Geologic Hydrogen

Recent successes in the exploration, drilling, and discovery of geologic hydrogen have generated notable excitement. This new energy resource has the potential to make an important contribution to our nation’s energy supply, resiliency, and security. Contemporary studies of geologic hydrogen have a common theme of suggesting places where it might be found or even more specifically, what rocks in what geologic formations may contribute to its formation — either naturally or via artificially induced means. This vital ongoing body of work sets the stage for imagining what may be possible with vast available quantities of naturally occurring hydrogen in the subsurface. While acknowledging current approaches to characterizing geologic hydrogen, this report advances the discussion by suggesting next steps, including the critical science and engineering necessary to make geologic hydrogen an affordable and reliable part of the U.S. energy portfolio.

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Industry has used hydrogen for over 100 years in oil and gas refining, rocket fuel, and fertilizer production. For decades, it was even utilized in “town gas,” a mix of natural gas and hydrogen that served municipal heating and lighting needs before the switch to a natural gas-only grid in the 20th century. More recently, hydrogen has been proposed as a potential energy source for transportation and electricity generation.

Hydrogen can be produced by splitting water or natural gas, requiring significant amounts of energy, or by natural processes within the Earth (Klein et al., 2020). Geologic hydrogen refers to hydrogen sourced from underground reservoirs or released from underground rocks by replicating natural processes. Recent U.S. Geological Survey (USGS) reports (Ellis & Gelman, 2024; Gelman et al., 2025) suggest that geologic hydrogen exists in quantities large enough to make a significant contribution to the U.S. energy portfolio.

Recent interest in geologic hydrogen traces back to 1987 when a water well drilled in Mali, West Africa, unexpectedly produced a gas that was more than 97% hydrogen (Prinzhofer et al., 2018). More than 30 years later, the discovery was presented in scientific literature, describing how the well’s hydrogen production had been utilized to provide a village’s electricity. Recent scientific reviews (e.g., Boreham et al., 2021; Zgonnik, 2020) have documented the global occurrence of hydrogen in wells drilled for oil, natural gas, and water (Figure 1).

In early 2022, multiple opinion articles were published that suggested hydrogen could be found in various forms in the subsurface (Moretti & Webber, 2021; Webber, 2021). Then in 2023, a modern-day watershed article appeared in Science magazine sporting an iconic natural flame burning on rocky ground of Mount Chimera in Turkey (Hand, 2023). The scene is a combined hydrogen and methane seep in Turkey that has reportedly burned for centuries. The Science piece seemed to ignite palpable interest in the notion of geologic hydrogen – free for the taking in the subsurface, suggesting the promise of an affordable way to harvest large quantities of free energy for an alternative way of powering our global society. Since then, efforts have been made in bringing geologic hydrogen’s promise to reality.

What is geologic hydrogen?

Hydrogen is the third most abundant element in the Earth’s crust, occurring mostly in the form of water, in oil and natural gas, and in mineral structures like hydrates and hydroxides. Hydrogen can also occur as a free gas in the subsurface alongside methane, helium, nitrogen, hydrogen sulfide, and many other gases. The term geologic hydrogen can refer to either hydrogen occurring naturally in the Earth (natural hydrogen) or generated by engineered activities (stimulated hydrogen). The scientific community acknowledges that natural hydrogen exists in the Earth and that it is generated via three primary subsurface processes, as shown in Figure 2: hydrothermal alteration, radiolysis, and deep mantle degassing (Klein et al., 2020).

Current knowledge suggests hydrothermal alteration (or serpentinization) is likely the largest source of naturally occurring subsurface hydrogen. Hydrogen is liberated as water reacts with reduced iron (iron 2+) in deep iron-rich continental and oceanic rocks, converting it to oxidized iron (iron 3+) and producing serpentine minerals in the process (a.k.a. serpentinization). Radiolysis produces hydrogen as naturally occurring radioactive elements split water molecules. Found in abundance in deep, quartz-feldspar-rich continental rocks, these elements include uranium, thorium, and potassium. Deep mantle degassing may come from the exsolution of hydrogen gas from deeper layers in the continental crust along faults, though some speculate this source of natural hydrogen occurs in smaller amounts.

