Mechanistic Study of Oil/Brine/Solid Interfacial Behaviors during Low-Salinity Waterflooding Using Visual and Quantitative Methods

Despite the many studies of low-salinity waterflooding (LSWF), its underlying mechanisms are not well understood as a result of the complexity of the oil/brine/solid interfacial behaviors. Moreover, the widely held belief that LSWF is effective only under certain conditions has not been conclusively proven. Therefore, the static and dynamic interfacial behaviors during LSWF were visually and quantitatively studied in this work to elucidate the underlying mechanism(s). The results showed that LSWF effectively promotes oil recovery by causing double-layer expansion (DLE) and hydrocarbon solubilization. The DLE resulted from multicomponent ion exchange (MIE), as revealed by contact angle, ζ potential, and conductivity measurements. Emulsions prepared with low-salinity brines (≤0.21 wt %) were noticeably heavier and quite stable, demonstrating the significant solubilization effect of LSWF. The oil displacement dynamics observed in a visual micromodel indicated that LSWF increased the oil recovery factor by 4%...