Geothermal borehole sunk in Tullamore in search for new energy source

A ONE kilometre deep bore hole was sunk in Clonminch last Summer in a search to see if the area was suitable for the creation of geothermal energy, a recent meeting of Offaly County Council was told.
Deep bore geothermal wells are becoming more popular as sources of alternative energy. For example, a number of these deep bore wells in Paris are supplying about 250,000 homes in the city, removing, the authorities say, thousands of tonnes of carbon which otherwise would have been emitted through fossil fuel systems.
The recent Offaly County Council meeting was told by a member of the executive that the logistics involved are becoming easier to manage and the cost benefit analysis for a possible well in Tullamore is favourable. “As it stands at the moment, we are quite hopeful about this technology.”
In a brief aside, the member of the executive also pointed out that one of the benefits of Data Centres is the possibility of accruing “Waste Heat” from them. Cllr John Leahy, Cathaoirleach, commented that there is a growing support from the people of Offaly for creating Data Centres in the county.
During the Summer of 2025 the Council worked in collaboration with the Sustainable Energy Authority of Ireland (SEAI) Pathfinder Team and their colleagues in the newly formed District Heating Centre of Excellence. As part of this work Offaly County Council commissioned and delivered a “District Heating pre-Feasibility Study” for the “Tullamore Decarbonising Zone.”
Tullamore was designated a “candidate area” by SEAI. In this work the Council built upon existing strong working networks across the HSE, Uisce Eireann and other local stakeholders while introducing data gathered from their “1km deep investigative geothermal borehole located in Clonminch drilled in partnership with the Geological Survey of Ireland (GSI) and the Department of Climate, Energy and the Environment (DCEE). The conclusions of this study are overwhelmingly positive, and we have gained approval from the SEAI to move towards Step 2, i.e. a full feasibility study as detailed in their framework document.”
“Geothermal power plants,” says the SEAI, “generate electricity from deep wells that tap into high-temperature water or steam. Ground source heat pumps use heat from shallower depths. We can then use the natural heat in various ways, such as heating buildings and generating power.”
In August 2024 it was announced that the Geological Survey of Ireland (which is a division of the DCEE) was inviting tenders from external service companies to provide geological information from the 1,000 metre deep borehole that it was then planning to drill in Clonminch, Tullamore. Subsequently, during Summer 2025, The GSI's Drilling Unit sunk two one-kilometre deep boreholes, one in Tullamore and one in Cork City. External service companies also participated during the work, undertaking “Downhole Geophysical Logging” during the work. Downhole Geophysical Logging refers to the method of making measurements in drill holes and geologically interpreting these measurements. The Clonminch borehole was cored vertically at a diameter of 75.7 mm.

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