The well was drilled to a depth of 693.5m and secured with steel casing ready for down-hole temperature and geophysical logging, according to Petratherm.

The logging crew will move on-site in about a week after allowing for the temperatures in the hole to re-equilibrate following drilling.

“Yerila-1 intersected, for the most part, fine-grained mudstone and carbonaceous claystone, ideal cover insulators, before passing into fine-grained sandstone at 650m,” Petratherm said.

“An artesian aquifer was present between 400-430m. Should initial results prove promising, the well will be extended at a later date with cost-effective diamond drilling.”

According to Petratherm, the basement granite in this area produces an average of six times the heat by volume of normal granite. Some areas are 25-times hotter.

Petratherm said the results from the drill hole suggested that the Callabonna Gravity Low heat anomaly was due to a large buried granite.

“This supports the company’s initial geophysical modelling, which placed the top of the potential hot rock granite at approximately 2.2-2.7km,” Petratherm said.

Geophysical data and modelling of the Callabonna Gravity Low, along with historical seismic data, indicates a major sub-basin above the granite in this area, providing an insulating blanket that retains heat in the granite.

"The potential combination of a suitable capping insulator and basement heat engine below means this region may contain vast geothermal energy supplies," the company said.

The rig is now relocating to Paralana (GEL 178), 65km south-south-west of Callabonna to begin phase 1 of the Paralana geothermal evaluation well.