Geothermal Energy Resources

Geothermal energy is an emerging industry in Australia, with exploration being conducted in all states and the Northern Territory. While significant resources have been identified and there are several companies in advanced stages of exploration, presently there is no commercial production of geothermal energy in Australia. That said, there is significant potential for geothermal energy in Australia. It is estimated that one per cent of the geothermal energy shallower than five kilometres and hotter than 150°C could supply Australia's total energy requirements for 26 000 years (based on 2004-05 figures).

Geothermal energy uses

Geothermal energy is heat contained within in the earth. Australia has great potential for geothermal energy to be used for electricity generation and for direct use applications. Electricity can be generated using temperatures as low as 100°C, although higher temperatures than this may be required for larger scale production. For direct use applications, temperatures of 30°C and above can be used in industry, agriculture and for heating and cooling of residential buildings (see Fact sheet Direct-use of Geothermal Energy Opportunities for Australia).

Geothermal energy exploration

Currently drilling technology limits economic development of geothermal resources to a maximum depth of about five kilometres. Thus companies are exploring for regions of elevated temperatures at five kilometres deep or less. The temperature at five kilometres depth varies across the continent due to a range of geologic factors. It is possible to identify areas of higher potential through the use of a variety of geoscience data.

Geoscience Australia programs

Geoscience Australia is undertaking significant work to better understand where these hot spots are in order to support the geothermal industry and encourage exploration in Australia. As part of the federal government's Onshore Energy Security Program, a field logging program has been set up with the aim of improving the heat flow coverage of Australia. Heat flow is determined by taking the product of thermal conductivity and temperature gradient in a borehole and can be used to predict temperatures at greater depths. Geoscience Australia has released the first set of Heat flow interpretations for the Australian Continent.

Another product that has been released is the OZTemp database. This has been generated using temperature measurements from a variety of sources and extrapolating these to five kilometres depth. The extrapolated temperature can be horizontally interpolated between drillholes, and then contoured to produce a continuous map of temperature at five kilometres depth across the entire continent. This technique was pioneered by Somerville et al. (1994 - Geotherm94 database) at the Bureau of Minerals Resources (now Geoscience Australia) and the Energy Research and Development Corporation. The database and the image for the current iteration are available on their website.

Geoscience Australia has also been involved in the development of the Geothermal Reporting Code, a geothermal reserves definition scheme similar to the minerals-based Joint Ore Reserves Committee (JORC) code and petroleum-based SPEE scheme. This was produced in collaboration with the Australian Geothermal Energy Group (AGEG) and the Australian Geothermal Energy Association (AGEA) and is critical to the large-scale development of the geothermal industry. In addition, Geoscience Australia has collaborated with the Department of Resources, Energy and Tourism (RET) and AGEA to develop the Australian Geothermal Industry Development Framework and Technology Roadmap with the aim of assisting geothermal exploration in Australia.