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Quantification of Oil and Gas Methane Emissions in the Delaware and Marcellus Basins Using a Network of Continuous Tower-Based Measurements

Z. Barkley1, K.J. Davis1,2, N. Miles1, S. Richardson1, A. Deng3, B. Hmiel4, D. Lyon4 and T. Lauvaux1

1The Pennsylvania State University, Department of Meteorology and Atmospheric Science, University Park, PA 16802; 570-905-7621, E-mail: zrb5027@gmail.com
2Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802
3The Pennsylvania State University, University Park, PA 16802
4Environmental Defense Fund, Austin, TX 78701

According to the United States Environmental Protection Agency, leaks from oil and gas infrastructure contribute to 30% of all anthropogenic methane emissions in the US. However, studies in the last decade have shown emissions from this sector to be substantially larger than bottom-up assessments, highlighting both an increased importance of methane emissions from the oil and gas sector towards their overall climatological impact, as well as the need for independent monitoring of these emissions. In this study we present a methodology for achieving continuous monitoring of regional methane emissions from oil and gas basins through the use of observational tower networks. Continuous methane measurements were taken at 4 tower sites in the northeastern Marcellus basin from May 2015 through December 2016, and 5 tower sites in the Delaware basin in the western Permian from March 2020 through October 2021. These measurements are combined with an atmospheric transport model and prior emission fields, and an inversion is performed to estimate monthly methane emissions in the two regions. This study finds emissions in the Delaware basin to average 160-209 Mg/hr (energy-normalized loss rate of 0.9-1.2%), with the largest emissions occurring before and at the onset of the COVID-19 pandemic. In the Marcellus, this study finds emissions to be 17-22 Mg/hr (loss rate of 0.27-0.35%), with relative consistency in the emission rate over time. These totals align with aircraft top-down estimates during the same period, providing confidence in the overall capability of the tower network while contributing additional spatial and temporal constraints to emissions within each basin.

Figure 1

Figure 1. (left) Prior and posterior monthly O&G methane emission totals for the Delaware basin based on the EIME prior (blue) and Zhang inventory (red) from this study. (right) Prior and posterior monthly O&G methane emission totals for the Marcellus basin based on the production-based prior (blue) and the PADEP prior (red). In both charts, the shaded area represents the minimum and maximum emission rate from a sensitivity analysis performed.