Many of the onshore sedimentary basins in Australia are underexplored with respect to hydrocarbons. With domestic oil production in steady decline, and increasing offshore exploration costs, the Onshore Energy Security Program was funded by the Australian Government over five years (2006-2011), for Geoscience Australia to provide precompetitive geoscience data and assessments of the potential for onshore energy resources. As part of the Onshore Energy Security Program, deep seismic reflection data have been acquired across several frontier sedimentary basins to stimulate petroleum exploration in onshore Australia. The basins studied in this project include the Arrowie Basin (South Australia) and the Burke River Structural Zone of the Georgina Basin (northwest Queensland). The interpretation of deep seismic reflection profiles from these onshore sedimentary basins focussed on the overall stratigraphic and structural architecture of the basins. Petroleum systems maturation modelling was also undertaken to increase the understanding of the petroleum potential of these basins.

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Surprisingly few natural hydrocarbon seeps have been identified in Australia's offshore basins despite studies spanning thirty years. Initial studies of natural hydrocarbon seepage around the Australian margin were generally based around the geochemical analysis of stranded bitumens, water column geochemical `sniffer' sampling, synthetic aperture radar or airborne laser fluorsensor. Later studies involved the integration of these remote sensing and geochemical techniques with mutli-channel and shallow seismic. A review of these earlier studies indicates that many seepage interpretations need to be re-evaluated and that previous data sets, when set in a global context, often represent normal background hydrocarbon levels. Relatively few sites of proven natural hydrocarbon seepage in Australia's offshore sedimentary basins can be reconciled with the dominantly passive margin setting and low recent sedimentation rates, which are not favourable for high rates of seepage, and difficulties in proving seepage on high energy, shallow carbonate shelves, where seabed features may be rapidly reworked and modern marine signatures are overprinted on authigenic seep carbonates. Active thermogenic methane seepage on the Yampi Shelf, the only proven documented occurrence in Australia, is driven by deposition of a thick Late Tertiary carbonate succession and Late Miocene tectonic reactivation. Therefore, to increase the success of detecting and correctly interpreting natural hydrocarbon seepage, data need to be analysed and integrated within the context of the local geological setting, and with an understanding of what is observed globally.

Under the Australian Government's Energy Security Program, Geoscience Australia conducted a seismic survey and a marine reconnaissance survey to acquire new geophysical data and obtain geological samples in frontier basins along the southwest Australian continental margin. Specific areas of interest include the Mentelle Basin, northern Perth Basin, Wallaby Plateau and southern Carnarvon Basin. The regional seismic survey acquired 7300 km of industry-standard 2D reflection seismic data using an 8 km solid streamer and 12 second record length, together with gravity and magnetic data. These new geophysical datasets, together with over 7000 km of re-processed open-file seismic data, will facilitate more detailed mapping of the regional geology, determination of total sediment thickness, interpretation of the nature and thickness of crust beneath the major depocentres, modelling of the tectonic evolution, and an assessment of the petroleum prospectivity of frontier basins along the southwest margin. The scientific aim of the marine reconnaissance survey was to collect swath bathymetry, potential field data, geological samples and biophysical data. Together with the new seismic data, samples recovered from frontier basins will assist in understanding the geological setting and petroleum prospectivity of these underexplored areas.

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.

Seismic acquisition for the joint BMR-Woodside Petroleum program in the Dampier Sub-basin started at 0800 am on October 24, 1990 and was completed at 1150 am on Sunday October 28, 1990. A total of 352 km of high resolution seismic data was collected along the 17 agreed survey lines, of which 336 km were full stack data with a total 390 magnetic tapes being used. Data quality appears to be good. In addition to the seismic, a total of 530.6 km of water column geochemical data were also collected.

Legacy product - no abstract available

Legacy product - no abstract available

Legacy product - no abstract available