Research on the Adaptability of Polymer Flooding in High Salinity Reservoirs

This paper conducts a study on the adaptability of polymer flooding under high salinity conditions (25,000 mg/L) for a chemical flooding target block — a multi-layered sandstone reservoir with active bottom water and significant differences in vertical permeability. The main oil-producing layers of the study area, AB 13 and AB2-3, have a small permeability difference and a high degree of oil extraction, and are unaffected by bottom water, providing favorable conditions for the application of polymer flooding technology. Based on the screening and evaluation of more than ten types of salt-resistant polymers, the best polymer flooding system formula was optimized through physical simulation experiments. The experimental results show that the molecular cluster size analysis indicates that HDP3 and GY polymers have larger molecular cluster sizes (greater than 500 nm), while the sizes of other polymers range between 40 nm and 300 nm. In terms of viscosity, KY51, HDP3, ZC10, GY, KY08, and 5115 polymers can achieve an increased viscosity effect of 20 mPa·s at relatively low concentrations. The power law index of the polymer solutions is less than 1, indicating that they are pseudoplastic fluids, and the magnitude of the consistency coefficient directly affects the overall viscosity enhancement capability of the liquid. Stability experiments found that as the concentration increases, the viscosity retention rate of the polymer solution decreases, with ZC10 polymer demonstrating the best aging stability. In terms of polymer flooding performance, KY51 polymer shows the strongest oil displacement capability, with an overall polymer flooding recovery rate of 14.58%, and the numerical model prediction for the chemical flooding target block suggests that polymer flooding can increase the recovery rate by 11.7 percentage points. This study provides a theoretical basis for polymer flooding technology in high salinity oil reservoirs..