Jeff Peischl and John Hollway checking instruments source: CIRES
Methane leak rates from gas fields in Texas, Louisiana, Arkansas and Pennsylvania, at about 1 percent, are lower than some previous estimates, according to a new study by University of Colorado researchers.
Using sophisticated measurements taken from aircraft, the researchers assayed methane emissions on five flights over natural gas basins in 2013.
While the scans showed tens of thousands of pounds of methane leaking each hour from some equipment, the overall leak rate was calculated at around 1 percent. The research was a joint-venture of the Cooperative Institute for Research in Boulder and the National Oceanic and Atmospheric Administration.
The federal Environmental Protection Agency, using inventories from oil and gas operators, has estimated the leak rate at 1.8 percent. But , Texas and Pennsylvania, including some done by CIRES researchers, indicated the rate might be two to six times higher.
Another found human produce methane up to 1.7 times higher than EPA estimates.
“We are beginning to get a sense of regional variation in methane emissions from natural gas production,” said Jeff Peischl, lead author of the study and a CIRES scientist
The gas fields studied – the Marcellus in Pennsylvania, the Haynesville in Texas and Louisiana and the Fayetteville and the Fayetteville in Arkansas – produce more than 20 percent of the nation’s natural gas and half of all the shale gas.
The use of horizontal drilling, which has enabled oil and gas companies to drill two-mile-long wells, and hydraulic fracturing, or fracking, to crack hard rock to release gas has made it possible to develop shale reserves.
Natural gas has been held out a fossil fuel that is cleaner burning than coal and releases half as much carbon dioxide, the prime greenhouse gas linked to climate change.
Methane, however, is a 70 times more potent greenhouse gas than carbon dioxide over 20 years and some critics have argued adding in leak rates reduces the value of using natural gas as a fuel.
Researchers have also found that the more methane escaping from operations thes such as benzene and toluene also coming from wells.
“If leak rates are too high, natural gas does not compare favorably with one alternative, coal, in terms of climate impact. Where leak rates are low, the comparison favors natural gas,” said Joost de Gouw, a researcher with NOAA and CIRES and co-author of the study.
The researcher calculated the leak rates are follows
* Methane emissions in the Marcellus region of northeastern Pennsylvania were about 16.5 tons (33,000 lbs) per hour, or 0.18-0.41 percent of production.
* Methane emissions in the Haynesville shale of eastern Texas/northwestern Louisiana of about 88 tons (176,000 lbs) per hour, or 1.0-2.1 percent of production.
* Methane emissions in the Fayetteville shale region of Arkansas were roughly 43 tons (86,000 lbs) per hour, or 1.0-2.8 percent of produced gas.
In other published papers, CIRES, NOAA and other researchers have found methane losses of:
* about 4 percent of natural gas production in the Denver-Julesberg Basin
* 6-12 percent of natural gas production in Utah’s Uinta Basin (also called Uintah)
* about 17 percent of natural gas production in the Los Angeles Basin
The variable methane leak rates in the different studies suggests that other chemicals emitted during gas production, including compounds that contribute to episodes of poor air quality, are also variable, de Gouw said.
