GEOTHERMAL PROJECT FOR DISTRICT HEATING IN THE NEW TOWN OF CERGY-PONTOISE

Ziel

To use geothermal energy to heat about 3.400 new dwellings (yet to be built), allowing an energy saving of about 5,400 TOE/y (providing some 41,500 Mwh/year). Backup will be provided by connection to the Cergy Prefecture district heating scheme. The geothermal reservoir to be exploited by a pair of wells is the Triassic sandstone formation lying at a depth of 1,900 m; it is expected to produce between 200 and 250 m3/h of water at 70 deg C and 20 g/litre salinity.
The entire project is completed. All substations (22) are connected to the geothermal plant. Project works correctly with the exception of pumping problems. During the first heating season (84-85) FeS2 production in geothermal well led to the modification of the submerged pump, the installation of a special filter between the production and injection wells. And to the need for scavenging oxygene with a nitrogen blanket thereby avoiding corrosion in the pumping chamber. Since those modifications the geothermal station is operating without problems.
The economic analysis shows a payback of 13 years and annual energy savings of 3155 TOE. Final flow rate gained from the Dogger reservoir is 150 m3/h.
Drilling of production well CG1 through the Trias completed in May 1980. Triassic sandstone formation encountered between 1,929 and 1,997 m. Air-lift test produced following results: net pay of aquifer: 12,4 m. porosity: 14%, productive strata between 1,940 and 1,970 m, temperature: 77 deg C, salinity: 95 g/l, transmissivity: 9 D.m. with one + 10 skin (equivalent to a transmissivity of 3 D.m.). A DST test during drilling produced the following results: productive strata between 1,929 and 1,960 m, net pay of aquifer: 13,5 m, transmissivity: 10,2 D.m. which was better than the actual results obtained when drilling was completed. Aquifer in the Trias probably damaged by drilling mud and thick mud plug inserted through the full height of the reservoir in order to cement the 9"5/8 tube which had not been installed whilst drilling progressed through the reservoir. Reinjection well CG2 was drilled down to a depth of 1,470 m in January and February 1981, traversing the Dogger limestone rocks. The potential flow rate obtained was 170 m3/h at 56 deg C. On the basis of these data the contractor decided to abandon the main target (Trias) and to exploit only the Dogger, using the two wells drilled. A side-track was resumed on production well CG1 between 1,200 and 1,400 m (successful at the second attempt) in order to reach the Dogger formation sufficiently far away from the area cemented. Characteristics of the Dogger reservoir are:
- CG1: net pay of aquifer: 32 m, porosity: 19%, transmissivity: 23 D.m. water temperature: 55 deg C, salinity: 14 g/l.
- CG2: net pay of aquifer: 19,5 m, porosity: 21%, transmissivity: 10 D.m. water temperature: 57 deg C, salinity: 14 g/l.

Programm/Programme

ENG-ENALT 1C - Programme (EEC) of financial support for projects to exploit alternative energy sources, 1979-1984

Thema/Themen

2.2 - HEATING

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

DEM - Demonstration contracts

Koordinator

EPA CERGY-PONTOISE

EU-Beitrag

Keine Daten

Adresse

95012 CERGY-PONTOISE
Frankreich

Gesamtkosten