A 3D map of the Cooper Basin region has been produced over an area of 300 x 450 km to a depth of 20 km. The 3D map was constructed from 3D inversions of gravity data using geological data to constrain the inversions. It delineates regions of low density within the basement of the Cooper/Eromanga Basins that are inferred to be granitic bodies. This interpretation is supported by a spatial correlation between the modelled bodies and known granite occurrences. The 3D map, which also delineates the 3D geometries of the Cooper and Eromanga Basins, therefore incorporates both potential heat sources and thermally insulating cover, key elements in locating a geothermal play. This study was conducted as part of Geoscience Australia's Onshore Energy Security Program, Geothermal Energy Project.

A 3D map of the Cooper Basin region has been produced over an area of 300 x 450 km to a depth of 20 km (Figure 1). The map was constructed from 3D inversions of gravity data using geological data to constrain the inversions. It delineates regions of low density within the basement of the Cooper / Eromanga Basins that are inferred to be granitic bodies. This interpretation is supported by a spatial correlation between the modelled bodies and known granite occurrences. The map, which also delineates the 3D geometries of the Cooper and Eromanga Basins, therefore incorporates both potential heat sources and thermally insulating cover, key elements in locating a geothermal play. A smaller region of the Cooper Basin 3D map (Figure 1) has been used as a test-bed for GeoModeller's 3D thermal modelling capability. The thermal modelling described herein is a work in progress and is being carried out to test the capability of the thermal modelling component of 3D GeoModeller, as well as to test our understanding of the thermal properties of the Cooper Basin region.

Work at the Bureau of Mineral Resources (now Geoscience Australia) in the early 1990s was instrumental in bringing hot rocks geothermal research and development to Australia. The Energy Initiative of the Federal Government, announced in August 2006, has restarted a geothermal project in GA. This paper outlines the scope of the Onshore Energy Security Program, the development and implementation of the new Geothermal Energy Project, and progress to date. The Onshore Energy Security Program A program to acquire pre-competitive geoscience information for onshore energy prospects has begun following the Prime Minister's Energy Security Initiative. The initiative provides $58.9 million over five years to Geoscience Australia for the acquisition of new seismic, gravity, geochemistry, heat flow, radiometric, magneto-telluric and airborne electromagnetic (EM) data to attract investment in exploration for onshore petroleum, geothermal, uranium and thorium energy sources. The program will be delivered in collaboration with the States and Territory under the existing National Geoscience Agreement. A set of principles have been developed to guide the program. According to the principles, proposed work must: promote exploration for energy-related resources, especially in greenfields areas; improve discovery rates for energy-related resources; be of national and/or strategic importance; and data acquisition must be driven by science. The program is structured with national-scale projects for each energy commodity (geothermal, petroleum, uranium and thorium) and for geophysical and geochemical acquisition. Regional scale projects in Georgetown-Isa, Gawler-Curnamona, Northern WA and the Northern Territory areas will assess the energy potential of those areas in detail. Other regions will be prioritised at a later stage of the OESP. Formulating the Geoscience Australia Geothermal Energy Project Based on consultation with State and Territory geological surveys and geothermal exploration companies, a list of the impediments faced by geothermal companies was identified. The Geothermal Energy Project addresses those that require geoscience input. The greatest geological problem facing explorers is a lack of understanding of the distribution of temperature in the upper crust of Australia. The two existing datasets that map temperature and heat distribution - the Austherm map of temperature at 5 km depth, and a database of heat flow measurements - both require a great deal of infilling. It is also possible to make predictive maps of expected heat based on geological models. These three ways of mapping heat, and the work that the project will do in each of these areas, is described in more detail in later sections. Other geoscience inputs that will help improve discovery rates and/or reduce risk to explorers and investors include a comprehensive and accessible geothermal geoscience information system, a better understanding of the stress state of the Australian crust, better access to seismic monitors during reservoir stimulation, and a Reserve & Resource definition scheme. Increasing the awareness of Australia's geothermal potential amongst decision makers and the general public may also help the funding of the development of the industry through Government support and investor confidence. The Geothermal Project has involvement in all of these activities, as outlined in later sections.

