Experimental and numerical analyses of creep-fatigue behavior in sandstone for energy storage applications
Deyan Tian, Zhengyang Song, Kavan Khaledi, Zhen Yang, Florian Amann
Abstract
Porous sandstone formations are recognized as suitable hosts for the geological storage of clean energy sources such as hydrogen and compressed air. From a geomechanical perspective, the deformation mechanisms of the host rock must be understood under various loading and unloading conditions resulting from daily or hourly injection/production cycles. This study presents a combined experimental and numerical analysis of sandstone behavior under cyclic loading conditions. We present the results of several multi-level, multi-frequency cyclic loading experiments conducted on sandstone specimens. Three distinct deformation regimes are identified in these tests: 1) instantaneous elastic deformation; 2) transient and steady-state strain accumulation associated with creep; and 3) accelerated deformation and fatigue failure at high stress levels caused by the progressive development of micro-cracks. Furthermore, the experiments show that fatigue failure is accompanied by a rapid stiffness degradation within the specimens. Based on these observations, we propose a viscoelastic-damage model to characterize the creep-fatigue behavior in sandstone. The model combines the standard Burger's viscoelasticity with an energry-driven energy-driven damage model. The performance of the model is verified against results obtained from laboratory experiments. Finally, a parametric analysis is presented to assess the effects of the frequency and magnitude of the cyclic loads on the fatigue life of sandstone. These findings indicate that increasing the magnitude and frequency of cyclic stress can accelerate fatigue failure. These insights can be used to optimize design parameters to maintain the stability of sandstone rock masses in geological energy storage applications. • Sandstone under multi-level, multi-frequency cyclic loading showed creep-fatigue behavior. • A viscoelastic-damage model is developed/calibrated to replicate the creep-fatigue response of sandstone. • Numerically evaluate the impact of frequency and loading amplitude on the creep-fatigue behavior of sandstone.