Frome Project (North Eastern SA)
The Frome project area consists of 10 geothermal exploration licences (GELs) covering more than 5000 km2 that are located in the Frome basin region of northeastern South Australia. The tenements cover buried Cambrian basins known as the Moorowie and Yalkalpo sub-basins that are underlain by relatively radiogenic Precambrian volcanic and intrusive basement rocks of the Curnamona Craton.
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The Frome project is based on the Hot Fractured Rock (HFR) geothermal model, similar to that successfully demonstrated by Geodynamics for their Cooper Basin project. In this model the heat source is radiogenic granitic rock that is buried deep beneath a thick pile of insulating sediments. The extensive amounts of trapped heat are exploited by setting up a heat exchanger hot water circulation system in the granite, whose natural fracturing is stimulated by hydrofracturing.
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Since commencement of exploration of the Frome project in 2006, Geothermal Resources has completed 8 exploration wells, with all but one located within an area of approximately 1000 km2 above the interpreted granite body (see above map). These wells have been drilled by various methods to varying depths, the deepest wells to date being Frome 12 and Frome 13 (to 1761 and 1809 metres depth, respectively). Systematic down-hole temperature logging has been completed for each well, allowing an accurate geothermal gradient to be calculated in each case. Geothermal gradients in the two deepest holes average approximately 41°C/km, with up to 47 °C/km in one shallower holes. These thermal gradients are capable of generating temperatures of around 185 to 190°C at 4 km depth.
Importantly, the bottom 290 metres of Frome 12 was cored in granite which shows well developed sub-horizontal fracturing. Based on strong seismic reflection data it is likely that the upper 1 km of the granite is extensively horizontally fractured, which is an essential feature required for effective hydro-fracturing and establishment of sufficient lateral water flow through the hot granite.
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Using the well temperature data, an Inferred Resource of 84,000 PJ* is estimated for the thermal energy contained within granitic rocks lying between 3-5 km depth over a 500 km2 portion of the Frome Project area (see above map). The Inferred Resource status reflects the uncertainty concerning how much of this in place thermal energy will ultimately prove to be recoverable.
Applying a conservative heat recovery factor of 20% and a conversion efficiency to electricity of 10% then this amount of recoverable thermal energy has an estimated electrical generating capacity of 460,000 GWh. This is sufficient energy to supply all of South Australia's electricity needs for more than 30 years at the current rate of consumption of 12,500GWh (www.escosa.sa.gov.au).
Resource Area |
Estimated thermal energy in place PJ |
Potential recoverable thermal energy PJ |
Electricity generating potential GWh |
500 km2 |
84,000 |
16,800 |
460,000 |
Determination of the heat recovery and reservoir parameters, so that the thermal energy in place estimate can be assigned a measured resource status, which implies a high level of confidence in the recoverability, is an ongoing objective of the project. This will involve drilling two deep wells (>3km), subsequent fraccing of the granite between the two wells, followed by open and then closed loop testing of water flow and heat energy extraction rates.
* This geothermal resource estimate has been compiled by Dr Chris Giles in accordance with the guidelines defined in Edition 1 (2008) of the “Geothermal Reporting Code, 2008”. Dr Giles is a member of The Australian Institute of Geoscientists and is employed by the Company on a consulting contract. He has sufficient experience which is relevant to the style of geothermal play under consideration to qualify as a Competent Person as defined in Edition 1 (2008) of the “Geothermal Reporting Code, 2008”.
Dr Giles geothermal resource estimate report may be viewed by clicking on the following link : Frome Project - Statement of Estimated Geothermal Resources.pdf
Geothermal Resources gratefully acknowledges support for the drilling work from the Commonwealth Government, via a $2.4 million REDI (Renewable Energy Development Initiative) grant and the State Government via a $100,000 PACE grant which in both cases match the Company’s drilling expenditure.
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