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Molecular dynamics simulation for the effect of cation replacement on the oil-brine-rock interaction

The low salinity waterflooding can increase oil recovery by 5%-20% in sandstones, which has attracted more and more attention. However, the mechanism of low salinity waterflooding is not clear. In this paper, the effect of cation replacement on the interaction between oil and silica is investigated via molecular dynamics simulation to reveal the mechanism of low salinity waterflooding. The results show that the stable adsorption of oil droplets on the silica surface is mainly due to the strong interaction between oil and rock caused by cations. Replacing Ca2+ with Na+ can effectively reduce the interaction between oil and rock and make oil droplets easier to be peeled off. This work is helpful for the further study of the oil-brine-rock interaction and can provide theoretical guidance for the oil film stripping of sandstone reservoir.