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The texture and porosity of Callovo-Oxfordian argillites, coming from the Meuse/Haute-Marne region, have been studied at different scales using borehole and laboratory measurements to more spot-like qualitative and quantitative analyses and descriptions of minerals and of the porous space. Due to their limitations and to their resolution, each of the experimental methods used explores differently and often complementarily the porous environment of argillites. The texture is characterised by two-dimensional imaging techniques (optical microscopy, scanning electron microscopy and autoradiography) that provide a view of the material from 0.1 micrometres to a few millimetres or even centimetres. Since borehole measurements are more integrative and representative of the rock in its natural state, they were used to analyse the spatial variability of the porosity. The measurements taken on laboratory samples served to characterise more finely the porous network by providing relevant geometric parameters in order to improve the understanding of the transfer and reaction processes occurring at the interface between fluids and minerals. In the end, a conceptual model for the spatial organisation of the porosity and of the minerals was developed for argillites on the basis of the overall information collected at each step. The reference values for the connected porosity of argillites are obtained by combining the mercury porosity and the calculated porosity in the domain still free from mercury as determined by gas-adsorption techniques. The total connected porosity then varies between 14% for carbonated levels and 19.5% for more argillaceous levels …