Nanofluid formulation based on the combined effect of silica nanoparticles and low salinity water for Enhanced Oil Recovery in sandstones

Recent studies have indicated that nanofluids that combine silica nanoparticles and low salinity water have a promising character as Enhanced Oil Recovery agents for application in sandstones. In view of that, this work aimed to investigate the stabilization mechanism of silica nanoparticles in aqueous medium and the effects that low-salinity silica nanofluids induce on fluid/fluid and rock/fluid interactions in order to generate contributions to the understanding of the oil recovery mechanisms of this potential injection fluid. Therefore, experiments were carried out with nanofluids containing silica nanoparticles at concentrations between 0.01 and 0.2 wt% dispersed both in deionized water (DW) and in a low salinity water (LSW) containing a Total Dissolved Solids of 1343.4 mg/L. The results showed that the dynamic viscosity of the nanofluids exceeds that of DW by, at most, only about 4.23%. The size of the silica nanoparticles in the nanofluids did not increase over 200 nm and was not consistently affected by factors such as nanoparticle concentration, dispersing fluid or time elapsed after sonication of the nanofluids. In general, the interfacial tension between the crude oil and DW was not substantially changed when the aqueous phase was replaced by the nanofluids. On the other hand, the zeta potential of silica nanoparticles was significantly decreased when they were dispersed in LSW in comparison to DW. The contact angle analyzes evidenced the ability of the nanofluids in altering the wettability of crude-oil aged sandstone surfaces towards more water-wet conditions, notably the nanofluids with higher concentrations of silica nanoparticles and prepared with LSW.