Analysis Of Macroscopic Fractures In Granite In The Hdr Geothermal Well Eps-1, Soultz-Sous-Forets, France

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Journal Article: Analysis Of Macroscopic Fractures In Granite In The Hdr Geothermal Well Eps-1, Soultz-Sous-Forets, France

Abstract
An exhaustive analysis of 3000 macroscopic fractures encountered in the geothermal Hot Dry Rock borehole, EPS-1, located inside the Rhine graben (Soultz-sous-Forets, France), was done on a continuous core section over a depth interval from 1420 to 2230 m: 97% of the macroscopic structures were successfully reorientated with a good degree of confidence by comparison between core and acoustic borehole imagery. Detailed structural analysis of the fracture population indicates that fractures are grouped in two principal fractures sets striking N005 and N170 °, and dipping 70 °W and 70 °E, respectively. This average attitude is closely related to the past tectonic rifting activity of the graben during the Tertiary, and is consistent with data obtained from nearby boreholes and from neighbouring crystalline outcrops. Fractures are distributed in clusters of hydrothermally altered and fractured zones. They constitute a complex network of fault strands dominated by N-S trends, except within some of the most fractured depth intervals (1650 m, 2170 m), where an E-W-striking fracture set occurs. The geometry of the pre-existing fracture system strikes in a direction nearly parallel to the maximum horizontal stress. In this favorable situation, hydraulic injections will tend both to reactivate natural fractures at low pressures, and to create a geothermal reservoir.

Authors 
Albert Genter and Herve Traineau








Published Journal 
Journal of Volcanology and Geothermal Research, 1996





DOI 
Not Provided
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Citation

Albert Genter,Herve Traineau. 1996. Analysis Of Macroscopic Fractures In Granite In The Hdr Geothermal Well Eps-1, Soultz-Sous-Forets, France. Journal of Volcanology and Geothermal Research. (!) .