Hydro-Mechanical Coupling of CO2 injection into Homogeneous and Naturally Fractured Rock Mass with Permeable Matrix

ABSTRACT: Geological storage of CO2 and H2 in sedimentary formations are pivotal technologies in transitioning to a net-zero carbon energy economy. These geo-energy applications require the injection of fluids into permeable geological formations that are naturally fractured and have a permeable matrix. To achieve economic performance, high rates should be used, which may trigger hydraulic fractures (HFs) and activate pre-existing natural fractures (NFs). The interactions among the injected fluid, fractures, and the rock matrix must be understood to control the response of such energy and environmental geo-systems. Previous studies underscore that the distribution and properties of NFs, the stress state in the geological formation, the rock matrix permeability, and the rate and viscosity of the working fluids are crucial factors in controlling the hydro-seismo-mechanical response of the formation. This study utilizes the combined finite-discrete element method (FDEM) to model the complex interactions between hydraulic fractures, pre-existing NFs, and the rock matrix permeability to reveal hydro-mechanical response of the rock mass subjected to CO2 injection. These insights will contribute to more effective management strategies for CO2 and H2 storage in sedimentary formations.