PIA : Etude expérimentale des conditions biogéochimiques adaptées au stockage souterrain de l'hydrogène en présence ou non de CO2

Keywords

hydrogen, bacterial activity, underground storage, methanogénèse

Subject details

Hydrogen should be a key player in the future energy mix and gives promising prospects as a clean and sustainable vector for renewable energy storage and for decarbonizing industries. This promotes the development of large-scale hydrogen storage solutions to meet energy demands and mitigate the intermittency of wind and solar energy. Major concerns remain, however, about the biogeochemical conditions which could affect hydrogen or mixtures of gases stored during underground geological storage in saline aquifers or depleted reservoirs. Combining hydrogen and CO2 storage to reduce greenhouse gas emissions and to favor methanogenesis (production of methane) through microbial processes is also an avenue to be considered for future research. Methane is less reactive than hydrogen and infrastructures for its storage, transportation and utilization have existed for a very long time throughout the world. CO2 can also be used as a cushion gas to improve hydrogen recovery. The injected gases (H2 and CO2) into underground storage sites may interact with the reservoir rocks, the overburden rocks, the reservoir fluids and the microbes. H2 and CO2 reactivity with rock minerals, well equipments (steels, cements, elastomers) and the microorganisms present lead to changes in the stored gas composition that could be unwanted such as the production of certain corrosives compounds (e.g., hydrogen sulfide) which could cause degradation within caprock and in the vicinity of wells (wells plugging, reduced injectivity, loss of seal efficiency). Related impact on rock properties (porosity, permeability, mechanical properties) driven by dissolution and precipitation mechanisms needs also to be investigated. This project aims at investigating how biogeochemical conditions could affect the gases (H2, CO2 or mixture of both) stored in subsurface formations. Since the injected gases can interact with several elements of deep reservoirs, a better understanding of the extent and rate of possible biogeochemical processes is mandatory for quick development of sustainable and competitive hydrogen storage solutions in France. A preliminary baseline survey is currently being conducted to collect data on reservoir formations suitable for gas storage in the Aquitaine Basin and characterize their properties. Then, a multiscale analysis from batch and microfluidic reactors to flow-through experiments will be carried out to assess gas reactivity in subsurface conditions mediated or not by indigenous microorganisms. Experiments in laboratory pilots or through microfluidic approaches are necessary to closely simulate the study sites and the behaviour of the gas stored. Different levels of experiment will be designed to reproduce the storage conditions and enable upscaling to the reservoir scale. Experimental results, and possibly forward 1D/2D modeling, will provide robust key indicators to define optimal bio-geochemical conditions to improve the efficiency of underground H2 storage in the target reservoirs.