The NW?SE trending Perth Basin (172,300 km2) and the deep-water Mentelle Basin (36,400 km2) are part of the southwest Australian extensional terrain. The complex architecture of this margin is the result of NE-SW extension in the Permian followed by predominantly E?W extension in the Middle Jurassic to Early Cretaceous. During both extensional phases the segmentation of the margin was strongly influenced by N-S and NW-SE oriented basement structures such as the Darling Fault and Proterozoic shear zones. This has produced a series of N-S to NW-SE trending depocentres that are separated by shallow basement highs. The Mesozoic extension culminated in the breakup between Australia and Greater India in the Valanginian.
The Vlaming Sub-Basin is a major Jurassic-Early Cretaceous depocentre in the southern Perth Basin. It contains more than 12 km of basin fill, the bulk of which are syn-rift sediments. A new tectonostratigraphic framework for the Vlaming Sub-basin, produced during recent studies by Geoscience Australia, redefined the stratigraphy and key source rock intervals. This information, together with gridded surfaces generated from the main sequence boundaries were used for 3D burial history modelling.
Modelling results suggests the presence of an active petroleum system with oil being generated from several stratigraphic intervals. For Jurassic and Early Cretaceous source rocks the main phase of petroleum generation started at about 150 Ma, however depending on the initial depth of burial and the amount of removed section it continues to a lesser extent today. This creates favourable conditions for charging potential traps. A number of accumulations were modelled in the eastern and southern parts of the basin indicating significant undiscovered potential.
The unexplored Mentelle Basin is a frontier basin lying in 500 to 3300 m water depths. Structural restoration of the margin has shown that major tectonic and accommodation cycles in the Mentelle Basin are similar to those in the Vlaming Sub-basin. Seismo-stratigraphic correlations are made to the DSDP well 258 on the Naturaliste Plateau and to the exploration wells in the Southern Vlaming Sub-basin for the Late Cretaceous to Recent part of the section. Ages of the syn-rift sequences have been interpreted using the new Vlaming Sub-basin tectonostratigraphic framework. Seismic facies analysis was then applied to define potential source rock intervals and correlate them to the known source rocks in the Vlaming Sub-basin.
2D burial history analysis has been performed for three transects testing different scenarios for source rock properties. Modelling results indicate potential for hydrocarbon accumulations generated by Jurassic source rocks. The main risk relates to the presence of good quality seals at the right stratigraphic level. Provided suitable structures can be delineated, the Mentelle Basin may emerge as a prospective frontier basin.
