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Salt caverns can be created through a process called solution mining

Salt deposits can be converted into salt caverns through a process called solution mining. The following is a brief summary of the solution mining process.

  1. Drilling: A well is drilled into a salt formation deep underground. Most existing salt caverns are between 500 to 1,500 meters underground, but new research indicates that caverns as deep as 2700 meters underground are feasible.1
  2. Injection of Water: Freshwater is injected into the well to dissolve the salt. This creates a brine solution that is pumped back to the surface.
  3. Formation of the cavern: As the water dissolves the salt, it creates a large, hollow cavity known as a salt cavern. The shape and size of the cavern can be controlled by managing the flow of water and brine. The adaptability of this process enables project developers to create salt caverns specific to the project's needs.
  4. Removal of Brine: The brine is continuously pumped out of the cavern, allowing for the further dissolution of salt and the expansion of the cavern.
  5. Cavern Development: The process continues until the desired size and shape of the cavern are achieved. The walls of the cavern are smooth and free from fractures, providing an ideal environment for storing gasses like hydrogen.
  6. Sealing and Testing: Once the cavern is formed, it is sealed and tested to ensure its integrity and impermeability.
  7. Installation of the wellhead: Wellhead equipment, including valves and pressure control systems, are installed to facilitate the injection and withdrawal of hydrogen.
  8. Final hydrogen preparation: Before hydrogen is injected, the cavern is often purged with an inert gas like nitrogen to remove any residual brine or impurities.2

This process is highly controlled to ensure the structural integrity and safety of the caverns, which can then be used for storing various substances, including natural gas and hydrogen.

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Footnotes​

  1. Zhao, K., Liu, Y., Li, Y., Ma, H., Hou, W., Yu, C., Liu, H., Feng, C., & Yang, C. (2022). Feasibility analysis of salt cavern gas storage in extremely deep formation: A case study in China. Journal of Energy Storage, 47, 103649. https://doi.org/10.1016/j.est.2021.103649 ↩

  2. Derouin, S. (2023, September 13). What makes a salt cavern useful for hydrogen storage? American Society of Civil Engineers. [https://www.asce.org/publications-and-news/civil-engineering-source/civil-engineering-magazine/article/2023/09/what-makes-a-salt-cavern-useful-for-hydrogen-storage#:~:text=The%20hydrogen%20storage%20caverns%20are,hydrogen%20for%20the%20long%20term](https://www.asce.org/publications-and-news/civil-engineering-source/civil-engineering-magazine/article/2023/09/what-makes-a-salt-cavern-useful-for-hydrogen-storage#:~:text=The hydrogen storage caverns are,hydrogen for the long term). ↩