ABSTRACT
Hydrogen is a high power density energy for the energy transition. Recently, the need for large-scale underground storage in order to supply the market has increased. Storage in salt cavities is known to be the most effective due to the low permeability of salt rock: However, the risk of leakage can arise in case of damage which occurs if the mechanical dilatancy threshold is exceeded. On the other hand, in the hardening phase, a self-healing phenomenon appears and may restore its impermeability. In this study, petrophysical properties of initial rock salt are characterized. Then, salt samples are subjected to different levels of deviatoric stresses in a triaxial compression cell. Permeability measurements are carried out under steady conditions at different pore pressures and confinement pressures. The slippage effect of the gas is taken into account for the interpretation of permeability measurements. The results showed an evolution of the intrinsic permeability, which is related to the changes in the rheological behavior of the salt during the deviatoric loading. The permeability increases in the damage domain, then decreases in the strain-hardening domain. The increase in confining pressure decreases the permeability.
Hydrogen is a versatile, green energy carrier that will make it a powerful enabler to the energy transition. The increasing need in different sectors in economy requires to ensure the flexible availability of this gas. This prompts to foster hydrogen storage in large quantities. Worldwide, hydrogen storage in salt caverns is the most successful solution (Ozarslan, 2012; Pellow, et al., 2015). It's praised for the high reservoir storability but mostly because of its sealing integrity (k < 2×10−21 m2 in undamaged zones, Cosenza, et al., 1997). The impermeability of the salt is essentially related to the mineralogical composition, texture and structure of halite. This influences its visco-elastoplastic behavior; any crack is healed (Urai and Spiers, 2007; Loof and Rautman, 2010). However, in the excavation damaged zone, rock salt is exposed to severe deviatoric stresses that could induce fractures and disturb its sealing property.
