[en] This study deals with the impact of CO₂ leakages out of geological storage into overlying freshwater aquifers. Compared to other existing studies, the major added value of this study lies, on the one hand, in the research of new monitoring tools and isotopic approach in the context of CCS aiming at early and sensitive detection of CO₂ leakage and, on the other hand, in the application of these tools at the (limited) laboratory scale as well as at field scale. In order to test these tools, solid and liquid materials were sampled out of the major strategic drinking water Albian aquifer in the Paris Basin (France). We have then precisely characterized and used them within a batch experiment. This experiment yields interesting results which help understanding and constraining precisely the water-rock-CO₂ interactions as well as the isotopic responses. A real scale application of the method was then performed in Norway. It was an opportunity to develop this isotopic program and to track the isotopic evolution composition, while differentiating the natural processes and the system response to the CO₂ injection. When applied to the detection of CO₂ leakage context, the two case studies open the way for choosing the 'best' isotopic tools as indirect indicators of CO₂ presence in these specific systems. The efficiency of these isotopic tools comes from the recording of the CO₂ footprint all along the water-rock-CO₂ interactions. Using such tools imposes a rigorous methodology, which is tackled in this manuscript. Furthermore, future application will require adapting to the specifics of a proposed site. (author)