The Potential for Geologic Hydrogen for Next-Generation Energy
band of iron-rich rock layers buried deep beneath the ocean floor. These rocks were deposited as the Atlantic Ocean basin formed. Geophysical surveys have confirmed that some of the iron in these rocks has reacted with water and produced hydrogen, which most likely escaped from the iron-rich rocks and migrated along sedimentary layers toward the shore.
The central U.S. area of interest is related to rocks that were formed when an ancient rift almost split North America in two. The failed rift, known as the Midcontinent Rift, occurred about 1.1 billion years ago, and underlies Lake Superior and much of Iowa, Minnesota, and Michigan. Although the rift did not succeed in dividing the continent, it did bring vast quantities of minerals to the upper layers of the Earth’s crust, including iron-rich minerals that could form hydrogen.
Despite the significant potential for generation of hydrogen in these regions, this does not necessarily equate to high potential for geologic hydrogen resources.
Ellis explained, “Remember, we have to have all of the hydrogen system components present in order for the system to work. We still have more work to do to determine the extent that other components, such as reservoirs and seals, are present in these areas before we will know how likely they will be to contain significant amounts of geologic hydrogen.”
Exploring for and Producing Hydrogen
Exploration for geologic hydrogen resources is likely to employ many of the same strategies and technologies that are currently used in petroleum exploration, with some added elements taken from mineral and geothermal resource exploration. Because of the potential for hydrogen to cause steel to become brittle, production of hydrogen trapped in reservoirs will require slightly different materials. Otherwise, the same drilling and completion equipment that is currently in use for natural gas development can be used.
However, unlike natural gas fields, some of the gas in natural hydrogen fields may be renewable given the rapid rate of hydrogen generation via water reduction. Moreover, some researchers have proposed that reservoirs, traps and seals may not even be necessary to produce geologic hydrogen. They suggest that we might be able to tap into rocks that are generating hydrogen, or have hydrogen migrating through them, and produce the hydrogen gas as it is being generated. Other scientists go even further and propose that hot water could be injected into iron-rich rocks that are not currently generating hydrogen in order to stimulate generation, somewhat similar to enhanced geothermal energy production.
“If you add up the amount of hydrogen we think might be trapped in reservoirs, plus the amount that might be produced directly as it is generated, and the amount that could be made through stimulation, you get a very large potential resource”, Ellis said.
What’s Next for the Science
While geologic hydrogen offers a lot of promise, realizing its actual resource potential still requires further investigation to reduce the uncertainty surrounding the components of the hydrogen system and to develop exploration strategies. At the USGS, we’re using our expertise in fields such as petroleum, geothermal, and mineral resources to advance our understanding of geologic hydrogen resource potential.
Next steps include publishing the global resource potential and hydrogen system models, as well as releasing a preliminary map of the areas that are most likely to contain geologic hydrogen resources. But there is more work to be done beyond that. The USGS is directing ongoing research efforts to develop exploration tools and strategies that will improve our understanding of this previously unrecognized energy resource to help meet the nation’s future energy needs.
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