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Exploration fundamentals related to predicted world economic growth and higher oil prices suggest a resurgence in exploration for oil and gas liquids in the Timor Sea in the next two years, despite a slow down in exploration drilling in the last 12 months.
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Predictive maps of the subsurface can be generated when geophysical datasets are modelled in 2D and 3D using available geological knowledge. Inversion is a process that identifies candidate models which explain an observed dataset. Gravity, magnetic, and electromagnetic datasets can now be inverted routinely to derive plausible density, magnetic susceptibility, or conductivity models of the subsurface. The biggest challenge for such modelling is that any geophysical dataset may result from an infinite number of mathematically-plausible models, however, only a very small number of those models are also geologically plausible. It is critical to include all available geological knowledge in the inversion process to ensure only geologically plausible physical property models are recovered. Once a set of reasonable physical property models are obtained, knowledge of the physical properties of the expected rocks and minerals can be used to classify the recovered physical models into predictive lithological and mineralogical models. These predicted 2D and 3D maps can be generated at any scale, for Government-funded precompetitive mapping or drilling targets delineation for explorers.
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The Australian Solid Earth and Environment Grid (SEEGrid) is an eResearch infrastructure established to link diverse and distributed datasets in the geosciences, enable seamless interoperability between these, and undertake remote data processing. We present an integration between the GPlates plate-tectonic geographic information system and SEEGrid. Such a linkage is for the first time providing the necessary computational aids for abstracting an enormous level of complexity required for frontier solid-Earth research, in particular 4D metallogenesis. We present a continental reconstruction case study involving a proterozoic link between the greater Northern and Southern Australian cratons by combining evidence from several data sets. Faults are extracted from SEEGrid via Web Feature Services, and are used in conjunction with gravity anomaly data to test competing spatial alignment models of the reconstructed cratons. Additional information obtained from palaeomagnetic poles, granite geochemistry, geochronology, age-dated igneous provinces and other geophysics datasets can be used to further constrain the reconstruction. The metallogenic consequences of the best-fit reconstruction are profound, since they raises the possibility that the mineral systems hosting the giant Olympic dam, Broken Hill and Mt Isa could be linked in a particular geometry, resulting in a revised metallogenic map. The flexibility and extensibility of this spatio-temporal data analysis platform lends itself to a wide range of use-cases, including linking high-performance geodynamic modelling to kinematic reconstructions, creating the framework for future 3D and 4D metallogenic maps.
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We report four lessons from experience gained in applying the multiple-mode spatially-averaged coherency method (MMSPAC) at 25 sites in Newcastle (NSW) for the purpose of establishing shear-wave velocity profiles as part of an earthquake hazard study. The MMSPAC technique is logistically viable for use in urban and suburban areas, both on grass sports fields and parks, and on footpaths and roads. A set of seven earthquake-type recording systems and team of three personnel is sufficient to survey three sites per day. The uncertainties of local noise sources from adjacent road traffic or from service pipes contribute to loss of low-frequency SPAC data in a way which is difficult to predict in survey design. Coherencies between individual pairs of sensors should be studied as a quality-control measure with a view to excluding noise-affected sensors prior to interpretation; useful data can still be obtained at a site where one sensor is excluded. The combined use of both SPAC data and HVSR data in inversion and interpretation is a requirement in order to make effective use of low frequency data (typically 0.5 to 2 Hz at these sites) and thus resolve shear-wave velocities in basement rock below 20 to 50 m of soft transported sediments.
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The Beagle Sub-basin is a Mesozoic rift basin in the Northern Carnarvon Basin. Oil discovered at Nebo-1 highlights an active petroleum system. 3D seismic interpretation identified pre, syn and post-rift megasequences. Pre-rift fluvio-deltaic and marine sediments were deposited during a thermal sag phase of the Westralian Super Basin. Low rates of extension (Rhaetian to Oxfordian) deposited fluvio-deltaic and marine sediments. During early post-rift thermal subsidence, sediments onlapped and eroded tilted fault blocks formed during the syn-rift phase. Consequently the regional seal (Early Cretaceous Muderong Shale) is absent in the centre. Subsequent successions are dominated by a prograding carbonate wedge showing evidence of erosion from tectonic and eustatic sea level change. 1D burial history modeling of Nebo-1 and Manaslu-1 show that all source rocks are currently at their maximum depths of burial. Sediments to the Late Cretaceous are in the early maturity window for both wells. The Middle Jurassic Legendre Formation reaches mid maturity in Nebo-1. Source, reservoir and seals are present throughout the Triassic to earliest Cretaceous, however, the absence of the regional seal in the central sub-basin reduces exploration targets. The lack of significant inversion increases the likelihood of maintaining trap integrity. Potential plays include compaction folds over tilted horst blocks, roll over and possible inversion anticlines, basin floor fans and intra-formational traps within fluvio-deltaic deposits. Late Cretaceous and younger sediments are unlikely to host significant hydrocarbons due to lack of migration pathways. Source rocks are of adequate maturity and deep faults act as pathways for hydrocarbon migration.
