Geoscience researchers at the University of Calgary, UBC and the University of Guelph have found that methane gas leaked from oil and natural gas wells can affect surrounding groundwater quality and can disperse much more widely than previously assumed, a result which speaks to the potential environmental consequences of energy drilling.
Published in the journal Nature Geoscience, the new study precisely tracked the movements of a controlled amount of methane gas injected into a shallow sand aquifer at the Canadian Forces Base Borden in Ontario. Researchers used ground-penetrating radar and chemical monitoring to chart how far the gas travelled over an eight-month observation period and found that while half of the methane made its way up into the atmosphere, half stayed in the groundwater for the full observation period, some of it covering larger distances than expected.
“Our results show rapid and widespread horizontal migration of free-gas methane along bedding coupled to buoyancy-driven upward migration in the Borden aquifer, resulting in an extensive, continuous, dispersed zone of dissolved methane and hydrochemistry changes,” say the study’s authors.
Gas leakage from drilled wells has always been a challenge in the oil and gas industry, says John Cherry from the G360 Institute for Groundwater Research at the University of Guelph and study co-author. “When energy wells are constructed, the cement used might not seal fully, or will initially seal but as it matures little cracks can form, allowing gas to escape. While drilling is better than ever before, leaky wells are still common and represent a large liability for the oil and gas industry,” Cherry said.
The new results indicate that more precaution is needed to protect both surrounding groundwater from contamination and to keep methane gas from entering the atmosphere, where it acts as a climate change contributor.
“For larger leaks over longer times and greater areas, these findings would indicate that the groundwater would become unusable,” says Aaron Cahill, lead author, now with the Department of Earth, Ocean and Atmospheric Science at UBC. “Methane is 30 times more potent than carbon dioxide at trapping heat when in the atmosphere, so we need to consider both the air and the groundwater when monitoring for leaks,” says Cahill. “The impact to groundwater is likely to be long-term and persist long after a methane leak is fixed.”
In Alberta, which leads the nation in greenhouse gas emissions, the provincial government’s Climate Leadership Plan includes a reduction in methane emissions from the oil and gas sector to 45 per cent below 2014 levels by the year 2025 as well as a total emissions cap on the oil sands of 100 megatonnes a year.
The federal government is said to be following suit and is drafting its own methane emissions regulations, to be released this spring, which are expected to call for similar nationwide reductions. Minister of Environment and Climate Change Catherine McKenna met with industry spokespeople in Calgary last month, saying that tackling the problem of methane leakage is one of the clearest and easiest ways to reduce greenhouse gas emissions.
“We’re moving forward with industry, we’re going to develop thoughtful regulations, because we know it’s the right thing to do,” said McKenna. “It will reduce emissions, but it’s also a real opportunity for Canada.”