Once formed, geologic hydrogen can accumulate in fractures and voids locally or elsewhere by migrating horizontally or vertically, similar to how natural gas accumulates in underground reservoirs. This type of geologic hydrogen would be the easiest to produce as most of the needed collection technologies and methods already exist in the oil and gas industry. Like in the oil and gas industry, challenges would lie in finding the deposits.

In addition to naturally occurring hydrogen, the term geologic hydrogen also encompasses hydrogen that has been artificially stimulated or stored. Stimulated hydrogen can be made in two ways: 1) injecting fluids into rocks that can liberate hydrogen; and 2) processing rocks from a mine (including legacy mine wastes) in industrial facilities to liberate hydrogen, like one might process a copper ore to extract its metal content. This method of producing geologic hydrogen would be the easiest to source — we have numerous maps of where candidate rocks exist — but the drilling and stimulation technologies needed would likely require significant modification from the mining and geothermal industries.

Currently, stored hydrogen in the subsurface exists only at a small scale. While some commercial entities store hydrogen in underground salt caverns, only three facilities of this type exist in the U.S. compared to the nation’s more than 400 natural gas storage facilities. Several hydrogen storage caverns are currently under construction in Texas and Utah, while several more have been permitted in Texas and Louisiana. Although an active area of research, currently no facilities store hydrogen in underground porous media reservoirs. Comparatively, porous media reservoirs mak up 90% of the current gas storage fleet.

The U.S. Department of Energy (DOE)-funded Subsurface Hydrogen Assessment, Storage, and Technology Acceleration (SHASTA) project brings together the Pacific Northwest National Laboratory, National Energy Technology Laboratory, Lawrence Livermore National Laboratory, and Sandia National Laboratories to evaluate the technical, economic, and regulatory aspects of derisking the storage of hydrogen underground. Many project results (e.g., how microbes react to hydrogen underground, how hydrogen flows in underground reservoirs, regulations for surface hydrogen transport) are source-agnostic and thus directly applicable to geologic hydrogen.

This report addresses scientific and engineering investments needed at the national scale to realize the full potential of geologic hydrogen. These critical areas of research investment include advancements in subsurface reservoir modeling, improved subsurface access, effective systems engineering across the hydrogen supply chain, and better means of hydrogen sensing. Today’s ongoing research investments are largely focused on subsurface reservoir management, which includes locating areas of potential natural hydrogen accumulation, mechanisms by which hydrogen is geologically produced, and efforts to reproduce reactions that drive geologic hydrogen production in the subsurface along with techno-economics of such notional stimulation systems. We briefly summarize these in the next section, followed by potential areas for our nation’s efforts to advance research in making geologic hydrogen a vital part of America’s energy security.

Current geologic hydrogen research activities

As of 2023, 40 companies were searching for natural hydrogen deposits, up from just 10 in 2020 (Rystad Energy, 2024). Current US exploration and drilling occurs most intensely along the Midcontinent Rift in Kansas, Nebraska, and Iowa. One company, Koloma, has attracted over $300 million in capital, including funding from the Bill Gates-backed venture capital firm Breakthrough Energy (Meredith, 2024). Industry is investing considerably in the areas of cross-company collaboration, partnering, and venture capital; research into extraction methods; exploration to locate and recover geologic hydrogen; and planning for eventual availability and use of geologic hydrogen.

The federal government also began supporting geologic hydrogen research. In 2024, the U.S. DOE’s Advanced Research Projects Agency–Energy (ARPA-E) funded ~$20 million across 16 projects (ARPA-E, 2024) to research stimulating the production of geologic hydrogen via subsurface engineering. DOE national laboratories have also invested portions of their internal research and development budgets to study production processes and mechanisms to capture and utilize geologic hydrogen.

The U.S. Senate Committee on Energy and Natural Resources held a 2024 hearing to examine opportunities and challenges associated with developing geologic hydrogen in the U.S., which included witnesses from DOE APRA-E, the USGS, and the geologic hydrogen exploration company Koloma (Senate Committee on Energy & Natural Resources, 2024). The witnesses each echoed the promising nature of geologic hydrogen, the challenges associated with understanding how to produce it economically, and what actions each of their respective organizations were undertaking in the effort.

