Wettability Alteration Induced by Nanoparticle Nonuniform Adsorption and its Impact on Water–Oil Relative Permeability in Heterogeneous Porous Media

The nonuniform adsorption of nanoparticles (NPs) on the solid surfaces within porous media plays a pivotal role in altering wettability and oil–water relative permeability. However, the complexity of accurately simulating oil–water–NPs transport has left a gap, especially in the research of nonuniform adsorption of NPs. This study introduces a novel lattice Boltzmann (LB)–Langevin dynamics (LD) microsimulation method that enables precise simulation of nanofluid behaviors, including fluid migration, surface adsorption, and alteration in surface wettability. It concludes that the nonuniform adsorption of NPs leads to a heterogeneous distribution of wettability probability density on the solid surface. By formulating a microscopic equation of the wettability probability density distribution of the solid surface, our approach can predict the wettability characteristics under varying nanofluid concentrations and saturation with an average error of 6.68%. Furthermore, simulations identify an effective nanofluid saturation range (0.2–0.3) for altering the wettability from oil-wet to water-wet, with an optimal nanofluid saturation point at 0.4 from the economic efficiency aspect. With the increase of nanofluid concentration, the water-wet properties increase obviously according to enhancing the intensity term of nanofluids. The study fills a crucial research gap but also offers a framework for predicting and optimizing the wetting properties of porous media, with substantial implications for enhanced oil recovery (EOR) and environmental engineering applications.