The venting occurred during recovery operations to free up a lost drill stem, said managing director Bertus de Graaf.

“The lost 245 metres of drill stem is most likely left behind at the bottom of the well but this requires confirmation,” de Graaf said.

"Overpressures encountered during the recovery operations, before the drill stem was freed, required temporary release which was accompanied by venting of geothermal steam, a first for the project. This is a clear indication that the underground reservoir is in direct communication with the well."

Preparations are in place to resume operations with the side track drilling as soon as the drill stem is out of the hole, he said.

Geodynamics chairman Martin Carl Albrecht said the forthcoming circulation test program would establish the design parameters for what may yet become the world’s first HFR geothermal reference plant and would be the next step towards the ultimate commercial development of geothermal hot rocks for electricity generation.