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.

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.

Geoscience Australia's Geothermal Energy Project is part of the Energy Security Initiative announced by the Prime Minister in August 2006. Geoscience Australia received $58.9 million over five years to implement the Onshore Energy Security Program by acquiring new data to attract investment in exploration for onshore petroleum, geothermal, uranium and thorium energy sources. The Program will acquire national-scale geophysical and geochemical data, including seismic, gravity, heat flow, radiometric, magneto-telluric and airborne electromagnetic data in collaboration with the state and Northern Territory governments under the National Geoscience Agreement. Formulating the Geothermal Energy Project The key geological ingredients of the "hot rock" geothermal model are high heat-producing granites overlain by thick accumulations of low thermal-conductivity sediments. The decay of low concentrations of radiogenic elements (mostly uranium, thorium and potassium) over millions of years produces heat in the granite. This heat may be trapped at depth within the crust by a sedimentary cover that lies above the granite like a blanket. Where temperatures are high, water circulating through the hot rocks can be used to generate electricity. At lower temperatures, the heat can be used for indirect use applications, such as space and water heating. By raising awareness of Australia's geothermal potential among decision-makers and the general public, the Geothermal Energy Project aims to support development of a geothermal energy industry by encouraging investor confidence. Extensive consultation with state and Northern Territory geological surveys and geothermal exploration companies has identified a list of key impediments faced by geothermal explorers. The project aims to reduce those impediments through geoscience input. The greatest identified geoscience need is for a better understanding of the distribution of temperature in the continent's upper crust. Two existing datasets the Austherm05 map of temperature at five kilometres depth, and a database of heat flow measurements suffer from having too few data points, compounded by poor distribution. Geoscience Australia aims to provide additional information for both datasets. A third way to predict heat distribution is to use geological modelling of high heat-producing granite locations and overlying low thermal-conductivity sediments. Other geoscience inputs to be developed to improve discovery rates and reduce risk for explorers include: -a comprehensive and accessible geothermal geoscience information system -an improved understanding of the stress state of the Australian crust -increased access to seismic monitors during reservoir stimulation -a reserve and resource definition scheme.

Australia's hot rock and hydrothermal resources have the potential to fuel competitively-priced, emission free, renewable baseload power for centuries to come. This potential and the risks posed by climate change are stimulating geothermal energy exploration projects in Australia. Extracting just 1 percent of the estimated energy from rocks hotter than 150°C and shallower than 5,000m would yield ~190 million PJ or about 26,000 times Australia's primary power usage in 2005. This figure does not take into account the renewable characteristics of hot rock, nor the resource below 5,000m. To year-end 2007, thirty-three companies have joined the hunt for geothermal energy resources in 277 licence application areas covering more than 219,000 km2 in Australia. Companies are targeting resources that fall into two categories: (1) hydrothermal resources in relatively hot sedimentary basins; and (2) hot rocks. Most exploration efforts are currently focused on hot rocks to develop Enhanced Geothermal Systems (EGS) to fuel binary power plants. Roughly 80 percent of these projects are located in South Australia. The basic geologic factors that limit the extent of hot rock plays can be generalised as: - source rocks in the form of radiogenic, high heat-flow basement rocks; - traps defined by favourable juxtaposition of low (thermal) conductivity insulating rocks to radiogenic heat producing basement rocks; - heat-exchange reservoirs under favourable stress conditions within insulating and basement rocks; and - a practical depth-range limited by drilling and completion technologies (defining a base) and necessary heat exchange efficiency (defining a top). A considerable investment (US$200+ million) is required to prove a sustainable hot rock play, and demonstrate the reliability, scalability and efficiency of EGS power production. The proof-of-concept phase entails the drilling of at least two deep (>3,500m) hot holes (one producer and one injector), fracture stimulation, geofluid flow and reinjection and heat exchange for power generation. Compelling demonstration projects will entail up-scaling, including smooth operations while drilling and completing additional Hot Rock production and injection wells and sustained power production, most probably from binary geothermal power plants. Australian government grants have focused on reducing critical, sector-wide uncertainties and equate to roughly 25% of the cost of the private sector's field efforts to date. A national hot rock resource assessment and a road-map for the commercialisation of Australian hot rock plays will be published in 2008 by the Australia federal government. Play and portfolio assessment methods currently used to manage the uncertainties in petroleum exploration can usefully be adapted to underpin decision-making by companies and governments seeking to respectively push and pull hot rock energy supplies into markets. This paper describes the geology, challenges, investment risk assessment and promising future for hot rock geothermal energy projects in Australia.