Since that Senate hearing, a series of scientific papers have illustrated further advancements in the thinking surrounding geologic hydrogen. USGS released its long-awaited prospectivity map of the potential for geologic hydrogen in the conterminous U.S., which is based on several factors, including the locations of rocks suitable for producing hydrogen, potential migration routes for hydrogen, and potential reservoirs and caprocks (Gelman et al., 2025). USGS also published a paper that provided a mass balance method to estimate the resource potential of in-place hydrogen that may be recoverable (Ellis & Gelman, 2024). These estimates and approaches to prospecting or quantifying geologic hydrogen are based on what has become normalized scientific thinking on the occurrence of subsurface geologic hydrogen through publications, discussions in Congress, projects within ARPA-E, and other venues.

Advancing geologic hydrogen research

The primary questions driving recent geologic hydrogen research are 1) How can we find and recover subsurface hydrogen, and 2) Can we replicate (or stimulate) natural hydrogen production processes using engineered systems. Advanced research must seek to answer these questions through characterization of rock and mineral samples, systematic experimentation examining conditions favorable for hydrogen generation, and production technology development.

The key challenge to making geologic hydrogen a beneficial reality is understanding where hydrogen is being generated and how. Discovering deposits of gaseous geologic hydrogen via drilling may be the best-case scenario because the existing oil, gas, and water well drilling industries could be employed to develop it. Otherwise, whether one stimulates natural production processes through engineered approaches deep in a well or by processing ore or mine waste, significant new industry capabilities must be developed.

While data documenting the natural occurrences of large volumes of geologic hydrogen are scant, our best current understanding is that hydrogen should accumulate in the subsurface like other gases (e.g., methane, helium, nitrogen, hydrogen sulfide). This reasoning stems from previous discoveries of hydrogen when drilling for other resources like water and hydrocarbons. Furthermore, the hydrogen molecule is larger than helium, so if helium can be trapped in subsurface deposits (which we have found in thousands of wells in the U.S.), hydrogen should as well.

Several arguments have been used to support the lack of significant hydrogen discoveries during pas drilling. First, natural gases in production-level systems historically were not often tested for hydrogen. Hydrogen burns like methane at most concentrations, so a separate test was not deemed necessary. Second, recent work by the USGS has suggested that any hydrogen entering a hydrocarbon deposit will likely be consumed through upgrading the trapped hydrocarbon to shorter chain molecules (Ellis & Gelman, 2024). Third, the highest abundance of hydrogen will likely be in igneous and metamorphic rocks that have rarely been drilled or sampled for gases.

Understanding what geological, hydrological, and geochemical processes cause the natural production of hydrogen can help us narrow the scope of rocks to investigate. Also, understanding how geochemical, microbiological, and other processes influence hydrogen behavior (e.g., consumption, trapping, migration) in the subsurface can illuminate natural settings for exploration and discovery, as well as guide its collection from the ground. Alternatively, this knowledge could enable the artificial stimulation of these processes to release hydrogen in an engineered manner.

Critical science and engineering needs for geologic hydrogen

There are several key areas where new knowledge is needed to support the development of geologic hydrogen resources. Knowing that hydrogen production can be stimulated from certain types of rocks provides an existing scientific basis to launch more advanced research to refine the methods and materials used in that process.

A desired end state for geologic hydrogen would be one where a reliable percentage of the U.S. energy grid is powered by engineered systems that gather, condition, process, compress, store, and utilize hydrogen from subsurface reservoirs in porous rocks, fault-based conduits from the deep subsurface, or produced hydrogen from artificially induced stimulation. Research priorities to achieve this end state include: 1) continuing to develop tools and methods for geologic hydrogen reservoir management and modeling, 2) improving techniques for drilling and stimulating geologic hydrogen deposits, 3) advancing techno-economic and other systems models for geologic hydrogen’s role in current and future energy systems, and 4) advancing sensing methods to find geologic hydrogen and monitor production.

Learn more about Sandia’s geologic hydrogen capabilities

Subsurface reservoirs

To realize the above end-state scenario, research is needed to deepen our understanding of subsurface hydrogen reservoirs. Gaseous hydrogen in the subsurface is produced by the various natural processes described earlier in this paper as well as by artificially inducing or accelerating these natural processes (i.e., stimulation). Although researchers have identified candidate rock types most likely to host geologic hydrogen and those suitable for stimulation, these rocks belong on a geological spectrum governed by factors like the relative abundance of mineral types, trace element chemistry, porosity, density, and permeability that can produce different quantities of hydrogen and impurities with and without stimulation. We need to increase our understanding of production processes at the molecular and atomic levels to advance the science on effective stimulation methods and conditions.

