The first attempt to exploit the hot waters occurring in the Dogger carbonate formations of mid-Jurassic age dates back to year 1962, at Carrières-sur-Seine west of Paris. The well, despite its high productivity, was abandoned due to highly mineralized brine incompatible with the disposal of the wastewater in the natural medium (a surface stream). This led, in 1969, Sthal, a private joint venture (Cgc, now Vivendi, operator, and Laurent-Bouillet) to commission the first field application of the geothermal doublet concept of heat mining combining a production well and an injection well pumping the heat depleted brine into the source reservoir