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Poster Paper submission detailing the progress, benefits and vision of the Unlocking the Landsat Archive Project
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The Australian Government formally releases new offshore exploration areas at the annual APPEA conference. In 2010, thirty-one areas in five offshore basins are being released for work program bidding. Closing dates for bid submissions are either six or twelve months after the release date, i.e. 11 November 2010 and 12 May 2011, depending on the exploration status in these areas and on data availability. The 2010 Release Areas are located in Commonwealth waters offshore Northern Territory, Western Australia, and South Australia, comprising intensively explored areas close to existing production as well as new frontiers. The Westralian Superbasin along the North West Shelf continues to feature prominently and is complimented by a new frontier area in offshore SW Australia (Mentelle Basin) and by two areas in the Ceduna/Duntroon Sub-basins in the eastern part of the Bight Basin. The Bonaparte Basin is represented by three areas in the Petrel Sub-basin and two areas in the Vulcan Sub-basin. Further southwest, four large areas are being released in the outer Roebuck Basin, a significantly underexplored region. This year, the Carnarvon Basin provides 16 Release Areas of which three are located in the Beagle Sub-basin, five in the Dampier Sub-basin, five in the Barrow Sub-basin, three on the Exmouth Plateau and three in the Exmouth Sub-basin. The largest singular Release Area covers much of the Mentelle Basin in offshore SW Australia and two areas are available in the Ceduna and Duntroon sub-basins as part of South Australia's easternmost section of the Bight Basin. The 2010 Offshore Acreage Release offers a wide variety of block sizes in shallow as well as deep water environments. Area selection has been undertaken in consultation with industry, the States and Territory. As part of Geoscience Australia's Offshore Energy Security Program, new data has been acquired in offshore frontier regions parts of which are being published on the Mentelle Basin
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Now in its third year, Geoscience Australia's Onshore Energy Security Program has acquired several suites of regional geological and geophysical data. The data include several deep seismic reflection surveys that have been designed to image: - basement provinces with high geothermal gradients that may contain Uranium enrichments and are potential candidates for geothermal energy, - geological terrane boundaries and - sedimentary basins that are known to host petroleum system elements but are under-explored. Seismic signals are recorded down to 20 seconds two-way-time (TWT) which corresponds to 25-35 km depth depending on dominant lithologies. Basinal sections normally extend down to 6-8 secTWT and the data is of such high quality that any section of the seismic profile can be enlarged without significant loss of resolution. Deep reflection surveys are able to image the relationship between crystalline basement and overlying basin sequences very clearly and also allow interpretations of structural styles as well as impacts of deformational processes on the basin-fill. A new basinal section was discovered beneath the Eromanga Basin suite of sediments. Named the 'Mullangera Basin', its structural style and basement relationship seem to indicate some affinity with the Georgina Basin further west. The succession is clearly composed of several sequences that contain both fine-and coarse-grained sediments. If a geological relationship with the Georgina Basin can be ascertained, a new hydrocarbon prospective area could be delineated. Another new section was discovered beneath the Devonian section of the Darling Basin. Judging by the fast acoustic velocities the entire basin-fill sequence appears to be very dense and therefore largely non-porous and of low permeability.
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Geoscience Australia has developed an interactive 3D viewer for three national datasets; the new Radiometric Map of Australia (Geoscience Australia 2009b), the Magnetic Anomaly Map of Australia (Geoscience Australia 2004), and the Gravity Anomaly Map of the Australian Region (Geoscience Australia 2008). The interactive virtual globe is based on NASA's open source World Wind Java Software Development Kit (SDK) and provides users with easy and rich access to these three national datasets. Users can view eight different representations of the radiometric map and compare these with the magnetic and gravity anomaly maps and satellite imagery; all draped over a digital elevation model. The full dataset for the three map sets is approximately 55GB (in ER Mapper format), while the compressed full resolution images used in the virtual globe total only 1.6GB and only the data for the geographic region being viewed is downloaded to users computers. This paper addresses the processes for selecting the World Wind application over other solutions, how the data was prepared for online delivery, the development of the 3D Viewer using the Java SDK, issues involving connecting to.
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Climate change is expected to increase severe wind hazard in many regions of the Australian continent with consequences for exposed infrastructure and human populations. The objective of this paper is to provide an initial nationally consistent assessment of wind risk under current climate, utilizing the Australian/New Zealand wind loading standard (AS/NZS 1170.2, 2002) as a measure of the hazard. This work is part of the National Wind Risk Assessment (NWRA), which is a collaboration between the Australian Federal Government (Department of Climate Change and Energy Efficiency) and Geoscience Australia. It is aimed at highlighting regions of the Australian continent where there is high wind risk to residential structures under current climate, and where, if hazard increases under climate change, there will be a greater need for adaptation. This assessment is being undertaken by separately considering wind hazard, infrastructure exposure and the wind vulnerability of residential buildings. The NWRA will provide a benchmark measure of wind risk nationally (current climate), underpinned by the National Exposure Information System (NEXIS; developed by Geoscience Australia) and the wind loading standard. The methodology which determines the direct impact of severe wind on Australian communities involves the parallel development of the understanding of wind hazard, residential building exposure and the wind vulnerability of residential structures. We provide the current climate wind risk, expressed as annualized loss, based on the wind loading standard.