R&D needs include:

• Analyzing candidate rock types across a spectrum of mineralogical, chemical, and physical properties to determine the most favorable mineralogical contents for natural production and artificial stimulation potential.
• Furthering our understanding of hydrogen generation mechanisms in candidate rock types at molecular and atomic levels to determine the most effective methods and conditions for stimulating hydrogen production.
• Applying science from nuclear waste disposal research on hydrogen generation from radiolysis, hydrogen movement in subsurface pore and fracture systems, simulating subsurface fluid flow, and uncertainty quantification in subsurface systems.

Closely related to advanced rock type assessment, research must advance to determine where and how industry and government may locate naturally occurring sources of free hydrogen in the subsurface. The USGS prospectivity paper is a great start, but areas of highest prospectivity need to be explored in the many elements that make up overall prospectivity. Other considerations affecting geologic hydrogen production include geochemistry and microbiological activity in different reservoir conditions. National-level test beds (i.e., laboratories-in-the-field) with data accessibility and shareability could be important tools for maturing this body of research.

R&D needs include:

• Characterizing areas with high geologic hydrogen prospectivity for their stimulation potential.
• Characterizing fault systems, geologic structures, and other potential hydrogen migration pathways and traps in the subsurface.
• Establishing consistent methods to characterize reservoir heterogeneity, assess subsurface reduction/oxidation environments, and measure the effects of geochemical and microbiological influences in subsurface natural and engineered production systems.
• Developing methods for assessing in-place and recoverable hydrogen from identified hydrogen source rocks or hydrogen accumulations.

Improving Subsurface Access

Next, geologic hydrogen development requires access to the subsurface for both exploration and storage. We must take advantage of cutting-edge drilling methods to access the subsurface in faster and less expensive ways — particularly to access deeper and harder rocks than those commonly drilled for oil and gas exploration. These new methods may be necessary to discover caches of gaseous geologic hydrogen trapped in porous media reservoirs (like sandstones and limestones), and it will likely be necessary to install large-scale stimulation systems in candidate rock formations. Further, constrained resources demand cross-cutting approaches to accessing subsurface systems for geologic hydrogen with an eye toward simultaneously developing geothermal systems and extracting critical materials.

Large quantities of captured hydrogen will also require large quantities of storage to facilitate a resilient distribution system — the same as what is needed for natural gas today. Large volume storage is best situated in the subsurface in geologic formations (e.g., porous media, depleted oil/gas wells, brine aquifers, salt caverns) or modified borehole storage concepts where local geology does not support geologic storage.

R&D needs include:

• Developing deep drilling methods to achieve efficiency and effectiveness to access, characterize, and assess geologic hydrogen prospects.
• Identifying the cross-application of cutting-edge geothermal, critical materials and geologic hydrogen stimulation in hard rock systems.
• Advancing methods to map and characterize subsurface fracture networks to assess exposed rock surface area and fluid circulation in a potential stimulation system.
• Applying decades of nuclear waste repository research where methodologies such as deep drilling and hard rock mining can be applied to the development of stimulated geologic hydrogen production systems.
• Continuing research into hydrogen storage in porous geological formations, like sandstones, where significant new knowledge has been generated over the last decade around the geochemical and geomicrobiological behavior of hydrogen in the subsurface.
• Understanding the geomechanical effects of cyclic gaseous storage on cavern and borehole system structures.
• Advancing borehole storage concepts through technology demonstrations.

Systems Analysis

Developing surface-engineered infrastructure concepts with an understanding of the economics surrounding these systems is necessary to fully capitalize on successful research, exploration, characterization, and exploitation of geologic hydrogen. A systems understanding is vital to integrate and upscale new-found resources into the nation’s energy economy — and to incentivize industry to make affordable, reliable energy security a reality.

