Objectif
To provide an estimated 70,000 MWh of geothermal energy to heat 4,200 existing dwellings in Cronenbourg (a suburb N.W. of Strasbourg).
Two wells are planned: the first, a vertical production well will traverse the Buntsanstein formations (Trias) between 2,500 m and 2,900 m, with the following expected characteristics: pump assisted flow-rate - 150 m3/h; temperature at the top reservoir - 140 C; salinity - 80 g/l. In the course of drilling an investigation of the Great Oolite (Dogger) and the Muschelkalk Dolomite is planned. The second is an injection directional well of 3,300 m in length: it will reach the top of the reservoir 1,000 from the production well.
An injection temperature of 75 C is planned, and water reinjection without treatment.
The available geothermal energy (25 to 30 m3/h) and surface temperature (105 C) is insufficent for a drawdown of 300 m, and for commercial exploitation. Oil drilling reports, and the losses (partial and total) recorded between 2,840 m and 3,200 m suggest that the recorded characteristics underestimate the potential yield of the damaged aquifer. Tests performed in the Great Oolite have proved the hydrocarbon occurrence without sufficient reservoir permeability to produce oil or water. The final depth achieved, of 3,220 m proved the existence of Permian formations (60 m) which were not known in that area of Rhine Graban.
The production well was drilled between May and November 1980. However no geothermal production test was ever carried out in the Great Oolite due to the presence of oil. The well had reached a depth of 3,220 m in detrital formations Permian dated maximum (extrapolated) temperature in the well is 148 C. The principal target (Buntsanstein sandstone) was crossed between 2,700 m and 3,200 m, revealing the presence of a reservoir (homogenous sandstone 2,980 m to 3,028 m; fractured sandstone 2,845 m to 2,860; and 2,875 m to 2,885 m.
Tests obtained by air lift show the following; a flow rate of less than 16 m3/h; porosity - 10% transmissivity - 0.7 to 1 D.m.; skin + 5 to + 10; salinity - 56 g/l; temperature in the aquifer - 116 C Installation of 600 m of liner between 2,600 and 3,200 m ruled out further reservoir exploration since this had been plugged by heavy drilling mud, unsuitable for traversing the sandstone reservoir.
Calculations show this well (the first) can produce 25 m3/h 105C at wellhead.
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DEM - Demonstration contractsCoordinateur
6700 Strasbourg
France