UT study measures methane emissions in natural gas production

Posted Monday, Sep. 16, 2013  comments  Print Reprints
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So-called “green” completion equipment is very effective at capturing methane emissions on new natural gas wells, but other devices at well sites allow more gas to escape than previously estimated, a new study shows.

Overall, the emissions from natural gas well sites were in line with current estimates by the U.S. Environmental Protection Agency, and are much lower than earlier estimates by drilling critics.

It’s not known exactly how many of the thousands of gas wells drilled annually in the United States now use green completion equipment. The EPA already requires drillers to either capture or flare methane during completions, and starting in 2015 the gas must be captured. In April 2012, the agency estimated that about half of new wells had green completion devices or flared methane.

The University of Texas at Austin conducted the $2.3 million study, which was mostly financed by nine energy producers and included funding from the Environmental Defense Fund. Researchers said it was the first study to take on-site measurements rather than relying on estimates.

“There has been a raging debate over what are emissions surrounding natural gas production. This is actual data. This is a really important step,” said Steven Hamburg, head of the U.S. climate and energy program at the Environmental Defense Fund.

Methane, the principal component in natural gas, is a potent greenhouse gas. After hydraulic fracturing, gas and fracturing fluid flow back from the well, and without equipment that captures or burns that gas, methane would be vented into the atmosphere — potentially enough that some researchers have suggested greenhouse gas emissions from natural gas are worse than those from coal.

The UT study said that 0.42 percent of the natural gas produced from wells escapes from the well site. It said that figure, combined with EPA estimates for other segments of the natural gas supply chain, show that 1.3 percent of all natural gas produced escapes.

That’s still a lot — about 330 billion cubic feet of the 25.3 trillion cubic feet produced in the U.S. last year. But it is also low enough to produce immediate climate benefits when burning natural gas instead of coal to generate electricity, according to the UT study.

Those benefits increase over time, because natural gas leaves the atmosphere faster than carbon dioxide.

“The way in which wells are drilled and brought into production has been evolving,” said David Allen, UT professor of chemical engineering and the study’s principal author. “The net emissions for completion flowbacks is significantly lower than previous estimates, indicating the type of emission control activities observed during these events are very effective.”

The study team looked at 489 wells at 190 sites across the country, barely one-tenth of 1 percent of all the natural gas wells in the United States. It measured emissions from 27 completions, 18 of which used emissions-reducing equipment, and measured emissions from pumps and controllers at well sites.

“Even very high-quality measurements cannot overcome the small number of operations or sites measured,” said Gabrielle Petron, a top methane monitoring scientist for the National Oceanic and Atmospheric Administration. Petron said she worried about high-emitters, which are rare but can account for a whopping portion of emissions.

Some environmental groups that oppose hydraulic fracturing, or fracking, said the industry funding presented a conflict. But Ralph Cicerone, president of the National Academy of Sciences and an atmospheric scientist who has researched methane, said the authors represent “some of the very best experts around the country.”

Drew Nelson, Texas manager of special projects for the Environmental Defense Fund in Austin, said the study shows that the EPA is right to regulate methane emissions in the field. Leaks and venting from valves and pneumatic controls accounted for 40 percent of all methane emissions at well sites, the UT study found.

“There are still plenty of opportunities to reduce emissions,” Nelson said.

Ed Ireland, who heads the industry-funded Barnett Shale Energy Education Council, said “a lot” of producers in the Barnett Shale already use green completion equipment “and more and more companies are doing that.”

He added that the study “should lay to rest allegations that methane leaks from natural gas drilling and production are so high as to make natural gas from shale a climate disaster. The results show that shale gas in fact makes significant positive contributions when it comes to greenhouse gas emissions.”

Fort Worth-based XTO Energy, a subsidiary of Exxon Mobil, was one of the producers that allowed researchers access to well sites in the Barnett Shale and other U.S. shale gas fields.

In a prepared statement, XTO said it “allowed researchers access to all our operations, but had no input on the conduct of their field research.” It said XTO operations in the Barnett Shale and the Haynesville Shale in Louisiana and East Texas were included.

This report includes material from The Associated Press.

Jim Fuquay, 817-390-7552 Twitter: @jimfuquay

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