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'Hydrogen could be stored in depleted oil and gas reservoirs — but it might get contaminated with methane'

US government scientists tested H2 reactions with a variety of rock types and found there would not be significant leakage

Sandia National Laboratories geosciences engineer working on the hydrogen storage project.
Sandia National Laboratories geosciences engineer working on the hydrogen storage project.Photo: Craig Fritz/Sandia Laboratories
Deputy Editor
It may be technically feasible to store hydrogen in depleted oil and gas reservoirs, opening the door for more widespread geologic storage of H2 in areas without an abundance of salt caverns, scientists in the US have found.

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But the tests at Sandia National Laboratories in Alberquerque, New Mexico, also reveal that there is a risk that the H2 might become contaminated with small amounts of methane, which means that it would not be free of carbon dioxide when burned.
Scientists at Sandia, which is privately owned but contracted out to the US government, aimed to determine whether America’s plethora of depleted oil & gas wells could be used for H2 storage, as part of the Department of Energy’s Subsurface Hydrogen Assessment, Storage and Technology Acceleration (SHASTA) project.
The hydrogen sector has so far focused on using either man-made H2 tanks or salt caverns for large-scale storage. However, salt deposits are not widespread across the US, meaning that there are fewer salt caverns available.

“If we want to create a hydrogen economy, we really need widely distributed means of storing large quantities of hydrogen,” said Don Conley, the manager for Sandia’s underground hydrogen storage work. “Storage in salt is excellent where it exists, but it can’t be the sole option. So, we’re turning to depleted oil and gas reservoirs and aquifers as more geologically distributed means of storing large quantities of hydrogen.”

To this end, scientists at Sandia and the University of Oklahoma carried out tests using computer simulations and lab experiments, examining how hydrogen interacts with sandstone and shale clay — the latter of which can “trap” oil & gas deposits underground.

They explain in a recent peer-reviewed paper published in the International Journal of Hydrogen Energy that around 10% of the hydrogen pumped into the sandstone and shale samples got “stuck” in the shale when researchers tried to pump it out, indicating that shale can also trap hydrogen, as well as oil and gas.

The team also carried out computer modelling of hydrogen’s interactions with layers of water and montmorillonite clay — a specific type of shale common around oil & gas reservoirs — and found that hydrogen tends not to leach into the water gaps in the shale, Sandia said.

“This means that the loss of hydrogen in clay due to getting stuck or moving through it would be tiny,” the lab said in a press release, citing Sandia chemical engineer Tuan Ho, who is leading the research. “This is quite positive for underground storage of hydrogen.”

However, further tests also found that storing hydrogen in depleted oil & gas wells also risks contaminating the H2 with small amounts of methane.

“That’s not terrible because natural gas still has energy, but it contains carbon, so when this hydrogen is burned, it will produce a small amount of carbon dioxide,” Ho said. “It’s something we need to be aware of.”

This may be a problem for customers who need hydrogen of very high purity, for example for use in fuel cells, where contaminants can “poison” the system.

However, Ho considers the use of depleted oil & gas wells as ideal for seasonal storage of hydrogen, in which H2 demand is likely to be directly related to demand from the power and heating sectors.

“Hydrogen would be good for seasonal and long-term storage,” he said. “If you think of solar energy, in the summer you can produce a lot of electricity, but you don’t need a lot for heating. The excess can be turned into hydrogen and stored until winter.”

In power and heating applications, high purities of hydrogen may not be technically required — although some regulations and subsidies may depend on hydrogen fuel having zero emissions.

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energy storageoilgashydrogenUS
Published 11 April 2024, 07:55Updated 11 April 2024, 07:55