The hydrogen rainbow

Hydrogen offers a potential low-emissions way forward to help decarbonise Australia’s energy, transport and industrial sectors. Hydrogen has been classified into colours related to the greenhouse gas emission profile of the energy source or process used to generate or extract hydrogen, forming a hydrogen rainbow:

• Gold or white hydrogen – natural hydrogen from geological sources.
• Green hydrogen – electrolysis of water with no GHG emissions.
• Blue hydrogen - steam reforming to separate hydrogen from natural gas with Carbon Capture and Storage (CCS).
• Grey hydrogen – as above but no CCS.
• Orange hydrogen - hydrogen generated from chemical reactions initiated in iron-rich formations through CCS.
• Brown and black hydrogen – made from coal gasification (if there’s CCS = blue hydrogen).
• Turquoise hydrogen – pyrolysis of natural gas produces solid carbon.
• Yellow hydrogen - direct water splitting.
• Purple/pink hydrogen - nuclear power.

Introduction

It is very early days in Australia for natural hydrogen exploration with hundreds of hydrogen indications in wells, mines and seeps (Boreham et al. 2022). Globally, only a handful of wells have specifically targeted natural hydrogen and as yet there’s only one producing field in Mali, west Africa (Maiga et al. 2023). Exploration techniques and methodologies are currently being developed and tested.

Natural hydrogen exploration become possible in South Australia on 11 February 2021 via regulatory changes to include hydrogen as a ‘regulated substance’ under the Petroleum and Geothermal Energy Act 2000 which was amended in 2023 to establish the Energy Resources Act 2023.

Gold Hydrogen Ramsay 1 is the first well drilled in Australia specifically targeting natural hydrogen. In October-November 2023 the company reported hydrogen and helium indications in their Ramsay drillholes.

A diversity of hydrogen plays in South Australia are being explored and evaluated through Petroleum Exploration Licence work programs over the next five years increasing our understanding of this potential new source of energy.

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Why the interest in South Australia?

South Australia has attracted interest from explorers because:

1. Zgonnik (2020) found online SARIG records revealing significant hydrogen contents from Government analyses of gas samples taken from three historic South Australian drillholes:

• 1915 – Robe 1 (25.4% hydrogen)
• 1921 – American Beach Oil 1 (64.4-80% hydrogen)
• 1931 – Ramsay Oil Bore 1 (51.3-84% hydrogen)

2. Moretti et al. (2021) postulated that salt lakes on Yorke Peninsula and Kangaroo Island were natural hydrogen seeps – circular depressions formerly known as ‘fairy circles’.

3. Natural hydrogen exploration become possible in in SA in February 2021 when changes to the Petroleum and Geothermal Energy Regulations 2013 added hydrogen as a ‘regulated substance. This enabled grant of exploration licenses targeting natural hydrogen. Figure 1 shows the State’s regulatory framework for hydrogen.

Figure 1. South Australia's hydrogen legislative framework.

Historic drilling and exploration

Hydrogen has been detected in wells in the Cooper and Eromanga basins, Otway Basin, Kangaroo Island and southern Yorke Peninsula (Zgonnik, 2020; Boreham et al. 2021). L.K. Ward, (Chief Government Geologist) reported high levels of hydrogen in gas samples taken from shallow bores around the State (Ward 1917,1932, 1933 and 1941) - Robe 1 in the Otway Basin, American Beach Oil Bore 1 drilled on Kangaroo Island and the Minlaton Oil Syndicate Bore 1 (now Ramsay Oil Bore 1, referred to as Minlaton Oil Bore by Boreham et al., 2021) drilled on central Yorke Peninsula in 1931 (Figure 2 and Tables 1 and 2).

The gas samples taken by LK Ward from Robe 1 (drilled in 1915) were analysed by the Department of Chemistry, the samples he took from the other wells were analysed by the Works Chemist at the SA Gas Works. Gas sample volumes were not reported. Boreham et al. (2022 and 2023) report elevated hydrogen contents in gas samples from Cooper Basin wells and concluded that hydrogen is being generated by over-mature natural gas source rocks.

