Inventory of the French salt formations for energy storage in salt cavities (FLUIDSTORY ANR project)
Résumé
The major hurdle of energy transition in France is the energy storage, since the renewable sources with great potential (wind and solar) are highly intermittent. The FLUIDSTORY project, funded by ANR explores the innovative concept consisting in storing energy trough fluids vectors (O2, CO2 and CH4) in salt caverns. The Electrolysis–Methanation–Oxy-fuel (EMO) concept is designed to bring a closed-loop solution able to absorb renewable electricity surplus and recover it later, via the transient storage of O2, CO2 and CH4. During the storage phase, the electric energy excess is used in an electrolysis process. The resulted O2 is stored, while H2 is combined with CO2 in a methanation process. CH4 formed is also stored. During the retrieval phase, electric energy is produced in a thermal generator, where the fuel is the methane and oxygen previously stored. The produced CO2 is in turn stored for later use in the methanation process.
The main objectives of the FLUIDSTORY project are to study the operability, the safety and the integrity of O2 and CO2 storage in salt caverns as well as to investigate the medium to long term (2030-2050) requirements for reaching the energy efficiency and economic profitability of the EMO concept in France.
In order to achieve this goal, availability of storage volumes required by EMO development has to be investigated through systematic inventory of the existing salt caverns and geological study of suitable salt formations.
We present the main results of the inventory of the French salt formations and estimation of the French geological energy storage potential. It consists in an exhaustive inventory of salt formations in France with a special focus on halitic series. This review is based on public and accessible data.
Six sedimentary basins were targeted: Paris Basin, Aquitaine Basin, South-East Basin, Valence Basin, Bresse Basin and Upper Rhine Graben. For each basin, we looked for:
•the general lithostratigraphy: Position of the evaporitic series in the sedimentary pile and relationship between evaporites and the caprock;
•the geographical extension of the evaporitic series;
•the depth and thickness of the evaporitic series;
•Nature and content of insoluble rocks.
Two main conclusions can be drawn from this inventory:
•Salt bearing series of the Paris Basin (Lorraine region) are shallow and thin enough to satisfy the operational constraints of a small storage operated at low pressures.
•Evaporitic series of Apt-Forcalquier, Valence, Bresse or Mulhouse Tertiary basins may be interesting targets for larger storages. Their depths are great enough to increase operating pressures compared to the Paris Basin.
This work will be then valued in the techno-economical tasks of the project. Storage capacity needs for optimal use of EMO technology will be assessed in order to define the optimal location for the EMO technology deployment in France.