In situ determination of anisotropic permeability of clay

► Hydraulic anisotropic permeability of clay rock determined by a developed 'slot packer' system with orientated application in one borehole. ► Hydraulic anisotropy of Opalinus clay (parallel/perpendicular to the bedding). ► Fracture characterisation by a 'slot packer' in future may be possible. ► Interpretation method to determine the hydraulic anisotropy using numerical back analysis.