Evaluation of anti-swelling and stability of pressure reducing and injection increasing agents for low-permeability reservoirs

Low salinity water entering the reservoir can cause hydration, expansion, dispersion, and migration of clay minerals, thereby damaging the reservoir. For low-permeability water sensitive reservoirs, the decrease in permeability caused by clay swelling should be given more attention. Therefore, the anti-swelling performance of pressure reducing and injection increasing agents is also a key focus that needs to be paid attention to. After evaluating the reservoir sensitivity of MB 2 reservoir, it was found that MB reservoir has moderate to strong water sensitivity. Therefore, it is necessary to further study the anti-swelling performance of the initially screened pressure reducing and injection increasing agents. The compound system C₁₂TAB+C₁₆TAB+14-4-14, as a pressure reducing and injection increasing agent, has excellent anti-swelling performance, and the pretreated core anti-swelling rate reaches 90%. The compatibility and aging stability of the system with MB block water samples were studied, and it was found that the system has good compatibility and aging stability. Through the evaluation of wetting performance, the depressurization and injection system can improve the wetting performance of the rock surface to a certain extent, and the contact angle of the rock before and after treatment increases from 61.4° to 73.6°. The control group FC-4430 modified the rock wetting to neutral wetting, while JFC-1 treated the rock surface to be more hydrophilic.