Sensing Hydrogen

Finally, advancements in sensing may help pinpoint hydrogen seeps that could give clues to locating either gaseous hydrogen in subsurface reservoirs or the presence of conduits for hydrogen migration from deeper sources. These advancements could also suggest candidate rock formations for further exploration — and perhaps correlate to USGS prospectivity areas of interest. New scientific research and engineering is needed to sense hydrogen both at depth and at the surface. Some technology exists to detect hydrogen, so the community has a starting point.

Sensors must be applied to well drilling operations to detect the presence of subsurface hydrogen in newly drilled wellbores to increase our understanding of where geologic hydrogen occurs in gaseous form. Operational drilling procedures need to be modified to include sensing for hydrogen where it is not currently tested. Additionally, exploration-quality sensing needs to be developed for surface surveys of hydrogen seeps and to make sure engineered systems are not leaking hydrogen once developed.

R&D needs include:

• Developing sensor technologies that can be deployed via airborne or space-based platforms to differentiate hydrogen seeps from atmospheric hydrogen and to sense hydrogen at the surface over regional areas to guide exploration.
• Developing and integrating hydrogen sensing throughout engineered-surface infrastructure to detect and locate points of hydrogen leakage.

Economics of geologic hydrogen

These vital areas of research must be framed by a commonsense approach to the economics of making geologic hydrogen a reliable and affordable part of U.S. energy security. A key economic question is whether stimulated hydrogen can be produced in sufficient quantities to capture and drive industrial processes, thereby incentivizing private investment. While the cost of producing hydrogen from current methods is high, future geologic hydrogen production systems have the promise to become very competitive, as shown in Figure 5 (Ball & Czado, 2022; IEA, 2020). The R&D approaches outlined earlier may incentivize private industry to invest in projects necessary vital to making geologic hydrogen an important part of our nation’s energy security.

Furthermore, the DOE hydrogen economy roadmap did not recognize sourcing and storing hydrogen underground (Figure 6), and only focused on connecting electricity producers with hydrogen end users in the manufacturing, chemical, and refining industries through current natural gas infrastructure. This strategy failed to account for the anchoring role the subsurface has played in our national energy infrastructure as a source and store of energy and manufacturing feedstocks over the past 150 years.

The nation’s previously stated approach for building a hydrogen economy seemed to exclude the traditional upstream oil and gas industry. By not including traditional subsurface activities, this model for a hydrogen economy may adversely affect finances of small, local governments, especially in rural areas, that rely on taxes from oil and gas production. Repurposing existing subsurface infrastructure (e.g., wells, pipelines) can fast track bringing geologic hydrogen resources to U.S. energy markets. Finally, recent large deployments of solar and wind electricity-generating systems may have limitations in providing sufficient baseload power necessary for full energy security. Geologic deposits of hydrogen may be able to support small, disconnected communities or resource-intensive operations, such as critical mineral extraction and processing.

It should be noted that collaboration incorporating the expertise of the national laboratories and their partners (e.g., academia, industry, local/state/tribal governments) has the potential to dramatically advance the science and engineering of our nation’s efforts to make geological hydrogen an important part of our nation’s energy security and can serve to incentivize investment by the private sector.

Conclusion

Continued efforts around geologic hydrogen research, exploration, utilization, and system development could bring affordable, reliable, and secure energy to the U.S. economy and energy infrastructure. If the quantities of recoverable subsurface hydrogen cited by the USGS are any indicator, there is potential for significant payoff, further enabling U.S. energy independence and resilience. Compared to other hydrogen-generating technologies, such as electrolysis, geologic hydrogen has the potential for a more positive technological development outlook.

Geologic hydrogen is a high-risk, high-reward technology, facing challenges related to our limited and largely academic knowledge base and nascent ability to economically explore for, develop, and produce it. Furthermore, the possibilities for production, transportation, storage, and utilization of geologic hydrogen to drive affordable and reliable industrial processes are largely unknown. Significant, concerted R&D activities spanning multiple areas of expertise supported by focused funding mechanisms with collaborative approaches are needed to reap its rewards.

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Cover photo: Thin slice of a potential hydrogen source rock (kimberlite). Pink epoxy was added to highlight permeability pathways for stimulated hydrogen production. (Photo by Sandia National Laboratories)

Contact

Don Conley
Manager, Geotechnology & Engineering
dconley@sandia.gov

References

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