The Maryborough Basin is located in southeast Queensland, occupying 9,100 km2 onshore and 15,500 km2 offshore. The Maryborough Basin consists of up to 9,500 metres of Late Triassic to Cainozoic sediments, under water depths up to 1,000 metres. Five petroleum onshore exploration wells were drilled in the basin and all were dry except for gas shows in Gregory River 1. The basin overlies Permo-Triassic metasediments and granites and forms one of the thickest Mesozoic sedimentary sections in eastern Australia. During the Permian and Mesozoic, eastern Australia was in a back-arc tectonic setting dominated by a strike slip regime. Basins developed as the oblique extension stepped eastward. The Maryborough Basin development was in two main stages: transtensional rifting followed by thermal subsidence.
The Maryborough Basin consists of two main successions:
Sedimentation in the basin commenced with the deposition of thick fluvial quartzose sandstone (Myrtle Creek Sandstone). This was followed by the deposition of a coal measure sequence, which probably contains some marine section (Tiaro Coal Measures). A period of substantial volcanic activity terminated this sedimentation in the Early Cretaceous (Grahams Creek Formation). Sedimentation recommenced in the Aptian with a fluviatile sequence, which later gave way to marine conditions (Maryborough Formation). Deposition terminated with a fluviatile-lacustrine sequence (Burrum Coal Measures). Major folding and faulting occurred in the Cretaceous-Palaeogene, during which significant erosion occurred. A veneer of fluvial sediments and some basalts were deposited in the Eocene to Neogene. Potential source rocks have been identified in the basin's Jurassic and Cretaceous sequences. Possible reservoirs include: Myrtle Creek Sandstone, the lower sandstone member of the Maryborough Formation and sands within the Burrum Coal Measures and the Tiaro Coal Measures.