Optimal and sustainable use of the Dogger aquifer geothermal resource: long-term management and new technologies

Geothermal energy has been supplying heat to district networks in the Paris Basin for more than 40 years. In this densely urbanized area, the main target of all exploration and exploitation projects has been the Dogger aquifer (1500-2000 m deep). Initial difficulties, due to corrosion and scaling related problems, have been overcome in the mid-1980s and, since then, operations have been providing heat daily to more than 150,000 dwellings. Operating facilities use the “doublet” technology which consists of a loop with one production well and one injection well. Consequently, injection of the cooled brines leads to the progressive exhaustion of the resource at the local doublet scale. Most of the research effort has been focused on quantifying the temporal evolution of the cooling, and to forecast the lifetimes of doublets and the occurrence of the “thermal breakthrough”. Yet, with the need for carbon free energy sources there has been a revival of geothermal energy development in France: many projects are presently being considered and new operations have already been carried out. In this context, it appears that the aquifer geothermal resource has to be managed and modeled as a whole. For this purpose, BRGM maintains an up-to-date hydraulic and thermal model of the aquifer which can help policy makers to improve regulatory framework and which can support stake holders to carry out new operations. Moreover, because of potential conflicts of use which are emerging in densely exploited areas, a fine understanding of reservoir behavior is needed and new technological solutions must be developed: exploration and exploitation of underlying or overlying aquifers, seasonal heat storage...