Geoscience Australia has been acquiring deep crustal reflection seismic transects throughout Australia since the 1960s. The results of these surveys have motivated major interpretations of important geological regions, contributed to the development of continental-scale geodynamic models and improved understanding about large-scale controls on mineral systems. Under the Onshore Energy Security Program, Geoscience Australia has acquired, processed and interpreted over 5000 km of new seismic reflection data. These transects are targeted over geological terrains in all mainland states which have potential for hydrocarbons, uranium and geothermal energy systems. The first project was undertaken in the Mt Isa and Georgetown regions of North Queensland. Interpretations of these results have identified several features of interest to mineral and energy explorers: a previously unknown basin with possible hydrocarbon and geothermal potential; a favourable setting for iron oxide uranium-copper-gold deposits; and, a favourable structural setting for orogenic gold deposits under basin cover. Other geophysical data were used to map these features in 3D, particularly into areas under cover. Seismic imaging of the full thickness of the crust provides essential, fundamental data to economic geologists about why major deposits occur where they do and reduces risk for companies considering expensive exploration programs under cover.

The Mesozoic Beagle Sub-basin is in the Northern Carnarvon Basin, offshore Western Australia. Oil discovered at Nebo 1 in 1993 highlights an active petroleum system. The central Beagle Sub-basin, this study's focus, has a north-south trending horst-graben architecture. Detailed mapping of the 1529 km2 Beagle Multi-client 3D seismic survey gave insight into its geological history. The Rhaetian to Valanginian syn-rift succession comprises fluvio-deltaic and marine sediments deposited during low rates of crustal extension. During post-rift thermal subsidence, sediments onlapped eroded and tilted fault blocks formed during the syn-rift phase. Consequently, the Early Cretaceous regional seal is absent in the central study area. Overlying sedimentary successions are dominated by a prograding carbonate wedge. Potential source, reservoir and seal facies are present from the Triassic to earliest Cretaceous. 1D burial history modelling indicates that in Nebo 1, potential source rocks from the Middle Jurassic to Early Cretaceous became oil mature after the emplacement of the regional seal. At Manaslu 1, these sediments are immature. Potential source rocks are currently at maximum burial depth and thermal maximum. Trap integrity in the pre and syn-rift succession could be jeopardized by fault reactivation, however post-rift traps may be preserved. Potential plays include compaction folds over tilted horst blocks, anticlines, basin-floor fans and intra-formational traps. Hydrocarbons could use deep faults to migrate into Early Cretaceous plays. Younger sediments lack migration pathways so are unlikely to host significant hydrocarbons. Poor quality source rocks and reservoirs, and poor source rock distribution may also contribute to disappointing exploration results.

In this paper we present a new model to assess severe wind hazard in Australia. The model is especially suitable for regions where there is no recording data. The model uses simulation data produced by a high resolution regional climate model. It compares wind speeds produced by the climate model with speeds from observed records and develops a function which allows wind engineers to correct the simulation data in order to match the observed wind speed data. The model has been validated in a number of locations where observed records are available.

Hot Rocks in Australia - National Outlook Hill, A.J.1, Goldstein, B.A1 and Budd, A.R.2 goldstein.barry@saugov.sa.gov.au hill.tonyj@saugov.sa.gov.au Petroleum & Geothermal Group, PIRSA Level 6, 101 Grenfell St.Adelaide SA 50001 Anthony.Budd@ga.gov.au Onshore Energy & Minerals Division, Geoscience Australia, GPO Box 378 Canberra ACT 26012 Abstract: Evidence of climate change and knowledge of enormous hot rock resources are factors stimulating growth in geothermal energy research, including exploration, proof-of-concept appraisals, and development of demonstration pilot plant projects in Australia. In the six years since the grant of the first Geothermal Exploration Licence (GEL) in Australia, 16 companies have joined the hunt for renewable and emissions-free geothermal energy resources in 120 licence application areas covering ~ 67,000 km2 in Australia. The associated work programs correspond to an investment of $570 million, and that tally excludes deployment projects assumed in the Energy Supply Association of Australia's scenario for 6.8% (~ 5.5 GWe) of Australia's base-load power coming from geothermal resources by 2030. Australia's geothermal resources fall into two categories: hydrothermal (from relatively hot groundwater) and the hot fractured rock i.e. Enhanced Geothermal Systems (EGS). Large-scale base-load electricity generation in Australia is expected to come predominantly from Enhanced Geothermal systems. Geologic factors that determine the extent of EGS plays can be generalised as: - source rock availability, in the form of radiogenic, high heat-flow basement rocks (mostly granites); - low thermal-conductivity insulating rocks overlying the source rocks, to provide thermal traps; - the presence of permeable fabrics within insulating and basement rocks, that can be enhanced to create heat-exchange reservoirs; and - a practical depth-range, limited by drilling and completion technologies (defining a base) and necessary heat exchange efficiency (defining a top). A national EGS resource assessment and a road-map for the commercialisation of Australia's EGSs are expected to be published in 2008. The poster will provide a synopsis of investment frameworks and geothermal energy projects underway and planned in Australia.

