Fluid transport through heterogeneous pore matrices: Multiscale simulation approaches

Fluids confined in nanopores exhibit several unique structural and dynamical characteristics that affect a number of applications in industry as well as natural phenomena. Understanding and predicting the complex fluid behavior under nano-confinement is therefore of key importance, and both experimental and computational approaches have been employed toward this goal. It is now feasible to employ both simulations and theoretical methods, the results of which can be validated by cutting-edge experimental quantification. Nevertheless, predicting fluid transport through heterogeneous pore networks at a scale large enough to be relevant for practical applications remains elusive because one should account for a variety of fluid-rock interactions, a wide range of confined fluid states, as well as pore-edge effects and the existence of preferential pathways, which, together with many other phenomena, affect the results. The aim of this Review is to overview the significance of molecular phenomena on fluid transport in nanoporous media, the capability and shortcomings of both molecular and continuum fluid modeling approaches, and recent progress in multiscale modeling of fluid transport. In our interpretation, a multiscale approach couples a molecular picture for fluid interactions with solid surfaces at the single nanopore level with hierarchical transport analysis through realistic heterogeneous pore networks to balance physical accuracy with computational expense. When possible, comparison against experiments is provided as a guiding roadmap for selecting the appropriate computational methods. The appropriateness of an approach is certainly related to the final application of interest, as different sectors will require different levels of precision in the predictions.