Displacement of nanofluids in silica nanopores: influenced by wettability of nanoparticles and oil components†
The fundamental understanding of fluid 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 analyzed using molecular dynamics simulations for investigating their influences on the displacement of fluid flow into silica nanopores. The simulations indicated that heavy and polar oil components, carrying electronegative atoms (–N and –O), were more favorable to adsorb onto silica nanopores than light and apolar molecules. The polar molecules, such as pyridine and asphaltene, preferred to accumulate at the fluid interface, which led to increased viscosity of the oil phase and hindered the 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 the pressure difference in the fluids along the nanopores to govern the fluid flow process, which shed light on resolving the nanoscale water–oil displacement mechanism in sandstone reservoirs. The results provided guidance for designing suitable nanoparticles for targeted applications.