An analytical model for gas transport through elliptical nanopores

Effect of pore geometry on nanoconfined gas transport capacity has not been clearly revealed. Elliptical cross-section can vary from circular to slit-like shape by adjusting the aspect ratio (AR), which covers a wide range of pore shapes and shares more research value over that of regular cross-section. In this paper, a novel analytical model for gas transport in elliptical nanopores is established based on weighted superposition of continuum flow and Knudsen diffusion, which possesses more solidified theoretical background than existed models for elliptical nanopores. Results show that contribution of Knudsen diffusion will increase with the increase of AR at a certain pore scale. For a certain pressure point, the contribution of continuum flow mechanism within large pore scale will be greater than that within small pore scale. The discrepancy of simplifying elliptical cross-section as circle is about 90% in continuum flow, 50% in slip flow and 10% in transition flow as well as Knudsen diffusion. The proposed model can advance current understanding of gas transport characteristics through realistic shale matrix. (C) 2019 Elsevier Ltd. All rights reserved.