The strategy of the study starts with a simple approach in a free medium without CO2 flow, in order to study the reactivity of saline solutions of different chemical compositions, and to evaluate the impact of a thermal gradient on this reaction network.We have developed an experimental cell that allow to superimpose 2 to 3 layers of solution of different concentration and chemical composition. We studied the exchanges between a cold anhydrous CO2 phase flowing in high permeability zones, and a hot salty aqueous phase trapped in the porosity of the rock. These effects lead to highly coupled Thermo-Hydro-Mechanical-Chemical (THMC) processes, whose interpretations have not yet been completed nor formally implemented into the numerical models.This thesis work, combining experimental measurements and numerical modelling, focuses on the study of the coupling between the thermal gradients and the diffusive reactive transport processes taking place in the deep saline aquifers, particularly in the near-well injection zone. In addition to these effects, there is the added complexity of the presence of two immiscible phases: brine (wetting fluid) and CO2 (non-wetting fluid). This has a major impact on injectivity of the reservoir and the integrity of the storage. The near-well injection zone is particularly impacted with a strong geochemical reactivity associated with intense heat exchanges. However, the injection of CO2 into the porous medium considerabely disturbs its thermodynamic equilibrium. CO2 storage in deep saline aquifers has been recognised as one of the most promising ways to mitigate atmospheric CO2 emissions and thus respond to the challenges of climate change.
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