China measures natural hydrogen at 98.24% in Sichuan

A gas leak south of Chengdu looked like a local mystery in June. Laboratory tests turned it into a major geological clue: natural hydrogen made up between 97.33% and 98.24% of the samples collected in China’s Sichuan Basin. The researchers say the upper figure is the highest concentration recorded in the country.

The gas was almost pure hydrogen, with only trace amounts of nitrogen and methane. Chemical and carbon-isotope tests on the methane helped rule out standard organic decay and high-temperature methane breakdown. The team instead identified a deep inorganic fluid system within Earth’s crust as the likely source.

The surrounding rocks provide a possible explanation. The leak lies near Permian volcanic rock and the Shimian-Miaowan Neoproterozoic ophiolite belt. Geologists believe serpentinized peridotite or Permian diabase porphyry may act as an active, continuous underground hydrogen generator, while regional faults provide a rapid route upward. That speed may have allowed the hydrogen to bypass Fischer-Tropsch reactions that would otherwise turn it into other hydrocarbons.

The finding matters because natural hydrogen was long treated as too difficult to retain underground to become a practical energy resource. A commercial field in Mali is cited as producing natural hydrogen at stable concentrations between 97.40% and 98.00%, suggesting that very pure deposits are not limited to a single geological setting. The study also cites models estimating around 5.6 x 10 6 Mt of underground natural hydrogen, though the global estimate is not a measure of what can actually be recovered.

So what changes, concretely? Chengdu gives exploration teams a sharply defined target: identify deep source rocks, trace fault-controlled migration and measure the rate of ongoing production. Until those tests are complete, the discovery shows exceptionally pure gas at one site—not a proven reserve, a commercial project or a new fuel supply. The researchers’ next technical steps will determine whether the leak points to a continuously replenished resource or an isolated geological occurrence.