Well integrity assessment by a 1:1 scale wellbore experiment: Exposition to dissolved CO2 and overcoring.

tIn this work, we present the results of a new in situ experiment to complete the existing scientific dataseton well integrity in the context of CO2storage. This experimentation has been designed to evaluatethe sealing behaviour of a monitored well after mechanical and chemical stresses due to pressure andtemperature changes (stage A) and due to the exposure to carbonated brine (stage B), before a finalovercoring stage for retrieving the well system and the surrounding clay. The stage A has been the subjectof a first publication (Manceau et al., 2015; Water Resour. Res., 51, 6093-6109) and the two latter stagesare described in this paper. Multidisciplinary methods (hydraulic tests and modelling, fluid samplingand modelling, analysis of cement and clay samples on the overcore) are used to get better insight, in arealistic wellbore context, on the interplay between the geochemical questions, and the operational andconstruction issues. In particular, this study shows that when good integrity pre-exists before a well isin contact with carbonated water, the exposure to dissolved CO2does not seem to lead to a degradationof the well hydraulic properties but rather to their improvement.