The Federal Government has recently committed $58.9M in the Energy Security Initiative between mid 2006 to mid 2011 to identify potential on-shore energy sources such as petroleum and geothermal energy. Using the latest geophysical imaging and mapping techniques, this information will help attract companies to explore in new areas by enhancing the chances of discovery and reducing the risks to investors. The Onshore Energy Security Program includes the acquisition of new seismic, radiometric, magneto-telluric, gravity, magnetic, geochemical and drillhole data in support of exploration for onshore petroleum, uranium and thorium energy sources, in addition to an emphasis on geothermal. Maps of crustal temperature (e.g. Chopra & Holgate, 2005, Proceeding of the World Geothermal Congress, Turkey. www.wgc2005.org) show that the geothermal energy resource in Australia is vast. Electricity is expected to be generated from hydrothermal and hot fractured rock plays, while lower-temperature hydrothermal resources close to population or industry centres may be useable by direct means. The new Geothermal Energy Project in the Onshore Energy and Minerals Division at Geoscience Australia will provide precompetitive geoscience information for geothermal explorers. The two major activities directly in support of geothermal energy exploration are enhanced maps of heat distribution across Australia, and a geothermal information system. Heat distribution throughout Australia will be mapped in three ways: (1) new heat flow measurements in existing and new drillholes; (2) a granite source-sediment heat trap map to identify hot fractured rock systems; and (3) enhancements to the 5km temperature map method of Chopra and Holgate (op cit.). The geothermal information system will include thermal conductivity, thermal gradient, density, and heat production amongst other data types.

This is a paper submitted for the 29th NZ Geothermal Workshop, presenting information about the geothermal industy in Australia, the impediements the industry faces and Geoscience Australia's role in reducing the geoscience-related impediments. Paper abstract is as follows: Australia's emergent geothermal energy industry is growing rapidly, with 29 geothermal companies currently prospecting for Hot Rock and hydrothermal resources. The Hot Rock model in the Australian context comprises a thick sequence (>3km) of low-thermal conductivity sediments overlying deeper high-heat-producing granites. Until now, the key datasets available to industry to guide their geothermal exploration have been a map of crustal temperature at 5km depth, and heat-flow data. Both datasets suffer from regions of low data density and heterogeneous data distribution. The Australian Government has provided Geoscience Australia with funding for an Onshore Energy Security Program (OESP). Established as part of the OESP, a new Geothermal Project will generate precompetitive geoscientific information for geothermal explorers through two major activities: mapping heat across Australia, and developing a geothermal information system. The Australian Government has also awarded several renewable energy and start-up grants to the geothermal industry since 2000, and is currently funding the preparation of a Geothermal Industry Development Framework (GIDF). The GIDF aims to support the industry by developing strategies to ensure that technical, economic and regulatory obstacles are tackled in a coordinated way.

The thermal conductivity dataset is from the Geothermal Energy Project's thermal conductivity database. It contains thermal conductivity value for rocks sampled from minerals and stratigraphic wells across Australia. Currenlty there are 405 measurements from 45 drill holes in the database. Access to these drill holes and samples has been provided by mining and exploration companies and state surveys. Samples have been measured for thermal conductivity by either Geoscience Australia or by Hot Dry Rocks Pty Ltd (HDR) using the divided bar apparatus.

