ZnO- and SiO2-Nanoparticle-Based Surfactant–Polymer Systems for Enhanced Oil Recovery: Stability, Interfacial Properties, and Rheological Behavior

Abstract The increasing demand for oil and the need for improved recovery methods have increased interest in nanoparticle–surfactant–polymer systems for enhanced oil recovery (EOR). In this study, zinc oxide (ZnO) and silica (SiO2) nanoparticles were used with sodium dodecylbenzenesulfonate (SDBS) and two polymers, polyethylene glycol (PEG) and carboxymethyl cellulose (CMC). The nanofluids were prepared using high-energy ultrasonication, and their stability, rheological behavior, interfacial tension (IFT), wettability, and oil recovery performance were studied. ZnO nanofluids showed better colloidal stability than SiO2 nanofluids. The nanofluids showed shear-thinning behavior, and viscosity generally decreased with increasing temperature and salinity. The effect of NaCl salinity and formation water on the rheological behavior was also evaluated. FT-IR analysis indicated changes in the hydrocarbon-associated spectral features after oil recovery. Wettability analysis showed a change in sandstone wettability from intermediate-wet conditions to strongly water-wet conditions. Core-flooding experiments showed additional oil recoveries of 25.92%, 37.24%, 30.64%, and 30.34% OOIP for ZnO–CMC, SiO2–CMC, ZnO–PEG, and SiO2–PEG nanofluids, respectively. Among the tested formulations, the SiO2–CMC system showed the highest additional oil recovery of 37.24% OOIP. A preliminary economic evaluation was also performed to compare the estimated preparation costs of the developed formulations. Overall, the results show that ZnO- and SiO2-based SDBS–polymer nanofluids have potential for improving oil recovery through changes in fluid properties and rock wettability.