摘要：A well in Nebraska is the first in the world to have been drilled in search of naturally occurring geologic hydrogen, but tests to determine how much of the gas it might supply are on hold because of a broken pump

A well in Nebraska is the first in the world to have been drilled in search of naturally occurring geologic hydrogen, but tests to determine how much of the gas it might supply are on hold because of a broken pump

In mid-March, workers began pumping water out of a 3.5-kilometre-deep hole drilled in the middle of a Nebraska corn field. It would have been an unremarkable scene if they had been in search of oil or natural gas. But the well is the first in the world drilled in search of naturally occurring hydrogen, which some think could become a significant source of clean fuel.

“We want to make a new discovery from scratch,” says Viacheslav Zgonnik at Natural Hydrogen Energy, the Colorado-based company exploring the well in partnership with Australian firm HyTerra. The tests started in March are now on pause due to a pump failure, but should soon reveal whether the well contains significant concentrations of the gas.

Researchers have long known geologic processes generate hydrogen, which emits only heat and water vapour when burned, but they didn’t think it would make a viable source of energy. “No one was really expecting to find it in large quantities,” says Zgonnik. “Because of that, no one was looking.”

Now, new estimates of the amount of hydrogen within Earth have driven researchers and some 8start-ups to take the hunt for geologic hydrogen, also known as gold hydrogen, more seriously.

“If it can be produced in large quantities – still a big ‘if’ – it could play a major role in helping reduce carbon emissions,” says Adam Brandt at Stanford University in California.

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A sizable discovery in Nebraska would be “a very significant milestone in geologic hydrogen development,” says Geoffrey Ellis at the US Geological Survey. Globally, there is one well currently extracting geologic hydrogen that was accidentally discovered in Mali, and many wells drilled for methane or helium have encountered hydrogen, says Ellis. But the Nebraska well would be the first to go looking for hydrogen and find it.

Zgonnik offered few details about why the Nebraska well – which was completed in 2019 just outside the small town of Geneva – was drilled at that particular site, but there is some evidence hydrogen is present there.

According to a 2022 assessment of HyTerra data by an outside consultant, hydrogen concentrations above 30 per cent were detected in mud bubbles deep in the well. Gas from the well also burned with an invisible flame in direct sunlight, which Ellis says indicates there is at least some hydrogen in the gas.

However, the assessment concluded that “considerable uncertainty in the hydrogen gas concentration in the well remains” and more tests are needed.

On 14 March, the Nebraska site’s operators initiated a “flow test” to estimate total production, which first required pumping water out of the well. They intended to complete the test by April, but there was a mechanical issue with the pump and testing is now on hold.

Zgonnik declined to give more details, adding that other companies searching for hydrogen may have similar issues. “There are some technical challenges to be overcome,” he says.

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If the well contains sufficient hydrogen, Zgonnik says they plan to sell it to a nearby fertiliser plant, which produces ammonia by reacting hydrogen with nitrogen. Most ammonia production uses hydrogen created with an energy and emissions-intensive process to reform methane with steam.

According to modelling by Brandt, geologic hydrogen production would result in fewer emissions than any other method of producing hydrogen, including so-called green hydrogen, which is made using water and renewable electricity. Factoring in burning the fuel, he found that geologic hydrogen would generate 90 to 95 per cent fewer emissions than natural gas, joule for joule.

Zgonnik says the close proximity of the ammonia plant is also ideal for hydrogen, which is expensive to transport over long distances because of its low density. Developing the infrastructure needed to transport the gas is a major obstacle for an emerging hydrogen economy, whether green or gold.