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CO 2 sequestration in saline aquifers and hydrocarbon reservoirs is a promising strategy to reduce CO 2 concentration in the atmosphere and/or enhance hydrocarbon production. Change in subsurface conditions of pressure and temperature and CO 2 state is likely to have a significant impact on capillary and viscous forces, which, in turn, will have a considerable influence on the injection, migration, displacement, and storage capacity and integrity of CO 2 processes. In this study, an experimental investigation has been performed to explore the impact of fluid pressure, temperature, and injection rate, as a function of CO 2 phase, on the dynamic pressure evolution and the oil recovery performance of CO 2 during oil displacement in a Berea sandstone core sample. The results reveal a considerable impact of the fluid pressure, temperature, and injection rate on the differential pressure profile, cumulative produced volumes, endpoint CO 2 relative permeability, and oil recovery; the trend and the size of the changes depend on the CO 2 phase as well as the pressure range for gaseous CO 2-oil displacement. The residual oil saturation was in the range of around 0.44-0.7; liquid CO 2 gave the lowest, and low-fluid-pressure gaseous CO 2 gave the highest. The endpoint CO 2 relative permeability was in the range of about 0.015-0.657; supercritical CO 2 gave the highest, and low-pressure gaseous CO 2 gave the lowest. As for increasing fluid pressure, the results indicate that viscous forces were dominant in subcritical CO 2 displacements, while capillary forces were dominant in supercritical CO 2 displacements. As temperature and CO 2 injection rates increase, the viscous forces become more dominant than capillary forces.

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CO2 injection into subsurface formations involves the flow of CO2 through a porous medium that also contains water. The injection, displacement, migration, storage capacity and security of CO2 is controlled mainly by the interfacial interactions and capillary, viscous, and buoyancy forces which are directly influenced by changes in subsurface conditions of pressure and temperature; the impact of bouncy forces is assumed negligible during this study. In this study, gaseous CO2 is injected into a water-saturated sandstone core sample to explore the impact of fluid pressure (40-70 bar), temperature (29-45 °C), and CO2 injection rate (0.1-2 ml/min) on the dynamic pressure evolution and displacement efficiency. This study highlights the impact of capillary or viscous forces on the two-phase flow characteristics and shows the conditions where capillary or viscous forces become more influential. The results reveal a moderate to considerable impact of the parameters investigated on the differential pressure profile, endpoint CO2 relative permeability (KrCO2 max), and irreducible water saturation (Swr). Overall, the increase in fluid pressure, temperature, and CO2 injection rate cause an increase in the maximum and final differential pressures, an increase in the KrCO2 max , a reduction in the Swr. Swr was in the range of around 0.38-0.45 while KrCO2 max was less than 0.25. The data show a significant influence for the capillary forces on the pressure and production behaviour. The capillary forces produce high oscillations in the pressure and production data while the increase in viscous forces impedes the appearance of these oscillations. The appearance and frequency of the oscillations depend on the fluid pressure, temperature, and CO2 injection rate but to different extents.

CO2 injection into underground formations involves the flow of CO2 in subsurface rocks which already contain water. The flow of CO2 into the target formation is governed mainly by capillary forces, viscous forces and interfacial interactions. Any change in subsurface conditions of pressure and temperature during injection will have an impact on the capillary and viscous forces and the interfacial interactions, which, in turn, will have an influence the injection, displacement, migration, and storage capacity and security of CO2. In this study, an experimental investigation has been designed to explore the impact of fluid pressure (74-90 bar), temperature (33-55 °C), and injection rate (0.1-1 ml/min) on the dynamic pressure evolution and displacement efficiency when supercritical CO2 is injected into a water-saturated sandstone core sample. The study also highlights the impact of the capillary forces and viscous forces on the two-phase flow characteristics and shows the conditions where capillary forces or viscous forces become dominant. The authors are not aware of similar experimental studies conducted in the literature so far. The results revealed a moderate to considerable impact of the parameters investigated on the differential pressure profile, cumulative produced volumes, endpoint CO2 relative (effective) permeability and residual water saturation. The extent of the impact of each parameter (e.g. fluid pressure) was a function of the associated parameters (e.g. temperature and injection rate). Increasing fluid pressure caused the differential pressure profile of supercritical CO2water displacement to transform to the likeness of liquid CO2-water displacement, while, increasing temperature transforms it to the likeness of gaseous CO2-water displacement. Increasing fluid pressure caused a considerable reduction in the maximum and quasi-differential pressures, an increase in the endpoint CO2 relative permeability (KrCO2) and a reduction in the residual water saturation (Swr) and cumulative produced volumes. Overall, the impact of temperature is opposite to that of fluid pressure. However, with increasing temperature, the KrCO2 showed a declining trend at high-fluid pressures (90 bar) but an increasing trend at low-fluid pressures (75 bar). Increasing injection rate caused a considerable increase in the maximum and quasi-differential pressures, a rise in the KrCO2, a reduction in the Swr, and an increase in the cumulative produced volumes. The Swr was in range of 0.34-0.41 while KrCO2 was less than 0.37, depending on the operational conditions. Changing the operational conditions caused a higher impact on KrCO2 than that on Swr. The results indicate that capillary forces dominate the multiphase flow characteristics as fluid pressure and temperature are increased.