The Oceania region encompasses a range of geothermal environments and varying stages of geothermal development. Conventional geothermal resources in New Zealand, Papua New Guinea, Indonesia and the Philippines have been used for power generation for as long as 50 years, whereas Australia's non-conventional 'Hot Rock' geothermal resources have only recently been targeted as an energy source. New Zealand's geothermal resources are high-temperature convective hydrothermal systems associated with active magmatism, and these have been exploited for electricity generation since 1958. With a total installed capacity of ~445MWe, geothermal energy currently generates ~7% of New Zealand's electricity. This figure is likely to increase in response to the New Zealand Government's recent target of 90% of the country's electricity to be generated from renewable resources by 2025. Geothermal power plants used in New Zealand are either condensing steam turbines, or combined-cycle plants that utilise a steam turbine with binary units. In terms of energy consumed, direct-use of geothermal energy rivals electricity generation at approximately 10,000 TJ/yr. Applications include industrial timber drying, greenhouse warming and aquaculture, and may be stand-alone or cascading. Analogous high-temperature hydrothermal systems elsewhere in Oceania support installed electricity generation capacities of 56MWe in Papua New Guinea, 838MWe in Indonesia and 1931MWe in the Philippines. In contrast, Australia's geothermal plays are principally associated with high-heat-producing basement rocks. Typically these rocks are granites that are relatively enriched in the radioactive elements U, Th and K and thus have elevated heat generation (i.e. >6µW/m³). Elevated temperatures are found where this heat is trapped beneath sufficient thicknesses (>3km) of low-thermal-conductivity sediments. Low-temperature hydrothermal systems can be found in shallow aquifer units that overlie the hot basement. Hot Rock geothermal plays are typically found at greater depths (3 to 5km), where temperatures in the basement itself or in overlying sediments can exceed 250°C. Electricity can be generated from Hot Rock resources by artificially enhancing the geothermal system (e.g. increasing rock permeability at depth by hydro-fracturing). Although no electricity has yet been generated from Australia's Hot Rocks, a listed company (Geodynamics Ltd) has completed two 4200m-deep wells in the Cooper Basin, and expects to establish a 1MWe pilot plant by late-2008, a 50MWe plant by 2012, and 500MWe by 2015. As of January 2008, there are 33 companies in Australia prospecting for Hot Rock and hydrothermal resources, across 277 license-application areas that cover 219,00km². In support of industry exploration, and to increase uptake of geothermal energy in Australia, Geoscience Australia is currently compiling and collecting national-scale geothermal datasets such as crustal temperature and heatflow.

Hot Rock geothermal exploration in Australia is significantly different to methods used for conventional geothermal plays elsewhere in the world. Hot Rock geothermal plays in the most essential form comprise a heat source and insulating layer. In Australia, high-heat producing granites (HHPG) are the presumed heat source, while low-conductivity sedimentary rocks provide the insulator necessary to create an accumulation of heat and elevated temperatures. It is presumed that other elements of a geothermal play can be introduced, such as using hydrofracturing or chemical treatment to achieve the required permeability, or the injection of circulation water.

Work conducted at the Bureau of Mineral Resources (now Geoscience Australia) in the early 1990s was instrumental in bringing Hot Rocks geothermal research and development to Australia. Following the announcement of the Federal Government's Energy Initiative in August 2006, a new geothermal project has been started at Geoscience Australia. Pre-competitive geoscience previously made available for the minerals and petroleum industries has been extremely useful in assisting the geothermal exploration industry to date. This paper outlines the scope of Geoscience Australia's Onshore Energy Security Program and the development, implementation and progress to date of the new Geothermal Energy Project, including new data acquisition programs specifically aimed at assisting geothermal explorers. Geoscience Australia is the Australian government's geoscience and geospatial information agency within the Department of Resources, Energy and Tourism.

Poster describing synthetic thermal modelling and its application to geothermal exploration in Australia

