3D pore volume of a) EST27405-1, b) EST27405-2, c) EST26095-2 COx claystone samples, and d). Tournemire-1 sample. In red are the non connected and non crack-like pores – these are likely to be connected by micro- and small meso-pores below the resolution of the FIB/SEM device; in green, the connected porosity between the end surfaces perpendicular to the Z-axis; in yellow and blue-green are the crack-like pores (Tournemire-1 sample only).