Natural-gas producers can cut greenhouse-gas emissions associated with shale drilling by capturing more of the fuel that escapes when the well is first dug, a Cornell University professor said.
As much as 7.9 percent of the gas from wells tapping shale formations escapes into the atmosphere, according to a study published today in the journal Climatic Change Letters. The methane that escapes traps solar heat at many times the rate of carbon dioxide, contributing more to global warming than burning coal or oil, according to the study.
“There are clean completion technologies that are able to do a better job of controlling unwanted venting and flaring of gas,” said Anthony Ingraffea, an author of the report and professor of civil and environmental engineering at Cornell. “Some companies use those technologies, most do not, and I suspect more will do so because the cat is out of the bag.”
Burning gas for electricity produces about a third of the carbon dioxide as other fossil fuels, according to data from the U.S. Energy Department. President Barack Obama last month called for the U.S. to cut oil imports by a third, in part by relying on the use of gas.
Shale drilling techniques cause as much as 1.9 percent of the gas to be lost during completion of the well, compared with 0.01 percent for conventional wells, the study estimates.
‘Worse than Coal’
The study assumes that gas escapes during completion at a rate greater than the initial production flow, citing well-decline rates reported by Chesapeake Energy Corp., the most-active U.S. driller.
“Shale gas is worse than conventional gas and is in fact, worse than coal and worse than oil” at trapping heat in the atmosphere, lead author Robert Howarth said in a video presentation posted online. The research isn’t conclusive, said Howarth, a professor of ecology and environmental biology at Cornell in Ithaca, New York.
The Cornell report is based largely on decade-old data and overlooks steps taken by shale-gas producers to curb losses during completion, said Russell Jones, a senior economic adviser at the American Petroleum Institute, a Washington-based group that represents oil and gas companies.
“That’s not a good basis for an in-depth study making very strong conclusions,” Jones said. “This is new technology and using decade-old data is not very relevant.”
The data doesn’t adequately support the report’s finding that the heat-trapping “footprint” of shale gas is 20 percent higher than coal, Robert Harriss, chief executive officer of the Houston Advanced Research Center, said in an e-mailed message.
“It’s clear from their analysis that careful attention needs to be given to this issue before a rapid expansion of shale-gas extraction is approved,” Harriss said.
Gas from shale accounted for 23 percent of total U.S. production last year and it may reach 46 percent in 2035, according to the Energy Information Administration.
Harriss spent four years studying air pollution by oil and gas wells in the 1980s and 1990s. The research center is a nonprofit that has received funding from the oil and gas industry to study drilling techniques that cause less environmental damage.
Producers including Anadarko Petroleum Corp., BP Plc, Chesapeake Energy Corp. and Devon Energy Corp. captured 70 billion cubic feet of gas that would otherwise have leaked from wells in 2009, the last year for which figures are available, according to the U.S. Environmental Protection Agency.
The agency derived its data from a voluntary program to reduce methane emissions from wells, processing plants and pipelines begun in 2003. By 2005, companies were trapping as much as 80 percent of gas produced during well completions and repairs, the agency said that year.
“Methane is valuable stuff,” Jones said. “There’s no reason to let it go up in the atmosphere if you can sell it.”
The Cornell study cites 2010 EPA reports that less methane is being captured during completions.
To conclude that gas from shale may contribute more to global warming than coal, the Cornell researchers assumed that methane traps heat at 105 times the rate of carbon dioxide, compared with 23 times, the figure used by the EPA, Jones said. The study says the higher figure is based on more recent research.
“Better regulation can help push the industry toward reduced emissions,” according to the Cornell study. “The full greenhouse-gas footprint of unconventional gas should be used in planning.’”