The first satellite designed to continuously monitor the planet for methane leaks made a startling discovery last year: A little known gas-well accident at an Ohio fracking site was in fact one of the largest methane leaks ever recorded in the United States.
The findings by a Dutch-American team of scientists, published Monday in the Proceedings of the National Academy of Sciences, mark a step forward in using space technology to detect leaks of methane, a potent greenhouse gas that contributes to global warming, from oil and gas sites worldwide.
The scientists said the new findings reinforced the view that methane releases like these, which are difficult to predict, could be far more widespread than previously thought.
“We’re entering a new era. With a single observation, a single overpass, we’re able to see plumes of methane coming from large emission sources,” said Ilse Aben, an expert in satellite remote sensing and one of the authors of the new research. “That’s something totally new that we were previously not able to do from space.”
Scientists also said the new findings reinforced the view that methane emissions from oil installations are far more widespread than previously thought.
The blowout, in February 2018 at a natural gas well run by an Exxon Mobil subsidiary in Belmont County, Ohio, released more methane than the entire oil and gas industries of many nations do in a year, the research team found. The Ohio episode triggered about 100 residents within a one-mile radius to evacuate their homes while workers scrambled to plug the well.
At the time, the Exxon subsidiary, XTO Energy, said it could not immediately determine how much gas had leaked. But the European Space Agency had just launched a satellite with a new monitoring instrument called Tropomi, designed to collect more accurate measurements of methane.
“We said, ‘Can we see it? Let’s look,’” said Steven Hamburg, a New York-based scientist with the Environmental Defense Fund, which had been collaborating on the satellite project with researchers at the Netherlands Institute for Space Research in Utrecht, the Netherlands.
Natural gas production has come under increased scrutiny because of the prevalence of leaks of methane — the colorless, odorless main component of natural gas — from the fuel’s supply chain.
When burned for electricity, natural gas is cleaner than coal, producing about half the carbon dioxide that coal does. But if methane escapes into the atmosphere before being burned, it can warm the planet more than 80 times as much as the same amount of carbon dioxide over a 20-year period.
The satellite’s measurements showed that, in Ohio in the 20 days it took for Exxon to plug the well, about 120 metric tons of methane an hour were released. That amounted to twice the rate of the largest known methane leak in the United States, from an oil and gas storage facility in Aliso Canyon, Calif., in 2015, though that event lasted longer and had higher emissions overall.
The Ohio blowout released more methane than the reported emissions of the oil and gas industries of countries like Norway and France, the researchers estimated. Scientists said the measurements from the Ohio site could mean that other large leaks are going undetected.
“When I started working on methane, now about a decade ago, the standard line was: ‘We’ve got it under control. We’re managing it,’” Dr. Hamburg said. “But in fact, they didn’t have the data. They didn’t have it under control, because they didn’t understand what was actually happening. And you can’t manage what you don’t measure.”
An Exxon spokesman, Casey Norton, said that the company’s own scientists had scrutinized images and taken pressure readings from the well to arrive at a smaller estimate of the emissions from the blowout. Exxon is in touch with the satellite researchers, Mr. Norton said, and has “agreed to sit down and talk further to understand the discrepancy and see if there’s anything that we can learn.”
“This was an anomaly,” he said. “This is not something that happens on any regular basis. And we do our very best to prevent this from ever happening.”
An internal investigation found that high pressure had caused the well’s casing, or internal lining, to fail, Mr. Norton said. After working with Ohio regulators on safety improvements, he said, the well is now in service.
Miranda Leppla, head of energy policy at the Ohio Environmental Council, said there had been complaints about health issues — throat irritation, dizziness, breathing problems — among residents closest to the well.
“Methane emissions, unfortunately, aren’t a rare occurrence, but a constant threat that exacerbates climate change and can damage the health of Ohioans,” she said.
Scientists said that a critical task was now to be more quickly able to sift through the tens of millions of data points the satellite collects each day to identify methane hot spots. Studies of oil fields in the United States have shown that a small number of sites with high emissions are responsible for the bulk of methane releases.
So far, detecting and measuring methane leaks has involved expensive field studies using aircraft and infrared cameras that make the invisible gas visible. In a visual investigation published last week, The New York Times used airborne measurement equipment and advanced infrared cameras to expose six so-called super emitters in a West Texas oil field.
In a separate paper published in October, researchers detailed the use of two satellites to detect and measure a longer-term leak of methane from a natural gas compressor station in Turkmenistan, in Central Asia. Researchers estimated emissions from the site to be roughly comparable to the overall release from the Aliso Canyon event.
The leak has now stopped, satellite readings show, after the researchers raised the alarm through diplomatic channels.
“That’s the strength of satellites. We can look almost everywhere in the world,” said Dr. Aben, a senior scientist at the Dutch space institute in Utrecht and an author on both papers.
There are limitations to hunting for methane leaks with satellite technology. Satellites cannot see beneath clouds. Scientists must also do complex calculations to account for the background methane that already exists in the earth’s atmosphere.
Still, satellites will increasingly be able to both rapidly detect large releases and shed light on the rise in methane levels in the atmosphere, which has been particularly pronounced since 2007 for reasons that still aren’t fully understood. Fracking natural-gas production, which accelerated just as atmospheric methane levels jumped, has been studied as one possible cause.
“Right now, you have one-off reports, but we have no estimate globally of how frequently these things happen,” Dr. Hamburg of the Environmental Defense Fund said. “Is this a once a year kind of event? Once a week? Once a day? Knowing that will make a big difference in trying to fully understand what the aggregate emissions are from oil and gas.”
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