Mechanisms for CO2 storage in the presence of residual oil

CO2 storage in mature oil reservoirs is an attractive strategy because infrastructure exists, and the geology is knownfrom the oil production phase. Such reservoirs often contain residual oil trapped as disconnected ganglia in the porespace after water injection. Thus, a CO2 storage strategy requires knowledge of how water and this residual oilinfluence the CO2 flow pattern and storage mechanisms, and conversely how CO2 invasion impacts the behavior ofthe residing fluids. CO2 dissolution in oil and water will change the fluid properties, lead to oil swelling, andpotentially alter the wetting state of the porous rock. These processes can serve both oil recovery and CO2 storage.Cyclic injection, which often is a realistic storage option when CO2 availability is low, can optimize residual trapping,but reservoir simulation is challenging because flow mechanisms are complex. Little is known about how thebehavior changes when residual oil ganglia are present. This project will bring forth advanced pore-scale models forthree-phase flow to explore how CO2 dissolution in the presence of water and oil affects residual CO2 trapping, oiltrapping and mobilization, capillary pressure, relative permeability, and hysteresis behavior over multiple CO2/waterinvasion cycles in porous rock. The models will be validated against a wide range of advanced CO2/oil/water porescaleexperiments provided by our international research partners. The validated pore-scale simulators will bereleased as open-source so that users can make their own calculations with the aim at reducing the number ofrequired lab measurements for CCUS operations. The project will also bring forth suitable macroscale three-phaseflow models that capture the effective three-phase flow behavior observed at pore scale. This is a first necessary steptowards reliable simulation of large-scale CCUS operations in mature oil reservoirs.