The onshore Canning Basin covers an area of about 530,000 km2 in central-northern Western Australia, and extends offshore for a total basin area of more than 640,000 km2, of which 110,000 km2 is in State waters. The succession in the onshore basin ranges in age from Ordovician to Cretaceous, but is predominantly Paleozoic. World-renowned Devonian reefs exposed on the Lennard Shelf in the northeast part of the Canning Basin provide excellent insight into the subsurface carbonate geology. The Blina oilfield produces from these reefs.
Two urban centres, Broome and Derby, have shipping and air support and service the Canning Basin. Broome serves as the shipping terminal for crude oil, while minor pipeline grids lie mainly near Derby. Major roads service parts of the basin, particularly near the coast and along the northern margin, where there are settlements and pastoral leases.
The Canning Basin initially developed in the Early Paleozoic as an intracratonic sag between the Precambrian Pilbara Craton and the Kimberley Basin. The basin contains two major northwesterly-trending troughs separated by a mid-basinal arch and flanked by marginal shelves.
The northern trough comprises the Fitzroy Trough and the Gregory Sub-basin, which are estimated to contain up to 15 km of predominantly Paleozoic rocks. The southern trough includes the Kidson and Willara Sub-basins, which are formed by thinner sedimentary successions (4–5 km thick) of predominantly Ordovician to Silurian and Permian-aged sediments with extensive Mesozoic cover.
The central arch is divided into the Broome and Crossland Platforms, with structural terraces that downstep into the troughs on either side. The subdivisions of the basin are based on presently expressed structural elements; however, the troughs developed and were active at different times, with some elements forming through growth faulting.
Petroleum exploration activity began in the Canning Basin in the early 1920s, when the Freney Oil Company encountered asphaltic shows in drillholes on the Lennard Shelf. Minor exploration continued with Associated Australian Oilfields later joining the search in the 1950s, and exploration intensified again in the 1960s and 1970s when the Bureau of Mineral Resources (BMR, now Geoscience Australia) and West Australian Petroleum Pty Ltd (WAPET) conducted gravity, magnetic, and seismic reflection surveys. As of September 2014, 287 onshore and 14 offshore wells have been drilled in the region, accompanied by acquisition of 175,591 km of 2D seismic data, of which 89,587 km is onshore and 86,004 km is offshore.
Up until the mid-1980s, exploration largely focused on the northern and central parts of the Canning Basin. Primary exploration targets were Devonian and Permian strata. Many exploration wells had shows, especially of oil, but few yielded commercial hydrocarbons. Oilfields were first discovered on the Lennard Shelf in 1981. The Blina field was discovered first, followed by the Sundown, Lloyd, Boundary, West Terrace, and West Kora oilfields; the Point Torment gas discovery occurred in 1992. The sub-salt Ordovician section was later targeted by companies such as Shell, who, in 1996, recovered hydrocarbons in the southern Canning Basin well Looma 1.
The Fitzroy Trough and the Lennard Shelf were long considered the most prospective areas of the Canning Basin, owing to their thick sedimentary successions, reefal carbonate buildups along a half-graben hingeline to the north, and structural development in the southwest. Shows in the area confirm petroleum generation and migration.
Other prospective areas of the Canning Basin include the Broome Platform and the Kidson Sub-basin. The Ordovician, subsalt Looma discovery first proved the presence of mature, migrated oil from a source pod in the southern Canning Basin and thereby provided a new exploration play.
In the south of the basin, there is potential for gas generation from the Permian and Ordovician carbonaceous shales and for oil expulsion from shales in the Ordovician Goldwyer Formation. Potential reservoirs are the Nita Formation (Ordovician), the Devonian reef complexes, the Tandalgoo Formation (Devonian), and Permian sandstones. Salt diapirism is evident in the region and may provide traps in areas that lack major block faulting.
Permian, Triassic, and Jurassic fluvio-deltaic sandstones are considered the primary objectives of the offshore Canning Basin. The producing units of the onshore area are deeply buried in the offshore, however, and possess lower reservoir quality. Thick Lower Triassic and Cretaceous shales do provide adequate seals.
The search for shale gas resources in the Canning Basin is in the early exploration phase. However, similarities exist between the Ordovician Goldwyer Formation and gas shales of the United States (US).
Canning Basin Prospectivity
The onshore Canning Basin is a large, intracratonic, predominantly Paleozoic basin that ranges in age from Ordovician to Cretaceous. It is significantly under explored for hydrocarbon resources, with relatively minor oil and gas production, although widespread shows at many stratigraphic levels and in different geological settings indicate that there are four active petroleum systems. Despite these positive indicators, the Canning Basin may be the least explored Paleozoic basin in the world. Further exploration is warranted given that:
- The Canning Basin has only four wells/10,000 km2, compared with the Paleozoic basins of North America which average 500 wells/10,000 km2.
- Only a small number of valid structural tests exist in the basin.
- There are more than 130 giant and supergiant oilfields and gasfields with Paleozoic sources and reservoirs that are similar to the Canning Basin, including basins in North America, North Africa, and the North Caspian Basin of Kazakhstan and Russia.
- The US Energy Information Agency reported in 2013 that the Canning Basin has the largest shale gas potential in Australia, and in fact the eighth largest in the world; they estimated it has in excess of 225 TCF of recoverable shale gas based on the Goldwyer Formation play alone.
- Further exploration could be highly successful based on the presence of five discovered oilfields, new gas discoveries, widespread and numerous petroleum shows, a huge shale gas potential, and low well density.
- There are established pathways to markets: Oil is being trucked to the Kwinana oil refinery in the Perth metropolitan area and, in the past, it was also exported from the port of Broome. A gas pipeline runs along the southern margin of the Canning Basin to Telfer, the site of one of Australia’s largest gold mines.
Location and area
The Canning Basin is located in central northern Western Australia, approximately 1500 km northeast of Perth. It is the largest sedimentary basin in Western Australia and has an onshore area of about 530,000 km2 and an offshore area of about 110,000 km2.
The Canning Basin initially developed in the Early Paleozoic as an intracratonic sag between the Precambrian Pilbara and Kimberley Cratons. Significant tectonic events affected the basin in the:
- Early Ordovician (extension and rapid subsidence)
- Early Devonian (compression and erosion)
- Late Devonian (extension and subsidence)
- Middle and late Carboniferous to Permian (compression then subsidence)
- Early Jurassic (transpressional uplift and erosion)
The southern Canning Basin is less intensely deformed than the northern part, which underwent major fault block movements.
The Canning Basin is subdivided into a series of troughs, sub-basins, platforms, shelves, and terraces, bounded by northwesterly–southeasterly trending, syndepositional fault systems.
The basin subdivisions are based on present-day structural elements. However, growth faulting initially developed some of these, and troughs developed and were active at different times during the basin’s history.
Read more about the petroleum prospectivity of the Canning Basin (page 35)