Uncertainty about emissions highlights need for better measurements and leak control.

When Mary Kang landed an environmental policy fellowship at Princeton University in 2012, she decided she was going to model methane emissions from abandoned oil and gas (AOG) wells. It didn’t take long to discover a major roadblock.

“I couldn’t find any data. And you need data for modelling,” recalls Kang, now a civil engineering professor at McGill University.

At the time, methane emissions from AOG wells were not included in any government inventory and industry was suggesting they were close to zero anyway. So, she and her team got out their flux chambers and headed into Pennsylvania’s oil and gas country.

“I thought, ‘It’s one thing to assume it’s zero, but it’s another thing to measure it, and maybe I will find it is in fact zero,” she says.

It didn’t turn out that way. In fact, Kang found some wells “were emitting quite a lot.”

After extrapolating methane emissions from direct measurements of abandoned wells to all the state’s known wells, Kang and her team estimated they represented four to seven per cent of Pennsylvania’s total anthropogenic methane emissions.

She has since made something of a career out of bringing attention to fugitive methane emissions. In December, Kang published a meta study showing that annual methane emissions from AOG wells in Canada and the United States have been greatly underestimated—by as much as 150 per cent in Canada, and by 20 per cent in the US.

The discrepancy is due to lack of data on both the number of wells and how much they are emitting.

Kang analyzed information from 47 state, provincial and territorial databases, as well as from research articles and national repositories of drilled and active wells in the US and Canada.

Of the over 4,000,000 AOG wells she and her team estimate to exist in the US, they say more than 500,000 are undocumented by government. In Canada, they estimate there are over 370,000 AOG wells, 60,000 of which are not included in databases of provincial or territorial agencies.

Part of the problem in this country is that the Canadian Association of Petroleum Producers only has records going back to 1955, although historical documents confirm that oil and gas activity in Canada began in the 1850s.

To gain a better sense of exactly how much methane was being emitted from the wells, Kang and her team analyzed nearly 600 direct measurements of methane emissions from studies covering the AOG wells in various states in the US and from British Columbia and New Brunswick in Canada. They developed different scenarios to attribute different levels of annual methane emissions to the wells.

“What kind of wells are being measured is important,” says Kang. “Whether it’s plugged, or primarily produced oil or gas, they have different emissions, but there are many other factors that need to be considered as well.”

Their research suggests that methane gas emissions from AOG wells are the 10th and 11th largest sources of anthropogenic methane emission in the US and Canada, respectively. This is important because methane has more than 30 times the heat trapping ability of CO2.

Thanks to studies like Kang’s, a clearer picture of fugitive emissions from AOG wells is beginning to emerge. In 2019 – for the first time – methane emissions from abandoned wells were included in US and Canadian greenhouse gas inventories submitted to the United Nations.

“Canada is a signatory to the Paris agreement,” says Kang. “It’s important to know rates of emission so we can come up with an effective emission reduction strategy.”