The stage 3 geothermal test at the Paralana-1B well is designed to measure temperature gradients at depth and to determine reservoir properties.

The South Australian company said the results would help determine whether the project is economically viable. If so, Petratherm plans to start development of a full demonstration power plant at Paralana.

Petratherm chief executive Peter Reid said the company expected the well would take up to 30 days to drill.

“Due to the circulation of cool waters during the drilling process, it will take approximately another three weeks before the well reaches thermal equilibrium with the surrounding rock, whereupon final temperature readings will be taken,” he said.

Last September, temperature readings from the initial 491m stage 2 evaluation drilling recorded an extrapolated geothermal gradient of about 81.5C per kilometre. At the time, Petratherm said it believed this was among the highest reported shallow temperature gradients in Australia.

“This gradient is well above the company’s initial target expectation of a hot rock resource in excess of 200C at a depth of 3.5 kilometres,” Reid said.

“The Paralana resource is potentially very large. Simple energy calculations based on thermal models indicate the resource could support up to 13,000MWe of power output over a 20-year period if fully utilised.”

In March, the company announced it had raised $A1.97 million to fund its planned drilling and exploration program, which included the extension of Paralana-1B.

The site is located 130km from the main grid infrastructure, and 11km from the existing Beverley Uranium Mine.