In situ study of dynamic mechanical behavior and fatigue damage evolution of Shale rocks under cyclic loading and unloading

Cyclic loading often causes rocks to fail at a stress level lower than their determined strength obtained under static conditions. This phenomenon termed ‘fatigue’ is crucial in studies focusing on the evaluation of extensive storage of CO2 relying on shales as an efficient sealing caprock. Shale rocks suffer cyclic loading during drilling, leading to possible near-well fracturing. In addition, thermal stresses may arise during these cycles due to the expansion cooling of the injected CO2. All these processes may affect the mechanical stability of such geological formations. Therefore, it is necessary to understand the response of the rock mass under cyclic loading conditions. The proposed experiment aims to investigate in detail the fatigue damage evolution in rocks due to the cyclic loading expected for the rock mass through the lifetime of a CO2 storage operation by using dynamic in-situ X-ray imaging using the Hades apparatus.