Study on the Mobility Control and Oil Displacement Mechanism of a Polysaccharide Polymer

Resistance factor (R f ) and residual resistance factor (R ff ) are key metrics for evaluating polymer mobility control. This study examines the performance of hyperbranched polymer HPDACS in porous media under varying permeability, concentration, flow rate, temperature, and salinity conditions, analyzing its R f /R ff establishment capability and postflow viscosity/particle size changes. Results show Rf and Rff increase with concentration (1500 mg/L: R f > 35%, R ff > 20%) but decrease with higher permeability, flow rate, temperature, and salinity. After porous media shear, HPDACS maintains > 40% viscosity retention, with particle size shifting smaller—more pronounced at lower permeability. Subsequently, core flooding experiments were conducted to evaluate oil displacement efficiency at different injected pore volumes (PV). Microscopic imaging and nuclear magnetic resonance (NMR) displacement experiments were used to visualize HPDACS’ displacement behavior. The tests demonstrated HPDACS’ exceptional performance: 0.3 PV injection in 327 mD cores boosted recovery by 19.20%, showing effective residual oil mobilization. Microscopy revealed improved sweep efficiency, while NMR quantified 28.41%, 29.85%, and 19.43% recovery increases in micropores, mesopores, and macropores, respectively. These findings confirm HPDACS’ strong potential for enhancing oil recovery in heterogeneous, low-medium permeability reservoirs through stable displacement fronts and pore-scale residual oil extraction.