Extended DLVO Modeling of Nanoparticle-Assisted Wettability Alteration in Unconventional Reservoirs

Wettability alteration is a key mechanism for enhancing oil recovery in unconventional reservoirs. This study utilizes an extended Derjaguin–Landau–Verwey–Overbeek (DLVO) framework that integrates van der Waals, electrostatic double-layer (EDL), structural hydration, and nanoparticle-induced hydrophobic forces to quantify additive-assisted wettability shifts across salinity and concentration gradients. The model links total disjoining pressure to contact angle via a concentration-dependent scaling factor, α(c), and is validated against published data for tight-rock systems treated with silica nanoparticles under low-salinity water and brine conditions. Predictions match experimental contact angles with a root-mean-square error (RMSE) of 8.97°, capturing wettability change of rock surface in water and brine conditions under different nanoparticle concentrations. Disjoining pressure analysis indicates that EDL enhancement is the dominant mechanism of nanoparticle-induced wettability alteration, while structural hydration contributes as a short-range repulsive interaction and hydrophobic forces act as short-range attractive interactions. The framework suggests optimal nanoparticle concentrations of approximately 1 wt% in fresh water and 2 wt% in brine, providing a scalable tool for designing nanoparticle–surfactant formulations to promote spontaneous imbibition in unconventional reservoirs.