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Hot rocks boost as Petratherm spuds second geothermal well

Posted: 2 August 2005

Australia ’s emerging hot rocks energy sector has been boosted with the spudding by Petratherm Limited of its second geothermal well in South Australia .

The Yerila-1 well, which spudded today, will seek to define the potential for a hot granite resource northeast of the eco-tourism resort at Arkaroola, in South Australia ’s far north.

The well will be sunk up to 1,000 metres in depth to test temperature gradients and rock pressures for the likely presence of source hot rocks at depths three to four times that of Yerila-1.

“This is an evaluation well to help confirm the profile necessary to select a target and then drill into one of the hottest known granite corridors in the world,” Petratherm’s Chief Executive, Mr Peter Reid, said today.

“Significantly, the potential of hot rocks as a renewable and clean energy source has become increasingly recognised since Petratherm floated on the ASX in July last year,” Mr Reid said.

“With several geothermal explorers now active in Australia , the sector is at a point where the potential now exists within the short to medium term for direct contributions to the energy grid through exploration success.”

Petratherm has worked with the University of Adelaide to develop a specific exploration and thermal model based on geological and geophysical data regarding Australia ’s hottest near-surface granites.

Mr Reid said Yerila-1, located within the Callabonna geothermal exploration licence (GEL157), 90 kilometres northeast of Arkaroola, would also be the first well to be drilled through the 600-metre base of the artesian aquifer in the province, and into underlying strata below.

“No historical drilling has penetrated below the artesian aquifer, so there will be wide interest in this outcome, in addition to our geothermal objectives,” Mr Reid said.

“Seismic data suggests that flat-lying Cambrian or possibly younger Cooper Basin sediments lie below the aquifer.

“Yerila-1 will be drilled into the underlying sequence in order to accurately measure the geothermal gradient beyond the influence of the artesian aquifer, an objective that may require drilling to a maximum depth of 1,000 metres.”

The cost of drilling Yerila-1 is being assisted with a $140,000 contribution under the South Australian Government’s “Plan For Accelerating Exploration” (PACE) program.

Petratherm has also reached agreement with Sydney-based coal bed methane group, Planet Gas Ltd, to provide the results and logging program from the well.

Logs from Yerila-1 will also measure the physical properties of the overburden and determine the regional stress field, factors that have a bearing on the viability of the potential hot rock resource.

“This data is critical to understanding how injected water will heat up and circulate between wells, if the project is to move into the next stage of development,” Mr Reid said.

On completion of Yerila-1, the rig will move immediately onto the former Paralana target in GEL 178, 65 kilometres to the southwest.

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