Data-Driven Quantitative Study of Synergistic Effects on CCUS-EOR-A Case Study of Ultralow-Permeability Sandstone Reservoirs

CO2 capture, utilization, and storage of CO2 with enhanced oil recovery (CCUS-EOR) technology is an important method to achieve net-zero carbon goals. The two objectives of enhancing oil recovery and CO2 storage exhibit both alignment and conflict, especially in the ultralow-permeability reservoir. However, current research often ignores the impact of reservoir heterogeneity, chemical reactions induced by CO2, and the lack of quantitative characterization of synergies. This paper constructed a three-dimensional multiphase, multicomponent, thermal-hydraulic-chemical multifield coupled model for an actual well group. This paper thoroughly examines the mechanism of CO2 storage in oil reservoirs and investigates the influence of geological and engineering parameters on CO2-enhanced oil recovery and storage by establishing a realistic CO2-water-oil-rock physicochemical reaction system. The gray correlation method was used to analyze the impact of various factors on the CO2 oil displacement and storage, and the synergistic parameters were analyzed. The results show that reservoir pressure, WAG alternating cycles, and injection rate are synergistic parameters. In addition, the storage form of CO2 is mainly structural storage, and mineralization storage can be ignored during the development of oil reservoirs. The amount of dissolved storage, however, gradually transforms into the amount of mineralized storage over time. During the 200 years of shut-in period, the amount of mineralized storage increased 13.6 times. It is also found that introducing hydrodynamic theory into the water-gas alternating injection process can effectively utilize the gravity of water and the buoyancy of CO2 to increase the swept volume of CO2. When the depth of the gas and water injection points is small, the oil recovery and the CO2 storage rate can be improved. The oil recovery of the final optimized plan is 40.5%, and the CO2 storage rate is 64.5%. This study helps to better formulate development designs for ultralow-permeability reservoirs to achieve dual goals.