The Cooper Basin, and overlying Eromanga Basin, comprise Australia’s largest and most prolific onshore oil and gas province. Significant volumes of gas, condensate and oil have been produced from the Cooper-Eromanga Basins since the 1970’s. The Eromanga Basin covers an area of approximately 1,000,000 sqkm and extends over South Australia, Northern Territory, Queensland and New South Wales. The Cooper Basin covers an area of approximately 127,000 sqkm and extends over South Australia and Queensland. Despite decades of exploration and development, the Cooper-Eromanga Basins continue to yield new oil and gas discoveries with operators continuing to undertake active exploration, appraisal and development programs.
Exploration in the Cooper Basin began in 1954 with the first well drilled in 1959 (Innamincka 1). Indications of hydrocarbon in the well suggested the possibility of a working petroleum system. The discovery of commercial gas in the Gidgealpa-2 well in 1963 resulted in an acceleration of exploration activity in the Cooper Basin. In the decades since the first major commercial discoveries of gas in the Cooper Basin, there has been continual exploration and development of gas resources.
The Eromanga Basin hosts Australia’s largest onshore oilfield, Jackson, in Southwest Queensland. The discovery of oil in the Eromanga Basin occurred in the late 1970’s with many significant oil discoveries made in both South Australia and Queensland.
Major relinquishment of South Australian acreage in the early 2000’s opened up the Cooper-Eromanga Basins to new explorers, including Beach Energy. As the operator in a number of joint ventures, Beach continues to have success from new oil and gas discoveries in both the Cooper and Eromanga Basins.
The Cooper Basin is a Permian to Triassic aged sequence of sediments deposited in a terrestrial fluvial-lacustrine environment. The major source rock units within the Cooper Basin are the Permian aged coals and carbonaceous shales in the Patchawarra and Toolachee Formations. Gas reservoirs are found in sandstones in multiple formations including the Patchawarra Formation, Epsilon Formation and Toolachee Formation. The Triassic aged Nappamerri Group sequence provides a regional seal for the Cooper Basin and separates the Cooper Basin from the overlying Eromanga Basin. The Eromanga Basin is Jurassic to Cretaceous in age and is a sequence of sediments of marine and fluvio-lacustrine in origin. Oil is commonly found within the high deliverability sands of the Namur and Hutton sandstone units and is sourced from the underlying Cooper Basin.