1.2.1 Available coal and coal seam gas resources


The Namoi subregion is underlain by the geological Gunnedah and Surat basins, both major coal-bearing basins in eastern Australia. The Gunnedah Basin has a history of coal and conventional petroleum exploration, and coal mining, and more recently the basin’s potential coal seam gas (CSG) targets have attracted much interest in the Namoi subregion. Coal and CSG exploration in the Surat Basin in Queensland has focused on areas of the basin where it overlies the Bowen Basin. Surat Basin coals in NSW are thin (Goscombe and Coxhead, 1995) and thermally immature (Stewart and Alder, 1995), and are therefore not a major focus for CSG production. Thus, Section 1.2.1 focuses on the distribution and development of coal and CSG resources in the Gunnedah Basin strata only.

Economic coal deposits are located mainly within the Maules Creek and Mullaley sub-basins of the Gunnedah Basin, where the Maules Creek Formation and the Black Jack Group host numerous coal seams varying in thickness and quality.

The coals in the Namoi subregion have attained thermal maturities indicative of the potential to produce significant volumes of thermogenic gas. Furthermore, numerous igneous intrusions into the coal measure sequences have resulted in local enhancements of coal rank, and possibly also the gas generation and storage potential of the coals. The limited number of studies that have been conducted on CSG resources in the basin report gas contents that range from approximately 4 m3/t to as high as 19 m3/t, with gas compositions varying between predominantly methane (CH4) and predominantly carbon dioxide (CO2). High concentrations of carbon dioxide are associated with areas where igneous intrusions are present.

Last updated:
5 January 2018
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