Abandoned Coal Operations Could Become Methane Time Bombs
- Researchers in Queensland found a single abandoned coal borehole emitting as much greenhouse gas as 10,000 cars.
- Methane, 80 times more potent than CO? over 20 years, is leaking from thousands of old coal operations worldwide.
- Proper decommissioning and plugging of boreholes could deliver rapid emissions reductions and help meet climate targets.
Poorly plugged coal boreholes could be releasing vast amounts of greenhouse gas emissions into the atmosphere, several studies show. Abandoned coal operations worldwide have been found to be a key source of greenhouse gas emissions that could be mitigated through stricter decommissioning regulations and correctly plugging any boreholes found to be leaking methane.
Methane, the gas commonly found leaking from old boreholes, is colourless, odourless and invisible to the naked eye. Yet, it contributes heavily to climate change and is responsible for over 25 percent of the global warming we are seeing today. Methane traps more heat in the atmosphere per molecule than carbon dioxide (CO2), making it 80 times more harmful than CO2 for 20 years after it is released, according to the UNEP. Reducing methane emissions by 45 percent by 2030 could help us meet the Paris Agreement’s target of limiting global warming to 1.5°C.
Researchers in Queensland, Australia, have discovered a coal borehole that is releasing as much greenhouse gas as 10,000 cars, leaking dangerous levels of methane into the atmosphere. The emissions readings were taken by University of Queensland Gas and Energy Transition Research Centre researchers at a farm in the Surat Basin in central southern Queensland using a portable Quantum Gas LiDAR system.
The researchers took emissions measurements over a week to see how they varied with temperature and different weather conditions. The researchers also monitored a second coal exploration borehole that was emitting a similar level of methane, forcing groundwater several metres into the air like a geyser.
Associate Professor Phil Hayes said, “This was the first long-term measurement of methane emissions from an abandoned coal exploration borehole. This borehole is one of an estimated 130,000 in Queensland where the quality of sealing by coal explorers is unknown.”
The researchers said that the old borehole looked like normal bare ground in a cattle paddock, but they suspected the site might be relevant when they saw a gas company doing survey work in the area. Although the borehole was not visible from the surface, the researchers’ camera, which explored the 100-metre-deep hole, found it was releasing methane at an annual rate of 19,768 tonnes of CO2, if using a calculation of methane’s impact over 20 years, the equivalent of 10,000 cars each driving 12,000 kilometres a year.
This is worrying given that there are thousands of abandoned coal boreholes across the country, and there is little information on how old operations were sealed and their current state. This specific borehole had been at the site for around two decades, although it is not clear how long it had been leaking for. “While the majority of these boreholes won’t be emitters, our measurements show they could be a major source of greenhouse gas emissions that is currently unreported,” the University of Queensland’s Sebastian Hoerning said.
The findings indicate that Queensland may be able to reduce its greenhouse gas emissions by ensuring that its abandoned coal activities are properly decommissioned and plugged. Sealing the highest-emitting boreholes could rapidly reduce emissions in the region. The researchers hope to expand their study to assess more coal boreholes and water bore emissions across Queensland.
Many boreholes were poorly sealed by energy companies due to cost and a lack of strict regulations. The Queensland researchers found that some were found to have a bag of cement sealing the whole before being covered with soil, which is not sufficient to stop emissions from leaking. Hayes said, “These boreholes are drilled by coal exploration companies. They can be done in one day, and they tell the company about the quality of the coal or how it changes from one area to the next.”
Researchers believe this could be the tip of the iceberg when it comes to old fossil fuel operations leaking dangerous greenhouse gas emissions into the atmosphere. For example, in the United States, roughly 4.5 million oil and gas wells have been drilled across the country since the 1850s, and around 3.5 million of these wells have been abandoned. The U.S. Environmental Protection Agency estimated that non-producing oil and gas wells emitted as much as 275,000 metric tons of methane in 2020, equivalent to the emissions produced by around 1.7 million gasoline vehicles.
Thousands of oil, gas, and coal companies have managed the decommissioning of activities worldwide over several decades, making for a highly fragmented shutdown process, likely leaving a huge quantity of improperly plugged boreholes and oil wells in its wake. While exploring old oil and coal regions could be costly, it could help significantly decarbonise and reduce air pollution in certain regions of the world.
In Australia, the government must now consider conducting retroactive mapping of coal regions alongside exploration companies to understand just how many boreholes were improperly plugged to plug them properly. This could be a fast hit to help reduce methane emissions in the region in line with government aims to tackle climate change.
By Felicity Bradstock for Oilprice.com
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