Caleb Hamilton
A single abandoned coal borehole in Queensland, Australia has been found leaking methane at a rate equivalent to the annual emissions of 10,000 cars, a discovery that highlights how poorly sealed fossil fuel sites worldwide may be quietly fueling climate change through unreported greenhouse gas emissions.
A Farm Paddock Hiding a Major Emitter
The site looked like nothing more than bare dirt in a cattle paddock. Researchers from the University of Queensland's Gas and Energy Transition Research Centre only became curious after noticing a gas company conducting survey work nearby in the Surat Basin, a coal region in the state's south. What they found beneath the surface was far from ordinary.
Using a portable Quantum Gas LiDAR system, the team lowered a camera roughly 100 meters into the old borehole and measured methane escaping at a pace equal to 19,768 tonnes of CO2 per year, calculated using methane's 20 year warming impact. That is roughly what 10,000 cars would produce driving 12,000 kilometers annually. A second nearby borehole was found releasing a similar volume of gas, with enough pressure to shoot groundwater several meters into the air like a small geyser.
Why Methane From Old Boreholes Matters So Much
Methane doesn't have a smell or color, so it can leak for years without anyone noticing. Despite being invisible, it is doing outsized damage: the gas is blamed for more than a quarter of the warming the planet is currently experiencing, according to the United Nations Environment Programme. Molecule for molecule, it traps far more heat than carbon dioxide, and UNEP estimates it is about 80 times more potent than CO2 over a 20 year span after release.
That outsized effect is exactly why cutting methane is considered one of the faster ways to slow warming. A 45 percent reduction in methane emissions by 2030 has been identified as a meaningful step toward keeping the Paris Agreement's 1.5 degree Celsius target within reach. Finding and sealing leaking boreholes, rather than waiting decades for slower fixes, could offer a relatively quick win.
How Many More Boreholes Are Out There
Associate Professor Phil Hayes, who worked on the research, said this marked the first long term measurement of methane escaping from an abandoned coal exploration borehole. He noted that Queensland alone has an estimated 130,000 such boreholes, and nobody really knows how well most of them were sealed.
The borehole in question had sat at the site for around two decades. Researchers could not say exactly when the leak began. Sebastian Hoerning, also with the University of Queensland, said the team's measurements suggest these sites could represent a meaningful, currently unreported source of greenhouse gas emissions, even though most individual boreholes likely emit little or nothing.
Hayes explained that many of these holes were drilled quickly by coal exploration companies to sample coal quality or track how seams change underground, often finished within a single day. Some were sealed with little more than a bag of cement before being covered over with soil. That kind of patch job, researchers found, is not enough to stop methane from escaping over the long run.
A Global Pattern, Not Just an Australian One
Queensland's findings echo a much larger problem playing out elsewhere. In the United States, roughly 4.5 million oil and gas wells have been drilled since the 1850s, and about 3.5 million of those are now abandoned. The Environmental Protection Agency has estimated that non producing oil and gas wells released as much as 275,000 metric tons of methane in 2020 alone, comparable to emissions from around 1.7 million gasoline powered vehicles.
| Comparison | Methane Impact |
|---|---|
| Queensland borehole (annual) | Equivalent to 10,000 cars driving 12,000 km/year |
| US non producing wells (2020) | Equivalent to 1.7 million gasoline vehicles |
Part of the challenge is that decommissioning has never been handled by one entity. Thousands of oil, gas and coal companies have overseen shutdowns across different decades and jurisdictions, leaving a fragmented and inconsistent record of what was sealed properly and what wasn't. Revisiting old sites is expensive, but researchers argue it could meaningfully cut both greenhouse gas output and local air pollution.
What Happens Next for Queensland's Coal Boreholes
The University of Queensland team plans to expand its work to survey more coal boreholes, along with water bores, across the state to get a clearer picture of how widespread the problem is. Researchers have suggested that Australian authorities work with exploration companies to retroactively map coal regions, identifying which boreholes were inadequately sealed so they can be fixed.
Whether that mapping happens on any meaningful timeline, and how many other leaking sites are waiting to be found, remains uncertain. What the Surat Basin discovery does make clear is that a problem long assumed to be minor could be larger, and more fixable, than regulators have accounted for.
