO 2 , which rendered the scCO 2 phase to become increasingly more stable in the pore spaces over time. In support of this hypothesis, a recent study by Wang and Tokunaga [2015] presented similar observations of significant increases in residual trapping (attributed in that study to time-dependent wettability alteration due to scCO 2 exposure). As cycle number increased, the solid surface experienced additional contact time with scCO 2 , and thus, surface reactions progressed further (and occurred on additional surfaces within the sandstone core) each time a D-I cycle was accomplished.…”

“…This conclusion has been echoed by ambient condition experiments that indicate that residual trapping is limited by the shape of the main imbibition curve [Raeesi et al, 2014]. Additional studies of scCO 2 flow processes have produced observations of time-dependent wettability alteration [Kim et al, 2012;Wang and Tokunaga, 2015], an impact which would certainly influence cyclic flow processes. Additional studies of scCO 2 flow processes have produced observations of time-dependent wettability alteration [Kim et al, 2012;Wang and Tokunaga, 2015], an impact which would certainly influence cyclic flow processes.…”

Interfacial tension and contact angle in CO2‐water/nanofluid‐quartz system

“…Carbon dioxide tends to de‐wet surfaces, which results in a CA variation after CO 2 invades water‐saturated porous media. The capillary pressure does not scale with the IFT because of this wettability change . In the studies of CO 2 invasion into porous media, the effect of IFT is considered important; however, the effect of CA is overlooked .…”