Experimental investigation on the characteristics of gas diffusion in shale gas reservoir using porosity and permeability of nanopore scale

The aim of this study is to investigate the diffusion characteristics of nanoscale gas flow in a shale gas reservoir. An experimental apparatus was designed and set up to measure porosity and permeability at the nanopore scale. The measured properties have been used to determine a diffusion coefficient by classification standard of gas flow regime. To investigate the impact of pressure and pore size, the analysis of diffusion flow was conducted using Knudsen and Fick diffusion coefficients. From the results, it was revealed that Knudsen diffusion coefficient gradually increased with the growth of pressure and pore radius and Fick diffusion coefficient was dependent on the gas molecular diameter and temperature. It was also found that Knudsen diffusion coefficient was equal to Fick diffusion coefficient if pore radius is too small. The study implied that the characteristics of gas diffusion should be implemented by using the diffusion coefficient theory based on gas flow regime in shale gas reservoirs.