Modeling Underground Hydrogen Storage in Saline Aquifers with Different Types of Cushion Gases

Abstract

Underground Hydrogen Storage (UHS) is a promising technology for
large-scale energy storage. Geological formations, in which buoyant
hydrocarbons have been retained for a long term, provide vast capacity
for hydrogen storage in a safe manner. Different types of formations
have been considered, such as salt caverns, saline aquifers, and
depleted gas reservoirs. In this study we focus on saline aquifers.
Although lessons were learnt from similar studies such as carbon capture
and sequestration and underground gas storage, the unique thermodynamic
and physical properties of hydrogen make UHS distinguished from the
other subsurface storage projects. To this end, we developed a
two-phase, three-component reservoir simulator, which incorporated
essential physics based on the fully-coupled multi-physics framework of
the DARSim simulator. Particularly, properties of fluid mixtures were
computed using the thermodynamic model of GERG-2008. In the simulation,
different types of cushion gases (CO2, CH4, and N2) were saturated at
the top of the aquifer. Hydrogen was then injected into and produced
from the aquifer periodically. Results showed that most of the injected
hydrogen stayed at the top of the aquifer due to its light density,
which led to a high extraction purity. The low solubility of hydrogen
was favorable in UHS because dissolution trapping had a negligible
impact. Our study confirmed the feasibility of large-scale underground
hydrogen storage and showed the impact of different types of cushion
gases on UHS.