Speaker
Description
Underground hydrogen storage in porous formations (UHSP) is emerging as a critical technology for large-scale energy buffering, enabling TWh-scale capacity, geographic flexibility, and cost advantages over surface storage. However, unlike conventional hydrocarbon reservoirs, UHSP involves cyclic injection and withdrawal of hydrogen, imposing repeated stress variations on reservoir rocks over decades. These cycles can significantly influence porosity, permeability, and long-term storage integrity.
This work first outlines the geomechanical context of UHSP. Suitable reservoirs typically lie at depths of 500–2500 m, where porosity and permeability are strongly lithology-dependent. At these depths, stress conditions are governed by overburden and regional tectonics. Seasonal pressure fluctuations during injection and withdrawal generate complex stress paths that may induce dilation, compaction, and shear mobilisation. Such processes can degrade reservoir properties, trigger fault reactivation, cause surface deformation, and compromise caprock integrity.
We then present laboratory experiments on carbonate rocks subjected to cyclic loading designed to replicate UHSP operations. Stress paths include both pure compaction and shear-enhanced compaction. Our results show that moderate depletion leads to minor creep, while significant depletion causes irreversible, time-dependent compaction. Under high-depletion scenarios, cyclic stress variations amplify compaction and consistently reduce permeability. Notably, regardless of loading type (time-dependent or cyclic), porosity change emerged as a robust descriptor linking mechanical behaviour to permeability evolution.
To interpret and predict these behaviours, an advanced constitutive framework was developed. The model combines an elastoplastic formulation with time-dependent elements to capture creep and progressive compaction. Furthermore, an additional rheological component was introduced to represent time-independent ratcheting, enabling accurate simulation of irreversible strain accumulation during repeated loading. This modelling framework was calibrated and validated by the experimental data.
| Country | France |
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