What has been finished
The Coriance Group has announced that the drilling work is finished at Aulnay-sous-Bois, a commune in the Île-de-France region. The operations took roughly four months; their start was announced at the end of March 2026.
Well parameters
The wells reached a depth of around 2000 m and tapped the Dogger formation, which holds thermal waters at a temperature of about 70 degrees C. The drilling was carried out by the company SMP Energies. Heat from the doublet is to be fed into the local district heating network. According to an earlier release, construction of the heating plant had also begun.
Outcome and scale
Commissioning of the installation is scheduled for the end of 2026, after which geothermal energy is to meet 93% of the heating network's demand. Annual geothermal heat output will be about 140 GWh, an amount matching what 14,000 households need for heating and hot water. The project is an investment of some EUR 73 million.
The Coriance Group also ran information activities in Aulnay-sous-Bois neighbourhoods and with fourth-grade pupils of the Les Petits Ormes primary school, presenting the project through an educational module called "Discovering Geothermal Energy". The project fits into wider use of geothermal energy in Île-de-France, drawing on decades of familiarity with the Dogger formation. The GEOSCAN project, concluded earlier in 2026, added insights into the geothermal potential of the region's western and southern parts, which are less developed.