Gold Hydrogen reported elevated hydrogen and helium indications on logs and in mud gas samples from Ramsay 1 and 2 which appear to confirm the 1931 measurements (Table 2):

Table 1. Analysis of gas samples taken from Robe 1.

Table 2. Analysis of gas samples taken from Ramsay Oil Bore 1 and American Beach Bore 1, with hydrogen levels highlighted.

Figure 2. Collecting gas from the Ramsay Oil Bore 1 near Minlaton in 1931. The well reached ~548m, and a small gas flow of almost pure hydrogen was recorded (SADEM photograph N001671).

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Natural hydrogen occurrences and prospectivity

Bendall (2022) provides a recent synopsis of the geology of natural hydrogen occurrences and exploration methodologies. Gaucher (2020) indicated that there are two main geological settings where hydrogen could be generated - Proterozoic crystalline shields and serpentinized ultramafic rocks in mid-ocean ridges and in land-based ophiolite-peridotite massifs. Potential natural hydrogen source rocks include:

• ultrabasic rocks and iron-rich cratons - hydrogen generated when Fe²⁺ is oxidised in the crust e.g.: 3FeO (in silicates) + 1 H₂O ---->Fe₃O₄ (magnetite) + 1 H₂ (aqueous) - Sleep and Bird (2007).
• and uranium-rich basement – hydrogen generated by radiolysis of water.

South Australia has favourable geology for natural hydrogen generation:

• Ancient basement complexes which contain iron and/or uranium rich rocks e.g. Iron-rich Archaean greenstone and Neoproterozoic cratons (e.g. Gawler Craton, Curnamona and Musgrave Provinces, Kanmantoo Fold Belt) with ultrabasic and basic rocks and iron-rich minerals (hydrogen generation from the oxidation of Fe²⁺ bearing mineral such as siderite, biotite, or amphibole by water - serpentinization) and/or radiogenic granites (hydrogen generation via radioactive decay breaking bonds in water).
• fractured and seismically active source areas - deep-seated faults can both channel migrating hydrogen up from deep sources to surface and introduce water downward for further chemical reaction with exposed iron-rich rocks.
• Sedimentary cover may reservoir and trap migrating hydrogen particularly if aquifer systems and /or seal rocks like salt are present (see Bradshaw et al. 2023).
• Thermogenic decomposition of organic matter in the Cooper and Otway basins(e.g. over-mature source rocks in deep troughs, Boreham et al. 2023).
• Surficial hydrogen seeps? Seeps can be blind or coincident with visible sub-circular topographic depressions on the metre to kilometre scale (formerly ‘fairy circles’).

Using a hydrocarbon play analogue, once generated in basement source rocks, hydrogen needs a migration pathway to a trap with a reservoir (e.g. fractured basement, petroleum type reservoirs in sedimentary cover) and effective seal (e.g. intrusive volcanics, salt, shale/siltstones, aquifers) to accumulate and then be preserved in geological timeframes. Alternatively, explorers may seek to delineate fluxes of natural hydrogen as it is being generated in basement source rocks - a very different concept to our understanding of hydrocarbon generation and plays which will require different exploration approaches.

Salt is regarded as the most effective seal and Geoscience Australia have completed a review of Australian subsurface salt occurrences to identify potential sites for underground hydrogen storage (e.g. Feitz et al. 2022; Bradshaw et al. 2023) - this work will also inform natural hydrogen exploration. Volcanic intrusives could seal hydrogen – e.g. dolerite sills in the shallow (~30-140m deep) Bourakebougou Hydrogen Field in Mali, where groundwater also seems to act as permeability barriers (Maiga et al. 2023). Hydrogen is insoluble at low temperatures and pressures (Prinzhofer et al., 2018). Watkins et al. (2022) concluded that despite hydrogen’s low density and small molecular size, its seal capacity was similar to that of methane and potentially greater than carbon dioxide – i.e. shales can seal hydrogen.

