Objectif Initially this was to heat 100 new and 1,115 existing domestic dwellings by means of geothermal fluid extracted at 30 deg C from lusitanian limestone and cooled to 10 deg C by gas driven heat pumps, without re-injection.Following re-appraisal of requirements and potential in 1979, steps were taken to tap Dogger limestone between 1,120 m and 1,270 m to yield geothermal water at an estimated 100 m3/h, 42 deg C and 25 g/l salinity. The reservoir would be exploited by two directional wells, with water reinjected at 10 deg C and the energy used to heat public buildings in addition to the domestic dwellings originally intended: gas heating will provide the stand-by system.The use of heat pumps to heat geothermal water is expected to save 1,500 TOE/y. Pay back is estimated at +- 10 years.The project is successful and has yielded an annual energy saving of 1,200 TOE. As availability of geothermal water exceeds demand further developments may be possible. The geothermal reservoir (Dogger) presents good aquifer characteristics in this area near the Pays de Bray anticline.The high H2S content dissolved in brine and the presence of sulfate-reducing bacteria had caused the production of deposits of iron sulphur in the geothermal loop and blocking of submerged production pump. These problems should however not prevent the operation working. The residential area to be heated now comprises 1227 dwellings in all. The heat pump circuit has been fully operational since March 1983. At the moment local demand is still too low to tap the reservoir at maximum flow, despite the plans to connect the hospital as well. In all likelihood the reservoir will be exploited at less than its full potential. The last two heating seasons show savings corresponding to forecast calculations.The production well was drilled down to 1,287 m in March and April 1981 encountering the Bathonian limestone reservoir (Dogger) crossed between 1,157 m and 1,283 m (126 m) and left as an open hole from 1,165 to 1,223 m. Net pay: 40 m; porosity - 20%; temperature - 47 deg C; salinity - 28 g/l; transmissivity - 31,5 D.m.; artesian flow-rate - 72 m3/h; well head pressure - 4,8 bars; skin - 1; maximum operating flow-rate - 250 m3/h for a drawdown of approximately 200 m. The high concentration of H2S in the geothermal fluid calls for a closer watch to be kept on corrosion of the metal parts in the primary network. A directional reinjection well was drilled down to final (vertical) depth of 1,269 m in April and May 1981. The distance from the production well at aquifer level: 790 m; reservoir left as 6" open hole. The lithology is similar to well B1. Net pay: 25m; Porosity - 19%; temperature - 47 deg C; salinity - 24 g/l; transmissivity - 25 D.m.; artesian flow-rate - 78 m3/h; skin: -3,5 Reinjection is at 10 deg C, and at 42 bars for 200 m3/h and at over 53 bars for 250 m3/h. Reinjection tests at 63 m3/h and a water temperature at the surface of 15 deg C confirmed the theoretical results obtained during the production trials (i.e. pressure: 12,5 kg/cm2 and skin - 3,8).10 deg. C, and at 42 bars for 200 m3/h and at over 53 bars for 250 m3/h. Programme(s) ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984 Thème(s) 2.2 - HEATING Appel à propositions Data not available Régime de financement DEM - Demonstration contracts Coordinateur OPAC BEAUVAIS Contribution de l’UE Aucune donnée Adresse 1-3 COURS SCELLIER BEAUVAIS France Voir sur la carte Coût total Aucune donnée
