The Surat Basin, which is a major eastern Australian Coal Seam Gas (CSG) reservoir, produces gas from its Middle to Late Jurassic sub-bituminous Walloon Coal Measures, and shows variability in initial reservoir permeability across the basin. For a given lithostatic stress, the presence of vitrinite group or telovitrinite macerals within the coal can influence the fracture abundance within the coal reservoirs of similar rank, which in turn potentially impacts the initial reservoir permeability of the CSG reservoirs. The predictive relationship between megascopic banding character or lithotype, microscopic maceral composition and fracture intensity within CSG reservoirs is well explored in bituminous coals, but not so much in sub-bituminous coals. Here, we analyse wellbore image log data along with the conventional geophysical logs, maceral analysis data, core descriptions validated by core photos from the well completion reports and interpreted permeability data from well tests to systematically investigate the relationship between lithotype, maceral composition with a focus on vitrinite/telovitrinite, and fracture intensity in the sub-bituminous rank Walloon coals, to test their influence on permeability trends across the basin.

Permeability-depth trends in the Walloon coals vary regionally across the basin, and show different inclinations depending on coal measures stratigraphy, coal lithotype composition, fracture intensity and stress orientation between local anticlines, monoclines and synclines. Depth normalised permeability and thickness-weighted telovitrinite content data from 55 wells were analysed. Furthermore, analysis of 3.8 km of borehole image logs, along with 156 maceral composition data points and thickness-weighted average lithotypes derived from the core description across 10 vertical wells, revealed a moderately positive relationship between the coal type and fracture abundance. This indicates some coal compositional control on the fracture abundance at this lower rank. The derived average total fracture intensity (cleat and sinusoidal coal fracture) from borehole image logs and thickness-weighted average telovitrinite content from the core analysis also exhibited an exponential increase, with the increasing depth normalised permeability derived from the well test data within the 10 analysed wells. This relationship suggests the influence of the variation in coal composition and fracture intensity on the rheological behaviour of the CSG reservoir within the Walloon Coal Measures. Spatial distribution of depth normalised permeability from the 55 wells across different domains and their relationship with the maceral composition within the study area also suggests the influence of geological structures on the depth normalised permeability. Therefore, though coal composition controls the fracture intensity, under favourable stress and fracture conditions the relationship can be substantially modified in parts of the Surat Basin, and altogether these factors control the rheological behaviour of the Walloon Coal Measures.

苏拉特盆地是澳大利亚东部主要的煤层气（CSG）储层，从中侏罗世亚晚亚沥青质瓦隆煤系生产天然气，并显示出整个盆地的初始储层渗透率存在差异。对于给定的岩石静应力，煤中存在镜质组或钙铝石基体可以影响相似等级的储层中的裂缝丰度，进而有可能影响南玻集团储层的初始储层渗透率。在烟煤中，人们对CSG储层中的宏观带状特征或岩性，微观显微组成和裂缝强度之间的预测关系进行了很好的探索，而在次烟煤中则没有那么多的预测关系。在这里，我们分析井眼图像测井数据以及常规的地球物理测井，

在整个盆地，瓦隆煤的渗透深度趋势有所不同，并显示出不同的倾角，这取决于煤层状地层，煤岩性组成，裂缝强度和局部背斜，单斜和向斜之间的应力方向。分析了55口井的深度归一化渗透率和厚度加权斜方锰矿含量数据。此外，对3.8 km的井眼成像测井数据进行分析，以及从10口垂直井的岩心描述中得出的156个宏观组成数据点和厚度加权平均岩性，发现煤类型与裂缝丰度之间存在适度的正相关关系。这表明在这个较低的等级上，有一些煤成分控制了裂缝的丰度。从井眼图像测井中得出的平均总裂缝强度（裂隙状和正弦状煤裂缝）和岩心分析得出的厚度加权平均斜方锰矿含量也呈指数增长，而深度归一化渗透率的增加是由所分析的10口井中的试井数据得出的井。这种关系表明瓦隆煤系内煤组成和裂缝强度的变化对南玻天然气储层流变行为的影响。研究区域内55口井的深度归一化渗透率的空间分布及其与研究区域内的宏观组成的关系也暗示了地质结构对深度归一化渗透率的影响。因此，尽管煤的成分控制着断裂强度，