The southwest Australian margin comprises the NW-SE trending Perth Basin and the deep-water Mentelle Basin. The complex architecture of this margin is a result of NE-SW extension in the Permian followed by predominantly NW-SE extension in the Middle Jurassic to Early Cretaceous. The Vlaming Sub-basin is a major Jurassic-Early Cretaceous depocentre in the southern part of the Perth Basin containing more than 12 km of basin fill. Exploration activity in the Vlaming Sub-basin to date has identified an active petroleum system represented by oil and gas shows and a small non-commercial oil discovery in the central part of the sub-basin. The Mentelle Basin consists of two large unexplored depocentres lying to the west of the Vlaming Sub-basin and containing up to 9 km of sediments. Despite the close proximity of the two basins, direct sequence correlation is not possible as they are separated by a prominent basement high. A tectonostratigraphic framework for the Mentelle Basin has been developed using Vlaming Sub-basin as a proxy. Seismic facies analysis was then applied to interpret potential petroleum systems elements. Based on this interpretation 2D petroleum systems modelling has been carried out for three regional seismic lines. Modelling results indicate that the postulated source rocks entered the oil window in the Late Jurassic and generated most oil in the Early Cretaceous, however some source rocks continued generating small amounts of oil throughout the Tertiary up to the present. Potential plays in the Mentelle Basin include anticline, fault block and sub-unconformity types. Several hydrocarbon accumulations have been modelled across the Mentelle Basin suggesting potential prospectivity in this untested frontier basin.

Rock samples recovered during the Australian-French AUSFAIR MD153 Survey in 2006 from the northern Lord Howe Rise (LHR) and the Fairway Ridge provide new constraints on the region's tectonostratigraphic evolution. SHRIMP age dating of these rocks indicates alkali volcanism in the area at 97 Ma and 74 Ma, which was accompanied by the deposition of coarse-grained volcaniclastic sediments. The earlier volcanic activity is probably related to the widespread Upper Cretaceous magmatism along the eastern Gondwana margin, whereas the later activity may have been a precursor to the Tasman Sea opening. The pebbly clasts and shell fossils in some of the volcaniclastic rocks provide evidence both for the existence of landmasses in the northern LHR region and initial marine incursion into the area around the Campanian. The results represent significant new information in a region characterised by a paucity of dated rock samples.

This invited contribution reviews applications of small angle neutron scattering (SANS) and small angle x-ray scattering (SAXS) to study the microstructure of sedimentary and igneous rocks in the last two decades. It is demonstrated how SANS can be used to explore the microstructure of rocks and help gain insights into internal specific surface area, porosity, pore size distribution, mercury intrusion porosimetry, compaction, subsurface generation of oil and gas, adsorption of gases, imbibition of water, distribution of crystalline precipitates and the microstructural effects of heat treatment. The article is intended to provide both a comprehensive introduction for newcomers to the subject and a reference text for those already familiar with small angle scattering techniques. Individual sections are self-contained and can be read in isolation.The article includes a review of theoretical results, worked examples, description of experimental procedures, examples of interpreted data for various types of rocks and references to original work.

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The Bremer Sub-basin is the first new frontier exploration opportunity under the Australian Government's New Oil Program. This follows the release of results from Geoscience Australia's Bremer Sub-basin Study to the petroleum exploration industry at the Australian Frontier Basins Workshop in October 2005.

The Capel and Faust basins are located on the northern Lord Howe Rise between eastern Australia and New Caledonia in water depths of 1300-2500 m. Under the Australian Government's New Petroleum (2003-2007) and Offshore Energy Security (2007-2011) programs, Geoscience Australia acquired new geological data including high quality 2D seismic data, high resolution multibeam bathymetry, gravity and magnetic data, and rock dredge samples. These data have been analysed and synthesised for a geological and petroleum prospectivity assessment of the area. Prior to this phase of data collection, geoscientific data was limited to regional seismic profiles acquired during the 1970s to 1990s, shiptrack potential field and bathymetric data, and one DSDP drill hole. The interpretation of new data has improved definition of depocentres previously indicated by regional satellite gravity data. The largest depocentres are approximately 150 km long and 40 km wide. Seismic data suggest that the basin fill attains a maximum total thickness of over 6 km and consists of two syn rift and one sag megasequence packages, overlying a pre rift basement. The basement includes an older (?Mesozoic) sedimentary succession and a possible rift precursor volcanic succession. The early syn rift megasequence (Syn rift 1) is inferred to be dominated by Early Cretaceous (or older) volcanics and volcaniclastic sediments. It may also include coaly and lacustrine sediments. The late syn rift megasequence (Syn rift 2) is likely to be dominated by Late Cretaceous non marine clastic sediments, with localised volcanics and coal. The upper part of this megasequence was deposited under increasingly marine influence and is likely to include deltaic and shoreline sandstones. The post rift megasequence is essentially a Late Cretaceous to Recent deepeningupward marine succession that becomes increasingly calcareous and fine grained. Presented to the Australian Earth Sciences Convention (AESC) 4 - 8th July 2010

The Oils of Western Australia II report summarises the findings of a collaborative research program between Geoscience Australia and GeoMark Research undertaken on the petroleum geochemistry of crude oils and condensates discovered within the basins of western Australia and the Papuan Basin, Papua New Guinea prior to March 2000. The interpretations documented herein build on research that Geoscience Australia and GeoMark Research undertook previously in The Oils of Western Australia (AGSO and GeoMark, 1996) and The Oils of Eastern Australia (Geoscience Australia and GeoMark, 2002) studies. To make informed decisions regarding Australia's petroleum resources, it is important to understand the relationship between the liquid hydrocarbons within and between basins. This Study has geochemically characterised the liquid hydrocarbon accumulations of western Australian basins and the Papuan Basin into genetically related families. From a total of 316 samples, 33 oil/condensate families were identified in the western Australian basins; Bonaparte (10), Browse (2), Canning (4), Carnarvon (11) and Perth (6), as well as some vagrant and contaminated samples. Three oil/condensate families were recognised in the Papuan Basin. The geographic distribution of each oil/condensate family is mapped within each basin/sub-basin. Using the geochemical characteristics of each family, the nature of their source facies, thermal maturity level and degree of preservation has been determined. This Study used a set of standardised geochemical protocols that include bulk geochemical (API gravity, elemental analysis of nickel, vanadium and sulphur), molecular (gas chromatography of the whole-oil and gas chromatography-mass spectrometry of the saturated and aromatic hydrocarbons) and bulk stable carbon isotopic analyses. n-Alkane-specific 13C isotopic analyses were carried out on only a selected set of oils and condensates. Statistical analyses were performed on these data using the software Pirouette provided by Infometrix. In addition to this report, the geochemical data acquired for the crude oils and condensates in this Study are provided in the accompanying Microsoft Access2000 database. These data may be viewed spatially and plotted on x-y cross-plots in the charting application included in the ESRI Australia GIS ArcView3.2 georeferencing package that also accompanies this report.

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Legacy product - no abstract available