Synergistic Effect of Silica Nanoparticles and Rhamnolipid on Wettability Alteration of Low Permeability Sandstone Rocks

Wettability modification is one of the main mechanisms to increase oil recovery from low-permeability oil reservoirs. Nanofluids composed of nanoparticles can be used as modifiers to alter wettability from oil-wet to water-wet condition thus to promote hydrocarbon recovery. Biosurfactants, which are candidates to replace synthetic surfactants for industrial applications, have the potential to prepare nanofluids. In this study, nanofluids prepared by dispersing SiO2nanoparticles in rhamnolipid solution (hereby named bionanofluids) were considered potential wettability modifiers to apply to petroleum recovery from low-permeability sandstone reservoirs. Analyses via visual observation, optical absorbance measurement, ζ-potential determination, and particle size measurements demonstrated that the bionanofluids with 25 ppm rhamnolipids maintained an optimal stability. The effect of bionanofluids on wettability alteration was investigated through contact angle measurement and imbibition test. The results showed that bionanofluids could alter the wettability of oil-wet sandstone to strongly water-wet. The best performance was achieved with a nanoparticle concentration of 1000 ppm. Additionally, a micromodel test using rhamnolipid solution and bionanofluid was carried out to evaluate the synergistic effects of SiO2nanoparticles and rhamnolipid on displacing oil. Bionanofluid injection following biosurfactant flooding was shown to improve oil recovery, yielding an additional 5% production. These results reveal that the bionanofluid prepared with SiO2and rhamnolipids not only remained stable but also provided a potential way for enhanced oil recovery.