Exploration of blockage and release blockage mechanism of porous media under the influence of SC-CO2-high pour point oil permeation fluid system

The evaluation of separated wax-solid and its impact on reservoir permeability has long posed a significant challenge. Traditionally, most experimental methods have relied on an independent set of medium injection sequence, which cannot isolate the effects of wax-solid deposition alone. Although the use of two-dimensional models combined with high-speed cameras provides some insights into wax-solid deposition, current pressure equipment limitations prevent comprehensive analysis. This study addresses this gap by focusing on wax-solid deposition under higher pressure conditions. An innovative approach is introduced through a parallel comparison method employing artificial rock cores as carriers, which effectively eliminates interference from irreducible water and residual oil. Experimental results demonstrate that high-pressure reservoir damage occurs in 12-meter slim tube and 0.5-meter spliced core. Chromatographic analysis on collected oil samples led to the design of two composite core displacement experiments at pressures of 35 MPa and 53 MPa. Results show that the third and eighth cores in both group A and group B experienced the most substantial damage, with levels reaching 97.9% and 86.7%, respectively. Ultimately, the permeability of the advantageous channel decreased by 87.5% in group A and 67.0% in group B, mainly due to blockage and release mechanisms working together. In conclusion, the new experimental design significantly enhances deposition observation by enabling precise capture accuracy and practical applicability, offering valuable insights into permeability changes caused by wax-solid deposition.