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Methane emissions from Canada's non-producing oil and gas wells appear to be seven times higher than government estimates, according to a new study led by researchers at McGill University. The findings spotlight a major gap in the country's official greenhouse gas inventory and raise urgent questions about how methane leaks are monitored, reported and managed.

"Non-producing wells are one of the most uncertain sources of methane emissions in Canada," said Mary Kang, Associate Professor of Civil Engineering at McGill and senior author on the paper. "We measured the highest methane emission rate from a non-producing oil and gas well ever reported in Canada."

Methane is a potent greenhouse gas. Over a 20-year period, it traps about 80 times more heat in the atmosphere than the same amount of carbon dioxide. It's also associated with air pollution and health risks. Kang's team directly measured methane emissions from 494 wells across five provinces using a chamber-based method and analyzed well-level data such as age, depth and plugging status.

The national emissions estimate they arrived at—230 kilotonnes per year—is sevenfold higher than the 34 kilotonnes reported in Canada's National Inventory Report. The study was in Environmental Science & Technology.

There are more than , most of which are in Alberta and Saskatchewan. This means that the number of measured wells is very small, at only 0.1 percent.

"One surprising finding was just how much the drivers of emissions varied between provinces," said Kang. "We thought geological differences within provinces would matter more, but the dominant factors appear to be at the provincial scale, likely due to variations in policy and operational practices."

The results reveal that a small fraction of wells—especially unplugged gas wells—are responsible for the vast majority of non-producing well methane emissions. Kang says targeting these high emitters would be an efficient way to reduce emissions.

"Rather than just measuring more wells at random, we can use well attributes to identify where emissions are likely to be highest, and focus monitoring and mitigation efforts there," she said.

The study serves as a reminder of the need to rethink how old wells are managed.

"There's potential to in ways that generate funding for long-term monitoring and emissions reduction," said Kang.

"Many of these sites can be transformed to produce clean energy, such as wind, solar, and geothermal," said Jade Boutot, a Ph.D. student in Kang's lab and co-author of the study.

The researchers emphasize that improving methane data is critical to meeting Canada's climate targets.

"If we don't have accurate estimates of methane emissions, we can't ," Kang added.