Single Queensland coal bore emits as much methane as 10,000 cars, new study shows

Capping one coal borehole in Queensland would prevent the equivalent of 10,000 cars-worth of methane escaping into the atmosphere, University of Queensland researchers have found. 

And there are as many as 130,000 similar abandoned boreholes in the state – 1.3 billion car’s worth of emissions – that may or may not be properly capped.

The study in Science of Total Environment measured the emissions from a single borehole in the Surat basin (below) over seven days and found it had a mean emission rate of 235 tonnes a year. That’s the equivalent of 10,000 cars driving 12,000km a year.

A legacy coal exploration borehole that is pushing both methane and water to the surface. This hole has since been capped. Image: UQ.

“This was the first long term measurement of methane emissions from an abandoned coal exploration borehole,” said UQ associate professor Phil Hayes in a statement on the UQ website. 

“This borehole is one of an estimated 130,000 in Queensland where the quality of sealing by coal explorers is unknown.”

What is also unknown is how many were actually decommissioned and how many have just been left.

The findings show that more coal boreholes, and other sites in Queensland’s coal basins such as water bores, need to be sampled to find out just how much methane is being released. 

The researchers classified the borehole in the study as a “super-emitter” (25 kg/h), and sued a trailer-mounted Quantum Gas LiDAR system to monitor emissions over the course of the week. 

“Sealing the worst offending boreholes represents a straightforward and cost-effective way to quickly reduce greenhouse gas emissions,” Hayes said.

The Surat and Bowen basins are where Queensland’s coal seam gas industry lives and has “long been known to be ‘gassy’ during low pressure, humid weather conditions” the UQ study said.

One 2014 study cited a comment from a Queensland Department of Mines staff member as long ago as 1966 who said a particular water bore “will blow gas in very humid weather”.

Santos backlash

Australia’s gas industry hasn’t been good at cleaning up after it’s finished with a site.

A Santos-operated Darwin liquid natural gas facility has been emitting methane since it was built in 2006 by ConocoPhillips Australia.

The Northern Territory government has known about the leak for 19 of the 20 years it’s gone unrepaired, but pressure is building on all parties to finally fix the problem.

NT Environmental Protection Authority chair Paul Vogel said this week the leak is “insignificant” because it only accounts for just over 1 per cent of the facility’s total emissions, but a confidential report by ConocoPhilips shows that still equates to the equivalent of more than 8,000 cars on the road every year, the ABC reports.

Methane is a potent greenhouse gas some 80 times more powerful than CO2 over two decades, and rapidly reducing these emissions is a known way to slow future global warming.

In Western Australia, Santos is also underwater on gas leaks from old wells.

It claims An unknown number of disused wells it operated at the Legendre Field have been leaking gas into the ocean for the last decade. The company has previously said they are “not technically feasible” to plug.

Documents reported on by Boiling Cold reveal gas is seeping from 13 locations on the seabed near Santos facilities around Varanus Islands off the Pilbara coast, and there are an unknown number of disused wells in the Legendre Field have been leaking gas into the ocean for the last decade which the has previously said they are “not technically feasible” to plug.

Another source of unreported emissions

With eyes on coal mines and ongoing gas operations, abandoned bores are another source of methane emissions which are unlikely to be accounted for in already-low state or national estimates.

A report by Ember this year analysing Australia’s coal mine methane data produced their own estimates of government underreporting, estimating 40 per cent greater methane release than government reports.

Abandoned drilling holes is a problem that goes beyond Australia. In the US there’s as many as 300,000–500,000 abandoned and orphaned wells in Pennsylvania alone, according to research noted in the UQ study, and an estimated 60,000 to 760,000 abandoned wells in West Virginia. In the UK, of 102 abandoned and decommissioned gas wells a third had elevated methane emissions.

• * This article has been updated to show the boreholes are coal, not gas.