Pure app\. geophys. 160 (2003) 909-927 0033 -4553/03/060909-19 © Birkhiiuser Verlag, Basel, 2003 I Pure and Applied Geophysics Comparison of Measured and Modelled Hydraulic Conductivities of Fractured Sandstone Cores SALIMA BARAKA-LOKMANE,l.2 RUDOLF LIEDLl and GEORG TEUTSCH l Abstract-A new method for characterising the detailed fracture geometry in sandstone cores is presented. This method is based on the impregnation of samples with coloured resin, without significant disturbance of the fractures. The fractures are made clearly visible by the resin, thus allowing the fracture geometry to be examined digitally. In order to model the bulk hydraulic conductivity, the samples are sectioned serially perpendicular to the flow direction. The hydraulic conductivity of individual sections is estimated by summing the contribution of the matrix and each fracture from the digital data. Finally, the hydraulic conductivity of the bulk sample is estimated by a harmonic average in series along the flow path. Results of this geometrical method are compared with actual physical conductivity values measured from fluid experiments carried out prior to sectioning. The predicted conductivity from the fracture geometry parameters (e.g., fracture aperture, fracture width, fracture length and fracture relative roughness all measured using an optical method) is in good agreement with the independent physical measurements, thereby validating the approach. Key words: Fractured sandstone, hydraulic conductivity, fracture geometry, visualisation of natural fractures. 1. Introduction The importance of the fracture geometry as a control on flow processes is widely recognised in the disposal of radioactive waste, petroleum exploitation and underground energy storage. The hydrogeological response is governed by the size of the fractures, their connectivity and by the roughness of the fracture surfaces. The key to understanding flow in naturally fractured rocks lies therefore in determining the fracture geometry parameters such as fracture aperture, fracture width, fracture length and fracture relative roughness. Analysis of fluid flow behaviour in naturally fractured porous media is very difficult to perform because the fracture geometry is generally complex and unknown. Laboratory-scale studies of discrete fractures lead to better understanding I Department of Applied Geology, University of Tiibingen, Germany. 2 Department of Geology and Geophysics, University of Edinburgh, UK. E-mail: S.Baraka-Lokmane@glg.ed.ac.uk H.-J. Kümpel (ed.), Thermo-Hydro-Mechanical Coupling in Fractured Rock © Springer Basel AG 2003