Research raises concerns about methane emissions from shale leaks
Researchers from the University of Houston (UH) found that some natural gas wells, compressor stations, and processing plants in the Barnett Shale leak far more methane (CH4) than previously estimated, which could potentially offset the climate benefits of natural gas. The Barnett Shale is the site of the first widespread shale development in the United States and the region includes Dallas-Fort Worth and almost two dozen counties to the west and south in the state of Texas.
The Environmental Defense Fund coordinated the studies and all field measurements were conducted over 15 days in October 2013. Natural gas burns more cleanly than other fossil fuels and produces more energy per carbon dioxide molecule than oil or coal. Robert Talbot, professor of atmospheric chemistry at UH, noted that CH4, the primary component of natural gas, is a potent greenhouse gas. The paper says methane’s global warming potential over a 100-year time frame is 34 times higher than carbon dioxide (CO2).
Talbot authored the paper, along with UH graduate students Xin Lan and Azucena Torres and former post-doctoral research associate Patrick Laine. "In the past decade, the horizontal-drilling and hydraulic-fracturing techniques have led to a boom in natural gas production," they wrote. "However, CH4 emissions associated with the production and transmission of natural gas have raised concern from several parties."
There are natural sources of methane, including wetlands and landfills. The UH researchers measured emissions from a dozen landfills, as well as testing from public roads next to natural gas well pads, compressor stations and processing plants. All testing was done with a mobile laboratory. The emissions were measured and reported and the researchers also calculated measurements to gauge what percentage of the natural gas produced escaped through emissions.
A few individual sites had very high methane loss rates, which would make natural gas from these sites worse for the climate than coal in the short term. That finding drives interest in determining the prevalence of high-emission sites. Releases at specific installations ranged from 0.01 to 47.8%; the median was 2.1%. Methane releases from compressor stations and processing plants were higher than that at the well pads, the researchers reported.
Some emissions can be attributed to human error, which is compounded by the fact that the sites are often left unattended for long periods of time, Talbot said. "A lot of them are a broken valve, or someone leaves a hatch open. It’s human error. And nobody goes back to the site for a month or so."
In all, researchers tested 152 facilities and tested 125 well pads, 13 compressor stations, 12 landfills, and two gas processing plants.
University of Houston
– Edited by Chris Vavra, production editor, Control Engineeering, email@example.com.
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