Objetivo To use geothermal energy to provide a district heating network for the town of Jonzac (pop. 5,000). Additional energy will be supplied by a waste incinerator and multifuel boiler. Primary energy savings of 1,660 TOE/yr are expected, and payback estimated at 9 years.The main target consisted of Triassic sandstone and dolomite. The geothermal reservoir is to be found at a depth of 1,600 m : of 120 m total thickness the estimated natural geothermal water flowrate is 30-40 m3/h (100 M3/h pump assisted) at 60 C. and 6 g/l salinity. Unless there is a pressure drop in the reservoir, water will be discharged at 20 C in the Seugne river. The threshold below which the project becomes unprofitable has been fixed at between 77 m3/h and 100 m3/h with corresponding temperatures of 60 C and 50 C.This unsuccessful project is reimbursed (only 10% of the initial sum). The annual energy saving of 200 TOE has been achieved in 1983 with a payback period of over 20 years. The geothermal water comes from an argilaceous sandstone layer thicker but less productive than expected. Due to the high cost of such wells - 1,800 m depth and stainless steel screen completion there is no prospect of replication in the North Aquitaine region.The production well had been completed between October 1979 and February 1980. The Triassic reservoir (sandstone, sand, dolomites and clays) was traversed between 1,630 and 1,870 m. The characteristics of the well completed with a 4" screen and gravel pack are: transmissivity 5.5 D.m. : net pay aquifer - 10 m out of a productive height of 50 m : possible pumping flow-rate - 40 m3/h for a drawndown of 300 m : temperature at surface - 65 C : salinity - 5.9 g/l.The attempts to stimulate the well have not improved the productivity of the aquifer. Bad readings on the flowmeter left no sure indication of productive levels and net pay. Possible damage by mud plugs and cement plugs before cementing of 7" casing. The real reservoir characteristics remain uncertain. A last test had been set up in the Triassic dolomite limestones (1487.1515) which are separated from Triassic formations by anhydritic layer (90 m). A negative production test using air lift had been performed after perforatingthe cemented 7" casing and acidizing. Programa(s) ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984 Tema(s) 2.2 - HEATING Convocatoria de propuestas Data not available Régimen de financiación DEM - Demonstration contracts Coordinador VILLE DE JONZAC Aportación de la UE Sin datos Dirección MAIRIE DE LA VILLE DE JONZAC 17500 JONZAC Francia Ver en el mapa Coste total Sin datos
