Extended DLVO-based estimates of surface force in low salinity water flooding

We estimated the effect of cation types (NaCl, MgCl2 and CaCl2), concentrations (0.2, 1, and 5 wt.%) on disjoining pressure with the presence of various clays, two different oils and Berea sandstones. We also compared the disjoining pressure results with core-flooding experiments in the literature [1]. Our results show that disjoining pressure is extremely sensitive to cation types rather than salinity level. Divalent cations (0.2 wt.%, CaCl2 and MgCl2) exhibits negative disjoining pressure with oils, clays and Berea sandstone, but monovalent cations (0.2, 1 wt.%) shows positive disjoining pressure, suggesting that removing divalent cations from the injected brine is essential to alter the wettability, in line with results of core-flooding experiments in the literature [1]. While we did not explicitly investigate the influence of multi-component ion exchange on low salinity effect, DLVO-based model allows us to put boundaries on injected water chemistry, and deeply understand the interaction of Crude Oil/Brine/Rock system. Further, we argue that extended DLVO theory could be applied to screen candidate reservoirs for low salinity water flooding, providing industry with a guideline to manipulate water chemistry to maximize oil recovery. We also proposed a workflow to preliminarily evaluate the potential of LSE to constrain the intrinsic uncertainty of low salinity water flooding in fields.