Potential natural hydrogen source rocks may occur in South Australian basement provinces and cover as revealed by high level screening (Tables 3 and 4 and Bendall, 2022). For more information on basement provinces:

• Gawler Craton,
• Curnamona Province and
• Musgrave Province.

For further information and data, a basin-in-a-box well and seismic data package for the Stansbury Basin is available, the Minerals section contains maps and information on basement geology, and access spatial datasets from SARIG.

Upcoming company exploration activity in SA will test a diversity of natural hydrogen plays. Gold Hydrogen are the first in the nation to drill exploration wells specifically targeting natural hydrogen. H2EX commenced its exploration program in PEL 691 on Eyre Peninsula with a soil gas survey in May 2023, which recorded hydrogen occurrences, and followed up with an Ambient Noise Tomography survey in November 2023 conducted by Fleetspace. 2H Resources (a subsidiary of Buru Energy) are targeting hydrogen plays over the Adelaide Fold Belt.

Table 3. High level screening of SA basement provinces.

Table 4. High level screening of SA basins.

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Ramsay drillholes and American Beach Bore 1

Boreham et al. (2021) published a comprehensive review of the diverse abiogenic and biogenic sources of natural hydrogen. They used isotopic analyses to distinguish different sources of hydrogen occurrences in Australia and proposed a source-migration-accumulation model for hydrogen exploration. Their review of the hydrogen occurrence in Ramsay Oil Bore 1 concluded that “The Minlaton Oil Bore encountered moderately saline (NaCl rich with 9.44 g/L total salts) groundwater at 160 ft (48.77 m). Water radiolysis associated with a high radioactive element content of the granite basement is the most likely source for the H₂. However, a contributing H₂ source possibly results from the interaction of the heavy brines with the biotite granite within the fractured basement rocks of the Tickera Granite. The available seismic data  suggest that the basement faults in the vicinity of Minlaton Oil Bore extend into the Cambrian sediments (Fig. 8a). These faults could provide migration pathways for downward movement of heavy brines from the saline swamps as confirmed by the fact that the saline aquifer was penetrated by the Minlaton Oil Bore”. (Boreham et al., 2021).

In their paper presenting a screening methodology to scout for hydrogen occurrences in stable intracratonic settings above Archean to Proterozoic basement Moretti et al. (2021) referred to Ward’s reports on the hydrogen shows and identified ‘fairy circles’ on Yorke Peninsula and Kangaroo Island. ‘Fairy circles’ (now called circular depressions) are depressions on land caused by venting of hydrogen or other gases. They concluded that “The comparison suggests that Australia could be one of the most promising areas for H₂ exploration, de facto a couple of wells already found H₂, whereas they were drilled to look for hydrocarbons. The sum of areas from where H₂ is seeping overpasses 45 km² in Kangaroo Island as in the Yorke Peninsula.”

PEL 687 was granted to Gold Hydrogen in July 2021. An airborne gravity-magnetic survey was flown in March-April 2023 and soil gas surveys were carried out by Gold Hydrogen and CSIRO along roadsides in April 2023.

Gold Hydrogen spudded Ramsay 1 on 11 October 2023, close to the Ramsay Oil Syndicate Bore which was drilled in 1931 and recorded up to 84% hydrogen. Ramsay 1 is the first well drilled in Australia and one of the few globally specifically targeting natural hydrogen. On 31 October 2023, Gold Hydrogen reported to the ASX “Testing and laboratory results measured air-corrected hydrogen at 73.3% at 240m below ground level, consistent with the 76% air-corrected concentration of hydrogen reported in the Ramsay Oil Bore 1 in 1931. These measurements validate historical results and confirm the presence of a hydrogen play at shallow depths in the Ramsay Project area. Helium was also detected with an air-corrected content of 3.6% at 892mMD depth.”

