The Cambrian to Recent Bonaparte Basin is a fan-shaped hydrocarbon-bearing basin extending over 270,000 km2 in the northwestern offshore and onshore Australia. The basin contains up to 15 km of sediments and has a multi-phase history, comprising the southern Palaeozoic and northern Mesozoic depocentres. The latter forms part of the Westralian Super-basin.
The Bonaparte Basin had produced 11 GL of oil to end-2000 but only 0.11 BCM of gas due mainly to market limitations. Remaining known reserves are 33.42 GL of oil and 668.55 BCM of gas.
The basin developed during two phases of Palaeozoic extension and Late Triassic compression prior to the onset of Mesozoic extension. Initial rifting occurred in the Late Devonian (NW-trending Petrel Sub-basin) and was orthogonally overprinted in the Late Carboniferous to Early Permian by NE-trending rift basins (proto-Malita and proto-Vulcan depocentres). Regional N-S compression in the Late Triassic resulted in widespread uplift and erosion, and, together with salt tectonics, produced inversion structures and anticlines in the Petrel Sub-basin. Erosion and collapse of these uplifted areas led to the widespread deposition of Lower-Middle Jurassic 'redbeds' and fluvio-deltaic clastics. Late Jurassic extension resulted in a series of linked, NE-trending (Vulcan Sub-basin, Malita and Calder Grabens) and SE-trending (Sahul Syncline) intracontinental grabens.
The Jurassic depocentres contain thick marine mudstones flanked by fan delta sandstones. A thick post-rift Cretaceous-Tertiary succession is dominated by fine-grained clastic and carbonate facies. Late Miocene-Pliocene convergence of the Australian and Eurasian plates resulted in flexural downwarp of the Timor Trough and widespread reactivation of the previous extensional fault systems.
The most prospective part of the Bonaparte Basin includes the Vulcan Sub-basin, Laminaria-Flamingo High and northern Sahul Platform. Oils in the basin are normally very light. The Late Jurassic marine section is the major source interval in the outboard grabens, together with Middle-Lower Jurassic marine shales and coastal plain coals. In the Petrel Sub-basin the main sources are postulated Lower Carboniferous marine shales and Permian coastal plain coals and pro-delta shales. Reservoirs range in age from Carboniferous-Permian in the Petrel Sub-basin and Londonderry High, Triassic to Cretaceous in the Vulcan Sub-basin and Jurassic in the northern parts of the basin. Fault seal breach is one of the main risks in the western part of the basin.