Until very recently, I was unaware as a geologist that
hydrogen can occur in significant volumes as a natural reservoir gas to be able
to be produced. Hydrogen has developed quite a color scheme: black = coal
sourced; brown = biomass sourced; gray = natural gas sourced; blue = natural
gas w/carbon capture; green = renewables powered electrolysis; turquoise =
combo of renewables and blue H2 such as methane pyrolysis; pink = nuclear
sourced; gold = H2 from wells in depleted oil reservoirs. Natural hydrogen has
been proposed to be called ‘white hydrogen’.
Hydrogen is
the most abundant element in the universe. However, free hydrogen in nature at
significant volumes has long been thought to be quite rare. It may not be as rare as
thought. Hydrogen is quite reactive and diffuses quickly. Its high reactivity makes
it seemingly less likely to occur in a pure gaseous form. That may not be wholly
true. H2 has not been looked for or recorded in many chemical analyses of subsurface
gases and it may occur in different conditions than hydrocarbons or mineral
ores so many potential accumulations may be very much under-explored. It is
thought that free hydrogen in the vicinity of hydrocarbon systems will become
bound up with those hydrocarbons but may appear unbound where there are no
hydrocarbon systems.
“The processes that create natural hydrogen are not fully
understood. It is found in a large range of geological settings – in oceanic
and continental crust, volcanic gases and hydrothermal systems.”
Mechanisms of subsurface
hydrogen generation are thought to include:
● degassing of magmas and deep-seated hydrogen from the
Earth’s core and mantle
● cataclasis
● oxidation of divalent iron (Fe2+) rich minerals and lithologies through rock-fluid interaction (e.g. serpentinisation); equivalent redox reactions may also occur using other multivalent elements such as sulfur, nitrogen and manganese
● natural radiolysis of water
● biogenic and abiogenic decomposition of organic matter
● a combination of coincident genetic factor
Hydroma’s website gives the four main means of generating
hydrogen: serpentinization, radiolysis (separation of H2 from water), degassing
from earth’s crust, and rock crushing along fault lines.
It is found in
some geothermal brines. Natural hydrogen can have both abiotic (non-life) and
biogenic sources. Natural hydrogen has been ignored by explorers. However, it has
been known to occur in non-negligible quantities in a few places for about a
hundred years. It occurs in both sedimentary and igneous rock settings. It has
yet to be determined if natural hydrogen occurs in quantities that can be
commercially produced, aside from the accumulation in Mali, but it seems quite likely.
One
interesting factor in natural hydrogen exploration is that hydrogen can occur with
associated helium, which is a commercial drilling target as well. The company Natural
Hydrogen Energy, LLC, with offices in France and the U.S., is pursuing hydrogen
and helium prospects. Helium is a rare gas and demand currently exceeds supply.
The company believes they can produce both hydrogen and helium commercially.
Hydrogen was
known in the past from some natural seeps. There was a seep into a German salt mine
in the early 1900’s that kept up a similar rate for several years. A
groundwater aquifer in Mali in West Africa was known to contain H2 from the
late 1980’s but in 2012:
“Hydroma Inc. (a Canadian company previously known as
Petroma Inc.) re-discovered a hydrogen-rich aquifer in Bourakébougou, Mali and,
moreover, managed to flow the natural hydrogen to the surface in commercial
quantities.”
The hydrogen accumulation in Mali has a content of 98%
H2. It is apparently trapped and sealed differently than local hydrocarbons so
there may be differences in the trapping and sealing mechanism for hydrogen vs.
hydrocarbons.
In 2019
Natural Hydrogen. LLC drilled an exploration well in Nebraska, the Hoarty NE3,
that reported hydrogen. Volumes are unknown but the well is apparently still
being evaluated. The target is hydrogen sourced in Precambrian basement rocks.
In nearby Kansas there have been hydrogen shows recorded:
“In Kansas, hydrogen is present in several zones within late Mississippian sandstone, siltstone and limestone units, and an artesian aquifer directly overlying the Precambrian basement. Gas pressures and chemistry in the various Kansas drillholes appear to vary temporally and can be influenced by restricting exchange between the aquifer and the basement (Coveney et al. 1987; Guelard et al. 2017), suggesting recharge from an active hydrogen flux which may be migrating up adjacent fault structures from a deeper source (Coveney et al. 1987; Guelard et al. 2017).”
