Experimental Proof-of-Concept Study on the Hydromechanical Properties of Salt Caverns during Dimethyl Ether Storage

Hydrogen storage in underground salt caverns provides a possible solution for quickly managing fluctuations in energy demand, allowing for rapid retrieval and the ability to accommodate frequent injection and withdrawal cycles. However, the limited cavern volume constrains its capacity for long-term grid support. An alternative approach involves storing hydrogen in chemically bonded forms, such as Dimethyl Ether (DME), which has an energy density 14 times higher than hydrogen, presenting a promising solution to overcome this limitation.

This proof-of-concept study investigates the mechanical and petrophysical properties of salt caverns under conditions representative of DME storage. An interdisciplinary approach combines compaction experiments, petrophysical analyses, and advanced imaging techniques to assess variations in hydromechanical properties. Experimental works utilize an X-ray transparent oedometer to evaluate the deformation behaviours of DME-saturated NaCl aggregates under constant load, simulating long-term creep, and under cyclic loading to assess damage accumulation. The impact of applied stress on permeability is also measured, providing qualitative insights into in-situ integrity.

Additionally, time-resolved (4-D) X-ray microtomography is used to quantify displacement and strain fields, offering insights into deformation mechanisms such as dislocation creep, pressure solution creep, and the initiation and propagation of micro-cracks and fractures. This novel, multi-scale approach provides a foundational framework for understanding the hydromechanical behaviours of salt rocks under complex loading conditions. The findings pave the way for future studies on heterogeneous samples and more complex conditions, contributing to the development of safe and efficient DME storage systems and supporting the integration of chemical hydrogen carriers into energy storage infrastructures.