Phase Behavior and Flow in Shale Nanopores From Molecular Simulations

Abstract

Abstract Phase behavior and flow in shale nanopores, due to fluid heterogeneity, cannot be described by bulk and continuum-based formulations. The interactions between fluid and rock molecules are important in both phase behavior and flow. As a result, frameworks from bulk equations of state in phase behavior, and Knudsen diffusion and Klinkenberg slippage in flow may not have direct applications. Recently, we have studied both phase behavior and flow in nanopores using various molecular simulations. This work addresses a number of issues in relation to phase behavior and flow in nanopores. We model the excess adsorption of ethane in shale media. The data of ethane adsorption has been reported recently. Past data on hydrocarbon adsorption is limited to methane. We also model the effect of water on hydrocarbon adsorption in kerogen and compare the results with the effect in clay. In flow, as in our recent work, we use the dual control volume-grand canonical molecular dynamics (DCV-GCMD) simulations. We use a low pressure difference between high pressure and low pressure reservoirs connected to the nanopores. We find that similar to our past work, the flux of methane in the slit pores can be two orders of magnitude higher than the results from the Knudsen diffusion.