Canning Basin

The Canning Basin developed as an intracratonic sag between the West and North Australian Cratons during the Early Paleozoic. The bulk of the sedimentary succession is Ordovician to Middle Triassic, mostly composed of continental to marine carbonate and clastic sedimentary facies, including widespread Upper Ordovician to Silurian evaporitic deposits. Upper Cambrian sections may be present in depocentres but remain unconfirmed by drilling. Overlying Jurassic to Cenozoic sedimentary deposits are thin, especially inland from the coast, but thicken markedly offshore towards the Roebuck Basin.

The main phases of significant tectonism producing much of the present structural configuration in the basin developed during:

• possible Cambrian to Silurian extension and rapid subsidence
• early Devonian compression and erosion (Prices Creek Movement)
• Middle Devonian to early Carboniferous extension and subsidence
• middle Carboniferous compression (Meda Transpression)
• late Carboniferous to early Triassic subsidence
• Middle Triassic to Middle Jurassic uplift and erosion (Fitzroy Transpression).

Apart from faulting, these events did not greatly deform strata within the basin, making them difficult to differentiate at a local scale. Younger strata are relatively thin, flat lying and only weakly indurated as subsequent structural events, such as the late phases of the breakup of Gondwana, barely affected the basin.

The basin contains a series of mostly west-northwesterly striking sub-basins. These tectonic divisions apply chiefly to the succession pre-dating the Meda Transpression; overlying strata show considerably less deformation. The main divisions are:

• Fitzroy Trough and Gregory Sub-basin, representing a Devonian–Triassic northern depocentre containing a Phanerozoic succession estimated at up to 15 km thick. Strata older than the Devonian may be present but have not been penetrated by drilling.
• Kidson and Willara Sub-basins, representing an Ordovician–Devonian southern depocentre, which is up to 5 km thick overlain by a thin Permo-Carboniferous and Mesozoic succession.
• Broome and Crossland Platforms, a central basement high containing an extensive Ordovician–Devonian succession overlain by thin Permo-Carboniferous sections.
• areas flanking the margins of the basin are designated as structural ‘shelves’, where pre-Permian strata either abut, thin or pinch out. A series of minor grabens and platforms contiguous with the Anketell Shelf fringe the southwestern margin of the basin and grade westwards into a similar shelf along the northern edge of the West Australian Craton; however, identification of these features relies on limited data.

Petroleum exploration began in the Canning Basin in the early 1920s when the Freney Kimberley Oil Company drilled four shallow wells following reports of oil shows in a water bore on the Lennard Shelf. Minor exploration continued until the 1950s when West Australian Petroleum Pty Ltd (WAPET) carried out regional seismic surveys and drilled 17 wells. Over the 1960s to 1980s, exploration intensified and included regional gravity, magnetic and seismic surveys, and outcrop mapping by the Bureau of Mineral Resources (BMR, now Geoscience Australia). Of the 340 onshore and six offshore (in Commonwealth Waters) wells drilled in the basin, 103 were stratigraphic, 214 were new field wildcats and 29 were development or extension wells. Onshore there have been over 360 seismic surveys (totalling over 90 000 km of 2D lines and six small 3D surveys that cover 1930 km²), with the most concentrated coverage along the southern margin of the Lennard Shelf, southern Fitzroy Trough and adjacent areas. Offshore, there have been 70 seismic surveys encompassing over 70 000 line-km.

Until the mid-1980s, exploration focused largely on the northern and central parts of the basin, with the primary exploration targets being Devonian, Carboniferous and Permian reservoirs. Whereas many wells encountered shows (particularly oil), few yielded commercial hydrocarbons. The first commercial discovery in the basin was in 1981 at Blina on the Lennard Shelf, followed soon after by the Sundown, Lloyd, Boundary, West Terrace and West Kora oilfields, and the Point Torment gas discovery in 1992. Significant oil and gas shows in subsalt Ordovician plays found during the 1980s and 1990s, such as Looma 1, Pictor 1 and Cudalgarra 1, have yet to lead to production.

A renewed phase of exploration began in 2006 that focused mainly on the Broome Platform, Jurgurra Terrace and Fitzroy Trough, and included the basin’s first 3D seismic survey in 2009. During this phase, renewed drilling by Buru Energy led to the recognition of the Laurel Formation basin-centred gas system (BCGS) in 2010 and discovery of the Ungani oilfield in 2011, also in the Laurel Formation. More recently, Buru Energy announced the 2021 discovery of the Rafael gas and condensate accumulation in the same reservoir.