Energy companies are making a major dent in the amount of harmful methane emissions that escape from natural gas wells, according to a broad peer-reviewed study published Monday that appears to validate new federal mandates for technology to rein in the heat-trapping pollutant.
But the University of Texas study, which was published in the Proceedings of the National Academy of Sciences, also reveals bigger-than-expected methane leaks from valve controllers and other equipments at well sites.
The report shows that even as energy companies make progress in one area, there is still plenty of work to be done to reduce methane leaks that could undermine natural gas’s reputation as a cleaner alternative to coal and oil. Methane, one of the largest components of the fossil fuel, is a potent greenhouse gas that is 72 times more powerful at warming the atmosphere than carbon dioxide over the first two decades after it is released.
“The results show a clear need to reduce emissions from pneumatic valves and equipment on well pads,” said Steve Hamburg, chief scientist for the Environmental Defense Fund. “This represents a real opportunity to reduce methane emissions in the short term.”
The report is the first in a 16-part series organized by the Environmental Defense Fund with more than 90 partner companies and scientists that aim to create a detailed accounting of precisely how much methane is released across the entire natural gas supply chain, from initial production at wells to its end use on highways and in homes.
Previous estimates are decades old and don’t take into account new technology or the recent surge in natural gas production that has been driven by combining hydraulic fracturing technology with horizontal drilling.
This initial study focused solely on what is happening at the very tip of the supply chain, at nearly 500 natural gas wells around the United States. It did not look at methane emissions from storage, transportation and processing natural gas, which are believed to be a more significant source of the greenhouse gas pollutant.
Companies that cooperated in the University of Texas project included some of the nation’s biggest natural gas producers, including Anadarko Petroleum Corp., Chevron, Shell’s SWEPI LP, Pioneer Natural Resources Co., Southwestern Energy and ExxonMobil’s XTO Energy.
Using data collected from 190 production sites, University of Texas chemical engineer David Allen found that recent government calculations vastly overestimated the amount of emissions tied to well completions, the point when a newly-drilled well is prepared for continuous production. The completions process involves cleaning the well of injected sand and liquids, but when the so-called “flowback” fluid returns to the surface, it can carry dissolved gas.
Under a federal rule finalized last year, the Environmental Protection Agency is requiring oil and gas companies to use new “green completion” technology by 2015, which cuts down on volatile organic compounds and methane releases at the sites.
Roughly two thirds of the sites studied by Allen were already using the equipment, and other studied wells were low-emitting already, resulting in methane emissions from well completions that were, on average, 97 percent below the EPA’s 2011 national estimates.
Overall, the study found that total methane leakage from natural gas production was 0.42 percent of all produced gas. While that figure is slightly lower than EPA’s previous estimate, overall study reports seem to buck the findings of Cornell University researchers who said in 2011 that nearly 8 percent of natural gas production was ultimately escaping into the atmosphere.
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The oil and gas industry — which generally opposed much of the EPA’s rule — said the study proves energy companies are on the right track.
“The industry has led efforts to reduce emissions of methane by developing new technologies and equipment, and these efforts are paying off,” said Howard Feldman, director of regulatory and scientific affairs for the American Petroleum Institute. “This latest study shows that methane emissions are a fraction of estimates from just a few years ago.”
But the report shines new light on the extent of methane leaks from other equipment at drilling sites, including pneumatic devices that are designed to release small amounts of methane in normal operations. That equipment was found to have emissions on average 70 percent higher than the EPA’s recent estimates.
There also were gaps; researchers said they were unable to collect enough data from periodic unloading processes, when wells are cleared of water and other liquids that are curbing production. The study team made the first-reported measurements of methane emissions from unloading processes at nine wells, but more information is needed for the data to have statistical significance, Allen said.
The report is important because it comes as the EPA readies new greenhouse gas rules for power plants and as utilities increasingly replace coal-fired power with cleaner-burning natural gas. The Obama administration’s climate change plan also includes a vow to combat methane emissions tied to surging oil and gas production.
“Universally, people have been talking about the need to get actual data,” said Mark Brownstein, an Environmental Defense Fund associate vice president. “This is actual data, and it’s the first time we’ve had the opportunity to get actual data from unconventional natural gas development. There is more work to be done, but this is a really important step.”
Some environmentalists have questioned EDF’s involvement, observing that the group aims to make its multi-year study the definitive word on methane emissions nationwide, even if locally focused studies show bigger problems in some areas.
Greenpeace’s executive director, Philip Radford, suggested the sites were cherry-picked and don’t represent the majority of the more than 25,000 wells drilled last year. Just a few outlier wells with extremely high emissions could bust the nationwide average calculated by the University of Texas researchers.
The group Physicians Scientists and Engineers for Healthy Energy called the report “fatally flawed,” because it is based on a relatively small sampling of wells.
Others suggested the report shows the oil and gas industry can do a good job at keeping emissions low when it knows it is under scrutiny.
Many of the companies that cooperated in the UT study are employing green completions technology at their wells even before the EPA’s 2015 mandate kicks in — and possibly well ahead of smaller operators working across the United States.
But the participating companies also were responsible for more than half of the wells drilled in 2011. And Allen said his team had control in selecting the wells where direct measurements were taken and the study’s methodology.
Energy companies that participated in the study said they were eager to get real numbers around the methane problem, instead of relying on decades-old data.
“There are important conversations taking place around the value of natural gas as a source of energy and it’s critical that we understand every facet of the story we are trying to tell,” said Curtis Smith, a Shell spokesman. “We have more work to do, but this data validates that natural gas can offer climate benefits and will continue to play a significant role in a cleaner energy future.”
Future studies to be released over the next year evaluate emissions tied to long-distance transmission and storage of natural gas, local distribution to consumers and its use as a transportation fuel. Funding for the project has come from oil companies as well as a number of foundations and philanthropists, including California billionaire Tom Steyer, who has used some of his wealth to campaign against the Keystone XL pipeline.
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