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Theses

Développements de protocoles méthodologiques pour le monitoring géochimique appliqué à la détection de fuite d'hydrogène (H₂) à l'aplomb des sites de stockage souterrain

Abstract : Combined with the energy transition, underground H₂ storage is a storage solution for the energy. The research project named "Rostock'H" integrating this thesis work associated the University of Lorraine and Ineris to develop geochemical monitoring methods in order to analyze the risks and opportunities. This project aims to study the risks and opportunities of H₂ storage in salt caverns. The next goal is to be able to store H₂ in a volume of up to 1,000,000 m³ between 300 and 1,400 m deep. The development of an underground storage site involves controlling pre, syn and post-operational risks by geochemical monitoring methods. Colorless and odorless, H₂ is a volatile and explosive gas. A particular attention is therefore paid to the risks of subsurface leakage from these storage sites and to the metrology associated with this detection. This thesis work had three main objectives: (i) to experiment in-situ and continuous monitoring methods from dissolved gas injections on a dedicated experimental site, (ii) to determine the potential impacts of a leak in “soils” and “aquifers” with a modeled analysis of the geochemical behavior of H₂ and associated parameters, (iii) to establish recommendations and a monitoring strategy for existing or future underground storage sites to prevent potential H₂ leakages. Composed of a semi-confined aquifer from 13 m deep, this experimental site in the Paris Basin has several wells and equipments reaching the saturated and unsaturated zones. Oxidizing, oxygenated and moderately mineralized, the waters of this aquifer have an initial chemical composition belonging to the calcium bicarbonate facies with a slight alteration in nitrates and sulphates. Several steps were necessary to simulate and model a potential leak: - Preparation of the site and choice of the metrological systems that will be deployed - Establishment of the initial state of the site through the definition of a geochemical baseline from measurements of the piezometric level, physico-chemical parameters, analyzes of ionic species and dissolved gas measurements in a dedicated well by combining of the Raman and infrared spectroscopies - Co-injection of dissolved He and hydrogeological tracers to validate the experimental protocol of the H₂ injection and to allow a first analysis of the aquifer dynamics - Co-injection of dissolved H₂ and tracers selected according to the adapted protocol linked to the experience feedback from the He injection - Post-injection monitoring to determine the impacts and the kinetics of return in the initial state of the aquifer using in particular the monitoring system of dissolved gases by optical sensors. An initial concentration of H₂ dissolved at 1.78 mg.L-1 was injected under surface conditions for 2.5 hours into the aquifer. The migration of the dissolved H₂ plume as well as other gases initially present in the aquifer was monitored both by continuous method (Raman and infrared spectroscopies) and discontinuous measurements (partial degassing). A dynamic of H₂ transfer in the water table was observed up to 20 m downstream from the injection well: 0.6 mg.L⁻¹ at 5 m, 0.17 mg.L⁻¹ at 7 m then 1.8*10⁻³ mg.L⁻¹ of H₂ at 10 and 20 m during the first week. Following the addition of H₂(aq), the physico-chemistry of the aquifer was modified with an increase of pH, a decrease of redox potential and of the O₂(aq) concentration. From continuous measurements by Raman spectroscopy (at 7 m downstream the injection well), a 2D model was established on the basis of a mixed H₂ diffusion/advection process, assuming a single-channel flow in the aquifer. The experimental results acquired in this thesis work validate, over the long term, the metrological choices applied, with a detection limit of H₂ in aquifer lowered to 0.02 mg.L⁻¹. These results thus confirm the feasibility of monitoring dissolved H2 in shallow aquifers and highlight the potential impacts of leakages from underground storage reaching the surface.
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Submitted on : Wednesday, May 11, 2022 - 5:32:23 PM
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  • HAL Id : tel-03665471, version 1

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Elodie Lacroix. Développements de protocoles méthodologiques pour le monitoring géochimique appliqué à la détection de fuite d'hydrogène (H₂) à l'aplomb des sites de stockage souterrain. Géochimie. Université de Lorraine, 2021. Français. ⟨NNT : 2021LORR0342⟩. ⟨tel-03665471⟩

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