Enhanced Oil Recovery in High Salinity and Elevated Temperature Conditions with a Zwitterionic Surfactant and Silica Nanoparticles Acting in Synergy

Novel SiO2 nanoparticles (NPs) costabilized by a low-molecular-weight ligand (steric stabilization) and a zwitterionic surfactant (electrostatic stabilization) were developed for enhanced oil recovery purpose in sandstone reservoirs with high salinity and elevated temperatures. According to our experiments, the proposed NPs were not sensitive to either monovalent or divalent cations, whose size remained around 10.0 nm in API brine within 8 weeks at 25 °C and 4 weeks at 60 °C. Using the zwitterionic surfactant with NPs reduced the NP dosage required to induce wettability alteration and the possibility of severe permeability damage. The presence of NPs in return effectively decreased the surfactant adsorption loss on rocks, reduced the surfactant concentration needed to produce a low interfacial tension, and rendered the oil-wet solid surface toward a more water-wet condition beneficial for water imbibition and oil displacement. Core flooding tests showed that the nanofluid composed of 800 mg/L of zwitterio...