COMPUTATION OF THE THERMAL EFFECT OF HYDR OTHERMAL UPFLOW WITHIN A FRACTURED BASEMENT - APPLICATION TO THE GEOTHERMAL ANOMALY OF SOULTZ-SOUS-FORETS (NORTHERN ALSACE, FRANCE)

Temperatures measured within sedimentary layers in the vicinity of the Pechelbronn oil field define an elongated anomaly parallel to the mai n structural direction of the Rhine Graben. These temperatures have be en reviewed. The mapping at the top of the Muschelkalk, without any sm oothing, shows distinctive hot anomalies which can be interpreted as t he picture of an hydrothermal upwelling. In order to check this hypoth esis, the thermal effect of a vertical conduit has been simulated in t ransient conditions with a computer model. Results are consistent with observed temperature anomalies. These observations contribute to clar ify the network of natural flows in a geological environment studied f or ''hot dry rock'' experiments.