Abstract Underground hydrogen storage in porous formations (UHSP) subjects reservoir rocks to long‐term cyclic effective stress variations, potentially altering storage capacity and injectivity. In this study, we conduct hydrostatic loading tests on 18 Saint‐Maximin limestone (SML) samples (connected porosity 31.9%–37.2%) under various loading paths, complemented by measurements of permeability and acoustic wave velocities. A specific creep‐fatigue interaction test, combining stabilized creep and subsequent cyclic loading at identical peak stress, is conducted to distinguish cycle‐dependent ratcheting deformation from time‐dependent creep. Experimental results reveal that cyclic behavior of SML is governed by a dual stress‐threshold mechanism. The peak stress ratio governs initiation and evolution of damage, while the valley stress ratio describes the reopening of generated fractures during unloading. > 1 leads to enhanced creep and onset of ratcheting deformation and < 1 induces 1.2% additional porosity reduction within 50 cycles after creep stabilization. Across all loading paths, porosity change serves as a robust metric for mechanical hardening and permeability evolution within the experimental range of up to a 12.8% reduction in porosity and an order‐of‐magnitude decrease in permeability. These findings establish a reference testing approach for quantitatively partitioning different deformation mechanisms, providing an essential basis for more reliable predictions of long‐term UHSP performance.
Xu et al. (Fri,) studied this question.
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