Methane Adsorption\nand Transport in Tortuous Slit-like\nNanochannels: A Molecular Simulation Study

Tortuosity is a crucial\ncharacteristic of porous materials, such\nas the shale matrix where shale gas is stored. The presence of tortuous\nnanochannels significantly affects the adsorption and transport of\nnanoflows. In this research, we use molecular dynamics simulation\n(MD) to study the adsorption and transport properties of shale gas\n(methane) in a curved slit-like nanochannel constructed from bent\ngraphene sheets. Our findings reveal that the curvature of the tortuous\nchannel influences methane adsorption: convex surfaces exhibit stronger\nadsorption, while concave surfaces exhibit weaker adsorption; the\ndiscrepancy is amplified by the nanoflow. Additionally, nanoflow velocity\nis heterogeneously distributed within the curved channel, with higher\ntangential flow velocities observed near the entrance and the outer\nsurface. We also identify a “bouncing effect”, where\nthe nanoflow not only moves tangentially along the channel but also\nbounces between the inner and outer walls. Furthermore, methane in\nnarrower channels exhibits higher tangent flow velocity and higher\nbouncing frequency but smaller flux, whereas larger curvature results\nin shorter channel length and smaller tortuosity, but the transport\ntangent velocity and flux are both reduced. The findings of this study\ncan help in the better understanding of shale gas nanoflow properties\nin tortuous media and provide insights for simulating more general\nnonstraight nanoflows.