Wettability Alteration Modeling for Oil-Wet Calcite/Silica Nanoparticle System Using Surface Forces Analysis: Contribution of DLVO versus Non-DLVO Interactions

In this work, application of silica nanoparticles for wettability alteration of initially oil-wet calcite was investigated through analysis of surface forces and DLVO theory. Doing so, the wettability and zeta potential of calcite surfaces were measured through the sessile drop method and an in-house experimental setup, respectively. Primary evaluation indicated that incorporating DLVO terms in the Frumkin-Derjaguin model was not sufficient to describe the wettability in an oil-wet calcite/nanofluid system. Sensitivity analysis showed that calculating the double-layer interaction using constant potential-constant potential boundaries along with structural hydrophobic forces (non-DLVO interaction) incorporation improved the modeling performance. Considering hydrophobic interactions through linear correlation between hydrophobicity and wettability change for both single-exponential and harmonic equations provided some confidence on the modeling approach. Moreover, structural forces were suggested to be introduced as a combination of hydrophobic/hydrophilic interactions corresponding to stearic acid-coated/silica nanoparticle-covered sites, respectively; which in turn demonstrated a successful prediction of measured wettability data.