The well reached a total depth of 1005m in crystalline basement (Hiltaba Suite) and encountered faults and fractures which Gold Hydrogen indicated may form pathways for migrating hydrogen. Bourdet et al. (2023) examined fluid inclusions from the Roxby Downs granite, of the same age and magmatic origin as the Hiltaba Suite and concluded that “the dissolved hydrogen in water inclusions, the hydrogen gas inclusions and the presence of magnetite and hematite mineralization in the granite are together indicative of an active hydrogen generation system within the Roxby Downs granite”.

Gold Hydrogen drilled Ramsay 2 in November 2023 to a total depth of total depth of 1068 m, approximately 500m from Ramsay 1. The company announced to the ASX on 6 December 2023 that elevated hydrogen and helium (6.8%) contents have been measured in raw gas samples from Ramsay 2.

The American Beach Oil Bore was drilled to a total depth of 292m in 1921 in the Hundred of Dudley – there’s no surveyed location data so DEM have used L.K. Ward’s description to give it an approximate location. Ward visited the bore and took gas samples in 1931 for analysis, the sampling methodology and volume recovered was not reported. Kanmantoo Group metamorphic basement occurs at a depth of 89 m and is the potential source of the hydrogen. Although PEL 687 overlies Kangaroo Island, Gold Hydrogen are focussing exploration activity on the Ramsay area of Yorke Peninsula.

The fairy circles identified by Moretti et al. (2021) are roughly circular, pink ephemeral salt lakes (Jack, 1921) that occur on the downthrown side of the Warooka Fault and elsewhere on Yorke Peninsula and Kangaroo Island (MAITLAND and KINGSCOTE 1:250,000 Map sheets and MAITLAND Explanatory Notes).

Figure 2. Otway Basin, South Australia. Depth to top basement structure map, with location of selected wells.

Potential exploration methodologies

Screening

• Company exploration reports, well completion reports, maps, geophysical surveys, datasets, historical records (SARIG, PEPS).
• Satellite imagery/Google Earth to identify possible seeps.
• Source rocks – solid geology: mafics, granites, iron and uranium – geological maps, existing gravity, radiometric and aeromagnetic datasets.
• Seals - subsurface salt, but can shales (Watkins et al, 2022) or aquifers seal hydrogen?
• Cores – fluid inclusions, mineralogical studies.
• Analyses of existing gas samples (e.g. Boreham et al, 2021, 2022).

Field work

• Licence grant.
• Environmental approvals, stakeholder engagement, access notifications etc.
• Soil gas measurements - (e.g. Moretti et al. 2021, Truche et al. 2019). The CSIRO’s Dr Ema Frery is currently researching field methodologies to better understand Australian hydrogen systems (e.g. Frery et al. 2022).
• 24/7 monitoring of fairy circles/seeps (Moretti et al, 2021).

Surveys

• Geophysics – aeromagnetic, gravity, radiometric, resistivity surveys, magnetotelluric surveys, ambient noise tomography, seismic.

Drilling

• Well bore design, engineering, drilling operation planning.
• Site preparation.
• Drilling, testing operations utilising specialised hydrogen detection equipment (e.g. Buru’s Currajong 1 and Rafael 1 exploration wells drilled in 2021).
• Site rehabilitation or preparation for production activity.

Natural hydrogen legislation

On 11 February 2021 the Petroleum and Geothermal Energy Regulations 2013 were amended to declare hydrogen, hydrogen compounds and by-products from hydrogen production regulated substances under the Petroleum and Geothermal Energy Act 2000 (PGE Act). Companies are now able to apply to explore for natural hydrogen via a Petroleum Exploration Licence (PEL) and the transmission of hydrogen or compounds of hydrogen are now permissible under the transmission pipeline licencing provisions of the PGE Act (Fig. 1).  The PGE Act was amended in 2023 and is now the Energy Resources Act 2023. Generation of green hydrogen is now covered by the Hydrogen and Renewable Energy Act 2023.

You can find information about current hydrogen exploration projects in Petroleum Exploration Licences in the state under Projects of Public Interest.

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Current licences

Figure 5. Map of hydrogen licences and applications with underlying petroleum tenements.

