Drilling investigation works have been ongoing on the Hebburn Minewater scheme, which will draw geothermal energy from abandoned flooded coal mines.
Target mineworkings have now been hit, at a depth of 291m, which the team says is crucial to the success of the multi-million-pound project.
South Tyneside Council said testing has also revealed that the temperature of the minewater is warmer than anticipated, which will result in significantly higher annual carbon savings than previous estimates of 319 tonnes.
“This is a major achievement and excellent news for the viability of the scheme,” said Cllr Ernest Gibson, South Tyneside Council’s lead member for Area Management and Community Safety, with responsibility for climate change.
“The water is around eight degrees warmer than we estimated, meaning the heat pump can work more efficiently, we can take much more energy from the water and we will achieve considerably greater carbon savings.
“This is a real milestone and a lot of hard work and dedication has paid off.”
Cllr Gibson said it was essential for the project that the borehole remained vertical to ensure it reached the mine workings, with the team relying on the accuracy of old maps.
He said detailed testing will continue to determine the chemical make-up of the water, and the results will feed into the final design of the energy centre.
Specialist drilling company Dunelm Geotechnical and Environmental Ltd will now begin to construct a wider borehole for the permanent drill casings, as well as a reinjection borehole where the cooled water will be returned to the mines.
Associate Director Bryan Laycock said: “We have successfully drilled the pilot well, intercepting the mine workings at nearly 300m below ground level on the first attempt.
“This has removed the need for several pilot wells to establish the location of the mine workings which would have been a costly operation.
“We are looking forward to completing the works drilling the reinjection well and widening the pilot hole to form the abstraction well over the coming months.”
Cllr Gibson added: “Investing in the natural environment is one of South Tyneside Council’s key priorities, with a target of carbon neutrality by 2030.
“This scheme will now make an even more significant contribution towards that goal than we thought, reducing annual carbon emissions by hundreds of tonnes and allowing us to provide low carbon and sustainable heat to council buildings.”
Heat from the minewater will be extracted with a water source heat pump before it is compressed to a much higher temperature.
It will then feed into an energy centre located above ground and then be distributed via a new pipe network to buildings in the town centre, including a residential tower block.
Electricity generated locally using solar panels and a Combined Heat and Power Unit will be used to help power the system.
The council will be appointing a contractor to construct the energy centre and pipe network later this year, with a view to starting on site early next year.