Natural Helium and Hydrogen: Why Are These Two Resources Often Found Together Underground?
Introduction
Recent analyses have highlighted that helium and natural hydrogen can be found simultaneously in certain geological formations [1], whereas these two resources are typically sought separately in very different contexts. This phenomenon is not isolated: observations made across several continents indicate that these gases share common geological environments and can coexist in certain underground systems.
Helium is recognized as a critical mineral due to its indispensable applications in the medical, technological, and scientific sectors, while natural hydrogen represents a potential source of clean energy whose global interest is growing rapidly. Their joint presence is generating increasing interest, as it is rooted in common geological mechanisms and opens the way for integrated exploration approaches.
The Geological Origins of Helium and Natural Hydrogen
Geological helium, known in its He-4 form, is the product of the radioactive decay of uranium (U) and thorium (Th) present in crustal rocks, mainly granites and organic-rich shales. This process unfolds over hundreds of millions, or even billions, of years. This is why quality source rocks are generally Precambrian — that is, from the Archean or Proterozoic eras — among the oldest on the planet.
Geological hydrogen, on the other hand, can be generated by several distinct mechanisms. The best known is serpentinization, the chemical reaction between water and ultramafic rocks at depth. An important complementary mechanism is the radiolysis of water, whereby ionizing radiation emitted by uranium- and thorium-rich rocks breaks down water molecules (H₂O) and releases molecular hydrogen (H₂).
In these specific geological contexts, conditions are met to simultaneously generate helium and hydrogen, which partly explains their joint presence in certain formations.
A Geological Cohabitation: The Link Between Helium and Natural Hydrogen
Radiolysis: A Unifying Mechanism
When fluids circulate through rocks enriched in uranium and thorium, radiolysis promotes the production of molecular hydrogen, while helium gradually accumulates through radioactive decay. These two processes can coexist in the same geochemical environment, creating conditions conducive to the simultaneous presence of both gases.
Under the effect of pressure gradients and the permeability of formations, these gases migrate through fractures and porous zones in the Earth's crust. They can thus be transported over long distances and end up associated in shared systems, often in the presence of nitrogen [1].
Shared Reservoirs
After their formation and migration, helium and natural hydrogen can accumulate in similar geological traps, such as anticlines, sealed faults, or certain stratigraphic structures. In several cases, nitrogen constitutes a dominant component of the gas and acts as a transport vector, facilitating the joint accumulation of the other gases. This gas association (He + H₂ + N₂) constitutes a recurring configuration in certain deep geological contexts, particularly in ancient basins or crystalline environments [2].
What This Means for Exploration
This geological convergence is of interest for exploration. The detection of helium in a borehole can serve as an indicator of the potential presence of natural hydrogen, and vice versa. This supports the development of integrated exploration approaches, in which a single program aims to simultaneously evaluate multiple gases of interest. Therein lies one of the most compelling opportunities of this emerging sector: a single exploration investment can potentially reveal two resources of high strategic value.
Field Observations Confirming This Co-occurrence
The geochemical mechanisms described above are supported by observations from several in-depth gas analysis campaigns, which highlight the joint presence of hydrogen, helium, and nitrogen across different geological contexts.
In the Bohai Bay Basin (China), gas analyses revealed the simultaneous presence of helium at concentrations on the order of a few hundred ppm (approximately 372 ppm) and hydrogen reaching approximately 0.34% in certain deep formations [1]. These values, while variable, illustrate the coexistence of both gases in nitrogen-dominated systems, suggesting a combined contribution of radiogenic processes and deep fluid circulation.
Also in China, the scientific borehole Songke-2, drilled in the Songliao Basin, revealed particularly variable hydrogen concentrations, ranging from approximately 1.36% to 26.89% depending on the depth analyzed [1]. Although helium is not systematically reported at these same levels, this type of system illustrates the potential for significant hydrogen production in geological contexts compatible with the presence of radiogenic helium.
More broadly, work compiled by Gluyas et al. (2025) indicates that hydrogen concentrations ranging from trace amounts to several percent can be observed in uranium- and thorium-rich environments, often in association with helium and nitrogen [1]. Helium, for its part, is generally measured at concentrations ranging from ppm levels to higher concentrations in certain systems, depending on the age of the rocks and trapping conditions.
An independent synthesis of natural gas occurrences also highlights that the H₂ – He – N₂ association is observed in a variety of geological contexts, particularly in fractured crystalline basement rocks and intracratonic basins [2]. These environments favor both gas production (via radiolysis or water-rock reactions) and migration through deep fracture networks.
These studies also emphasize that the hydrogen detected in these systems may be of multiple origins (radiolysis, serpentinization, mineral reactions), while helium is primarily of radiogenic origin. Their coexistence in the same reservoir therefore reflects the superposition of several geological processes operating at different spatial and temporal scales [2].
Finally, it is important to note that these systems exhibit strong variability. Hydrogen and helium concentrations can fluctuate depending on depth, geological structure, fluid circulation, and the capacity of rocks to trap gases. This variability explains why some accumulations show significant concentrations, while others remain at trace levels, despite similar formation conditions.
An Association That Illuminates Exploration Strategies
The co-occurrence of helium and natural hydrogen underground is explained by common geological mechanisms, particularly in uranium- and thorium-rich environments where processes such as radiolysis contribute to their formation and accumulation. Observations made in different regions of the world confirm that this association falls within recurring geological contexts.
The publication of the first USGS map on geological hydrogen in January 2025 [3], combined with initiatives from IFPEN, the IEA, and other institutions [4], reflects a paradigm shift in the way the scientific and industrial world approaches these geological resources. What was once considered two distinct exploration sectors is now converging toward an integrated approach, where a single borehole can reveal two resources of high strategic value.
To explore these topics further, Squatex's articles on natural hydrogen and on its renewable potential offer complementary perspectives. You can also follow Squatex's news and publications directly on LinkedIn.
References
[1] Gluyas, Jon, et al. "Exploring for Hydrogen, Helium and Lithium: Is It as Easy as 1, 2, 3?" Geoenergy, Geological Society of London, 2025. Elsevier, https://www.sciencedirect.com/science/article/abs/pii/S030626192500128X.
[2] "Investigative Research for Occurrences of Hydrogen, Helium, Methane and Associated Gases." PubMed Central, 2025. National Institutes of Health, https://pmc.ncbi.nlm.nih.gov/articles/PMC12963835/.
[3] "USGS Releases Map Identifying Potential Geologic Hydrogen Deposits in the US." S&P Global Commodity Insights, 17 January 2025. https://www.spglobal.com/commodity-insights/en/news-research/latest-news/energy-transition/011725-usgs-releases-map-identifying-potential-geologic-hydrogen-deposits-in-the-us.
[4] "Focus on Natural Hydrogen: IFPEN Involved in IEA and DGEC Initiatives." IFP Énergies Nouvelles, 2024. https://www.ifpenergiesnouvelles.com/article/focus-natural-hydrogen-ifpen-involve-iea-and-dgec-initiatives.