Security of energy supply and pricing in addition to the desire for low-emission energy sources are driving interest in the development of a geothermal energy industry in Australia. Traditionally Australia has been regarded as having very limited geothermal potential. It is only relatively recently that the potential for Hot Rock and Hot Sedimentary Aquifer systems has started to be quantified. The realisation that parts of the Australian crust are anomalously hot at accessible depths came via compilations of bottom hole temperatures from petroleum drilling produced by the Bureau of Mineral Resources, Geology and Geophysics (now Geoscience Australia) in the late 1980-90s. This work was followed up at the Australian National University and directly resulted in development work at Innamincka (Cooper Basin, South Australia) by Geodynamics Limited. The Australian Government has several initiatives in place to support the exploration for and development of Australia's geothermal resources. Geoscience Australia is conducting a data acquisition program to make new heat flow measurements throughout the continent as part of the AUD58.9M five year Onshore Energy Security Program. Between 2000 - 2008, the Australian Government has awarded AUD32M in grants to geothermal companies through programs such as the Renewable Energy Development Initiative. The Department of Resources, Tourism and Energy (RET) conducted and published a Geothermal Industry Development Framework and Technology Roadmap. Launched in December 2008, the Framework contains a list of ten key recommendations and actions designed to encourage the development of a viable geothermal energy industry. Several of the recommendations are being addressed by the AUD50M Geothermal Drilling Program administered by RET. This program provides matching grants of up to AUD7M per proof-of-concept project via a multi-round competitive application process.

Sub-glacial geothermal heat flow is acknowledged to be a critical, yet poorly constrained, boundary parameter influencing ice sheet behaviour (Winsborrow et al 2010). Geothermal heat flow is the sum of residual heat from the formation of the Earth and the natural heat generated within the Earth from the radiogenic decay of the major heat producing elements (HPEs), U, Th and K. Estimates of the sub-glacial geothermal heat flow in Antarctica are largely deduced from remotely-sensed low-resolution datasets such as seismic tomography or satellite-based geomagnetics. These methods provide broad regional estimates of geothermal heat flow reflecting variations in the mantle contribution as a function of thickness of a thermally homogeneous crust. These estimates of sub-glacial geothermal heat flow, although widely utilised in ice sheet modelling studies, fail to account for lateral and vertical heterogeneity of heat production within the crust where HPEs are concentrated and that are known to significantly impact regional geothermal heat flow values. Significant variations in regional geothermal heat flow due to heterogeneous crustal distribution of HPEs have been recognised within southern Australia (e.g. McLaren et al., 2006), a region that was connected to east Antarctica along the George V, Adélie and Wilkes Lands coastline prior to breakup of Gondwana. The South Australian Heat Flow Anomaly (SAHFA; e.g. Neumann et al., 2000) is characterized by surface heat flows as high as 126 mWm-2, some '2-3 times' that of typical continental values, due to local enrichment of HPEs. The SAHFA forms part of a once contiguous continental block called the Mawson Continent, a now dismembered crustal block that is known, from geological and geophysical evidence, to extend deep into the sub-glacial interior of the Antarctic. It is highly probable that the high geothermal heat flow characteristics of the SAHFA also extend into the sub-glacial hinterland of Terra Adélie and George V lands, a possibility that has not been previously considered in ice sheet studies. In order to account for the occurrence of several sub-glacial lakes in Adélie Land, Siegert & Dowdeswell (1996) concluded that 'a further 25-50 mWm-2 of equivalent geothermal heat' was required over the assumed local geothermal heat flow of ca. 54 mWm-2. Although that study concluded that the additional heat required for basal melting was derived from internal ice deformation, they also acknowledged the possible role of variations in geothermal heat flow, and now that the SAHFA is well characterised, this is a possibility that appears very likely.

Exploration models for Rot Rock geothermal energy plays in Australia are based primarily on high-heat producing granites (HHPG) in combination with overlying low-conductivity sedimentary rocks providing the insulator necessary to accumulate elevated temperatures at unusually shallow (therefore accessible) depths. Unknowns in this style of geothermal play include the composition and geometry of the HHPG and thermal properties, and the thickness of the overlying sediments. A series of 3D geological models have been constructed to investigate the range of geometries and compositions that may give rise to prospective Hot Rock geothermal energy plays. A 3D geological map of the Cooper Basin region which contains known HHPG beneath thick sedimentary sequences, has been constructed from gravity inversions and constrained by geological data. The inversion models delineate regions of low density within the basement that are inferred to be granitic bodies. Thermal forward modelling was carried out by incorporating measured and estimated thermal properties to the mapped lithologies. An enhancement of the GeoModeller software is to allow the input thermal properties to be specified as distribution functions. Multiple thermal simulations using Monte-Carlo methods would be carried out from the supplied distributions. Statistical methods will be used to yield the probability estimates of the in-situ heat resource, reducing the risk of exploring for heat. The two thermal modelling techniques can be used as a predictive tool in regions where little or no temperature and geological data are available.