The Northern Carnarvon Basin encompasses the Exmouth Plateau, Wombat Plateau (on the northern part of the Exmouth Plateau), Investigator Sub-basin, Rankin Platform, Exmouth Sub-basin, Barrow Sub-basin, Dampier Sub-basin, Beagle Sub-basin, Enderby Terrace, Peedamullah Shelf and the Lambert Shelf.
The Palaeozoic-Recent Northern Carnarvon Basin, is a large, mainly offshore basin on the northwest shelf of Australia. The basin is Australia's premier hydrocarbon province where the majority of deepwater wells have been drilled (greater than 500 metres water depth). Since exploration drilling commenced in 1953, some 754 exploration wells have been drilled (at Dec 2001) and 145 GL of oil, 52 GL of condensate and 207 BCM of gas have been produced. Remaining known reserves are 76 GL of oil, 93 GL of condensate and 604 BCM of gas.
The major basin faults trend north or northeast and define a series of structural highs and sub-basins. The basin developed during four successive periods of extension and thermal subsidence. The first phase, Silurian to Permian, developed as a series of intracratonic basins during the breakup of Gondwana along the western margin of Australia. Subsequent Early Jurassic extension initiated the four main depocentres - the Exmouth, Barrow, Dampier and Beagle Sub-basins. A third extension phase in the Middle Jurassic resulted in the seafloor spreading in the Argo Abyssal Plain to the north and the fourth Tithonian-Valanginian rifting phase culminated in the creation of the Gascoyne-Cuvier abyssal plains to the west and south. The extensive deep-water (800 - 3000 metres) Exmouth Plateau forms a bathymetric plateau outboard of the main depocentres and developed in response to thermal sag after Valanginian breakup.
The main depocentres contain up to 15 km of sedimentary infill. Triassic to Early Cretaceous deposition is dominantly siliciclastic deltaic to marine, whereas slope and shelfal marls and carbonates dominate the Mid-Cretaceous to Cainozoic section. The carbonate-rich sediments were deposited as a series of northwestward prograding wedges as the region continued to cool and subside. This resulted in deep burial of the underlying Mesozoic source and reservoir sequences in the inboard part of the basin.
Almost all the hydrocarbon resources are reservoired within the Upper Triassic, Jurassic and Lower Cretaceous sandstones beneath the regional Early Cretaceous seal.