Geologic (white or gold) hydrogen has been in the news regularly in recent years, particularly since the reporting and production of hydrogen in the Bourakebougou field in Mali, Africa. This edition of Core Elements focuses on geologic hydrogen—in the United States, globally, and in a new find in the Philippines.
Rasoul Sorkhabi
Editor, Core Elements
Measuring Global Hydrogen Resources
Photo sources: USGS
How much natural hydrogen exists on Earth? Nobody knows, but a rough estimate by Zgonnik in his 2020 article placed the global generation of natural hydrogen in all geological environments at 15–31 million metric tons.
In December 2024, American geologists Ellis and Gelman provided another assessment published in Science Advances.
Model parameters:
The USGS prediction model takes into account:
Annual generation of natural hydrogen from deep and shallow sources
Faction of hydrogen detained in traps
Residence time in reservoirs
Proportion of biotic and abiotic loss
Rate of anthropogenic production
The calculated outputs of the model include:
The amount of hydrogen stored in reservoirs at a given time
The hydrogen flux to the atmosphere
Predictions:
Using a stochastic model, the authors reported that there was a wide range of potential in-place hydrogen values, ranging from 103 to 1010 million metric tons. The mean value was 5.6 million metric tons.
The authors acknowledge that most of this potential hydrogen will be impractical to produce; however, if two percent of the estimated geologic hydrogen resource can be recovered, that would amount to 100,000 metric tons, which contains 1.4 x 1016 megajoules.
This is twice as much as energy as is stored in the proven natural gas reserves (8.4 x 1015 megajoules).
Limitations:
The USGS model results are first-order approximations of the potential geologic hydrogen resource.
The model makes no predictions about the spatial distribution of hydrogen in the subsurface, which is the most critical factor to exploration and economic viability.
Go deeper: Read the full article in Science Advancesonline.
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The U.S. Geological Survey recently released its Professional Paper 1900 about prospectivity mapping for geologic hydrogen in the United States. Let’s take a look at what they did and their methods.
Sources: The USGS team considered three modes of geologic hydrogen:
Serpentinization
Radiolysis
Deep sources that may exist in various parts of the continental United States.
Other factors:
The presence or absence of “source layers” was evaluated by regional geological and geophysical indicators such as ophiolite belts, uranium deposits, faults, tectonic settings, heat flow, and magnetic anomalies.
The possibility and type of “porous reservoirs” (sedimentary or non-sedimentary) and “seals” (salt, sedimentary, and non-sedimentary) were also added to the source layers.
A probability metric called “chance of sufficiency” (0=impossible to 1=certain) was introduced to the 21 source-reservoir-seal layers.
The methodology also incorporates the possibility and extent of lateral migration of hydrogen.
Risk analysis and mapping:
USGS assumed that all three components (source. reservoir, and seal) should be present for a successful subsurface accumulation of geologic hydrogen.
All layers were mapped on an initial 1-kilometer square grid; the final risk analysis was performed on a slightly coarser, 5-kilometer square grid.
The Matlab script to calculate hydrogen prospectivity is given at the end of the report.
The end products are stochastic maps plotted for 5,000 Monte Carlo simulations of P10 (10 percent probability), P50, and P90.
Location, location, location: Of the 48 lower states, 30 states sit atop some sort of geologic hydrogen.
Highly prospective areas overlap with some of the major tectonic zones, including the:
Precambrian Midcontinent rift zone, from Kansas and Iowa to Michigan
Colorado Plateau and Rocky Mountain States
Williston basin saddling Montana and North Dakota border
Kentucky and the Appalachian trend from Tennessee to West Virginia
Permian Basin in Texas and New Mexico
Western California accretionary wedge
Why it matters: This is the first country-scale prospectivity map for geologic hydrogen in the United States.
Go deeper: Read the USGS Professional Paper 1900 online.
Geologic Hydrogen in the Philippines
N.Minton/ Shutterstock.com
A recent article by Aquino and colleagues has put the Philippines on the map for geologic hydrogen production. The situation is similar to the Samail Ophiolite in Oman where serpentinization of mafic rocks releases hydrogen.
Zambales ophiolite:
The Middle Eocene (45–43 Ma) Zambales ophiolite, located in the western province of Zambales, is bounded by faults separating the Masinloc, Cabangan, and San Antonio massifs.
It is a complete ophiolite suite comprised of a succession of volcanic rocks, dike-sill complexes, cumulates, and residual harzburgites and lherzolites.
Hydrogen flux measurements:
Researchers conducted field measurements of hydrogen outgassing in two bubbling springs and one gas seep in June and July 2024.
The two bubbling springs, Mangatarem and Botolan, are hosted by gabbro and peridotite in the Coto Block. They were first reported in 2012.
The hydrogen seep, Nagsasa, is hosted by peridotite in the San Antonio massif. It was first reported in 2006.
Findings:
The Nagsasa gas seep consists of 56 percent hydrogen and 39 percent methane. The gases are venting out of fractures rocks. There are a few smaller seeps near Nagsasa.
The researchers estimate up to 808 tons of hydrogen being released annually from the Nagsasa and nearby seeps. For comparison, the Mali hydrogen field has an annual flux of 45 tons.
The Nagsasa hydrogen seeps generate 1400 grams per square meter per day. This is one of the highest fluxes of natural hydrogen per unit area ever reported from ophiolites.
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Now, we return to our weekly quiz questions. This week’s question is: What are the most abundant and the rarest elements in the universe and on Earth?
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