Pore–Fracture Structure Characteristics of Low-Medium Rank Coals from Eastern Surat Basin by FE-SEM and NMR Experiments

The Middle Jurassic Walloon Subgroup coals in Australia’s Surat Basin are extremely rich in low-medium rank coal seam gas (CSG) resources, making it one of the world’s most productive CSG development basins. The desorption, diffusion and seepage behaviors of CSG are remarkably influenced by the pore–fracture structure characteristics of coals; therefore, their detailed characterizations are greatly significant for CSG exploration and development. There are, however, currently few researches on the pore–fracture structure characteristics of Surat Basin coals. Thus, 12 low-medium rank coals ( R r: 0.42–0.60