Integrative Modeling of Caprock Integrity in the Context of CO2 Storage: Evolution of Transport and Geochemical Properties and Impact on Performance and Safety Assessment

The objective of the “Geocarbone-Integrite” project (2005-2008) was to develop a methodology to assess the integrity of the caprock involved in the geological storage of CO2 . A specific work package of the project (WP5) was dedicated to the integration of (1) the phenomenology describing the evolution of the storage system with a focus on the mechanisms occurring in the caprock and at the interface with the caprock, and (2) the data obtained from the investigation of petrographical, geomechanical, and geochemical properties, before and after reaction with CO2 -rich solutions, performed in the other work packages (WP1 to WP4). This knowledge was introduced in numerical models and specific safety scenarios were defined in order to assess the performance of the CO2 storage system.The results of the modeling show that the injection of CO2 can potentially have a significant effect on the caprock by changing the porosity due to the dissolution and precipitation of minerals, but that the impact is limited to a zone from several decimeters to several meters of the caprock close to the interface with the reservoir depending on whether the supercritical carbon dioxide (SC-CO2 ) plume enters into the caprock and if fractures are present at this location.The methodology used in this project can be applied to a pilot site for the injection of CO2 in the Paris Basin. A key aspect of the safety of such a facility will be to look at the coupling of geochemical alteration and the evolution of geomechanical properties in the short and medium terms (several hundreds of years). The challenge for the future will be to structure and apply the safety assessment methodology with an operational finality, in order to support the robustness of the transition step to CGS projects at the industrial scale.