Stability evaluation of salt cavern hydrogen storage and optimization of operating parameters under high frequency injection production

Abstract

Hydrogen energy storage plays a crucial role in peak shaving of renewable energies, and underground salt caverns are ideal locations for large-scale hydrogen storage. The widespread utilization of hydrogen leads to wide-ranged injection production frequency (F) for salt cavern hydrogen storage (SCHS). To address the hydrogen demand under various scenarios, numerical simulation was employed to demonstrate the influence of F on the stability of SCHS at different buried depth (D), and the key operating parameters under high-frequency injection and production were optimized. A 3D geomechanical model was established for bedded salt formations, and evaluation criteria were proposed to quantitatively characterize the stability of SCHS. The stability of SCHS initially improves and then deteriorates with F at different D, and the optimal F is 6 times/year. The effect of F will be boosted as D increases. The recommended internal pressure (P) of SCHS at 900, 1700 and 2500 m under high-frequency injection and production is (0.25–0.85)σz, (0.35–0.85)σz, (0.5–0.85)σz MPa, respectively. And when P is reasonable, the pillar width (W) at different depths greater than 2 times the maximum diameter of salt cavern can meet the stability requirements. The stress difference and stress ratio of the surrounding rock increase with D, causing an increase in volume shrinkage and safety factor. The changes in volume shrinkage and plastic volume correspond well with the change of P when F is less than 6 times/year, while then it ceases to exist. The volume shrinkage growth model was established, and it quantitatively indicates that the small or large F is unfavorable to the stability of SCHS. The variation in the SCHS stability with F attributes to the different effects of creep and fatigue of salt rock.