Well-Log-Interpreted Reservoir Parameters Assisted Evaluation of Hydrophobically Modified Partially Hydrolyzed Polyacrylamide Flooding for Enhanced Oil Recovery in Heterogeneous Reservoirs

Polymer flooding is an important enhanced oil recovery technology for high-water-cut heterogeneous reservoirs, where long-term waterflooding commonly leads to preferential flow channels and insufficient mobilization of remaining oil in less-swept intervals. In this study, a hydrophobically modified partially hydrolyzed polyacrylamide-type polymer containing hydrophobic associative groups was evaluated for mobility control and enhanced oil recovery in heterogeneous porous media with the assistance of well-log-interpreted reservoir parameters. Reservoir heterogeneity was first characterized using interpreted effective thickness, porosity, permeability, oil saturation, and water saturation, and the polymer performance was then examined through rheological measurements, core-flooding experiments, and field production response analysis. The results show that the representative reservoir layers exhibit a wide permeability range of 7.9–186.5 mD, with higher water saturation in high-permeability layers and higher oil saturation in medium- and low-permeability layers. The polymer solution shows concentration-dependent thickening, shear-thinning behavior, salinity tolerance, and thermal-aging stability, retaining a viscosity of 139.5 mPa·s at 180,000 mg/L salinity and 74.9% viscosity retention after aging for 504 h. Core-flooding results indicate that the medium-permeability core achieves the highest polymer incremental recovery of 14.5 ± 0.8%, reflecting a favorable balance between injectivity and residual flow resistance. Field production data further show that daily oil production increases from 11.6 to 20.4 t/d, water cut decreases from 93.1% to 81.6%, and cumulative oil increment reaches 2055 t after polymer injection. The proposed mechanism involves associative thickening, pore-throat-adaptive transport, residual flow resistance, flow-path redistribution, and remaining-oil mobilization. This study establishes a heterogeneity-constrained mobility-control framework linking well-log-interpreted reservoir parameters, permeability-dependent polymer transport, residual flow resistance, and field production response, showing that effective polymer flooding depends on balancing injectivity, flow resistance, and remaining-oil availability rather than maximizing bulk viscosity alone.