| CO2 injection is one of the most efficacious EOR methods of oilfield development. It can be divided into miscible displacement, immiscible displacement and near-miscible displacement. When a reservoir and input gas are definite, MMP can be determined. Therefore, there will be different miscible characteristics with different displacement pressure. The correlation of relative permeability affects displacement efficiency. Numerical simulation results will vary widely if uses different correlations of relative permeability. So it needs a three-phase model that applys to displacement system of CO2 injection.This paper uses slim tube test to determine MMP. Based on displacement test, study the influence of injection way, pressure, permeability and original oil saturation on displacement efficiency, and reveal displacement mechanism. To find out the rule of relative permeability of different miscible fluid and provide a precise relative permeability model for reservoir modeling. We choose to improve Corey model based on literature investigation. This paper adopts a method of that IFT relating to a set of fictitious and interfacial relative permeability curves. First use the phase behavior software to calculate gas/oil interfacial tension and get the pressure corresponding interfacial relative permeability curves of miscible and immiscible states. Based on Corey exponent corresponding interfacial relative permeability curve, gives the interfacial relative permeability curves. Establish an improved Corey model through an assumption of linear function relation between exponent and pressure.Through numerical simulation software, use the relative permeability curves calculated from improved Corey model to match lab displacement tests, to verify if the model is correct. Simulation results are similar to experimental value, which shows that the model is practicable, therefore, improved Corey model applys to oil displacement of CO2 injection.
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