The INTERREG NWE DGE-ROLLOUT project: What are the contributions to the development of geothermal energy in Hauts-de-France?

In Northwestern Europe, the Dinantian limestone formation, could be a promising geothermal reservoir from 1 kilometer deep for heat production in densely populated regions. In the 1970s and 1980s, scientific drilling in Belgium encountered hot water at high flow rates in this layer, turning these wells into productive geothermal sources for district heating (e.g., Saint-Ghislain, Douvrain, and Ghlin). However, similar wells in France (Jeumont and Condé-sur-l'Escaut) were not productive enough for economic viability due to the heterogeneous nature of the Dinantian reservoir, influenced by the region’s complex geological history. To enhance understanding of this formation, an interdisciplinary study was conducted under the INTERREG NWE DGE-Rollout project. This study involved creating a cross-border map of the Dinantian structure and building a lithological chart to represent variations across the region, including Belgium, France, Germany, and the Netherlands. The formation is mainly composed of carbonate rocks but also contains significant heterogeneities, such as sedimentary breccias within the middle Visean (Livian), identified as a geothermal reservoir in Belgium's Mons region. Seismic surveys and petrophysical analyses were conducted across Belgium, France, and Germany. Results showed five main facies in the Dinantian: limestone, dolomite, anhydrite, sandstone, and clay. The Epinoy 1 well, for instance, revealed low porosity in dolomitic facies, while Jeumont 1 showed higher porosity levels in dolomitic intervals. Seismic data reprocessing further identified key geothermal targets, with dolomitic zones offering better reservoir properties in the north and east. Temperature data from wells in the region are scarce, though the Epinoy 1 well shows a normal geothermal gradient of 30°C/km. Favorable areas for geothermal development were identified based on energy demand and geothermal resource availability. The largest zone is located between Douai and Valenciennes, with significant heat demand and an existing district heating network. Another zone, around Maubeuge, also holds potential despite deeper Dinantian depths.