The hydrogen
in Kansas and Nebraska is associated with the Mid-Continental Rift System, a
long buried, failed rift system. Basement hydrogen outgassing is known around
the world from active oceanic rift systems, ie. the Mid-Ocean Ridges. The H2 in
Kansas occurs with N2, He, and occasionally CH4 (methane). The proposed
mechanism for hydrogen generation there is “deep crustal H2: water reduction
associated to iron oxidation in the Precambrian basement.” Some of the
hydrogen was also thought to be generated by chemical reaction within the
well-tubing which has high amounts of reduced iron and/or dissolved organic
carbon in the water.
Natural Hydrogen
Energy, LLC seems to think that hydrogen reservoirs are fed in such a way that
they will not deplete like hydrocarbons do after significant production. They
estimate a production cost for natural hydrogen at $0.1-1 per kg. Associated
helium production is also expected to improve economics.
As noted, natural
hydrogen can be generated in a number of geologic conditions. In the discovery
in Mali the hydrogen was sealed by dolerite that formed a volcanic sill. From
the article in Geoscientist magazine:
“Denis Briere introduced the concept of Hydrogen
System Logic (as opposed to the traditional approach of Petroleum System
Logic). Derived from his work on the Bourakébougou discovery in Mali, in the
Hydrogen System Logic model the hydrogen reservoir is not a pressurised
stagnant reservoir trapped under impervious shale barrier, but a slowly flowing
accumulation being regenerated in the fractures and matrix. Natural hydrogen is
periodically replenished via migration of hydrogen through fractures and then
the subsequent diffusion into a host rock.”
It is not known whether hydrogen is stored as gas
reservoirs over geologic time periods as oil and gas is. It is thought that
salts/halite, intrusions like the dolerite sills in Mali, and clay-rich rocks
like shales could act as hydrogen seals and barriers to migration. The Mali hydrogen
accumulation is thought to be more than 8km in areal extent and to be
producible from five stacked reservoirs. The potential of this prospect is that
it will be cheaper to produce than to manufacture hydrogen, either through
electrolysis or through fossil fuels. 24 wells were drilled in 2017-2019 to
assess the accumulation. Hydroma began a new drilling campaign in Mali in May
2022. Thus far gas with over 95% H2 content has been recovered in all wells drilled.
Hydrogen generation
in the subsurface may be much different than that of hydrocarbons. Betina
Bendall writes that:
“It is possible then that some natural hydrogen accumulations are long-lived dynamic systems resulting from continuous, diffuse generation of hydrogen approaching a steady state in the crust, similar to conductive geothermal systems, rather than static accumulations more akin to oil and gas fields. The permeability of individual rock layers and the presence of aquifers, together with subsurface hydrogen-fixing reactions, may mediate the balance between rates of migration from active generation sites and rates of continuous surface seepage.”
Natural
hydrogen exploration is taking off in some parts of the world but has yet to be
supported at the level of decarbonized manufactured hydrogen, ie. blue and
green hydrogen. There has been some legislative support in South Australia
where several exploration wells have been permitted. High hydrogen content was
found in gas samples in old wells. In two shallow wellbore examples hydrogen
makes up to 84% of the gas which also contains nitrogen and lesser amounts of
oxygen, CO2, and methane.
“Bendall
(2022) provides a recent synopsis of the geology of natural hydrogen
occurrences and exploration methodologies. Potential exists for natural
hydrogen plays in South Australia – 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 generation from
the oxidation of Fe(II) bearing mineral such as siderite, biotite, or amphibole
by water) and uranium-rich basement with hydrogen generated by radiolysis of
water (Gaucher, 2020).”
Salt/halite
and possibly volcanic intrusives are considered the best seal rocks for
hydrogen in South Australia. Despite H2 being a small molecule with low density
it has a similar seal capacity to methane and better than CO2. This is, of
course, why hydrogen can be successfully stored in underground storage
reservoirs, particularly salt dome storage fields as exist in the U.S.
Yet to be
determined are reserves estimates of local and regional deposits and what the
carbon intensity of drilling and producing natural hydrogen will be. Certainly,
the carbon intensity will be far less than natural gas, since burning hydrogen
produces no CO2 and there are no fugitive ghg emissions. One preliminary analysis
suggests that it will be much less carbon intensive (4 times less) than even
green hydrogen. That will depend on the production volumes and length of time
the wells produce. However, the energy produced per well or per projects will likely
be far less than natural gas and the energy content of hydrogen is also much
less (about two-thirds) than that of natural gas.
Betina Bendall
offers the following guidelines for exploring for natural hydrogen:
● Target basement areas which contain Fe2+ -rich and/or uranium-rich rocks as these have potential for generating hydrogen via oxidation and radiolytic processes, respectively (e.g. Archean greenstone and Precambrian basement terranes).
