Joachim Place, (EOST, Strasbourg, France)
Charles Naville (IFP, Paris, France)
Edouard Le Garzic, Yves Geraud, Marc Diraison (EOST, Strasbourg, France)

At the Soultz-sous-Forêts geothermal site and in general in Enhanced 
Geothermal Systems, the fluid flow paths between the injection and the 
production boreholes are mainly composed by a set of permeable structures. 
The aim of our work is to document the efficiency of multi-component VSP 
(Vertical Seismic Profiling) to define while drilling the architecture of these 
potential flow paths within the heat exchanger and to save drilling costs.

The test of 3C VSP efficiency at Soultz EGS in GPK1 (Place et al, 2007) is 
considered successful, as major permeable fault zones intersected by the well 
can be investigated far away from the well. Their structural parameters (dip 
and azimuth) can be indeed inferred from this VSP data set, and are in 
accordance with the results of logging data (UBI, ARI, FMI...). In addition, some 
fractured corridors are well imaged but are not drilled.

Thus, we focus our work on two main tasks:

•	First, we propose to go into detail in the interpretation of this 3C VSP 
data processed in an isotropic way, in order to deduce as much structural 
information as possible; the aim is to assess what can be reasonably learnt 
about the granite from the observed (and non observed!) seismic arrivals, P-P, 
P-S, S-S, S-P mode conversions.
•	Second, in an opposite approach, we show the kind of structural 
information which can be rapidly given by a VSP interpreter if a VSP survey is 
carried out while drilling. Even just after pre-processing (i.e. full and long 
processing is not required) some arrival can be exploited to locate some major 
structures affecting the reservoir. Thus, the VSP can complement with benefit 
2D or 3D reflection seismic images in order to deduce the position of the well 
relatively to permeable targets.

Thus, we expose how a VSP survey can help the deviation of a borehole while 
drilling to reach a permeable target for geothermal application. As a result, 
drilling cost can be significantly reduced thanks to such a fast multi-component 
VSP analysis; then, after drilling, the same data set processed in isotropic way 
can provide precious information for fluid flow to help to manage the 
geothermal resource of the reservoir.

Joachim PLACE, Charles NAVILLE, André GERARD, Marc SCHAMING, ORIENTED 
THREE COMPONENT VSP* METHOD APPLIED TO IMAGING HIGHLY DIPPING 
FAULTS IN THE DEEP GRANITE BASEMENT AT SOULTZ-SOUS-FORETS. Poster 
presented at Workshop ENGINE, Potsdam, November 2006.

Grensasvegur 9
Reykjavik,
Iceland