Drilling of geothermal doublet completed in Aulnay-sous-Bois, France

The Coriance Group has announced the completion of drilling of a geothermal doublet in the commune of Aulnay-sous-Bois in the  Île-de-France region of France. This follows about four months of work, with the start of drilling announced at the end of March 2026.

The wells were drilled to depths of around 2000 meters, accessing the Dogger formation where thermal waters at about 70 ºC are hosted. The drilling work was done by SMP Energies. Energy from this doublet will be supplied to the local district heating network. According to a prior release, construction of the heating plant had also already started.

The commissioning of the system is scheduled by the end of 2026, after which geothermal energy is expected to cover 93% of the heating network’s needs. The annual geothermal heating output will be about 140 GWh, or equivalent to the heating and hot water needs of 14,000 homes. The project represents an investment of EUR 73 million.

As part of their community engagement work, the Coriance Group organized activities in various neighborhoods in Aulnay-sous-Bois, as well as in fourth-grade classes at the Les Petits Ormes primary school, to provide information about the project through an education module called “Discovering Geothermal Energy.”

The Aulnay-sous-Bois project further expands geothermal heating utilization in the Île-de-France Region, building upon decades of experience and knowledge of the Dogger Formation. Earlier this year, the GEOSCAN project was officially concluded, valuable insights on the geothermal potential in the relatively less developed west and south parts of the Île-de-France region.

Source: Groupe Coriance