Real Gas Transport in Tapered Noncircular Nanopores in Shale Rocks
Jinze (Jason) Xu
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This work shows that with an increase in the taper ratio and aspect ratio under the constant mean cross-sectional area, conductance of Knudsen diffusion and viscous flow reduce, and the surface diffusion conductance first increases and decreases afterwards; Increasing the taper ratio and aspect ratio shrinks the pore volume occupied by free gas, decreases the free gas transport ratio, and thus lowers the transport capacity of nanopores; Tapered circular nanopores own the greatest transport capacity owing to the highest free gas transport ratio; The apparent permeability may be an indicator to predict the transport regime; The apparent permeability that is greater than 105 nd implies that the viscous flow dominates, and the apparent permeability that is lower than 100 nd implies that the surface diffusion dominates; With increasing a mean cross-sectional area, free gas transport gradually dominates, which increases the transport capacity indicated by the apparent permeability. Increasing the taper ratio and aspect ratio reduces the transport capacity of nanopores by shrinking the free gas -dominated region.