NUMERICAL STUDY OF THE CHEMO-PORO-MECHANICAL BEHAVIOUR OF THE CEMENT SHEATH DURING CO2 INJECTION

This paper aims at describing the influence of carbonation on the poromechanical behaviour of a wellbore cement. Attention is paid to the estimation of the damage risk of the cement sheath in the context of CO2 geological storage. A chemo-poromechanical model is presented. It accounts for the main chemical reactions occurring within the cement matrix and their consequences in terms of matrix dissolution and carbonates precipitation. These porosity changes are accounted for by introducing a chemical porosity associated to the cement matrix dissolution and the porous volume occupied by carbonate precipitates. The model has been implemented in a finite volume code. An axisymmetrical configuration is considered. Evolutions of transport characteristics and mechanical behaviour during carbonation process are predicted. The damage risk of the cement sheath is finally estimated through the calculation of the elastic energy stored within the solid matrix.