Hydrogen Flooding of a Coal Core: Effect on Coal Swelling

Hydrogen is a clean fuel which has the potential to drastically decarbonize the energy supply chain. However, hydrogen storage is currently a key challenge; one solution to this problem is hydrogen geo-storage, with which very large quantities of H-2 can be stored economically. Possible target formations are deep coal seams, and coal permeability is a key parameter which determines how fast H-2 can be injected and withdrawn again. However, it is well known that gas injection into coal can lead to coal swelling, which drastically reduces permeability. We thus injected H-2 gas into a coal core and measured dynamic permeability, while imaging the core via x-ray micro-tomography at reservoir conditions. Importantly, no changes in coal cleat morphology or permeability were observed. We conclude that H-2 geo-storage in deep coal seams is feasible from a fundamental petro-physical perspective; this work thus aids in the large-scale implementation of a hydrogen economy.