Impact of Brine on Disjoining Pressure and Rock Wettability of Oil, Brine, and Mineral Systems

Abstract

The alteration of rock wettability is essential for improving the efficiency of low-salinity water flooding. However, the fundamental understanding of this process remains unclear. In this paper, an extended Derjguin–Landau–Verwey–Overbeek (DLVO) theoretical model was applied to study the effects of cation types, brine concentrations, and mineral types on rock wettability in an oil–brine system. The zeta potential was measured to analyze the electric double layer. The oil–rock contact angles were tested to evaluate the wettability. The disjoining pressure was also estimated to analyze the rock wettability changes. The divalent cation showed a greater ability to compress the electric double layer. The lower concentrations of cations led to a thicker water film, promoting the detachment of oil from the rock surface. Clay minerals showed a greater impact on the wettability of rocks than quartz. This study improves the fundamental understandings of alteration of wettability in brine, oil, and rock systems and elucidates the mechanisms of disjoining pressure effects on low-salinity water flooding while shedding some light on improving the performance of low-salinity water flooding.