A chemo-mechanical model for well/caprock interface in presence of CO2

DIEGO MANZANAL; JEAN MICHEL PEREIRA; VALERIE VALLIN

Vienna

Conferencia; 5th Biot Conference on Poromechanics; 2013

Vienna University of Technology

In the context of CO2 geological storage, it is important to assess the safety and efficiency of the storage operation and thus to prevent CO2 leakage. Most probable leakage paths are constituted by the natural (faults) or artificial (around wells) interfaces. In this study, the effects of the presence of carbon dioxide on the behaviour of a particular interface are considered. A chemo-poro-mechanical model for the excavated damaged zone located at the interface between the injection well cement and the caprock has been developed. This constitutive model accounts for the precipitation of calcium carbonates coming from the carbonation of the well cement. Crystallisation pressure induced by these carbonates modifies the stress state in the materials at the interface. The model couples a simplified chemistry of carbonates precipitation with a poro-mechanical model accounting for damage of geomaterials due to tensile stress states. This poro-mechanical model is developed at the macroscale but an insight into the material's microstructure is also included through a description of the material's pore size distribution and its evolution with crystallisation and damage. Predictions using the developed model are qualitatively confirmed by experimental data obtained in laboratory conditions, during the same research project funded by the French Research Agency. It has been demonstrated that this crystallisation can, in some cases, induce damage of the geomaterials. This is particularly the case in the excavated damaged zone of the caprock, located around the well.