Hydro-mechanical analysis of Co2 storage in porous rocks using a critical state model

Abstract

A numerical model is presented to simulate the hydro-mechanical behaviour of the porous rocks that form the deep saline aquifers which are currently being considered as potential CO2 storage reservoirs. The model has taken into account the equations of state regulating the behaviour of CO2, in both the supercritical state in which will be injected, and under atmospheric conditions. Whilst the flow model is founded on a “conventional” advective/diffusive formulation, the geomechanical constitutive model used is a critical state model that includes a non-linear hypoelastic law, and a brittle/ductile yield which takes into account mechanical degradation and the effect of partial saturation caused by the CO2 flow. With this model, it will be possible to analyse the localisation of the deformation which may occur when a dilatant brittle yield is reached, and thus to analyse the role played by the preferential flow paths associated with this localisation. A partial differential equation solver based on the finite element method, which adopts a multiphysics simulation environment, has been used. After some examples of validation, the simulation of a synthetic example that highlights the capacities of the model is presented.