ATMOSFEAR: Scientists Find Gas Wells Leak Methane at Rapid Clip
Authors of a new study published recently in Geophysical Research Letters found that the natural-gas industry is failing to prevent significant amounts of its product from escaping into the air every day. The leaks result in a loss of millions of dollars in potential profits and raise anew questions about the true environmental benefits that come from relying increasingly on gas as an energy source.
The researchers behind the study were seeking to find ways to more accurately assess the climate benefits of natural gas relative to other fossil fuels but, according to author Colm Sweeney, the findings are important even if you’re not interested in climate change.
“From an economic point of view, this is a huge loss,” Sweeney said.
The report, entitled “Methane emissions estimate from airborne measurements over a western United States natural gas field,” concerns the airspace spread over about 100 square miles of wells. The gas field is sited atop the Uintah Basin, which stretches west from roughly the Colorado border over rural Utah to the mountains just east of Salt Lake City.
On Feb. 3, 2012, scientists of the National Oceanic and Atmospheric Administration (NOAA) and the Cooperative Institute for Research in Environmental Sciences (CIRES) – both based in Boulder, Colo. – sent out a single-engine aircraft to fly over the wells. The Uintah Basin is a section of the Colorado Plateau, which spreads over 337,000 square kilometers centered around the Four Corners region, where Colorado, New Mexico, Arizona and Utah meet.
The researchers were surprised by what they found. According to their calculations, around 9 percent of the natural gas being produced per year in the basin is leaking into the air.
“The research method [we used] is new,” Sweeney said. “It is one of the first methods that actually uses direct measurements and essentially no assumptions.”
Taking into account wind speed and direction, temperature and other weather conditions, the team waited for a day with high sun, steady wind and no snow. They then sent the plane downwind over the field at what Sweeney called the “mixing height” in the atmosphere, or 1,000 feet, where they believe emissions are evenly distributed.
Sweeney explains that other methods proceed “bottom up.” The Environmental Protection Agency, for example, typically counts the number of wells and processing plants in an area and takes samples at each one. The new method, Sweeney says, is “top down,” where the samples are taken up in the air, where it’s possible to measure the total amount of methane coming from the field rather than trying to add up individual small-scale figures to find a projected result.
Sweeney says the new method lowers uncertainty. The researchers found a 68 percent chance that the methane-leak rate is between 6.2 percent and 11.7 percent of total production and a 95 percent chance that the leak rate falls between 3.5 percent and 14 percent.
This report also showed a high correlation between methane leaks and propane and butane leaks, all of which contribute to high ozone levels in the Uintah Basin region.
“This potentially will affect air quality,” Sweeney said, not just in Utah, but at gas fields and production sites across the country.
This year, Colorado is working up new emissions regulations, looking to guard against what have become debilitatingly high ozone levels for some of the residents of the Front Range. Mid-size cities there sit atop rich natural gas formations that have drawn armies of drillers over the last decade. Tens of thousands of wells have been struck outside population centers like Greeley, Loveland and Longmont. Clusters of storage tanks, iron tubes and generators dot the landscape everywhere, leaking hundreds of tons of gasses into the air, according to state regulators.
Natural gas is widely promoted as a clean-burning efficient fossil fuel, but that efficiency has been called into question before, and the new study is sure to fuel debate.
“We need to more carefully consider each of these [gas fields] and understand their emissions,” he said. “It may turn out that they’re not quite the savior that we thought they were.”
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