A new study by the University of Texas at Austin shows that methane emissions from onshore natural gas drilling are much lower than previous estimates, in part because of the effectiveness of techniques required by the Environmental Protection Agency for completing a well and bringing it into production.
But the study released Monday also showed higher leakage rates than expected from valves and control devices used in the production of natural gas. Despite that, the overall level of methane leakage from gas production was 0.42 percent of total volume, slightly less than the most recent EPA estimates of 0.47 percent.
The paper, published in the Proceedings of the National Academy of Sciences, is the first of 16 studies measuring methane leakage throughout the natural gas supply chain, a project organized by the Environmental Defense Fund, nine oil and gas companies, and various individuals and foundations. The companies that cooperated with the study represented about half of the 4,000 wells drilled in 2011.
The level of methane leakage from natural gas wells and pipelines has been the focus of debate as the level of shale gas drilling and production surges. Foes of shale gas drilling argue that leaks of methane, which is a greenhouse gas 72 times more potent than carbon dioxide over a 20-year time frame, offset the benefits of substituting gas for coal.
Yet the oil and gas industry and many policymakers, including President Obama, favor natural gas because it emits half as much carbon dioxide as coal when burned.
Both advocates and opponents in the debate asserted that the study supported their positions.
“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 of the American Petroleum Institute, which has resisted new EPA regulation. He said in a statement Monday that “the industry will continue to make substantial progress to reduce emissions voluntarily and in compliance with EPA’s recent emissions standards.”
Yet drilling foes noted that even the low level of leakage found in the study would erase a substantial portion of the environmental benefits of clean-burning natural gas compared with coal. Sierra Club executive director Michael Brune said in an e-mail that the study “reaffirms what climate scientists have always said about natural gas: Natural gas is a dirty fuel and we can’t afford to keep it in our energy mix if we have any hope of reversing climate disruption.” Marvin Odum, head of Shell Oil Co.’s operations in the Americas, said, “I think we’ll all be a little surprised by how much alignment there is around actions that should be taken.”
The University of Texas study measured emissions at 150 production sites and 27 well completion flowbacks, when water, natural gas and gas liquids rush to the surface after hydraulic fracturing.