Effects of gas relative permeability hysteresis and solubility on associated CO2 storage performance

Abstract CO 2 enhanced oil recovery (EOR) has been carried out in the Bell Creek oil field since 2013. Together with the encouraging oil production results, a considerable quantity of CO 2 has also been trapped in the reservoir as a normal part of the EOR process, also referred to as associated storage. Because of the complex geologic conditions in the field, a series of experimental and modeling work have been conducted to better understand the CO 2 EOR and associated storage performance in the reservoir. Effects of gas relative permeability hysteresis and solubility on associated CO 2 storage performance are thoroughly investigated in this study. A proportion of injected CO 2 remains behind through residual and solubility trapping mechanisms when CO 2 flows through a reservoir during a CO 2 EOR process. Over 50 core plugs were collected from the reservoir to characterize the rock properties. Mineralogical analysis and capillary pressure measurements showed that the mineral composition and pore-size distribution in the reservoir are favorable for residual trapping of CO 2 . The hysteresis of gas relative permeability was measured to assess the effect of residual trapping on associated CO 2 storage using steady-state relative permeability tests and reservoir simulation. The reservoir oil was characterized based on pressure–volume–temperature experiments and Peng–Robinson equation of state modeling, which showed that CO 2 solubility in oil is much greater (≥5 times) than in water. Results indicated that depleted oil reservoirs have great potential to store a huge quantity of CO 2 associated with EOR operations, as residual oil saturation is 0.3 or greater in most conventional oil reservoirs after water flooding.