Exploring hydrogen storage potential in depleted Western Australian hydrocarbon reservoirs: A petrophysical and petrographic analysis

Hydrogen, recognised as a clean and sustainable energy carrier with excellent transportation fuel properties, drives numerous countries towards a hydrogen-based economy due to its high utilisation efficiency and minimal environmental impact. However, the gaseous nature of hydrogen necessitates larger storage surface areas. Underground Hydrogen Storage (UHS) has emerged as a promising and efficient method to overcome this challenge. Currently, only a handful of UHS locations exist globally due to the novelty of this field. With its abundant depleted hydrocarbon reservoirs boasting significant storage capacity, Western Australia presents a suitable region for hydrogen storage. This paper comprehensively analyses petrophysical and petrographic characteristics, employing XRD, MIP, and Micro-CT techniques on sandstone and claystone samples obtained from several fields in Western Australia. The suitability of these samples for hydrogen storage is evaluated based on mineral composition and porosity. The analysis reveals that more than 96% of Quartz is present in the sandstone samples. The claystone samples exhibit a mineral composition comprising Quartz, Calcite, K-feldspar, Kaolinite, Pyrite, Albite, and Muscovite. The study suggests that hydrogen storage in formation rock is favourable due to the low reactivity of hydrogen with silicate minerals, but interactions with cap rock minerals should be considered. Micro-CT results indicate the connected porosity in the 17.23–4.67% range. Pore distribution in sandstones ranges from nanometers to millimetres, with a substantial proportion of connected pores in the intermediate range, which is conducive to hydrogen storage. This is particularly advantageous as the hydrogen-water system is highly water-wet, with hydrogen primarily occupying medium and larger pores, minimising hydrogen trapping. In claystone, most pores were below 3 nm, but instrumental constraints limited their quantification. In conclusion, the petrophysical and petrographic analysis underscores the potential of Western Australian depleted hydrocarbon reservoirs for hydrogen storage. Understanding the mineralogical reactions with cap rock minerals is crucial, while the favourable pore distribution in sandstones further supports the viability of hydrogen storage.