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 (\({\overline{\text{R}}}\)r: 0.42–0.60%) from the Walloon subgroup of Eastern Surat Basin were obtained for this study, and then coal petrology analyses, field emission scanning electron microscopy and nuclear magnetic resonance (NMR) experiments were performed on these samples. The results show that the organic macerals of Surat coals are dominated by vitrinite, followed by liptinite, and the inertinite is generally rare. The average porosity, movable porosity and movable water saturation of the coal samples were 5.08%, 1.01% and 22.47%, respectively. The coal samples’ pore–fracture structure was characterized by an overwhelming predominance of MIT (micropores and transition pore) and relatively less developed ME (mesopore) and MAF (macropore and fracture), with average volume proportions of 74.58%, 14.06% and 11.36%, respectively. The movable porosities of different pore–fracture structure types were obtained, and the average values were presented as MAF > ME > MIT. The NMR experiments showed that the average movable spaces in the MIT, ME and MAF of the coal samples were 6.6%, 41.8% and 97.9%, respectively. The pore–fracture structure of the sampled coals was influenced by coal maturity, as well as the coal macerals. The coal facies have some impacts on the porosities of coal samples, and the coals with higher texture preservation index and vegetation index, and lower gelation index overall have higher porosities.

澳大利亚苏拉特盆地的中侏罗统瓦隆亚组煤炭蕴藏着极其丰富的中低阶煤层气（CSG）资源，使其成为世界上产量最高的CSG开发盆地之一。 CSG的解吸、扩散和渗流行为受煤的孔隙—裂隙结构特征影响显着；因此，对其详细表征对于CSG勘探开发具有重要意义。但目前针对苏拉特盆地煤的孔隙—裂隙结构特征的研究还很少。因此，本研究获得了来自苏拉特盆地东部瓦隆亚群的 12 个中低阶煤（\({\overline{\text{R}}}\) r: 0.42–0.60%），然后进行了煤炭岩石学分析对这些样品进行了场发射扫描电子显微镜和核磁共振（NMR）实验。结果表明，苏拉特煤的有机显微组分以镜质组为主，其次为脂质组，惰质组普遍较少。煤样的平均孔隙度、可动孔隙度和可动水饱和度分别为5.08%、1.01%和22.47%。煤样孔隙—裂隙结构以MIT（微孔和过渡孔）为主，ME（中孔）和MAF（大孔和裂隙）相对较不发育，平均体积比例分别为74.58%、14.06%和11.36。 ％， 分别。得到了不同孔隙—裂缝结构类型的可动孔隙度，其平均值表现为MAF>ME>MIT。核磁共振实验表明，煤样的MIT、ME和MAF的平均可移动空间分别为6.6%、41.8%和97.9%。煤样的孔隙-裂隙结构受到煤成熟度以及煤显微组分的影响。煤相对煤样的孔隙度有一定影响，质地保存指数和植被指数较高、胶凝指数较低的煤整体孔隙度较高。