Results from its recent exploration evaluation pushed Green Rock a step closer to becoming Australia’s first commercial geothermal energy producer, according to Green Rock managing director Adrian Larking.

“By way of illustration, just a small part of Green Rock Energy’s licence areas have an energy potential equivalent to the 2 trillion cubic feet (TCF) of gas extracted from the Moomba gas field in the Cooper Basin,” Larking said.

“This would be sufficient energy to produce 1,000MW of electrical power for 20 years.”

The company has now started design work and is finalising sites for the two geothermal wells to be drilled to between 5,500 to 6,000 metres next year.

“With the location of the wells near to existing potential markets, the company is well placed to quickly proceed to install a pilot power plant following the establishment of a geothermal circulation system,” Larking said.

Green Rock claims the geothermal host rock has the appropriate fracturing qualities, while nearby potential markets, voltage power transmission lines and existing infrastructure have improved the economics of the project. This has enabled the flexibility to stage the development in 50 to 100MWe modules, the company said.

The initial work included drilling and logging the Blanche-1 well to 1,935 metres, as well as conducting temperature evaluations in this and the surrounding wells.

At 1218 metres, Blanche-1 was also the deepest drill penetration of granite in Australia.

“This granite body, known as the Roxby Downs Granite, is interpreted to be widespread and to persist at depth,” Larking said.

“The granite demonstrated horizontal and sub-horizontal fracturing desirable for establishing appropriate and efficient geothermal circulation cells required to recover heat contained in the granite for geothermal energy generation.”

A significant formation in the cover rocks, the Tregolana shale, had measured temperature 60ºC at 1,000 metres. This was in line with its low thermal conductivities and nearby drill holes at Olympic Dam, which had readings up to 83ºC at 1,000 metres, Green Rock said.

“These results suggests a low grade geothermal resource - 120ºC to 185ºC - will occur from 3,000 metres to 5,500 metres, and a high grade geothermal resource from 5,500 metres and deeper,” Larking said.

He claimed that the market value of renewable electricity is expected to increase in line with a forecast shortage of electricity supplies in South Australia from 2008.

Green Rock plans to raise the funds needed for the development through a share purchase plan. Current investors can apply for up to $5000 of ordinary shares at 16c each – a 19% discount on the company’s current share value.