Exploration for petroleum in Queensland began in the Bowen and overlying Surat basins in 1908, according to Lindsay Elliott of CSR Petroleum Ltd. in Brisbane.
He noted in a paper in the APEA Journal, 1989, that 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 1960's 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 line in 1969.
To date, more than 680 wildcats and 350 appraisal wells have been drilled. About 16 x 10 9 M 3 of gas and 5 x 10 6 ML of oil have been found. There is potential for an additional 16 x 10 9 M 3 Of gas and 2 x 10 6 ML of oil reserves to be found in the basins.
The oil and gas reserves occur in Permian, Triassic, and Jurassic sandstone reservoirs.
The Bowen and overlying Surat basins lie in east central Queensland and extend into northern New South Wales, Australia. The sedimentary sections of the basins are composed almost entirely of clastics, with some limestone and volcanics.
The Bowen basin consists of three main structural provinces: the Denison trough in the northwest and the Taroom trough in the east, which are separated by the Comet platform.
The western Surat basin is a mature exploration area. Little remains to be found in conventional structural plays. Most of the new reserves will come from stratigraphic traps and fracturing of tight sandstone reservoirs.
The recent Taylor oil and gas discovery appears to occur in the Showgrounds sandstone onlapping basement. This field could be a large one. Larne oil fields are unlikely in the area, with most of the larger structures already drilled and the source rocks being gas prone. Any large oil fields will be stratigraphic traps.
Small oil fields are possible in the less-explored area south of Alton with the Showgrounds sandstone being the main play.
The Denison trough is the area with the most exploration potential. More large gas fields are expected to be found here in the Mantuan formation to Aldebaran sandstone section. There is limited potential for oil.
A major future potential is the fracture stimulation of tight gas sands. The main targets are the Reids Dome beds in the south and the Aldebaran sandstone in the northern area. The play has the potential to occur over all of the southern Denison trough with thick Reids Dome beds section.
The eastern margin/Taroom trough area is the hardest to assess for future potential. Exploration can be divided into two broad play objectives: the oil potential of the Surat basin sequence, and the gas potential of the Bowen basin sequence.
The Bowen basin sequence is poorly explored and significant gas finds are likely. The main problem is poor reservoir characteristics in the Permian and Triassic sections.
Large anticlines are present along and associated with the Moonie-Leichhardt fault system, with only Burunga and Cabawin anticlines adequately tested.
Consumers must be prepared to pay higher gas prices to allow the higher cost exploration that will be needed to search for the remaining small fields and the testing of new play concepts in the region of the Surat and Bowen basins.
Explorers and producers will need to keep their costs competitive with other suppliers of energy, whether it be a different commodity or a different area, according to Elliott.
He says the future of the basin lies in new ideas. New play types need to be identified to find the larger, more economic reserves which will keep the Bowen and Surat basins producing hydrocarbons for many more years.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.