Hydraulic communication in crystalline rocks between the two boreholes of the 
Conti¬nental Deep Drilling Project in Germany

Kessels, W.; Kück, Jochem

doi:10.1016/0148-9062(94)00017-W

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Hydraulic communication in crystalline rocks between the two boreholes of the Conti¬nental Deep Drilling Project in Germany

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Kessels, W.

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Kück, Jochem
4.2 Geomechanics and Scientific Drilling, 4.0 Geosystems, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

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Kessels, W., Kück, J. (1995): Hydraulic communication in crystalline rocks between the two boreholes of the Conti¬nental Deep Drilling Project in Germany. - International Journal of Rock Mechanics and Mining Sciences, 32, 1, 37-47.
https://doi.org/10.1016/0148-9062(94)00017-W

Cite as: https://gfzpublic.gfz-potsdam.de/pubman/item/item_5002742

Abstract

Hydraulic communication was established at a depth of about 4000 m between the two boreholes of the Continental Deep Drilling Project in the Federal Republic of Germany (KTB). The distance between the two boreholes at this depth is approx. 250 m. The proven communication was stimulated by a draw down test and by casing cementation in the KTB main hole. The observed very rapid pressure transmission suggests the presence of a fracture system connecting both boreholes. A “fracture evaluation” can be carried out by the determination of the hydraulic diffusion constant. The determination of the mechanical deformability (fracture compressibility) of the fracture system is critical for the evaluation of mean apparent fracture widths and mean apparent fracture numbers. We have shown how this determination is possible by the pressure dependence of the transmissibility. The result shows that mean fracture widths are around 5–7 μm and form a hydraulic connection.