● If these potential source areas are fractured and seismically active, then deep-seated faults can act to both channel migrating hydrogen from deeper sources to surface and introduce water downward for further chemical reaction with exposed Fe2+-rich rocks.
● A sedimentary overburden may enable entrapment of migrating hydrogen, particularly if aquifer systems and/or evaporites are present in the sedimentary sequence. Evaporites may also constitute a hydrogen source.
● Targets may be associated with surficial hydrogen seeps. Seeps can be blind or coincident with visible subcircular topographic depressions on the metre to kilometre scale, often associated with perturbed vegetation cover. Soil gas monitoring over extended periods can identify an active hydrogen flux.
● Routine monitoring for hydrogen in mines, and groundwater, oil and gas drillholes is a worthwhile practice which should be encouraged to bolster our understanding and existing records of natural hydrogen occurrences.
Company HHe
Exploration Technologies Ltd. Utilizes unmanned aerial systems (UASs), or
drones, to detect methane, hydrogen, and helium in anomalous quantities. They utilize
a combination of optical gas imaging (OGI) and ambient air analysis in tandem
to detect minute hydrogen and helium anomalies. They have entered into joint
venture agreements to explore the ambient air over certain areas, including South
Australia.
References:
Natural
hydrogen: the new frontier. Phillip J. Ball and Krystian Czado. Geoscientist. March
1, 2022. Natural
hydrogen: the new frontier - GEOSCIENTIST
Hidden
hydrogen might be the key to carbon-free fuel for future generations. Zeleb.es.
The Daily Digest. MSN. Hidden
hydrogen might be the key to carbon-free fuel for future generations (msn.com)
Hydrogen
in Australian natural gas: occurrences, sources and resources. Christopher J. Boreham A C, Dianne S.
Edwards A, Krystian Czado B, Nadege Rollet A, Liuqi Wang A, Simon van der
Wielen A, David Champion A, Richard Blewett A, Andrew Feitz A and Paul A.
Henson A. Journal of the Australian Petroleum Production & Exploration
Association (APPEA). Vol. 61. July 2021. CSIRO PUBLISHING | The
APPEA Journal
Natural
Hydrogen. Government of South Australia. Natural
hydrogen | Energy & Mining (energymining.sa.gov.au)
Current
perspectives on natural hydrogen: a synopsis. Betina Bendall. Energy Resources
Division, Department of Energy and Mining. MESA Journal 96, 2022 (37–46).
Current
perspectives on natural hydrogen: a synopsis (pir.sa.gov.au)
Natural
H2 in Kansas: Deep or shallow origin? J. Guélard, V. Beaumont, V. Rouchon,09
F. Guyot, D. Pillot, D. Jézéquel, M. Ader, K. D. Newell, E. Deville. Geochemistry,
Geophysics, Geosystems. Volume18, Issue5. May 2017. Pages 1841-1865. Natural
H2 in Kansas: Deep or shallow origin? - Guélard - 2017 - Geochemistry,
Geophysics, Geosystems - Wiley Online Library
Discovery
of a large accumulation of natural hydrogen in Bourakebougou (Mali).
Alain Prinzhofer, Cheick
Sidy Tahara Cissé, Aliou Boubacar Diallo. International Journal of Hydrogen
Energy. Volume 43, Issue 42, 18 October 2018, Pages 19315-19326.
Discovery
of a large accumulation of natural hydrogen in Bourakebougou (Mali) -
ScienceDirect
Press
release from Hydroma Inc. August 6 2022. New Natural Hydrogen Drilling Campaign
at Bourakougou. Hydroma-Press-Release-August-6th-2022-EN-.pdf
NATURAL
HYDROGEN ENERGY LLC – PIONEER OF HYDROGEN EXPLORATION. Key Player’s Insights.
H-Nat Summit 2022. Natural
Hydrogen Energy LLC – pioneer of hydrogen exploration | H-NAT SUMMIT
(hnatsummit.com)
CAN
WHITE HYDROGEN SOFTEN NET ZERO’S INCONVENIENT TRUTH? Key Player’s Insights. H-Nat Summit
2022. Can
white hydrogen soften net zero’s inconvenient truth? | H-NAT SUMMIT
(hnatsummit.com)
HHE
JUNE 2022 NEWSLETTER. Key Player’s Insights. H-Nat Summit 2022. HHe
June 2022 Newsletter | H-NAT SUMMIT (hnatsummit.com)
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