Methane Leaks from U.S. Energy Production Are Dominated by Unprocessed Gas Associated With Petroleum Exploration

Research Overview

Ariana Tribby

Paul O. Wennberg

Researchers in the lab of Professor Paul Wennberg, led by graduate student Ariana Tribby, have published anew report shedding light on the origin of methane leaks in the oil and gas sector. By analyzing the emissions of methane fossil tracers (ethane and propane), and comparing them to estimates from a new Bayesian statistical model the team developed, they were able to identify that most methane leaks are from unprocessed gas, i.e. from or near the wellhead or the equipment between the wellhead and the nearby processing facility, and that these leaks are dominated by oil-producing regions. You can read about their work in their paper, "Hydrocarbon Tracers Suggest Methane Emissions from Fossil Sources Occur Predominately Before Gas Processing and That Petroleum Plays Are a Significant Source."

Scientific Achievement

• We developed a new model to estimate emissions of methane fossil tracers (ethane and propane) to help diagnose the origin of methane leaks from the oil & gas sector.
• Our analysis provides evidence that methane leaks originate from unprocessed gas, and that leaks are dominated by heavy petroleum-producing regions.

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Significance and Impact

• Methane is a potent greenhouse gas. Diagnosing and quantifying methane emissions is key towards reducing climate impact.
• Natural gas & petroleum systems are estimated to be the highest human source of methane in the U.S. Yet, the origin and magnitude of emissions from oil & gas processes remains highly uncertain.

Methane emissions over time and by source

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Methane emissions over time and by source

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Technical details

We developed a Bayesian hierarchical model to estimate ethane and propane fossil emissions. Our seasonal estimates compare well to other studies and their average show a decadal increase in both gases. Our revised emissions of ethane and propane, combined with a statistical analysis of basin composition measurements and aircraft observations, inform our diagnosis of the origin of fossil methane leaks.

Our global revised ethane anthropogenic fossil emissions compared to other studies. Our emissions estimate for 2016-2018 and 2009-2011 includes our Bayesian estimates for the winter, fall, and spring seasons. The studies included here represent anthropogenic fossil emissions, except the work by Dalsøren et al., which also includes biofuel, agriculture, and waste. Our emissions estimates do not include biomass burning or biofuels.

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Our global revised ethane anthropogenic fossil emissions compared to other studies. Our emissions estimate for 2016-2018 and 2009-2011 includes our Bayesian estimates for the winter, fall, and spring seasons. The studies included here represent anthropogenic fossil emissions, except the work by Dalsøren et al., which also includes biofuel, agriculture, and waste. Our emissions estimates do not include biomass burning or biofuels.

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Tribby, A. L.; Bois, J. S.; Montzka, S. A.; Atlas, E. L.; Vimont, I.; Lan, X.; Tans, P. P.; Elkins, J. W.; Blake, D. R.; Wennberg, P. O. Hydrocarbon Tracers Suggest Methane Emissions from Fossil Sources Occur Predominately Before Gas Processing and That Petroleum Plays Are a Significant Source. Environ. Sci. Technol. 2022, acs.est.2c00927. https://doi.org/10.1021/acs.est.2c00927.

Contact: Paul Wennberg