GEOTHERMAL WELLS TO HEAT EXISTING DWELLINGS AT BORDEAUX-PESSAC

Ziel

To use geothermal energy to cover 50-90% of the heating requirements
(19 000 MWh/yr) for a group of 1 500 existing dwellings at formanoir. According to the project design a primary energy saving of 1 024 TOE/year is expected with a corresponding payback period of 11 years.
The main target, a reservoir with a temperature of 47 deg C, lies at a depth of 1 100 m, where there are dated Cenomanian-Turonian strata. The Mano dolomite (jurassic; temperature 57 deg C) is a secondary objective at the moment but could become the main target if the dolomite is directly under the Cenomanian-Turonian and sufficiently productive. The programme provides for investigating the Dolomite, whilst ensuring that the capacity of the Cenomian-Turonian aquifer remains intact. Further exploration of both levels is a possibility. At present, there are no plans for a reinjection well. In Cenomanian-Turonian formation the salinity is low but no estimate has been made for the dolomite formation.
Successful project already reimbursed (50% of the support amounted
to 600 000 FF, on the 30/12/83). An annual energy saving of 1 483 TOE (medium-high potential) has been achieved with a payback period of some 10 years.
The geothermal water comes from a bed of fresh water that presents a considerable potential (4 000 m3/h), situated at some depth under Bordeaux; on this way (low salinity, high hydro-potential) the project was designed on the basis of a single well and reinjection is postponed for several years; such a well would be contemplated only as a part of a general geothermal scheme for managing the resource by the Bordeaux authorities, with a silmultaneous exploitation of, at least, three production wells).
At present, 1 526 existing dwellings at Pessac (south-east of Bordeaux) have been already connected up with the geothermal source; since it has proved more abundant than expected, there were prospects to increase the number of dwellings (715 more), but due to difficulties in expanding the geothermal network, this extension has not been realized. The replication potential, in the area of Bordeaux is significant (existing already geothermal wells at Meriadeck - under exploitation - and at Benauge, Grand-Parc, Merignac) and many drilling operations can be mounted for managing and further developing this important geothermal resource of the Northern Aquitaine Bassin.
Production well drilled down to a final depth of 1 083m between November 1981 and January 1982. The reservoir extends from the 825m mark down to 1 034m and comprises Cenomanian strata, the upper section made up of Limestones and clays, and the lower section comprising sandstones, sands and clays. Well completion at the reservoir level: 8"1/2 hole with 5"1/2 filter screen and gravel pack. Characteristics: static level + 2 m, artesian flow-rate: 5m3/h, pump-assisted flow-rate at 155 m: 195 m3/h for a draw down of 100 m. Temperature: 48 deg C, salinity: 0.36 g/l. Monitoring of other wells in the region (at Meriadeck 6 km away and at Benauge, some 8.5 km away) confirmed that trials on this well had no significant side-effects on them. Estimated transmissivity: 120 d.m. loss at 200 m3/h: approximately 42 m of the drawdown. One particularly noteworthy point is that the 6" exploratory borehole drilled below the reservoir (from the 1 034 m mark down to 1 084 m) failed to strike Portlandian Mano dolomite although this was, in theory, the secondary target of the well. The Mano dolomite appears to be present only to the south, outside Bordeaux.
The inclusion of the two heat pumps was necessary because of a posterior decision of the Bordeaux Municipal services to limit the maximum temperature of the discharges to 30 deg C. After the heat extraction. The geothermal water is then treated (disulphurisation due to sulphides) and channelled into the city sewage system.

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

HLM LA GIRONDE SA

EU-Beitrag

Keine Daten

Adresse

AV DE LA JALLERE 110 QUARTIER DU LAC
33075 Bordeaux
Frankreich

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