The Parisian basin, birthplace of geothermics

The exploitation of low energy geothermics in France is mainly localized in the Parisian Basin. About 40 geothermal plants are established in urbanized areas for heating and sanitary hot water supplies and also for air conditioning. Each plant can supply about 2500 to 5000 lodgings of collective buildings. Excluding drilling costs, urban investments can reach 70% of the total operating cost. Most of the exploitations draw the geothermal fluids from the Dogger reservoir located at a 1500-2000 m depth using double-well technique. Water temperature is about 60 to 85 C and solutes (salts and sulfides) represent 15 to 35 g/l. The deeper Albian and Neocomian drinking water reservoirs are exceptionally used due to their strategic nature. The corrosion problems and the age of the installations are the principal problems of the existing installations but the operating costs remain competitive with other energy sources. (J.S.). 3 figs., 9 photos