Basin evolution of the Vlaming Sub-basin and the deep-water Mentelle Basin, both located offshore on the southwest Australian continental margin, were investigated using 2D and 3D petroleum system modelling. In the Vlaming Sub-basin has a proven petroleum system. Exploration activity in this area is limited and has mainly focused on structural highs/tilted fault blocks. The deep-water Mentelle Basin represents frontier exploration acreage but is assumed to have sedimentary facies and source poten-tial similar to the Vlaming Sub-basin.

The Permian-Cenozoic Vlaming Sub-basin contains siliciclastic fluvial-deltaic and marine rocks reach-ing up to 14 km in thickness. The Mentelle Basin, formed during the break-up of eastern Gondwana, contains more than 8 km of sedimentary section.

Compositional kinetics, determined on the main source sequences, were used to predict timing of hy-drocarbon generation and migration as well as GOR evolution and phase behaviour in our 2D and 3D basin models. The main phase of petroleum generation in the Vlaming Sub-basin occurred at 150 Ma and ceased during following inversion and erosion episodes. Only the areas which experienced later burial have generated additional hydrocarbons during the Tertiary and up to present day. Our results indicate the likely generation and trapping of light oils for the Jurassic intervals for a variety of struc-tural traps. It is these areas that are of greatest interest from an exploration point of view.

The 2D numerical simulations in the Mentelle Basin indicate the presence of active hydrocarbon gen-erating kitchen. Burial histories and generalized petroleum history will be presented.

• Talk title: Gas Generation and Retention in the Bakken Shale, Williston Basin
• Authors: B. Horsfield, G. P. Muscio, K. Grice, R. di Primio, P. Kuhn, E. Maslen
• When: Wednesday morning oral sessions at 10.25

• Talk title: New insights into Jurassic - Early Cretaceous rifting of the Southwestern Australian margin, Basin evolution magmatism and Petroleum system elements
• Authors: Borissova, C. Nicholson, A. Krassay, V. Neumann, R. di Primio and C. Boreham

The northwest 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 separated by shallow basement highs. The Mesozoic extension culminated in the breakup between Australia and Greater India in the Valanginian. It was associated with voluminous volcanism on the Gascoyne-Cuvier margin and significantly less magmatic output on the Perth margin. However, farther west in the Mentelle Basin and on the Naturaliste Plateau, there was significant breakup-related volcanism.

The Vlaming Sub-Basin is a major Jurassic-Early Cretaceous depocentre in the southern Perth Basin. It contains more than 12 km of sediments, the bulk of which are syn-rift section. A new tectonostratigraphic framework for the Vlaming Sub-basin produced during recent Geoscience Australia studies redefined the stratigraphy and key source rock intervals. This information, together with seismic grids generated for the main sequence boundaries, were used for 3D burial history modelling. Modelling results indicate 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 the breakup related erosion, 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 Mentelle Basin is a frontier basin lying in 500 to 3300 m water depths which has never been explored. 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 used 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 is the presence of good quality seals at the right stratigraphic level. Current seismic coverage in the Mentelle Basin is insufficient for the detailed structural interpretation needed to define potential plays. Provided suitable structures are found in the Mentelle Basin, it may be potentially prospective frontier basin.