Blockage Mechanism and Immiscibility Pressure Optimization of Slim Tube Porous Space in CO 2 Displacement Processes

ABSTRACT As the method of directly separate wax‐solid deposition from crude oil is difficult to achieve and its impact on the blockage mechanism of the permeation fluid channels cannot be independently explored, this study attempts to use indirect detection methods. When designing pressure parameters, factors such as rock mechanical properties should be considered. This article presents a detailed study of optimal immiscibility pressure and displacement processes. Through two sets of experiments, the minimum miscibility pressure of the target oil sample was determined to be 75 + MPa. For high‐pressure environments with pressures exceeding 30 MPa, the change in the productivity/injectivity index before gas breakthrough is relatively small, after and during gas breakthrough, fluctuations in the index increase significantly. Curve characteristics indicate that for this type of oil, when the pressure approaches a certain high‐pressure state, even before reaching the MMP, the permeate fluid channels may be blocked, which is not conducive to crude oil mining. This interpretation also supports and confirms the results of microscopic visualization simulation experiment. After comprehensively considering the rock fracture pressure value, end‐point reserve recovery trend line chart, and gas injection cost, 35 MPa was selected as the optimal immiscibility pressure.