Diffusion characteristics of nanoscale gas flow in shale matrix from Haenam basin, Korea

To develop a shale gas reservoir, the gas flow in shale matrix essentially needs to be analyzed. The shale matrix consists of fractures and nanopores that have separate flow mechanisms. The purpose of this study is to investigate the gas diffusion in the nanopores of a shale matrix from the Haenam basin, Korea. To examine gas diffusion, an apparatus was developed to measure shale properties at the nanopore-scale. Subsequently, the measured properties were used to describe gas diffusion based on the Knudsen and Fick diffusion models. During the investigations, the pressure condition ranged from 0.69 to 41.37 MPa, setting temperature condition of 298.15 K. From the results, it was revealed that Knudsen diffusion was controlled by the pore sizes and pressure, while the Fick diffusion was governed by gas molecular radius and temperature. Therefore, shale gas diffusion should be evaluated by considering the parameters such as pore size, pressure, temperature, and gas molecular radius.