1.2.1 Available coal and coal seam gas resources

Summary

Coals of the Sydney, Gunnedah and Surat geological basins occur within the Central West subregion, although coal is currently only mined in the northernmost extent of the Western Coalfield of the Sydney Basin. Multiple coal seams occur within the Illawarra Coal Measures and at the Ulan Coal site where there are ten seams. The Ulan Coal is one of the main coal sequences mined in the northern area of the Sydney Basin and has a total thickness of up to 14 m.

Areas west of the Rocky Glen Ridge are largely unexplored for coal. The structural units of the Gunnedah Basin in the subregion include the Oxley sub-basin, the Gilgandra Trough and the western edge of the Mullaley sub-basin. The Cobbora coal deposit is primarily in a sinuous syncline that has proven challenging to correlate between the Western Coalfield of the Sydney Basin and the Gunnedah Basin. In the Cobbora area the Upper Permian strata contain five potentially mineable coal seams.

Exploration for coal seam gas (CSG) in the Gunnedah Basin in the Central West subregion identified the Late Permian coals of the Black Jack Group as a potential resource, particularly the Hoskissons Coal. However, the coal seams were found to be either severely undersaturated with total gas content generally below 1 m³/t, or with maximum gas content of 4 to 5 m³/t but with high levels of CO₂ making them unattractive for commercial CSG extraction. The Early Permian Maules Creek Formation, which is the primary target for CSG recovery in the Namoi subregion, is either not present in this part of the Gunnedah Basin or only poorly developed.

Limited coal development in the Coonamble Embayment of the Surat Basin means this area has not been extensively explored for CSG. A single exploration well has been drilled to assess the CSG potential of the Cretaceous Rolling Downs Group of the southern Surat Basin in the north-western part of the Central West subregion. Individual coal seams were up to 1.58 m thick (net thickness 6.92 m), but the gas content was not measured.

The Sydney Basin has not been a target for CSG exploration in the subregion to date.