Molecular dynamics modeling and simulation of silicon dioxide-low salinity water nanofluid for enhanced oil recovery

Silicon dioxide nanoparticles (NPs) are known as one of the most widely utilized materials in the area of the nanotechnology of enhanced oil recovery (Nano-EOR) processes. However, its dynamic characteristics and performance require a deep understanding at the atomistic scale. Accordingly, in this research, molecular dynamics (MD) was used to investigate the wettability effects of silicon dioxide and its surface modifications through the Nano-EOR process at microscopic scale. Three different types of SiO2 NPs were modeled, including the molecular nanoparticles form (Type I), a modified crystalline nanoparticle with a negatively charge oxygen (Type II), and a crystalline nanoparticle with a hydrogenated surface (Type III). These nanoparticles, along with low salinity water, were modeled and simulated on a calcite rock surface. Also, sodium dodecyl sulfate (SDS) surfactant was modeled with Type III NPs. In these simulations, the modified forcefield was chosen as the calcite non-bonds and bond energies. For other molecules, however, CHARMM36 forcefields were selected. The obtained results demonstrated that although Type I NPs forced the oil molecules to detach from the calcite surface, the detachment occurred at 1,320,000 fs (fs). Type II NPs revealed a suitable dispersion on the surface during the simulation due to the strong adsorption of water towards NPs based on the radial distribution function (RDF) diagram. Finally, Type II NPs reduced the oil contact angle in less time rather than other NPs types. According to self-diffusion data, Type III NPs revealed no a good dispersion in the aqueous solution and the minimum wettability alteration improved by the SDS surfactant to rapidly detached oil from the calcite surface at 800,000 fs. These findings make it possible to demonstrate the mechanism of modification of the calcite surface wettability in contact with different nanoparticles. (C) 2021 Elsevier B.V. All rights reserved.