Study of liquid-liquid two-phase flow in hydrophilic nanochannels by molecular simulations and theoretical modeling

Multiphase flow in nanoporous media is ubiquitous in geophysics, physical chemistry, and bioengineering. The underlying mechanisms of two-phase flow are of great importance in the prediction of water and oil flow in shale nanoporous media. In this work, we use molecular dynamic simulations to investigate a laminar type oil-water two-phase flow (OW2PF) in quartz nanopores. We find that in nanochannels, due to liquid-liquid slip, the enhancement in oil phase flow may not be neglected. As water film thickness and pore size increase, such enhancement decreases gradually. According to MD results, a new hydrodynamic flow model considering fluid distributions, heterogeneous fluid properties, liquid-wall interaction, and liquid-liquid slip is proposed and compared to MD results and other hydrodynamic flow models. While previous hydrodynamic flow models generally underestimate oil phase flow in a laminar type OW2PF in quartz nanopores, our model shows an excellent agreement with MD simulations for a wide range of pore sizes. Our work could shed some lights into flow mechanism of a laminar type OW2PF in nanoporous media and provide insights into flow modeling development in shale oil exploitation.