The Cooper Basin is the largest onshore oil and gas province in Australia. The first commercial discovery of gas was made in 1963 (Gidgealpa-2) and the first commercial oil discovery was made in 1970 with Tirrawarra-1. Gas produced from the Cooper Basin supplies markets in South Australia, Victoria, NSW and Queensland. The basin is located in Central Australia, spanning north-eastern South Australia and the south-western region of Queensland, covering an area of 130,000 km².
Overall there are 160 gas fields and 75 oil fields in production containing over 600 producing gas wells and more than 340 producing oil wells. Cumulative sales are over 5 Tcf sales gas, 77 MMboe condensate, 158 MMbbl oil and 78 MMboe LPG.
Since the initial discoveries, explorers have encountered oil and gas accumulations from the Permian through to the Cretaceous aged sedimentary rocks.
Coal measures and shales are the principal source rock in the basin, with the Patchawarra Trough containing the bulk of the oil and wet gas reserves. Oil is produced principally from sands within the Tirrawarra Sandstone and at the basin margin, from the Patchawarra and Merrimelia Formations.
Intraformational shale and coal form the local seals in the major reservoir units, while the Roseneath and Murteree shales form important regional seals.
The unconformity between the Cooper and overlying Eromanga Basin basins acts as a migration pathway for hydrocarbons to reach the overlying younger reservoirs of the Eromanga.
Anticlinal and faulted anticlinal traps are proven exploration targets in the basin. However, potential remains high for discoveries in stratigraphic traps, especially where the overlying Eromanga Basin truncates Permian sediments.
Recent exploration efforts have targeted the flanks of the Cooper Basin and its unconventional gas plays. The Western Flank has been a source of many recent oil discoveries, with exploration success rates at over 50%. Much of this success is attributable to improvements in drilling technology and the use of modern 3D seismic data.
Unconventional gas exploration is expanding in the Cooper Basin, driven by increased demand for LNG and declining conventional gas production. Improving technology continues to lower the cost of unconventional field development, ensuring the Cooper Basin's value as an important petroleum province.