A map plotting the likelihood of natural hydrogen occurring at any specific point in the lower 48 US states has been released by the United States Geological Survey (USGS), an agency of the US Department of the Interior.
For natural hydrogen — also known as white or geologic H2 — to occur, three “system components” must be present: a source that generates H2 (see panel below), a reservoir that it allows it to accumulate, and a seal that prevents the reservoir of H2 from escaping into the atmosphere.
The likelihood of all three components being present and effective at a specific location is presented as a metric called “chance of sufficiency” (COS), which is measured on a scale between zero and one. The results are presented on a publicly accessible map, where the user can click on a specific location to find out its COS.
The highest COS in the lower 48 states (excluding Alaska and Hawaii) is 0.85 — a figure that can be found in the Texas panhandle, north-central Kansas, an area on the border between Illinois and Kentucky and a large chuck of the northwestern part of Michigan’s lower peninsula.
However, this does not mean there is an 85% chance of finding natural hydrogen at these locations.
As the separate scientific paper published alongside the map explains: “Because no volumes are known yet for subsurface hydrogen occurrences, this definition is not benchmarked to any specific volume. The minimum concentration for an occurrence is 0.5 mole percent [the proportion of gases or fluids that is made up of hydrogen molecules in terms of moles].
“The COS similarly does not imply a statistical likelihood of subsurface hydrogen being found. For example, a source COS of 0.5 does not imply that 50 percent of wells in a particular location will successfully observe hydrogen or even a hydrogen source.
“Rather, this COS metric is used in this early exploratory stage to establish a relative scale on which to evaluate prospectivity from one location to another, based on the stacking of hydrogen system components.”
It adds: “Although much remains unknown and untested in the geologic hydrogen system, this study seeks to integrate basic concepts for hydrogen generation, migration, and storage to provide a useful and publicly available methodology for continental-scale mapping of geologic hydrogen prospectivity.
“The method... provides critical information to guide further detailed studies.”
The US Geologic Hydrogen Prospectivity map can be accessed here, and the accompanying paper is available here.
