We measure primary drainage capillary pressure and the relationship between initial and residual non‐wetting phase saturation for a supercritical carbon dioxide (CO2)‐brine system in Berea sandstone. We use the semi‐permeable disk (porous‐plate) coreflood method. Brine and CO2 were equilibrated prior to injection to ensure immiscible displacement. A maximum CO2 saturation of 85% was measured for an applied capillary pressure of 296 kPa. After injection of brine the CO2 saturation dropped to 35%; this is less than the maximum trapped saturation of 48% measured in an equivalent n‐decane (oil)‐brine experiment. The dimensionless capillary pressure is the same to within experimental error for supercritical CO2‐brine, n‐decane‐brine and a mercury‐air system. CO2 is the non‐wetting phase and significant quantities can be trapped by capillary forces. We discuss the implications for CO2 storage.

We performed core flooding experiments on Indiana limestone using the porous plate method to measure the amount of trapped CO(2) at a temperature of 50 °C and two pressures: 4.2 and 9 MPa. Brine was mixed with CO(2) for equilibration, then the mixture was circulated through a sacrificial core. Porosity and permeability tests conducted before and after 884 h of continuous core flooding confirmed negligible dissolution. A trapping curve for supercritical (sc)CO(2) in Indiana showing the relationship between the initial and residual CO(2) saturations was measured and compared with that of gaseous CO(2). The results were also compared with scCO(2) trapping in Berea sandstone at the same conditions. A scCO(2) residual trapping end point of 23.7% was observed, indicating slightly less trapping of scCO(2) in Indiana carbonates than in Berea sandstone. There is less trapping for gaseous CO(2) (end point of 18.8%). The system appears to be more water-wet under scCO(2) conditions, which is different from the trend observed in Berea; we hypothesize that this is due to the greater concentration of Ca(2+) in brine at higher pressure. Our work indicates that capillary trapping could contribute to the immobilization of CO(2) in carbonate aquifers.

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We introduce a fast, easy and reliable methodology, using a stirred reactor, to equilibrate carbon dioxide with brine and measure the solubility of carbon dioxide in the aqueous phase at high pressure (9MPa) and elevated temperature (33, 50 and 70°C) conditions at the litre scale. The solubility of carbon dioxide in brine was measured using an isothermal depressurization method and compared with data in the literature. This methodology can be used in petroleum engineering, carbon storage and chemical engineering applications.

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