Localization and spatial orientation of planar discontinuities in the crystalline - results from the borehole Boettstein

The Boettstein-well showed that all groundwater-flow systems in the crystalline basement of Northern Switzerland are - in one way or the other - linked to planar discontinuities (fractures, shear zones or dykes). The location and spatial orientation of such discontinuities is therefore an important prerequisite for the safety analysis of a future repository. Today the acquisition of structural data in a borehole no longer depends on drillcores alone, the autcrops of fractures and other discontinuities can be detected on the borehole wall, if modern wireline imaging systems are used. This article compares the performance of these tools in a crystalline environment and tries to assess the respective merits of core data on the one hand and geophysical records on the other. (author)