Measuring Hydrogen Permeability of Salt Rock for Applications in Energy Storage

Abstract This study investigates the hydrogen permeability of salt-rock plugs from the Lotsberg Salt Formation and its caprock, the Ernestina Formation. We employed a newly-developed pressure pulse decay (PPD) system, which is modified and extended from the existing systems for shale-rock characterization. A series of experiments were conducted on each salt rock to measure hydrogen permeability across an average pressure range of 100 to 1000 psi. The results highlight the significant impact of the Klinkenberg effect, where hydrogen slippage leads to an overestimation of measured permeability values. After correcting for this effect, the absolute permeabilities to hydrogen were determined to be 0.313 nD and 4.32 nD for the salt rocks from Ernestina and Lotsberg formations respectively. The interface between the grains of the Lotsberg marlstone provides hydrogen flow pathways, thereby increasing its permeability. The sample from Ernestina caprock, primarily composed of 92% anhydrite with minor dolomite and halite, has fewer crystal boundaries and grain interfaces, resulting in lower permeability.