Potential impacts of CO2 geological storage on groundwater quality – CIPRES

To reach the abovementioned objectives, this project proposes three complementary study contexts: (i) the laboratory for the characterization of biochemical and geochemical (sorption/ desorption) processes that may impact water quality, and experiments carried out on Albian samples (ii) an experimental site to validate the monitoring methodology by experimental CO2 leakage in groundwater and to characterize the in situ mechanisms having an impact on water quality and (iii) a deep well to apply deep monitoring methodology for deep aquifers. 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 that take into account the diffusion of CO2 into the environment (unsaturated zone and aquifer) and reactive transport. This numerical calibration is designed to reinforce the numerical modelling work carried out for predictive purposes during the site characterisation, impact studies and design of monitoring networks.

The experimental approach on the Albien greensand from the Paris Basin has brought interesting results on the geochemical and biogeochemical plan. The study on the surface properties of glauconite demonstrated a significant reactivity of this mineral with respect to trace elements.
The experimental results obtained in the laboratory show that if a slight intrusion of CO2 has no impact on microbiological mechanisms, strong intrusion completely inhibits the biological activity targeted under the conditions imposed. These tests reveal a complex microbial endogenous mechanisms. Some activities have a strong impact on the geochemistry of water, mainly on trace elements are mobilized in solution. This impact is added to the impacts linked only to the presence of CO2 highlighted under 1 bar in previous work (Smell et al., 2013).
On the site of Catenoy, it has been shown very low physical-chemical impact of CO2 injected into the aquifer chalk and the important and fast buffer role of this carbonates. However, the monitoring of a carbonate aquifer, having a compex geometry, is very delicate.
The reactive transport modeling 3D simulating a leakage of CO2 in the greensand was performed including ion exchange and surface complexation from the experimental work of the green sands. .
A methodological guide for the implementation of the water monitoring is being drafted. Its preparation is accompanied by two workshops dedicated to exchange between the project partners and authorities and stakeholders.

One outcome of the project will be to integrate the results in order to propose recommendations for (i) taking into account the impacts on groundwater in the future characterization of geological storage sites, (ii) defining the mechanisms to be considered in the studies to qualify and quantify the impacts on groundwater quality, and (iii) setting up groundwater monitoring networks.

IEAGHG – juil. 2012, Montana, USA
Studium Conference, Fev 2013, Orléans, France
IEAGHG - Août 2013, Canberra, Australie
AFEM. Ecologie microbienne, Oct. 2013, Lyon
AGU Fall meeting, Dec 2013, San Francisco, USA
GHGT 12, 5-9 oct 2014, Texas
24ème Réunion des Sciences de la Terre 27-31 oct 2014, Pau, France
AGU Fall Meeting, 15-19 dec 2014, San Francisco, USA

France is committed to reducing its greenhouse gas emissions, which in particular includes the transposition of the European Directive on the geological storage of CO2. Indeed, groundwater protection is not explicitly taken into account in the European Directive on CO2 storage, although it is indirectly covered by the global philosophy of the text summarized in 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”. The main actions mentioned in the text in relation to groundwater protection are data collection and monitoring. In this context, the CIPRES project focuses on the characterization of potential impacts of CO2 leakage on groundwater quality.
The first objective is to characterize the biogeochemical mechanisms that may impair the quality of groundwater resources, especially in deep aquifers, such as the Albian in the Paris Basin in France, as yet little explored. The microbial composition of such deep aquifers and their role in controlling water quality is unknown. Another aspect already highlighted by previous studies is the role of sorption-desorption processes on the mobility of trace elements. The presence of glauconite in the Albian sands may play a role in the mobility of trace elements in the Albian aquifer.
The second objective, in view of the fact that future groundwater monitoring will be confronted with several issues, is to validate a monitoring methodology. The thresholds values of the parameters to be monitored will be validated in a natural context during an experimental CO2 leakage and our methods will be tested by equipping a monitoring observation well in a deep aquifer, the Albian aquifer (0 to 1000 m deep). The major parameters to be monitored in the case of CO2 leakage are pH, alkalinity and dissolved CO2. In deep conditions, pH sensors are not stable, CO2 sensors are not validated and measuring alkalinity requires particular sampling conditions to avoid degasing before analysis.
To reach the abovementioned objectives, this project proposes three complementary study contexts: (i) the laboratory for the characterization of biochemical and geochemical (sorption / desorption) processes that may impact water quality, and experiments carried out on Albian samples (ii) an experimental site to validate the monitoring methodology by experimental CO2 leakage in groundwater and to characterize the in situ mechanisms having an impact on water quality and (iii) a deep well to apply deep monitoring methodology for deep aquifers.
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 that take into account the diffusion of CO2 into the environment (unsaturated zone and aquifer) and reactive transport. This numerical calibration is designed to reinforce the numerical modelling work carried out for predictive purposes during the site characterisation, impact studies and design of monitoring networks.
One outcome of the project will be to integrate the results in order to propose recommendations for (i) taking into account the impacts on groundwater in the future characterization of geological storage sites, (ii) defining the mechanisms to be considered in the studies to qualify and quantify the impacts on groundwater quality, and (iii) setting up groundwater monitoring networks.