Synthetic thermal modelling, constrained by available geological and geophysical datasets, is used to aid in geothermal target identi9fication and prioritization

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 a 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. This process has been validated for one-dimensional models such as a drill hole, where extensive information can be provided for a specific location. The process has also seen increasing use in more 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. These geological formations will typically consist of a range of lithological compositions, resulting in a range of spatially variable thermal conductivity values. As a case study these new methods are then applied to the New South Wales extent of the Clarence-Moreton Basin. The structure of the basin has been built using Intrepid Geophysics' 3D GeoModeller software package using data from existing petroleum drill holes, surface mapping and information derived from the FrOGTech SEEBASE study. A range of possible lithological compositions was determined for each of the major geological layers through application of compositional data analysis, using data from deep wells only (>2000 m). In turn, a range of possible thermal properties was determined from rock samples held by the New South Wales Department of Primary Industries and analysed at the Geoscience Australia laboratories. These populations of values were then randomly sampled to create 120 different forward models which were computed using SHEMAT. The results of these have been interpreted to present the best estimate of the expected subsurface temperatures of the basin, and their uncertainties, given the current state of knowledge. These results suggest that the Clarence-Moreton Basin has a moderate geothermal energy potential within an economic drilling depth. The results also show a significant degree of variability between the different thermal modelling runs, which is likely due to the limited data available for the region.

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

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.

This is an extract from the OZTemp database, an updated and improved version of the AUSTHERM05 borehole temperature database previously described by Chopra and Holgate (2005). OZTemp currently contains 5513 individual wells and 17 247 temperature and/or temperature gradient data records.

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.

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.

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.