Performance Evaluation of Peanut-Shaped Polystyrene Nanospheres as Profile-Control Agents

Polymer microspheres are profile-control agents for plugging high-permeability reservoir zones, regulating injection profiles, and enhancing oil recovery (EOR) owing to their small size and strong retention. However, most studies focus on spherical microspheres, whereas peanut-shaped anisotropic particles remain rarely investigated. Herein, peanut-shaped polystyrene (P-PS) particles prepared through an optimized emulsion-polymerization route reported in our previous work were evaluated as anisotropic profile-control agents for EOR and compared with spherical PS particles (S1-PS and S2-PS). Core plugging tests showed that P-PS particles, with an apparent hydrodynamic diameter of 72 nm and an aspect ratio of 2.44, achieved a plugging efficiency of 85.72% in a 200 mD core, representing increases of 61.56% and 28.69% over S1-PS (160 nm) and S2-PS (65 nm), respectively. SEM confirmed that P-PS particles migrated into the porous medium and were retained within pore spaces. Under 70°C, 200 mD, 1.8 PV, and 1000 mg/L, P-PS produced an incremental EOR of 12.97%, 4.40, and 1.37 percentage points higher than those of S1-PS and S2-PS, respectively. At 5000 mg/L, EOR reached 18.70%, although injection pressure approached the limit. This study provides insight into anisotropic particle transport and retention in porous media and supports their profile-control potential.