Comparison of mining performance of carbon dioxide displacement and hot water displacement for high pour point oil based on index variation characteristics

Regarding the pressure difference and time elements, this study innovatively employs indirect detection methods using the productivity/injectivity index to explore the related oil production mechanisms, the experimental process was strictly carried out according to standardized procedures, and the accuracy of the data was guaranteed. The comprehensive experimental results show that under carbon dioxide displacement conditions, two peaks appear on the trend line of the oil productivity index at 0.3/0.4 PV and beyond 0.3/0.4 PV. However, in different directions, one points toward breakthrough phenomena and the other toward extraction effects. Overall, the oil recovery index does not increase with pressure, and even shows a downward trend. This implies that although the final recovery rate increases in higher-pressure environments, the risk of wax-solid deposition blockage also rises significantly, impacting production capacity. In long rock core hot water displacement experiments, when the water injection ratio exceeds 1.2 PV, the cumulative effect of injected fluid at high pressure (53 MPa) effectively flushes out residual oil, differing from the effect observed at medium pressure (35 MPa). Comparing the two displacement modes, there is a significant difference stage in recovery rate exceeding 10% occurs after the displacement medium breakthrough. Therefore, the extraction effect of carbon dioxide should be continuously strengthened.