LAUSR

Low-salinity water injection emerges to be a cost-effective and environmentally friendly enhanced oil recovery technique. Furthermore, additives, such as the surfactant and nanoparticles in combination with low-salinity water, appear to be promising formulations for rock wettability modification and surfactant adsorption control. The detailed interaction of these novel formulations and the rock surface is, however, not well understood. Thus, an experimental study was conducted here, and results show that the anionic surfactant (AOT, 11.247 mM) augmented the effect of silica nanoparticles (1000–3000 mg/L concentration) at low-salinity conditions as effective surfactant adsorption control agents when used at appropriate divalent cation/sulfate ion ratios. Low-salinity surfactant nanofluids may thus be applied for wettability alteration of oil-bearing sandstone reservoirs for recovering residual oil. Here, we demonstrate that the ratio of divalent cations to sulfate ions (0 ≤ M2+/SO42– ≤ 4.427) has a signifi...