Report | “Good luck” for ProSalz – A safe use of salt deposits for resource mining and underground energy storage

In Germany, salt deposits play a major economic role, not only in resource mining but, less known, also for energy storage. Salt is characterized by an impermeable structure and therefore is a preferred storage medium for various liquids and gases. Technical caverns in salt can serve as a storage medium for example for natural gas, hydrogen or mineral oil. It secures a reliable energy supply even during peak of demand. Cavernous structures are also naturally formed and occasionally found in active salt mines. Within such an active salt mine the project „ProSalt - process understanding, scalability and transferability of reactive multiphase transport in salt deposits“ investigates the processes acting between salt, gas, and water in the transition zone between cavern and solid rock.

Despite the generally assumed impermeability of salt rocks, the contact of fluids and salt may cause unintended changes of surrounding layers or loosen up the cavern structure. In the framework of the scientific program „Geoforschung für Nachhaltigkeit (Geo:N)“ the project ProSalt, led by Bettina Strauch, GFZ section Inorganic and Isotope Geochemistry, addresses open question on temporal and spatial dimensions of fluid migration at the rim of artificial and natural caverns.

Storage caverns are not directly accessible, which is why the scientists conduct their investigations within a salt mine close to Fulda, Germany. Here, various measurement profiles alongside the transition zone between a natural cavernous structure and the surrounding salt rock will be installed for geochemical and geophysical investigations. Comparative experiments on various laboratory scales are planned. From simulations in large 400 liter volume pressure vessels down to microscopic analyses the influence of mineralogy, moisture, gas composition, temperature and pressure gradients on fluid migration will be investigated. The data set is complemented with isotope and rock-geochemical analyses. The results serve the base for numerical simulations and models which can be transferred to other natural and artificial locations. Bettina Strauch: “Our aim is to support and assist the selection and monitoring procedure for storage caverns and to add to a secure exploration of potassium salt deposits.

On 4 July the kick-off meeting of the BMBF-funded joint research project took place at the project site near Fulda. Besides GFZ scientists from the sections Inorganic and Isotope Geochemistry, Fluid Systems Modelling, and the Centre for Scientific Drilling, representatives of the project partners from the Friedrich-Alexander University of Erlangen, K+S Incorporated, and Untergrundspeicher-Geotechnologie-Systeme (UGS GmbH) took part in the meeting. During a first entry to the mine the measuring profiles were defined, together with the local miners. Furthermore, a first measurement setup was installed for the continuous monitoring of gas release close to a natural cavern. While waiting for the approval of the underground works by the mining agency, laboratory work on first salt samples will start.

10.07.2017, Ariane Kujau