Debate has renewed around British Columbia’s liquefied natural gas (LNG) development, with groups calling for a public inquiry into the environmental impact of the province’s natural gas operations and particularly leakage of gas. But exactly how natural gas behaves when it leaks—particularly in the ground and groundwater—remains a mystery.
A unique test site in northeastern B.C. is enabling UBC hydrogeologists Aaron Cahill and Roger Beckie to take a multidisciplinary approach to understanding how leaked methane gas below ground migrates and ends up in the atmosphere, something known as fugitive gas. Recent research has shown that gas emission from natural gas operations are far higher than previously expected because of fugitive gas.
In this Q&A, Cahill discusses a new project, which aims to improve monitoring of existing LNG developments for underground leakage, and help industry and regulators better evaluate risks for new projects.
In the LNG context, what is fugitive gas and why is it important we monitor it?
It’s any unintentional release of gas resulting from natural gas resource development. It’s perhaps most easily related to leaks at the surface from infrastructure like wellheads and pipelines, but that’s just the tip of the iceberg. Most of the infrastructure for LNG development is underground, the well itself can be 3,000 metres deep, and in certain circumstances this underground part of the system can leak gas. Even at shallow depths like 100 metres or so, it’s very hard to see what’s happening, compared to a leak at surface. That’s the real unknown in terms of the science.
Our focus is what happens when gas leaks below ground. We want to understand how natural gas migrates through the geology, how much gas dissolves into groundwater, whether it changes water chemistry, and whether microbes ‘eat’ the gas. Most importantly, we want to know how much gas actually reaches the atmosphere as a greenhouse gas. Right now we simply don’t have a good handle on these processes.
You’re operating a field site in the Peace Region of B.C. How is your approach unique?
We’ve designed and built a specially engineered shallow “gas well” in reverse, using it to conduct controlled injections of gas into the ground so we can watch how the gas moves and where it ends up. The power of our approach, which we’ve been developing for more than five years, is that we will know exactly how much gas is entering the system and for how long. We’ll be able to correlate cause and effect.
We’re not working forensically in an area where a leak is suspected, an approach which has limited previous studies. In our case, there’s no debate about whether a leak occurred or not because we’ll be simulating a small controlled leak.
We’re also taking a highly multidisciplinary, comprehensive approach to monitoring the gas as it moves through the soil, groundwater and air. So if soil composition, water chemistry, geology, barometric pressure or precipitation levels have variable influence on gas migration and emissions, we’ll capture that to improve monitoring for industry. For example, our preliminary work shows that barometric pressure strongly influences the amount of gas that seeps from the ground into the air. That means if you monitor a site on a day with high air pressure, you might see no or very low levels of gas but that might not accurately reflect whether there is a leak underground or not. Our approach will help determine how big those variables are, and help us figure out how we can improve monitoring.
What do you want coming out of your research in B.C.?
We’re not using or working with an operational natural gas well, so we’re not looking to apportion blame, just trying to understand the basic science of how, and how much, methane moves through the system. The key is improving our understanding so we can predict what might happen if there is a leak, improve monitoring capabilities and perform a better risk assessment. If we better understand fugitive gas migration in the subsurface, we can improve methods to monitor and detect emissions. Even before the fact, we might be able to give regulators and industry a better idea of the risks involved in new developments. If an operation is proposed near a crucial water resource, how close is too close? We’re well positioned to help answer those types of questions.