Displacement of Nanofluids in Silica Nanopores: Influenced by Wettability of Nanoparticles and Oil Components

The fundamental understanding of fluids transportation in confined nanopores is essential for groundwater remediation, oil exploration, water purification, etc. Here, all-atom models of various oil components and nanoparticles were put into molecular dynamics simulations for investigating their influences on the displacement of fluid flow into silica nanopore. The simulations indicated that heavy and polar oil components, carrying electronegative atoms (-N, -O), were more favorable to adsorb onto silica nanopore than light and apolar molecules. The polar molecules, such as pyridine, asphaltene, preferred to accumulate at fluids interface, which leaded to increased viscosity of oil phase and hindered spontaneous displacement process. Silica nanoparticles (NPs) in the displacing phase could modulate the fluid-fluid meniscus regardless of hydrophobic or hydrophilic surface modification and slow down the displacement process. Most importantly, the presence of NPs induced pressure difference in the fluids along the nanopore to govern fluids flow process, which shed light on resolving nanoscale water-oil displacement mechanism in sandstone reservoirs. The results provided guidance of designing suitable nanoparticles for targeted applications