Fully coupled THM modelling of damage and healing interactions in rock salt: Application to hydrogen storage in salt caverns

Abstract

Hydrogen energy is recognized as a promising solution for decarbonisation, and underground storage in salt caverns presents a cost-effective option to address massive energy storage issues. In this study, we present an advanced rock salt mechanical model, which incorporates diverse key damage mechanisms - instantaneous, dynamic fatigue, and tertiary creep – as well as healing process. The fatigue damage is described by making use of an elastoplastic - damage model, while the healing mechanism allows to reduce the damage effects. The proposed model is validated against available experimental data and applied to the thermo-hydro-mechanical (THM) analysis of a deep salt cavern subjected to seasonal hydrogen cycling. Taking advantage of this framework, the obtained results highlight a critical influence of coupled THM processes and of the damage-healing mechanisms on the cavern stability. More specifically, the permeability significantly increases during gas extraction, promoting hydrogen penetration into the surrounding rock, while the healing process reduces permeability during gas injection. Furthermore, hydrogen transport is shown to be primarily governed by diffusion, with advection playing a role near the cavern walls where permeability is enhanced by damage. Temperature variations around the cavern induce changes of stress state, which in return affects the damage zones of the salt cavern and its stability. Interestingly, the cavern volume loss is more pronounced in the presence of healing mechanism. • A THM model integrating key damage mechanisms of rock salt with healing process. • Instantaneous, fatigue and tertiary creep damage and healing recovery are considered • Numerical simulations of salt cavern with cyclic hydrogen pressures are performed. • Permeability increases during gas extraction in the very near field of the cavern.

Topics & Concepts