Australia's emergent geothermal energy industry is growing rapidly. So far, 29 companies have applied for geothermal exploration licenses. The majority of these companies are prospecting for Hot Rock geothermal resources for electricity generation, with some companies targeting hydrothermal resources. The Hot Rock model in the Australian context comprises a thick sequence (>3km) of low-thermal conductivity sediments overlying deeper high-heat-producing granites. Until now, the key dataset available to industry to guide their geothermal exploration has been a map of crustal temperature at 5km depth1. Compiled from temperature measurements made in 5,722 petroleum wells across Australia, the map indicates a vast geothermal resource. Additional national-scale geothermal datasets are either incomplete, not publicly accessible, or have not been collected. In August 2006, the Australian Government announced an Energy Security Initiative. It provides $58.9M to Geoscience Australia (the national geoscience and spatial information agency) over five years for an Onshore Energy Security Program (OESP). The OESP aims to better understand Australia's geological potential for onshore energy resources such as petroleum, uranium and geothermal, and includes the acquisition of new seismic, radiometric, heat-flow, magneto-telluric, gravity, magnetic, geochemical and drill-hole data. Providing new data will help attract company exploration in new areas by enhancing the chances of discovery and reducing the risks to investors. Established as part of the OESP, a new Geothermal Energy Project will generate precompetitive geoscientific information for geothermal explorers through two major activities: creating maps of heat distribution across Australia, and developing a geothermal information system. Heat distribution will be mapped in three ways: (1) new heat flow measurements in existing and new drill-holes; (2) a granite source-sediment heat trap map to identify Hot Rock systems; and (3) enhancements to the 5km-temperature-map method of Chopra and Holgate1. The geothermal information system will include thermal conductivity, thermal gradient, geochemistry, density, and heat production amongst other data types. The Australian Government is also facilitating and funding the preparation of a Geothermal Industry Development Framework, which is being lead by the Department of Industry, Tourism and Resources. The Development Framework aims to support the growth of Australia's geothermal industry by identifying opportunities and impediments to the industry's growth, and developing strategies to ensure that technical, economic and regulatory obstacles are tackled in a coordinated way. 1 Chopra, P. and Holgate, F., (2005) A GIS analysis of temperature in the Australian crust, Proceedings of the World Geothermal Congress 2005, Antalya, Turkey, 24-29 April 2005.

Geothermal energy has received increasing attention over the last decade as a potentially abundant, large scale, cost competitive, base load, safe and low-emission energy source for electricity generation and industrial applications in Australia. Geothermal resources comprise a volume of rock of suitable temperature and permeability, and a heat-transport fluid. High crustal temperatures in Australia are thought to be generated by high heat producing granites being overlain by thermally insulating sediments. Two types of geothermal plays exist in Australia: Hot Rocks, which require reservoir enhancement and possibly the addition of water; and Hot Sedimentary Aquifers in shallow (<3,500 m), permeable, water-saturated sediments. Ground selection by early geothermal explorers in Australia was made based on direct temperature measurements from deep (up to 5 km) petroleum wells. In areas without previous deep drilling, the most robust measurement for predicting temperature at depth for Hot Rock geothermal resources is heat flow, but there are only ~150 publicly-available measurements continent-wide. Targeting for Hot Rock geothermal resources is increasingly being done using other geological datasets acquired for minerals exploration. These datasets include geological maps (lithology, stress, structure), seismic, geochemistry, gravity radiometrics and magnetics. Heat flow measurements are used in petroleum studies and can be of use in exploration for some types of mineral deposits.

The Federal Government has recently committed $58.9M in the Energy Initiative, a four year program scheduled to mid 2011, with the aim of identifying potential new energy sources in Australia. The program is targeted towards a specific range of energy commodities that include onshore geothermal energy. Using the latest geophysical imaging and mapping techniques, Geoscience Australia (GA) aims to provide pre-competitive geoscientific information that will help attract companies to explore in new areas by enhancing the chances of discovery and reducing the risks to investors. GA's Onshore Energy Security Program includes the acquisition of new seismic, radiometric, magneto-telluric, gravity, magnetic, geochemical and drillhole data in support of exploration for energy sources including geothermal, petroleum, uranium and thorium. Available maps of crustal temperature (Figure 1) clearly illustrate that the geothermal energy resource in Australia is vast. Electricity is expected to be generated from both hydrothermal (hot groundwater in situ e.g. the Great Artesian Basin) and hot fractured rock plays (e.g. buried hot granites within the Cooper Basin). Significant potential also exists for lower-temperature hydrothermal resources close to population or industry centres which may be useable by direct means. Currently the only geothermal energy being used in Australia is that which emanates from a 120kW plant located at Birdsville (Qld) which draws from the relative shallow hot waters of the Great Artesian Basin. The Geothermal Energy Project in the Onshore Energy and Minerals Division at GA aims to support ongoing geothermal energy exploration across Australia via the provision of enhanced maps of heat distribution together with a comprehensive national geothermal information system. Heat distribution throughout Australia will be mapped in three ways: (1) new heat flow measurements in existing and new drillholes; (2) a granite source/sediment heat trap map to identify hot fractured rock systems and potential geothermal plays (Figure 2); and (3) enhancements to the 5km temperature map of Chopra and Holgate (2005; Figure 1). The geothermal information system will comprise a wide range of information including (but not limited to) thermal conductivity, thermal gradient, density, and heat production data.