ABSTRACT
Two different scales of fractures collected in Hercynian granites were investigated. At the borehole scale, macrofractures properties were sampled continuously. The resulting fissural calculated permeability was evaluated versus depth and compared with the geometry (azimuth, dip) of fractured zones as well as with the fracture filling. Results shown that a global approach of borehole data are not representative of that on a local scale and that “efficient” fluid pathways can be decribed. At microscopic scale, cracks are modelized by finite shapes (discs). Water-rock interactions are therefore quantified in terms of precipitation or dissolution processes thanks to the knowledge of fissural permeability, porosity and surface exchange. The main results of the simulation indicate that a granitic rock can strongly and quicly be altered by a meteoric fluid.
