Geothermal on the crest of the wave in Galilee

By Freya Purnell

Professor Hal Gurgenci, director of the Queensland Geothermal Energy Centre of Excellence at the University of Queensland, said while the indications are good, more information is required to confirm that there is a large geothermal resource beneath the Galilee Basin.
He said the geology of the Drummond Basin, which underlies the Galilee Basin, appears to be quite similar to the Cooper Basin at Innamincka in South Australia, which is currently being explored by Geodynamics.
“Our knowledge of geothermal resources in Australia is extrapolated from the temperature logs of oil and gas drilling wells. So we know the geothermal resources very well near the areas where oil and gas exploration has taken place. But outside those areas, our knowledge is quite scant,” Gurgenci said.
And while the Queensland Government is this year conducting a $5 million coastal drilling program with the aim of establishing a geothermal resource near existing transmission networks, this will not include the Galilee Basin.
According to a spokesperson for the Queensland Department of Employment, Economic Development and Innovation, the Galilee Basin warrants serious consideration for geothermal energy development.
“Overlying metamorphic and granitic basement there is 1,000 metres to 10,000 metres of insulating sedimentary cover including coal. Geophysical anomalies, especially areas of low gravity, may indicate the location of these granitic bodies. Downhole temperature measurements from petroleum exploration wells indicate there are some areas with anomalously high temperatures (eg. EEA Rodney Creek 2 up to 77.8 degrees Celsius at 1077 metres),” the spokesperson told The Australian Journal of Mining.

Giving the Galilee a boost
Despite these challenges, recent developments regarding the Galilee Basin point to a promising future.
Aside from the geological evidence pointing to a sizeable resource beneath the Galilee Basin, a spike in interest in the geothermal potential of the region can be attributed to a couple of factors: the announcement of Waratah Coal’s proposed $7.5 billion China First coal mine and infrastructure development, which will provide an energy transmission network located close to the resource, and the proposal for the development of a $1.25 billion clean power station, incorporating carbon capture and storage technologies, as part of this development.
This has opened the door for the Geothermal Energy Centre of Excellence to potentially implement one of its innovative geothermal technologies. The centre has been working with American and Japanese colleagues on the ‘supercritical CO2 thermosiphon’ for several years.
“This is a new geothermal concept where, instead of water (which is traditionally used in conventional geothermal power plants), supercritical CO2 captured from the plant’s smoke stacks is sent down to extract the reservoir heat,” Gurgenci says. “The hot CO2 rises to the surface and drives a turbo-generator to produce electricity, and then is cooled and sent back underground to repeat the cycle. The favourable thermodynamic properties of CO2 make it possible for the two wells to operate as a self-sustaining heat pump that brings the subterranean heat to the surface and transforms it to electricity.”
This concept has the potential to improve geothermal power conversion efficiencies by up to 50 per cent – effectively overcoming some of the current difficulties with energy transfer.
Despite the promise of this technology, Gurgenci says several factors – the confirmation of the Drummond Basin resource and the Waratah development going ahead with a clean coal plant to power it – will be crucial in progressing the best opportunity so far to see a geothermal facility developed in the Galilee Basin.

Legislative approval
Queensland currently has Australia’s only operational geothermal plant – the Birdsville Geothermal Power Station, which has been operating on a hot sedimentary aquifer for many years. The Queensland Government has recently provided Ergon Energy with funding to expand this plant’s capacity significantly.
Elsewhere in Australia, geothermal projects at Innamincka and Paralana in South Australia are expected to be deployed within the next three years, funded by the Federal Government’s Renewable Energy Program. In fact, all the current geothermal exploration projects (around seven) are being leveraged from government funding.
Despite the Queensland Government’s encouragement, geothermal exploration in the State has been slowed partly due to problems with geothermal lease legislation. The Queensland Government is addressing this, with draft legislation on a framework to support geothermal production released in mid-2009 for public comment.
Gurgenci believes once the new legislation is in place, more companies in Queensland will be taking up leases to pursue geothermal resources.
Currently, companies which have been granted or have lodged applications for geothermal exploration permits (EPG) within or overlapping the boundaries of the Galilee Basin include Clean Energy Australasia Pty Ltd, GeoGen Victoria Pty Ltd, and Red Hot Rocks Pty Ltd.

Making the economics stack up
As with any new mining development, the economics for geothermal projects must stack up before there will be any significant development – in the Galilee Basin or elsewhere.
While Gurgenci believes the technology will be sufficiently advanced to get geothermal power plants of 1000-1500 megawatt capacity up and running by 2020, the relative costs are still an issue.
“Various people have made estimates, but they all come down to similar levels – about 9 to 10 cents per kilowatt hour for the electricity cost. That is still more expensive than coal and still more expensive than natural gas. If it is commercially viable for a power plant to produce electricity for 10 cents per kilowatt hour, then there are going to be power plants by 2020,” Gurgenci said.
There is no doubt that there is a need to find more energy capacity somewhere, with the National Electricity Market in eastern Australia requiring at least 5000 MW of new electricity generation over the next decade. The Queensland Government says under the Commonwealth’s expanded Renewable Energy Target (RET), geothermal energy is expected to make a significant contribution to this demand.
However, geothermal energy will need to compete with established energy sources already operating, and at this stage, it seems government sweeteners such as the RET and any future Carbon Pollution Reduction Scheme might be required to make it commercially viable.