Abstract: There are significant differences in geological characteristics of low-rank coal seams in Surat block on the eastern margin of Surat Basin, Australia. The optimal selection of favorable exploration area is the key to realize the large-scale and benefit CBM development in the study area. Based on a large number of logging, core lab test and well testing data, fine characterization of multiple and thin coal seams is conducted of a huge thick coal measure strata, and the spatial distribution of coal reservoir properties is quantitatively analyzed, such as coal thickness, gas content, and permeability. Based on the 3D geological model, the study area is divided into three classes of zones according to the spatial distribution of coal reservoir properties. Class I zone is located at the structural high on the slope and adjacent to the denudation zone, and the CBM reservoir is characterized by high permeability and high resource abundance, with coal seam thickness of 18-40 m (burial depth≥150 m), dry ash-free gas content of 3.8-6.5 m3/t, permeability of 20-500 mD (average 250 mD), which is the most favorable area for the large-scale development in the near future. Class Ⅱ zone is located at the denudation zone on the top of the slope, and the CBM reservoir is characterized by high permeability and low resource abundance, with coal seam thickness of 8-20 m (burial depth≥150m), dry ash-free gas content of 2.8-4.2 m3/t, and permeability of 500-900 mD (average 680 mD), which is a potential area. Class Ⅲ zone is located at the structural low on the slope, and the CBM reservoir is characterized by medium-low permeability and high resource abundance, with coal seam thickness of 18-41 m, dry ash-free gas content of 4.8-7.8 m3/t, permeability of 1-20 mD (average 5 mD), and poor natural recoverability. The classification of exploration zone shows that the Class Ⅰ zone is a favorable area for capacity construction in the study area; Class Ⅱ zone is the replacement and supplement area in the middle and late development stage of Class Ⅰ zone; Class Ⅲ zone has relatively low permeability, and small well spacing development can be applied to increase gas production.

Key words: Surat , Low rank, Coal reservoir characterization, Zone division, Favorable Area