Enhancing Aqueous Stability of Anionic Surfactants in High Salinity and Temperature Conditions with SiO2 Nanoparticles.

In chemical-enhanced oil recovery (cEOR), surfactants are widely used but face significant stability challenges in high-salinity brine, where they often degrade or precipitate. Existing methods, such as adding cosurfactants, offer limited compatibility with anionic surfactants and raise economic concerns, creating a need for more robust solutions. This study introduces a novel approach to enhance the stability of anionic surfactants in extreme salinity conditions by incorporating silicon dioxide (SiO₂) nanoparticles (NPs). Our optimized formulation effectively prevents surfactant precipitation and NP aggregation, demonstrating stability in brine with salinity as high as 57,000 ppm and temperatures up to 70 °C, thus addressing the salt tolerance issues seen with conventional anionic surfactants like sodium dodecyl sulfate (SDS). To validate our formulation, we employed multiple experimental techniques, including turbidity, ζ-potential (ZP), and hydrodynamic diameter (HDD) measurements, which confirmed the efficacy of our approach. Results indicated that an optimal SiO₂ NP concentration (0.01 wt %) significantly enhanced SDS stability, with no observed aggregation or precipitation over 7 days. High absolute ZP values (>25 mV), a small HDD (∼37 nm), and a consistent turbidity profile underscored the stability and dispersion of the formulation. This nanoparticle-based method offers a cost-effective and sustainable solution for cEOR, providing enhanced surfactant stability and improved NP dispersibility under high-salinity and high-temperature conditions, representing a valuable advancement in chemical-enhanced oil recovery technology.