Performing a push-pull test in a shallow aquifer to assess impacts of CO2 and impurities leakage on freshwater quality

Abstract : In 2015, INERIS has performed a push-pull test by injecting 3 m3 of brine saturated with dissolved CO2, containing impurities and tracers, in a shallow chalky aquifer. The objective was to simulate leakage from CO2 storage and to assess impacts on groundwater quality. This test has been performed in the framework of the FP7 CO2QUEST research project, funded by the European commission from 2013 to 2016. This project addresses issues regarding the impact of impurities in CO2 stream captured from power plants. The push-pull test has been done at the experimental site located in Catenoy city, about 60 km north of Paris. The site was equipped with 10 piezometers (~20m-deep wells dedicated to water table measurement and groundwater sampling in the saturated zone) and 4 air-wells (~10m-deep wells dedicated to underground atmosphere measurement and sampling in the unsaturated zone). During a previous research project (ANR CIPRES, funded by the French national research agency from 2011 to 2015), injections of food grade CO2 dissolved in fresh water was performed in Catenoy in 2013 and 2014. Taking feedback from this previous experiment into account, a new injection has been carried out in 2015 during the CO2QUEST project. This third injection was done with CO2 containing some impurities (Fe, Mn, Cu, As, Zn) and tracers (Li, He, uranine/C20H10Na2O5) dissolved in salted water. This salted water is similar to the brine contained in the deep saline aquifer where CO2 storages could be done. 3 m3 of salted water with CO2, impurities and tracers were injected for 3 hours during the push phase. After 3.35 days, 580 m3 of aquifer water were pumped for 95 hours during the pull phase. Between the end of the push phase and the beginning of the pull phase, we let the injected fluid migrate inside the aquifer and interact with groundwater and rocks. Both saturated and unsaturated zones have been monitored during all the experiment. During the push phase, we observed concomitantly an increase of salinity and concentrations of impurities and tracers, and a pH decrease. Despite a high pumping volume during the pull phase, we didn’t make equivalent observations, because of the combination of diffusion, gravity effects and chemical reactions. 1-D geochemical modeling helped us to better understand the behavior of CO2, impurities and tracers during the test. Authors will detail the design of the push-pull test and of the monitoring plan. They will also present results from monitoring and modeling to draw the conclusion that the impact of the experiment on groundwater quality was very limited. It would be useful to perform an extended injection test, to confirm the conclusion when leakage lasts longer.
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Submitted on : Monday, August 6, 2018 - 3:57:38 PM
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  • HAL Id : ineris-01854330, version 1

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Stéphane Lafortune, Philippe Gombert, Zbigniew Pokryszka, Maria del Camino. Performing a push-pull test in a shallow aquifer to assess impacts of CO2 and impurities leakage on freshwater quality. 33. Annual International Pittsburgh Coal Conference, Aug 2016, Cape Town, South Africa. ⟨ineris-01854330⟩

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