Study of Wax-Solid Deposition and Release-Blockage Effects on SC-CO2 Displacement Dynamics of High-Pour-Point Oil Through Slim Tube Experiments

The quantitative evaluation of the impact of wax-solid deposition on the CO2 displacement of high-pour-point oil has long been a challenge in gas-flooding experiments. This study employs slim tube experiments to simulate the displacement dynamics, and comprehensively evaluates the productivity/injectivity index formula and the GERG-2008 state equation. The results indicate that the fluctuations in this index remain stable within the 17–20 MPa range and become pronounced within the range of 30–40 MPa. The analysis of seepage velocity reveals an initial increasing trend for supercritical CO2 under the conditions of 30 MPa, 35 MPa, and 40 MPa, followed by inflection points at different time steps. The observed decline in seepage velocity inflection is associated with the occurrence of wax-solid deposition in high-pour-point oil. Notably, there is a significant surge in CO2 seepage velocity at 40 MPa during the latter stage of the experiment due to the release-blockage effect of supercritical CO2. To systematically analyze the influence of wax-solid on the CO2 displacement in high-pour-point oil, a methodological framework is established in this study. This approach enables precise analysis of displacement dynamic characteristics in the target areas and provides pressure parameters for oilfields.