Analysis of seismic data from the Bowen and Surat Basins has yielded valuable information on the Permian and Triassic evolution of eastern Australia. When combined with seismic data from the Clarence-Moreton and Maryborough Basins, a new understanding of the post-Triassic evolution of the region can be gained, with widespread implications for other eastern Australian basins.The Early Permian-Middle Triassic Bowen-Sydney Basin is a foreland basin system extending 2000 km in preserved section from Nowra in the south to Collinsville in the north. Permian outcrops as far north as Cape York were probably part of the same system prior to deformation and erosion. The basins in the Bowen-Sydney system were linked by similar structural and stratigraphic patterns controlled by a magmatic arc to the east. The Esk Trough and associated remnant basins east of the Taroom Trough were part of the Middle Triassic foreland sequence. The structural style in the system is dominated by thrusting from the east. An Early Triassic deformation is shown to be the most important, rather than the previously believed Middle Triassic event.The overlying Jurassic-Cretaceous foreland system, which included the Surat, Maryborough and Clarence-Moreton Basins, were once joined behind another magmatic arc, east of the Triassic arc position. A major mid-Cretaceous deformation is documented which fragmented the Jurassic-Cretaceous foreland basin into a number of remnant basins prior to the opening of the Tasman Sea in the Cenomanian. The dominant structural style is again thrusting from the east. Given the severity of the deformation, its effects are expected to be present in continental margin basins around Australia.

Exploration for petroleum in Queensland began in the Bowen and overlying Surat Basins in 1908. During the next 50 years a few small fields were found. The discovery of oil at Moonie in 1961 and a number of gas fields on the Roma Shelf during the 1960s triggered extensive seismic and drilling programs. This resulted in additional discoveries and the construction of an oil pipeline to Brisbane in 1964 and a gas pipeline in 1969. To date more than 680 exploration and 350 appraisal wells have been drilled. Approximately 16 × 109 m3 of gas and 5 × 106 ML of oil have been discovered. There is potential for an additional 16 × 109 m3 of gas and 2 × 106 ML of oil reserves to be found in the basins. There is a much greater risk in finding the oil reserves than the gas reserves. The oil and gas reserves occur within Permian, Triassic and Jurassic sandstone reservoirs.

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Four gas fields (Glentulloch, Westgrove, Rolleston and Arcturus) were discovered by AAR Limited in the Denison Trough in the early 1960's. Permian gas reservoirs were encountered in Late Triassic wrench anticlines. The fields were not developed because of low gas prices and exploration technology problems at that time. Exploration activities ceased in 1970.Increased gas prices, the opportunity of an expanded gas market, and improved seismic technology provided the incentive to recommence regional seismic surveying of the basin in 1979. More than 2600 km of multi-fold seismic data have been recorded by the AAR Limited/Oil Company of Australia N.L. Joint Venture. The enhanced seismic resolution resulted in a revision of the structural and stratigraphic interpretation of the basin. Exploration drilling in 1981 was directed initially at deep Early Permian structures; however, reservoir quality of the Lower Permian sequence was poor and gas flow rates minimal.Exploration was therefore redirected towards the definition of prospects which were structurally and stratigraphically similar to the known fields. Five exploration wells have been drilled since November 1981, resulting in the discovery of a further three gas fields — Merivale, Yellowbank and Punchbowl Gully. Appraisal wells were drilled on the Glentulloch, Westgrove, Merivale and Yellowbank Fields, and were cased for future production.It is estimated that nine billion cubic metres (x 109m3) of conventional gas reserves are present within the basin. In addition, tight reservoirs contain large volumes of gas which may be producible by hydraulic fracturing. The basin is being actively explored to realize its full potential and to supply industrial and domestic markets in central and southeastern Queensland.

Water washing is a significant hydrocarbon alteration process that has not been widely recognized in the literature. An earlier review investigated the geochemistry and water washing relationship associated with Australian North West Shelf oils and gases. This review investigates and incorporates the Cooper/Eromanga Basin hydrocarbons in central Australia to gain additional insights into the water washing processes, controls, and whether they can be used to predict hydrocarbon type. Water washing is controlled primarily by water movement in the aquifer and the solubility of individual hydrocarbon compounds. Porosity determines the water volume available to dissolve soluble components, while permeability controls the rate of flow. The sedimentary facies and associated architecture control the reservoir connectivity and thus the regional aquifer flow. This review examines the relationship between reservoir porosity and permeability with temperature/maturity providing a predictive relationship. This was compared with the changes in hydrocarbon composition particularly in the nC1-C10 range. These indicate that reservoir architecture including overpressure development and temperature/maturity plays a role in determining hydrocarbon composition. Permeability in particular is important in determining nC1-C10 hydrocarbon composition in the reservoir. The processes and controls on water washing allow prediction of hydrocarbon type, with a number of key predictive parameters outlined.