Numerical simulation of gas injection induced hydro-Mechanical coupling and damage in COx claystone

Abstract

This study, part of international research project DECOVALEX-2023, investigates the impact of gas injection on COx claystone proposed by the French National Radioactive Waste Management Agency. A biphase flow model, accounting for both liquid and gas phases in porous materials, is developed to analyze the hydro-mechanical coupling behavior induced by high gas pressure. A phase field model is incorporated to describe the coupled cracking behavior. The model is validated using a one-dimensional benchmark, confirming the reliability of the numerical simulation. Subsequently, a series of two-dimensional benchmarks are utilized to study the effects of initial stress isotropy, material anisotropy, and damage zones on the gas injection process. Key findings include the identification of symmetric distributions in isotropic conditions, altered pressure distributions in anisotropic initial stress conditions, and the effect of transversely isotropic material properties on the shape and propagation of high-pressure zones and damage areas. The phase field model successfully captures the transition from diffuse damage to localized cracks.