Potentially explosive methane gas may be lurking in groundwater, according to a new study by researchers from the University of Guelph in Ontario.
The new research shows that the methane gas is leaking from energy wells and may travel extensively through groundwater and pose a safety risk.
The researchers at the University of Guelph-based G360 Institute for Groundwater Research found the gas to be highly mobile in groundwater, traveling far beyond the shale wells where it is drilled and changing the water chemistry. They also concluded the gas will escape into the atmosphere as a greenhouse gas, which can contribute to climate change.
“If this water is extracted, say, by a farmer, the dissolved gas can be released and form an explosion risk or change the taste of the water,” G360 director and principal investigator Beth Parker, said in a statement. “Depending on conditions of groundwater and aquifer minerals, microbes can ‘eat’ the methane and generate undesirable by-products such as hydrogen sulphide, and induce the release of trace metals into the water.”
The researchers injected methane over 72 days into a shallow sand aquifer and monitored it for more than eight months at Canadian Forces Base Borden in Ontario. They found that the gas traveled through the ground and was sometimes released into the atmosphere and dissolved extensively into the groundwater, where it changed water chemistry.
Aaron Cahill, a former University of Guelph post-doctoral researcher, said the study found only small changes in water quality and covered only a short time period of time, using only small amounts of methane.
“For larger leaks over longer times and greater areas, these findings would indicate that the groundwater would become unusable,” Cahill said in a statement.
Leaky wells could pose a significant danger to the environment on several different fronts.
“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,” Cahill said. “The impact to groundwater is likely to be long-term and persist long after a methane leak is fixed.”
However, according to John Cherry, a School of Engineering adjunct profess and co-author of the study, sealing energy wells thoroughly can be a challenge because energy wells can run deep underground through several layers of rock and sediment.
“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,” Cherry said in a statement. “While drilling is better than ever before, leaky wells are still common and represent a large liability for the oil and gas industry.”
Cherry added that monitoring groundwater for methane leaks is rarely done.
“The industry needs a level playing field where the rules and reasonable expectations are clear,” he said. “The gas will spread up and out in groundwater, so it is the responsibility of government to set science-based groundwater monitoring standards for all companies to meet.”
The study was published in Nature Geoscience.