The Late Triassic to Late Jurassic Clarence-Moreton Basin is situated in southeast Queensland and northeast New South Wales and covers about 26,000 km2 onshore and at least 1,000 km2 offshore in water depths up to 90 metres. The basin and its precursors, the Esk Trough, Nymboida Basin and Ipswich Basin developed on a basement cut by major long-lived, dextral strike-slip faults (West Ipswich, Coraki and Coast Range Faults). Movement along these produced crustal transtension which was followed in the latest Triassic to Late Jurassic by a period of thermal relaxation and subsidence which formed the Basin.
The Basin is subdivided into three main depocentres, the Logan, Laidley and Cecil Plains Sub-basins, with the much smaller Yamba Trough extending offshore from the eastern margin of the Logan Sub-basin. The Logan Sub-basin contains the greatest thickness of sediments with up to 3,000 metres of fluvial and lacustrine siliciclastics and coal with minor basaltic volcanics.
The Basin is poorly explored with sparse seismic coverage. Only about 30 wells have been drilled, two of which (Clifden-2 and Hogarth-2 in the Logan Sub-basin), flowed subeconomic gas. The basin has abundant oil-prone organic matter in the Walloon Coal measures and the subjacent Koukandowie Formation. These units grade from immature in the northwest to overmature in the southeast of the basin and petroleum generation probably commenced during the mid Cretaceous. This was at about the same time as a compressional tectonic episode led to erosion of up to 3,000 metres of Jurassic sediments from the Logan Sub-basin and the creation of the proven structural traps.
Proven reservoirs lie within the Woogaroo and Marburg Subgroups and potential plays in the basin are related to pinchouts and drapes over pre-basin topography, hangingwall anticlines on minor thrusts and stratigraphic traps. Limited seismic data suggest that the offshore extension of the basin may cover a greater area than is currently proven.