Since February 2021, over 40 ‘over the counter’ applications for petroleum exploration licences (PELs) primarily targeting natural hydrogen have been lodged (Fig. 5). The first of these licences (PEL 687) over Kangaroo Island and southern Yorke Peninsula was granted to Gold Hydrogen Pty Ltd on 22 July 2021. PEL 691 was granted to H2EX on Eyre Peninsula on 15 June 2022.

Some basins with potential for petroleum, natural hydrogen, geothermal energy and gas storage (e.g. Polda, Arrowie and Arckaringa Basins) were designated as Competitive Tender Regions (CTR) in late 2022. Previously only the Cooper and Otway basins were under CTRs for petroleum exploration. CTRs now apply to all three categories of exploration licence: petroleum (regulated substances include natural hydrogen, helium, CO₂), geothermal energy and gas storage exploration. CTRs do not affect existing licences and applications.

Underground storage

The regulatory changes made in 2021 also enabled underground storage of hydrogen and some hydrogen explorers have applied for Gas Storage Exploration Licences to secure these rights for their potential project areas. Geoscience Australia stimulated interest in the potential to develop hydrogen storage in the thick salt discovered by Mercury 1 in the offshore Polda Basin (Feitz et al. 2023), however Commonwealth and State offshore regulatory regimes require amendment to enable this activity. Duffy et al. (2023) provide a review of the importance of salt for gas storage in salt caverns (e.g. hydrogen and compressed air), CO₂ sequestration and geothermal energy generation. This map shows current gas storage licences and applications.

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Hydrogen Action Plan

South Australia’s world class renewable energy resources give the state a competitive edge in the race to supply green renewable hydrogen. In September 2019 South Australia’s Hydrogen Action Plan launched with an initial focus on green hydrogen from renewable energy sources. SA also offers a free Hydrogen Export Prospectus and Online Modelling Tool, released in October 2020.

The Office of Hydrogen Power South Australia was established in 2022 with the responsibility of overseeing the design and delivery of the South Australian Government’s Hydrogen Jobs Plan, facilitating the Port Bonython Hydrogen Hub and industry development to accelerate South Australia’s emerging hydrogen economy.

CCS and hydrogen in the Cooper Basin

Santos are progressing clean (blue) hydrogen and by 2030 aim to use Carbon Capture and Storage (CCS) technology to improve economic feasibility of clean hydrogen while reducing Cooper Basin emissions. Santos state that Moomba has “the lowest-cost carbon capture and storage project in the world” with potential to inject 20 million tonnes of CO₂ per year for 50 years.

Hydrogen in Australia

The Australian Department of Industry, Science, Energy and Resources provides information on Australia’s national hydrogen strategy, hydrogen hubs and useful web links.

Geoscience Australia has developed an Australian hydrogen mapping portal - the HEFT tool, and there is more information about the geology of hydrogen in Australia on their website.

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References

This interview with Dr Viacheslav Zgonnik, whose company has drilled an exploration well in Nebraska, gives insights into natural hydrogen exploration basics. Episode 61, 'Natural Hydrogen Wells', HydrogenNowCast, dated 16 Sep 2022.

Alexander, E., 2022. Natural hydrogen exploration in South Australia. PESA SA Branch technical meeting, 23 June 2022.

Alexander, E., 2023. Natural hydrogen regulation in South Australia. HNAT World Summit 28 November 2023.

Alexander, E., 2023. Natural hydrogen exploration in South Australia (YouTube narrated presentation). The Geological Society Natural Hydrogen Conference 5 July 2023.

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Boreham, C.J., Murray, A, Mahlstedt, N. and Horsfield, B, 2022. Geologic H₂ from overmature organic sources: numerical modelling application in the Cooper Basin, Australia. Goldschmidt Conference 10-15 July 2022 Honolulu, Hawaiʻi, USA.

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Zgonnik, V., 2020. The occurrence and geoscience of natural hydrogen: a comprehensive review. Earth Science Reviews 203, 103140.

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