Geochemical reactions among CO2-fromation water-rocks can occur and affect the physical properties of the reservoir and the CO2 trapping mechanisms during CO2 EOR process. In this paper, based on the properties of the reservoir and fluids in a typical high-temperature oil reservoir in Jilin Oilfield, a comprehensive model was established to simulate the CO2 EOR and the subsequent storage, processes, in which formation water evaporation, dissolution and diffusion of CO2 in water, CO2-water-rock geochemical reactions and variations of porosity and permeability were considered. The geochemical reactions and various CO2 trapping forms in different stages were analyzed using the model, and the influences of different CO2 injection methods on EOR and CO2 storage were evaluated. The results show that, though the geochemical reactions can change reservoir porosity and permeability, their effect is not significant and most of the injected CO2 can be trapped as supercritical gas during CO2 EOR process. During CO2 storage, gaseous CO2 can be continuously converted into mineral forms due to geochemical reactions, which results in a reduction of reservoir pressure. A WAG (water alternative gas injection) method can be applied to enhance oil recovery and increase CO2 storage efficiency. Further injection of CO2 after CO2 EOR process can increase the CO2 storage capacity, and simultaneously maintain the reservoir pressure. © 2017, Periodical Office of China University of Petroleum. All right reserved.
