Potential impacts of CO2 geological storage on fresh groundwater quality : the CIPRES project

National audienceFresh groundwater protection is not explicitly taken into account in the European Directive on CO2 storage, although it is indirectly covered by article 1.2: 'prevent and, where this is not possible, eliminate as far as possible negative effects and any risks to the environment and human health'. In this context, the CIPRES project focuses on the characterization of potential impacts of CO2 leakage on fresh groundwater quality. One of the objectives is to characterize the bio-geochemical mechanisms that may impair the quality of fresh groundwater resources in presence of CO2. The microbial composition, especially in deep aquifers, such as the Albian aquifer in the Paris Basin (France), but also in superficial aquifers, has yet little been explored and its role in controlling water quality is not well known. Another aspect already highlighted by previous studies is the role of sorption-desorption processes on the mobility of trace elements. To reach the above mentioned objectives, this project proposes two complementary study contexts: (i) laboratory experiments to characterize biochemical and geochemical processes involved in deep Albian aquifer; (ii) field experiments to characterize in situ the mechanisms having an impact on water quality in shallow chalk groundwater (~20 m deep). The characterization of mechanisms in the laboratory and in situ will be based partly on the acquisition of experimental data and partly on the calibration of numerical models. This calibration is designed to improve the numerical modeling work carried out for predictive purposes during the site characterization, impact studies and design of monitoring networks. One outcome of the CIPRES project will be to highlight mechanisms that can impact fresh groundwater quality when a CO2 leak occurs and to propose recommendations to prevent or eliminate negative effects and any risks to the environment and human health