Underground hydrogen storage prospects in the Kingdom of Saudi Arabia

Hydrogen (H₂) production and its large-scale utilization as a clean energy source have gained considerable global attention to address the perspective on climate change. Approximately half of the global hydrogen production is achieved through the steam methane reforming (SMR) method. Among various methods, additional energy from renewable sources, particularly wind, and solar, is of great importance for green hydrogen production via electrolysis. A giant depleted gas field can store H₂ to fulfil the domestic energy requirements. In 2021, the Kingdom of Saudi Arabia (KSA) announced the Saudi Green Initiative as one of the key pillars to reach net-zero carbon released by 2060. Aramco has produced and shipped blue ammonia to Japan for hydrogen production to support climate change perspective. The purpose of this paper is to review hydrogen energy in terms of production, transportation, storage, and suitable geologic media for underground hydrogen storage (UHS) technology in the KSA. Notably, the KSA possesses abundant resources and well-established infrastructure, enabling it to efficiently and competitively produce clean hydrogen. We highlight that the production, transportation, storage, and the challenge of leakage are important factors to implement UHS in geologic media. Furthermore, depleted reservoirs composed of sandstone rocks offer lesser challenges in terms of storage capacity and injectivity compared to other types of storage media. The country has large underground reservoirs (igneous and sedimentary rocks) that can be used for hydrogen storage, however, the geological structures need a thorough characterization to ensure economic injectivity and containment security. Specifically, the western region is predominantly composed of igneous rock, and carbon mineralization is highly suitable. In contrast, the eastern part is enriched in sedimentary formations with potential for UHS. This review, including an assessment guideline, helps to understand and advance the deployment of UHS in the KSA and provides a framework for a comprehensive assessment of qualified reservoirs for large-scale storage projects.