Historically the emphasis on unraveling the structural geodynamic history of the Eastern Goldfields Superterrane of the Western Australian Yilgarn Craton has been on compression. A systematic study of: structural overprinting relationships; links with the rock record and architecture, reveals extension has been the dominant tectonic mode of the geodynamic history of the Eastern Goldfields. Extension was associated with: the deposition of the greenstone sequence; the emplacement of voluminous granites; the onset of Au mineralisation; dextral trans-tension and subsequent orogenic collapse. While compression or transpression structures host the majority of Au mineralisation these events are restricted to short protracted periods of time.

The thickness of the crust is usually defined seismologically by the depth to the Mohorovicic discontinuity or Moho. The Moho is defined as the boundary below which the seismic p-wave velocity of the rocks increases to values above about 7.8 km/s. These velocities are typical for mantle rocks under the expected temperature and pressure conditions. There are arguments that the Moho may not always be the base of the crust from a petrological point of view. In any case, the transition from crustal to mantle compositions may be gradational, and this is reflected by the common observation of a velocity gradient at the base of the crust.There are significant variations in the depth of the Moho under Australia. In general, within the Archean regions of Western Australia the Moho is relatively shallow with a large velocity contrast at the transition between the crust and the mantle. It is significantly deeper under the Proterozoic North Australian Platform, under Central Australia and Phanerozoic Southeastern Australia. Thicker crust in general is reflected in higher surface elevation, although the relationship between crustal thickness and elevation is not linear. Where the Moho is deep there is a very broad transition from crustal to mantle velocities. Other regions of Australia for which data exist generally have average depths to Moho.Crustal thickness patterns reflect the mechanisms of continental growth and tectonic evolution. The relative thickness of the upper and lower crust are characteristic of various styles of extensional or compressional tectonics and other processes such as underplating. Images across the Australian continental margin clearly demonstrate the role that upper and lower crustal extension have on crustal growth, by sedimentary deposition and magmatic emplacement on and within the attenuated crust.

Describes the development of the late Silurian-early Devonian Jemalong Trough in the eastern Lachlan Fold Belt.

Depth is the most fundamental logging parameter, but its accuracy is usually overlooked and remains enigmatic. It is not unusual that logger?s casing shoe and total depths are substantially different to driller?s. Wireline log interpretation booklets always contain correction charts for borehole size, mud weight and mudcake thickness. However, no chart is available for depth correction, probably because the sources and magnitude of depth errors are unique and temporally variable at each depth measurement point. The sources of depth errors include borehole doglegs, drill pipe stretch, incorrect lengths for drill pipes, wireline cable stretch and tides. Tidal effects on a floating drilling rig are significantly larger in the northwest continental shelf of Australia than in the North Sea or Gulf of Mexico. Depth mismatches occur between different suites of the same wireline logging run. Depth tie-in adjustments with the first suite are a common industry practice, but no guarantee is given to assure us that the depth of the first suite would be more reliable than that of subsequent ones. Sidewall cores taken from the middle of a thick monotonous shale interval, which is not uncommon in Northwest Australia, may not have an adequate depth tie-in reference point. This could result in obtaining off-depth sidewall core samples for biostratigraphic analysis. Depth mismatches also occur between MWD and wireline logging, between core cutting and wireline logging, and between equivalent wireline suite runs in multiple wells. The degree of wireline logging depth accuracy is a crucial factor for investigating pressure communication between wells and for calculating the hydrocarbon volumes of a multi-well gross geological structure. The economic impact of depth uncertainty on reserve estimates is growing because many recent discoveries are fairly small in size and complex in structure. For a small and geologically complex structure, a depth discrepancy of 0.1% (for example, 3m in a 3000m well) between wells could be too great to declare the project economically viable. Depth uncertainty often results in an open-ended discussion about whether two nearby wells have intersected the same continuous hydrocarbon pool or two separate pools. It also causes tension within a company over the decision making process of a field appraisal or development, between companies over a field unitisation process, and between a company and government agencies over an application for a location, retention lease, production licence or ?new oil? excise exemption.

No abstract available

The National Exposure Information System (NEXIS) generates a nationally consistent dataset of the best available exposure information for Australia. NEXIS was developed from the recommendations made to the Council of Australian Governments (COAG) in 2003. NEXIS integrates diverse datasets to produce detailed information at building and business level for multi-hazard risk assessments. The NEXIS Business Module enhances risk assessments for various natural and man-made hazards. The module involves detailed spatial analysis and the integration of numerous demographic, structural, statistical and cost factor datasets as well as engineering assumptions. Produced is the best available exposure information regarding business categories, employment figures, replacement value and locations. GA has currently completed the basic framework and generic version of the NEXIS Business Module with future scope to develop decision support systems suitable for policy makers and emergency managers. This emerging capability is informing assessments of risk and will lead to more resilient business activity.