Using silica nanoparticles and anionic surfactant in low-salinity water to enhance oil recovery in the Assam Shelf Basin

Surfactant flooding is a widely adopted Chemical Enhanced Oil Recovery (CEOR) method, but its efficiency is limited by the adsorption of surfactants onto reservoir rock surfaces. This study investigates the effect of silica nanoparticles (Nano-SiO₂) on the adsorption behavior of an anionic surfactant, sodium dodecyl benzoic sulphonate (SDBS), in kaolinite-rich sandstone cores from the Assam Shelf Basin. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) confirmed kaolinite as the dominant clay. Adsorption experiments fitted to Langmuir and Freundlich isotherms revealed that adding 0.05 wt% Nano-SiO₂ to 0.2 wt% SDBS reduced adsorption and shifted behavior from multilayer to monolayer adsorption. Zeta Potential increased to − 27.2 mV, and Contact Angle decreased to 21.5°, indicating enhanced wettability. Core flooding tests showed oil recovery improved from 24.84 to 34.89% of IOIP. These results support the potential of Nano-SiO₂-enhanced surfactant systems for effective CEOR in clay-dominant reservoirs.