Study on Energy Evolution Mechanisms and Damage Mechanisms of Shale under Hydration

Abstract

: Exploration and production activities targeting shale oil and gas have become an essential part of developing unconventional hydrocarbon resources. To clarify the damage mechanisms and mechanical property evolution of shale under hydration, uniaxial compression tests were conducted on shale specimens with different hydration states. Based on energy dissipation theory, the mechanical response characteristics, failure modes, and energy evolution behaviors of hydrated shale were systematically investigated. The results indicate that hydration leads to substantial reductions in shale peak strength and elastic modulus, which decrease by 60.8% and 49%, respectively, under saturated conditions. Meanwhile, hydration markedly alters the failure mode of shale, causing a gradual transition from brittle failure dominated by the rapid release of elastic strain energy to ductile failure governed by the sustained evolution of dissipated energy. In addition, the fracture surface energy exhibits an overall increasing trend with hydration time, increasing rapidly at the early stage of hydration and then tending to stabilize.