Isegoria

Hydrogen almost never turns up in oil operations, and it wasn’t thought to exist within the Earth much at all, but a 108-meter borehole in Mali yielded 98% hydrogen:

The Malian discovery was vivid evidence for what a small group of scientists, studying hints from seeps, mines, and abandoned wells, had been saying for years: Contrary to conventional wisdom, large stores of natural hydrogen may exist all over the world, like oil and gas — but not in the same places. These researchers say water-rock reactions deep within the Earth continuously generate hydrogen, which percolates up through the crust and sometimes accumulates in underground traps. There might be enough natural hydrogen to meet burgeoning global demand for thousands of years, according to a U.S. Geological Survey (USGS) model that was presented in October 2022 at a meeting of the Geological Society of America.

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Critically, natural hydrogen may be not only clean, but also renewable. It takes millions of years for buried and compressed organic deposits to turn into oil and gas. By contrast, natural hydrogen is always being made afresh, when underground water reacts with iron minerals at elevated temperatures and pressures. In the decade since boreholes began to tap hydrogen in Mali, flows have not diminished, says Prinzhofer, who has consulted on the project. “Hydrogen appears, almost everywhere, as a renewable source of energy, not a fossil one,” he says.

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One kilogram of hydrogen holds as much energy as a gallon of gasoline (just under 4 liters). But at ambient pressures, that same kilogram of hydrogen occupies more space than the drum of a typical concrete mixing truck. Pressurized tanks can hold more but add weight and costs to vehicles. Liquefying hydrogen requires chilling it to –253°C — usually a disqualifying expense.

These storage issues — along with a lack of pipelines and distribution systems — are the main reasons why, in the race to electrify cars, batteries have won out over fuel cells, which convert hydrogen to electricity.

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The oil and gas industry has punctured Earth with millions of wells. How could it have overlooked hydrogen for so long? One reason is that hydrogen is scarce in the sedimentary rocks that yield oil and gas, such as organic-rich shales or mudstones. When compacted and heated, the carbon molecules in those rocks consume any available hydrogen and form longer chain hydrocarbons. Any hydrogen the oil encounters as it migrates to a porous “reservoir” rock such as a sandstone tends to react to form more hydrocarbons. Hydrogen can also react with oxygen in rocks to form water or combine with carbon dioxide to form “abiotic” methane. Microbes gobble it up to make yet more methane.

Even if the hydrogen survives, geologists thought, it should not accumulate. Hydrogen is the smallest molecule of all: It can leak through minerals and even metals. If Earth were producing hydrogen, it seemed unlikely to hang around.

And so, historically, when well loggers cataloged their borehole emanations, they rarely bothered to measure for hydrogen.

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Yet the hints were there for those who did look. According to Zgonnik, a geochemist who recently published a review of natural hydrogen, the first scientific discussion of it dates to 1888, when Dmitri Mendeleev, the father of the periodic table, reported hydrogen seeping from cracks in a coal mine in Ukraine. Zgonnik, who was born and raised in Ukraine, says reports of hydrogen are relatively common throughout the former Soviet Union — because Soviet researchers were looking for it. They held to a now discredited theory that would have required significant amounts of natural hydrogen to produce oil from nonliving processes rather than from ancient life.

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