In the KTB field laboratory, porosity, internal surface and permeability were determined on identical mini cores with 25.4 mm in diameter and approximately 50 mm in length. These samples were drilled either axial or radial with respect to the drill core, or parallel or perpendicular with respect to the foliation. In the KTB field laboratory, the stationary sArcy method was used with nitrogen gas as the streaming medium. The measurements were made at a constant confining pressure of 5 MPa to 6.5 MPa. The nitrogen pressure gradient was up to 2 MPa at the inflow side minus atmospheric pressure at the outflow side of the sample. Because of the low pore pressures during the measurements (max 2 MPa) the data had to be corrected for the effect of gas friction along the matrix wall, the so called Klinkenberg effect (Huenges et al. 1990). Further details, regarding equipment and evaluation are given by Pusch et al. (1986).