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Petroleum accumulations have been discovered in the Bonaparte, Browse and Carnarvon basins over the last fifty years. However, a regional synthesis of the geochemistry of these North West Shelf hydrocarbons has not been published. To address this, this study documents the biomarker and isotopic analyses of ~300 North West Shelf oils/condensate samples that have been statistically characterised into genetically related families. Carbon and hydrogen isotopic signatures of ~50 gas samples, together with existing molecular data for ~1000 gas samples, show regional trends in wetness and abundance of non-combustible gases. These petroleum accumulations can be attributed to source rocks of Early Carboniferous, Permian, Triassic, Jurassic and Early Cretaceous age; however, most economic oil and gas accumulations are sourced from Mesozoic (Triassic Jurassic) sediments. The oils produced from the Bonaparte (Vulcan Sub-basin, northern Bonaparte) and Carnarvon (Dampier, Barrow and Exmouth sub-basins) basins are geochemically similar, being sourced from Late Jurassic marine rift-fill sediments (lower Vulcan Formation/Dingo Claystone) that contain variable amounts of terrigenous (particularly gymnosperm-derived) organic matter. Variations in their biomarker signatures can be explained by maturity differences, multiple charging and secondary alteration processes. Gas produced from the northern Rankin Platform is predominantly sourced from Triassic Jurassic fluvio-deltaic sediments. Proven and potential supergiant and giant gas accumulations occur in the deepwater areas of the North West Shelf. Case studies focussing on the geochemistry of the outer Browse (Scott Reef trend) and Carnarvon (deepwater Exmouth Plateau and Rankin Platform) gas accumulations will be presented with emphasis on d13C and d2H isotopic data.

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available

Thick packages of Cretaceous and Tertiary sediment with numerous diapirs fill the Southern Fairway Basin (SFB) on the Lord Howe Rise (LHR). A bottom-simulating reflector (BSR) also extends across much of this basin, perhaps indicating substantial amounts of CH4 as gas hydrate and free gas. As part of the ZoNiCo 5 survey, run on behalf of the New Caledonian government, 13 piston cores were taken by the RV L'Atalante in 1999 to assess the gas and petroleum potential of the SFB. Specifically, the cores were recovered to document the nature of sediment, pore water and gas in the shallow sedimentary section. The 13 cores, from 1250 to 2753 m below sea level (mbsl) and between 405 and 758 cm long, contain stiff nannofossil ooze. If average regional sedimentation rates apply (10 m/my), the maximum age at the bottom of cores is less than 800,000 years. The sediment typically grades from greyish orange at the top, to very pale orange in the middle, and then to either yellowish grey, very light grey or white at the bottom. Thin black horizons, presumably composed of pyrite, also occur. The changes in colour are related to variations in magnetic susceptibility (MS) and pore water SO42-. Pale and grey zones generally have low MS punctuated by MS highs, and low pore water SO42- concentrations. Methane was detected in most sediment samples, although at trace levels. The presence of ethane, propane and higher hydrocarbons suggests that gases in the SFB have a thermogenic component. With the available data, the best explanation for colour, MS and SO42- profiles is that Fe has been remobilised under anoxic conditions. Ferric iron in solid oxyhydroxide phases and SO42- in pore waters have been converted to dissolved ferrous iron and sulphide. Some of this iron and sulphur has then re-precipitated as pyrite or magnetite (the MS spikes). The overall process may be driven by CH4 from underlying gas hydrate deposits. Upward fluxes of CH4, perhaps of thermogenic origin, induce anaerobic CH4 oxidation in shallow sediment, a process that consumes SO42-. As a consequence, unexpectedly shallow redox fronts occur in the SFB. However, longer cores with less-oxidised sediment and additional analyses are needed to understand sediment, water and gas in this region.

This publication is the sucessor to Oil and Gas Resources 1999 and continues as the definitive reference on exploration, development and production of Australia's petroleum resources. It covers exploration, reserves, undiscovered resources, development, production and supporting information and statistics. It includes a forecast of Australia's crude oil and condensate production from 2001 to 2015, and sustainability indicators for petroleum resources. Information on Australia's petroleum data availability is also included. A revised estimate of Australia's undiscovered resources is included. The Appendices describe wells drilled and seismic surveys carried out in 1999 and 2000. There is also a chronological listing of offshore and onshore oil and gas discoveries to 2000, listings of all petroleum platforms and pipelines, and a map showing all Australian petroleum exploration and development titles, with a key of title holders and interests as at March 2001. OGRA 2000 provides the background for much of the advice on petroleum resources given to the Australian government and is a key source for petroleum exploration, production and service companies, petroleum engineers and geologists, energy analysts, stockbrokers and share investors.

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During April/May 1988, the BMR research vessel 'Rig Seismic' carried out a 21 day geochemical and sedimentological research program in the Otway (17 days) and Gippsland (4 days) Basins. Light hydrocarbon gases (C1-C6) were measured in sediments at 342 locations on thecontinental shelf and upper continental slope. Thermogenic hydrocarbons were identified in near-surface sediments at forty-two locations in the Otway (32) and Gippsland (10) Basins. The major results from the Otway Basin include: 1. Evidence of thermogenic hydrocarbon sediments was found at seven locations on the Crayfish Platform, seven locations on the Mussel Platform and eighteen locations in the VolutaTrough. 2. Wet gas contents ([C2-C4/C1-C4] x 100), which provide some indication of both hydrocarbon source type and maturity,are highest on the basin margins, i.e. the Crayfish and Mussel Platforms. Wet gas contents were consistently lower in the Voluta Trough. 3. Total C1-C4 gas concentrations were higher in the Voluta Trough than on the basin margins, probably because of more intense near-surface faulting in the trough. 4. The geochemical data, when integrated with thermal maturation modelling and well data, suggest that the principal liquidhydrocarbon source rocks are located at the base of the Early Cretaceous Otway Group (i.e. basal Pretty Hill Sandstone). The Late Cretaceous Sherbrook Group appears to be gas-prone. Preliminary data from the Gippsland Basin identify ten locations which show evidence of thermogenic hydrocarbons in near-surface sediments.

The objectives of Project 121.19 were: To understand the deep crustal architecture, the structural reactivation processes and the mechanisms of hydrocarbon generation, migration and entrapment within the Vulcan Sub-Basin, Timor Sea. To achieve the aims of the project, two surveys (Vulcan I & II) were conducted between October and December 1990. This report summarises the results of the Vulcan Sub-Basin I Survey (Survey 97), which focussed on the high resolution seismic and geochemical component of Project 121.19 (i.e. the structural reactivation, hydrocarbon generation and migration theme). The Timor Sea program achieved most of its objectives. The seismic data should, when processed, allow a much better understanding of the nature of the fault reactivation processes in the area. In addition, strike lines run along the Londonderry High show that near-vertical faults appear to correspond with the position of transfer faults which have been inferred from our interpretation of BMR's Timor Sea aeromagnetic data. The geochemical program identified a number of significant hydrocarbon anomalies in the area. The anomalies fell predominantly into two groups. One group was located over, and to the north-east to south-east of the Skua Field, while the other group was associated with transfer faulting, and a major aeromagnetic high, on the edge of the Vulcan Sub-Basin, south-east of Montara 1.