Coupled Reservoir-Geomechanical Simulation of Caprock Failure and Fault Reactivation During CO2 Sequestration in Deep Saline Aquifers

摘要

An aquifer suitable for underground carbon dioxide sequestration needs to be overlain by sealing caprock because carbon dioxide is less dense than the native brine and would tend to rise upward. This paper presents a thermal-hydrological-mechanical (THM) reservoir simulator that is applicable to assessing the sealing capability of such caprock. The geomechanical portion consists of an equation for mean stress, derived from linear elastic theory for a thermo-poro-elastic system, and equations for stress tensor components that depend on mean stress and other variables. The fluid and heat flow portion of our simulator is for general multiphase, multicomponent, multi-porosity systems. We add the capability of simulating caprock failure scenarios, namely tensile failure, fracture and fault reactivation, and shear failure, to the formulation. We then show simulation examples for code verification and demonstration of its capabilities, including a simulation of caprock leakage from carbon dioxide injection, a demonstration of the simulator's ability to predict of shear failure, and a simulation an experiment of pressure-induced fracturing of a concrete block that includes tensile failure.