HEATING OF DOMESTIC DWELLINGS BY GEOTHERMAL ENERGY

Obiettivo

To use geothermal energy to cover 75% of the heating requirements 2,500 existing dwellings and houses to be built (2,000). A primary energy saving of
3,600 TOE/yr is expected with a corresponding payback of 6 years.
The reservoir to be tapped is formed by detrital Stampian deposits (sandstone, sands, arkoses) at a depth of 1,700 to 2,000 m.
A geothermal doublet is necessary due to the salinity of the brine (over 20 g/l) and necessity to maintain sufficient pressure in the aquifer. Both wells are planned to be vertical - (spacing 1,100 m). Estimates put the flow-rate at 100 m3/h at 78 C to 95 C depending on the productive reservoir depth.
Since the fluid is expected to contain a large amount of dissolved CO2, all production exchange and injection equipment will have to be specially adapted.
Lack of success in this project is attributed to impermeability of the Stampian arkoses. The basement lay at the depth calculated with the existing geophysical data. The detrital formation (with a high content of clay) show cemented arkoses and suggests special depositional conditions. A second geothermal well was drilled in the Clermont area (Beaumont) without success. Both geothermal and oil-gas potential appears to be limited in this zone.
The production well was drilled down to 1,886 m in July and August 1981. The target reservoir (Stampian detrital deposits), encountered between 1,300
and 1,834 m. The formation is not very permeable due to a high proportion of clay. Two potential aquifers were struck (1,535 - 1,565 and 1,975 - 1,840 m) of which only the first was slightly productive. Neither the base conglomerate nor the quartz sand in the substratum displayed any apparent porosity. Casing 7" in diameter was cemented in between 100 m and 1,516 m after the top of the reservoir had been plugged. A 6" hole was drilled through the reservoir between 1,517 and 1,840 m, with a 4 1/2 filter screen anchored at 1,435 m (without gravel pack). Drilling problems were experienced in the section of the aquifer above 1,840 m. The polymer-based drilling mud was replaced with a bentonite-based mud which was used to compensate for the weakness of the walls. Air-lift-assisted trials at a flow rate of 20 m3/h revealed transmissivity of 1.1 D.m.; rising to 1.56 D.m. on stimulation and acidification, producing a flow-rate of 23 m3/h. Characteristics: temperature - 98 C at the bottom of the hole and 73 C at the surface; salinity -
between 20 and 25 g/l, plus CO2 gas and traces of hydrocarbons.
Doubts remain as to whether or not the upper, and even more so the lower, reservoir formations are genuinely plugged. Neither supplementary tests on the lower sections, nor stimulation of the middle sections and performance of the cased and untested reservoir at around 1,800 m were carried out. However, oil-prospecting data generated in the vicinity suggest that sandstone formations will predominate between 1,010 and 1,540 m where the sedimentation and tectonic conditions will be more favourable for exploitation of the reservoir.

Programma(i)

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

Argomento(i)

2.2 - HEATING

Invito a presentare proposte

Data not available

Meccanismo di finanziamento

DEM - Demonstration contracts

Coordinatore

SYNDICAT INTERCOMMUNAL DE CLERMONT-FERRAND

Contributo UE

Nessun dato

Indirizzo

MAIRIE DE CLERMONT-FERRAND
63300 CLERMONT-FERRAND
Francia

Costo totale