A compilation of extended abstracts as a record of proceedings of the 2nd Australian Geothermal Energy Conference, Brisbane, 11-13 November 2009

Hot Rock exploration and development has progressed rapidly in Australia in the last decade. A wealth of pre-competitive geological data acquired by government surveys and mineral and petroleum explorers is available in Australia, but heat flow data specific to geothermal exploration is sparse. A methodology is presented that sets out the key parameters required in Hot Rock exploration. Mappable practical proxies corresponding to these parameters can utilise existing geological datasets. Australia has an enviable amount of geological data that is publicly available, and this can be used to show that many parts of the continent are attractive Hot Rock exploration areas.

This volume is a compilation of Extended Abstracts presented at the 2008 Australian Geothermal Energy Conference, 19-22 August 2008, Rydges Hotel, Melbourne, organised by the Australian Geothermal Energy Association and the Australian Geothermal Energy Group. This Conference is the first dedicated conference organised by the geothermal energy community in Australia and has been made possible by the seed funding from the Australian Government under the Sir Mark Oliphant Conference funding scheme with additional sponsorship of the companies acknowledged earlier and paying delegates. This Conference is being held at a time of rapid growth in all sectors of the geothermal community. The number of companies engaged in exploration stands at 33, the number of leases held or applied for is 320, and the value of the work program for these companies exceeds $850 million between 2002-2013. The Australian Geothermal Energy Association has been incorporated to serve as the peak industry representative body. The Universities of Queensland, West Australia, Adelaide and Newcastle have new funding specifically for geothermal research programs. The Australian Government has continued its strong support of the sector through the Geothermal Industry Development Framework and Technology Roadmap, the Geothermal Drilling Program, and the Onshore Energy Security Program. All of the States now have legislation regulating geothermal exploration activity in place, and the Northern Territory has drafted legislation for presentation to parliament. This volume of Extended Abstracts starts with a summary snapshot of the global and national geothermal energy sectors. The rest of the volume is organised under three headings: Underground Science and Technology Power Conversion Technologies Legislation, Policy and Infrastructure

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.

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.

Report on energy assessment of north Queensland as part of the Onshore Energy Security Program. As part of the Onshore Energy Security Program, Geoscience Australia has undertaken a series of energy potential assessments, both on a national scale and on a regional scale in association geological framework studies. These framework studies, which are designed to provide information on geodynamic and architectural controls on energy systems, are linked to the acquisition of deep seismic, magnetotelluric and airbourne electromagnetic data. The focus of fiscal year 2008-2009 was north Queensland, stretching from the Northern Territory border to the coast, between 17° and 22° south latitude. In addition to the seismic data acquisition and interpretation, these framework studies have included geochronological studies as well as uranium mineral system and geothermal system studied in collaboration with the Uranium and Geothermal Projects. The main goal of these studies is to provide background data that can be used by industry for exploration, however the data also provide new information that can be used in assessing the potential of north Queensland for uranium and geothermal resources using geosystems (i.e. mineral and geothermal systems) methodologies in a GIS environment. This report provides such an assessment in a qualitative to semi-quantitative way. One of the goals of this analysis is to define the extent of areas or regions with known deposits; another goal was to define areas with previously unrecognised potential.

The development of the Australian geothermal industry over the last decade owes much to compilations of drill hole temperature data undertaken in the early 1990s in Canberra. The portrayal of this data on maps of predicted temperature at five kilometres depth, and contained heat resource calculations from this data, have shifted the perception that because Australia does not have significant current magmatic activity there is no geothermal potential. The Australian geothermal industry arguably now leads the world in terms of development of amagmatic geothermal systems for electricity generation.

Like many of the basins along Australia's eastern seaboard, there is currently only a limited understanding of the geothermal energy potential of the New South Wales extent of the Clarence-Moreton Basin. To date, no study has examined the existing geological information available to produce an estimate of subsurface temperatures throughout the region. Forward modelling of basin structure using its expected thermal properties is the process generally used in geothermal studies to estimate temperatures at depth in the Earth's crust. The process has seen increasing use in complex three-dimensional (3D) models, including in areas of sparse data. The overall uncertainties of 3D models, including the influence of the broad assumptions required to undertake them, are generally only poorly examined by their authors and sometimes completely ignored. New methods are presented in this study which will allow estimates and uncertainties to be addressed in a quantitative and justifiable way. Specifically, this study applies Monte Carlo Analysis to constrain uncertainties through random sampling of statistically congruent populations. Particular focus has been placed on the uncertainty in assigning thermal conductivity values to complex and spatially extensive geological formations using only limited data. As a case study these new methods are then applied to the New South Wales extent of the Clarence-Moreton Basin. The geological structure of the basin has been modelled using data from existing petroleum drill holes, surface mapping and information derived from previous studies. A range of possible lithological compositions was determined for each of the major geological layers through application of compositional data analysis. In turn, a range of possible thermal conductivity values was determined for the major lithology groups using rock samples held by the NSW Department of Primary Industries (DPI). These two populations of values were then randomly sampled to establish 120 different forward models, the results of which have been interpreted to present the best estimate of expected subsurface temperatures, and their uncertainties. These results suggest that the Clarence-Moreton Basin has a moderate geothermal energy potential within an economic drilling depth. This potential however, displays significant variability between different modelling runs, which is likely due to the limited data available for the region. While further work could improve these methods, it can be seen from this study that uncertainties can provide a means by which to add confidence to results, rather than undermine it.

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.

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.