HR: 16:05h
AN: S34A-03    [Abstracts]
TI: Four Dimensional Velocity Structure of the Soultz-sous-Forets Geothermal Reservoir During the 2003 Stimulation
AU: * charlety, j
EM: jean.charlety@eost.u-strasbg.fr
AF: EOST-ULP, 5 rue rene Descartes, STRASBOURG, 67084 France
AU: Dorbath, C
EM: catherine.dorbath@eost.u-strasbg.fr
AF: EOST-ULP, 5 rue rene Descartes, STRASBOURG, 67084 France
AU: Dorbath, C
EM: catherine.dorbath@eost.u-strasbg.fr
AF: IRD - LMTG, CNRS - UMR 5563 14 avenue Edouard Belin, TOULOUSE, 31400 France
AU: Dorbath, L
EM: louis.dorbath@eost.u-strasbg.fr
AF: EOST-ULP, 5 rue rene Descartes, STRASBOURG, 67084 France
AU: Dorbath, L
EM: louis.dorbath@eost.u-strasbg.fr
AF: IRD - LMTG, CNRS - UMR 5563 14 avenue Edouard Belin, TOULOUSE, 31400 France
AB: The stimulation of 2003 carried out on the HDR site of Soultz-sous-Forˆts (Alsace, France) has generated a continuous, small magnitude earthquake activity. During this experiment, a seismological network composed of about 25 stations was installed by the Ecole et Observatoire des Sciences de la Terre (EOST). More than 3500 seismic events have been pointed and located. In order to estimate the variation of the physical properties of the reservoir due to the fluid circulation, we have performed a four dimensional tomography: the 3D velocity structure for different time windows. The whole data set has been apportioned into different temporal sets with a fixed number of events. We use a new, more accurate tomographic algorithm based on a double difference tomography (Zhang & Thurber, 2003). This method gives a good resolution on the reservoir volume and allows a relatively good resolution in the vicinity of this volume. It enlights the velocity structure variation of the reservoir through the stimulation period. Simultaneously, this 3D velocity model is used to relocate the events. The final uncertainty in the location is therefore lowered and ranges from 15 to 30 meters in each direction. In this study, we propose a dicussion about the variation of the velocity in time during the stimulation based on the correlation with the hydraulic parameters and other known geological features, for example the fracture zones near the injection well. This analysis allows us to point out the effect of the water circulation on the reservoir properties. The finality of this study aims to appreciate the mechanism which controls the velocity change: fracturation, overpressure, saturation, etc.
DE: 1857 Reservoirs (surface)
DE: 5104 Fracture and flow
DE: 5114 Permeability and porosity
DE: 8180 Tomography
SC: Seismology [S]
MN: 2005 Joint Assembly