Review on Pore-Scale Physics of Shale Gas Recovery Dynamics: Insights from Molecular Dynamics Simulations

Abstract

Reliable prediction of gas recovery from shale formations is essential for achieving the full potential of shale gas. A distinguishing feature of shales is that nanoscale pores dominate their porosity. Hence, confinement and fluid–wall interactions modulate shale gas storage, transport, and recovery, which are neglected in conventional gas recovery models. Because these nanoscale effects can be simulated using molecular dynamics (MD), related works have proliferated. Here, we review MD modeling of shale gas recovery at the pore scale. The design and simulation protocols of MD systems for studying gas recovery are surveyed first. Then, the gas recovery in three scenarios, i.e., recovery of single-component gas, recovery of multicomponent gas, and gas recovery involving multiphase flows, are reviewed. In particular, works exploring and elucidating new pore-scale phenomena and guiding and validating new pore-scale continuum models are highlighted. Finally, we recommend best practices in MD shale gas studies and suggest several research directions.