CO2 flooding can effectively enhance the recovery of low-permeability reservoirs and realize CO2 storage. However, the strong heterogeneity of low permeability reservoirs makes it difficult to accurately determine the miscible state of CO2 and oil. In this study, first, a PR-EOS is modified by considering the shifts of critical properties. Second, the parachor model is coupled with the modified PR-EOS to predict the minimum miscible pressure (MMP). Third, considering the multiple contact process between CO2 and oil, a MMP prediction model based on the microscopic heterogeneity is established. Afterwards, the model calculation results are compared with the prior experimental results of CO2 flooding to verify its applicability and superiority. Finally, the model is applied to the actual low-permeability reservoir to determine the miscible state of CO2 and oil.
Keywords CO2-oil, miscible state, CO2 flooding, microscopic heterogeneity, carbon capture and storage, low-permeability reservoir