Experimental and molecular dynamics studies on the multiscale permeability properties of various gases in salt rock

To respond to the challenges posed by the intermittent nature of renewable energy sources, salt caverns are considered as ideal storage sites for energy such as hydrogen, compressed air, etc., as well as various other gases such as methane, helium, CO2, etc., due to their unique properties. However, the microfractures of salt rock are characterized by multiscale features and the microscopic flow properties of different gases in them are not yet clear. Here, we combine experiments and molecular dynamics simulations to investigate the multiscale flow of the above gases in salt rocks. First, the permeability of six gases has been evaluated to elucidate the microscopic mechanisms underlying the Klinkenberg effect. Second, based on the adsorption and flow characteristics of the gas, a multiscale permeability curve (ranging from 10−9∼10−3 m) was obtained for the salt rock slit. Furthermore, a fast method for predicting the permeability of salt rock samples was proposed, with predictions in the same order of magnitude as the experimental results. Finally, the storage requirements for different gases in salt caverns were discussed. This work provides multiscale insights into gas storage in salt caverns, which can guide the construction of salt cavern gas storage reservoirs and the assessment of leakage risk.