Australia’s natural hydrogen – where, when and how

A low greenhouse gas emissions future will involve hydrogen (H2) as an energy vector, with natural hydrogen playing an uncertain role. However, Australia is considered a prime target for natural H2 exploration (Moretti et al., 2021) with its supportive geology and a large potential H2 resource (Boreham et al., 2021). Australian natural gases generally show low concentrations of H2 with ~80% of the gases having H2 < 0.1 mol%. All states and the Northern Territory contain examples of natural gas with H2 > 1 mol% and in South Australia up to ~90 mol% H2 (air-free) (Boreham et al., 2021); the latter fact being more than enough encouragement for a nascent exploration phase in SA specially targeting natural H2. Regions for exploration across Australia will include most rocks types involving Archean–Proterozoic cratons, banded iron formations, gold mineralisation, igneous intrusions, metamorphic rocks and in deep, hot sedimentary basins (Boreham et al., 2021 and references therein; Geymond et al., 2022; Mahlstedt et al., 2022; Malvoisin and Brunet, 2023). Fluid-rock interactions can generate H2 through radiolysis of water, ferroigenesis and the thermal decomposition of organic matter, with these three processes amenable to modelling the H2 system.

Exploration strategies will employ many tools developed for the petroleum and mineral exploration sectors, with surface expressions of H2 seepage being one simple approach. Here, indirect measurement based on satellite imagery of semi-circular depressions or ‘fairy circles’ together with direct measurement of H2 concentration in soil gas can be used to infer deeper fluxes of natural H2 in Australia (Larin et al., 2015, Frery et al., 2021 and 2022; Moretti et al., 2021; Geymond et al., 2022). This talk will highlight recent and present research on the identification and understanding on natural H2 occurrences in Australia.