ABSTRACT
The underground geological storage of gases, including natural gas, hydrogen, and CO2, is a key enabler for a reliable and cost-effective low-carbon economy. Furthermore, large-scale underground gas storage capacities for natural gas and hydrogen (blue or green) are essential to compensate for possible disruptions and seasonal supply and demand fluctuations. Underground gas storage facilities also function as secure strategic reserves that can be deployed rapidly during emergencies to cover demand. However, while the energy industry has extensive experience of natural gas storage, its experience of underground hydrogen storage is limited. Further, although hydrogen storage mechanisms (including secure compression, injection, and withdrawal) are not fundamentally different from those of natural gas, the unique thermodynamic properties of hydrogen, its embrittlement to metals, and its reactivity with pore fluids and rocks make hydrogen storage in porous sedimentary rocks underground technically more challenging than storing natural gas. In this chapter, we review the fundamental mechanisms of storing compressed hydrogen in underground rocks, including depleted hydrocarbon reservoirs, saline aquifers, and salt caverns. The main technical challenges and recent developments are also discussed. In addition, the availability and suitability of the potential formations for underground hydrogen storage in Saudi Arabia are presented.
