Abstract

Changes in matrix texture of chalk are observed in the walls of normal faults, with a decrease in porosity and pore-sizes, mainly due to pressure-solution and cementation. A closer analysis of a 50 mm thick fringe along a fault plane using SEM and image analysis indicates the possible formation of wall-like structures partitioning the medium and of few large pores forming channels. A method of 3D reconstruction of porous media is applied in order to quantify the geometrical properties and to predict macroscopic transport properties such as permeability. The strained material forms a sort of barrier, with a lowered permeability, between the unstrained material (50 mm from the fault plane) and the faulted material (5 mm from the fault plane). The latter displays heterogeneous permeabilities which seem to be randomly distributed.

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