Dynamic pore network modelling of real gas transport in shale nanopore structure

Gas transport in shale nanopores is controlled by the complex transport mechanisms and pore structure characteristics. So far much work has been done on the single pore and regular structure based pore network but lithe is known on real gas transport behavior on a realistic shale pore structure model. In this work, a dynamic pore network model is proposed to describe single component methane transport in nano-scale porous media. Gas transport behavior takes transport mechanisms of slip flow, transition flow, surface diffusion and ad/desorption into account. Real gas effect under high pressure and temperature is considered when calculating gas properties. A three dimensional pore network model is built from a three dimensional image that is reconstructed using multi-point statistics from a small organic-rich area on a two dimensional shale SEM image. This pore network model is used to analyze dynamic gas transport and pressure drop transmission process. Our simulated results reveal that there exists a time period that gas permeability on the pore network is influenced by the pressure drop transmission process and pore structure that flows on. When pressure drop reaches outlet, gas transport turns steady state. At steady state period gas permeability becomes constant and is influenced by the effective stress, pressure, temperature and shale rock property.