Characterization of transport and water retention properties of damaged Callovo-Oxfordian claystone

International audienceIn the context of the underground storage of radioactive waste, the aim of this experimental study is to characterize the effect of damage on transport and water retention properties of Callovo-Oxfordian (COx) argillite. The originality of the study is to simultaneously investigate the pore-size distribution, water retention, the dry, effective and relative gas permeability, and the gas breakthrough pressure (GBP) of damaged COx argillite. These different properties are all relevant to characterizing the fluid transport ability of COx argillite.Results show that the damage has a significant impact on the properties of the COx argillite. It induces a decrease in its water retention capacity and GBP, and it increases its gas permeability and apparent porosity available to water owing to the creation of micro-cracks.Another objective is to show which of these properties is the most suitable to detect early damage states in COx argillite, with a potential use being to identify them in situ. GBP appears to be the best ‘detector’ of damage because of its sensitivity to damage even under high confinement pressures. Gas permeability could be a good indicator of damage, as it increases significantly (one or several orders of magnitude) after the damage. Finally, the water permeability curve is a poor indicator of COx argillite damage