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.

Current understanding of Australia's geothermal resources is based on limited data such as temperature measurements taken in petroleum and mineral boreholes across the country. Heat flow studies are rarer, with existing publicly available compilations containing less than 150 heat flow data-points for Australia. Both temperature and heat flow data are unevenly distributed and, where no data exist, the available information has been interpolated over large areas to generate national-scale maps. Geoscience Australia has acquired the field and laboratory equipment required to measure heat flow. It began thermal logging of boreholes across Australia in late 2008 and has since collected 155 temperature logs. In late 2009, the thermal conductivity meter became operational, allowing the project to begin thermal conductivity measurements of samples collected from logged boreholes. To help clear some of the backlog of samples collected during 2008-09, the measurement of some of these samples has been contracted out. This record details the first set of new heat flow interpretations to be released by Geoscience Australia. The remaining temperature logs will be interpreted for heat flow and released, as thermal conductivity data for these holes become available.

The geothermal industry has expanded rapidly in Australia, with 48 companies holding 385 license areas as of August 2009, with 10 listed on the ASX and with work programs excluding upscaling valued at ~AU$1.5B to 2013. Projects range from early to advanced exploration, proof-of-concept and pilot stages. Targets are for Hot Rock and Hot Sedimentary Aquifer resources, for the purposes of electricity generation or direct use applications. Ground source heat pump technology continues to struggle to attain the recognition it deserves.

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.

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.

An extension of previously developed methods to calculate in-situ 3D temperature directly from 3D geology models in 3D GeoModeller software now allows for quantification of the uncertainty associated with those calculations. This work is being collaboratively undertaken by Intrepid Geophysics and Geoscience Australia, and will offer Australia's geothermal industry both: i) a new predictive tool helping to reduce the risk of Enhanced Geothermal System (EGS) exploration and heat resource estimation, and ii) stochastic temperature and heat flow maps of Australia.

The hot rock geothermal model in the Australian context comprises high-heat producing granites overlain by thick accumulations of low-thermal conductivity sediments. The granites have low concentrations of radiogenic elements, and over hundreds of millions of years, these elements decay and produce heat. The passage of this heat to the Earth's surface via upwards conduction is slowed by layers of sediments that have low thermal conductivity, creating "hot spots" beneath the blankets. This thematic map shows granites attributed by heat production and basin depth. The majority of the granites depicted are of surface outcrop. The presence of high-heat producing granites adjacent to deep sedimentary basins may be used as a first-order indicator of where to further investigate the possibility of hot rock geothermal plays. The main frame of the map shows all granites (attributed by calculated heat production where available), sedimentary basins and their order (e.g. where one basin is overlapped by another) and geothermal licenses and applications. The top right inset map shows only those granites with a calculated radiogenic heat generation of >5 Wm-3, and the depths of the sedimentary basins. This map provides a rapid view of areas that may be expected to have the greatest hot rock potential. The second-from-top inset map shows all suitable geochemical analyses from OZCHEM, attributed by calculated radiogenic heat generation. This shows both the distribution of data that goes into attributing the granite polygons, and also analyses of granites (and other rocks) that fall outside the mapped granite polygons and are otherwise excluded from the main map. The third-from-top inset map shows the distribution of drillholes that have temperature measurements. The bottom inset map shows an image of the Austherm07 database, which is derived from the drillhole temperature information. The image shows the projected temperature of the crust at a depth of 5km, interpolated between the drillholes. Overlain on this image is the small number of publicly-available heat flow data. This map is GA GeoCat record 65306. ISBN (print): 978-1-921236-44-0; ISBN (web): 978-1-921236-45-7. Webpage: http://www.ga.gov.au/minerals/research/national/geothermal/index.jsp.

This service is for the 'OZTemp Interpreted Temperature at 5km Depth' image of Australia product. It includes an interpretation of the crustal temperature at 5km depth, based on the OZTemp bottom hole temperature database and additional confidential company 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.

Extended abstracts from various authors compiled as the Proceedings volume of the 2011 Australian Geothermal Energy Conference, 16-18 November, Sebel Albert Park, Melbourne.