San Juan Basin flux data from "Bottom-up characterization of geologic methane emissions in the San Juan Basin in the southwestern USA"

Atmospheric methane is the second most important anthropogenic greenhouse gas and a key contributor to atmospheric chemistry and global warming. Significant uncertainties remain in the global methane budget, particularly regarding emissions from natural geologic sources. This study provides a detailed bottom-up characterization of natural geologic methane emissions from the San Juan Basin, a high-seepage hydrocarbon basin located in southern Colorado and northern New Mexico. The dataset includes methane, carbon dioxide and ethane flux measurements across the San Juan Basin. Seepage was measured using a dynamic closed-system flux chamber, first developed by Kazemi et al. (2021), connected to portable greenhouse gas analyzers (Los Gatos Research Ultraportable Greenhouse Gas Analyzer (“LGR”) or a Picarro G4302 Mobile Gas Concentration Analyzer (“Picarro”)). Fluxes were calculated using Equation 1 in Kazemi et al. (2021). The d[CH4]/dt is found by taking the average of slopes of 1-minute segments of the concentration stepping every 10 seconds. The uncertainty associated with d[CH4]/dt is the standard error of these slopes.Our results show that natural geologic emissions are limited to the Fruitland coal outcrop and are associated with coal cleats, faults, and/or areas of hydrodynamic overpressure. Significant positive fluxes were observed on the Fruitland outcrop, particularly in the northwestern region.The code used to produce these calculated fluxes is available at https://github.com/KatieHall1919/Flux-Calculation/tree/main. This work is associated with "Bottom-up characterization of geologic methane emissions in the San Juan Basin in the southwestern USA" by Margaret R. Scholer, Kathleen R. Hall, Thomas S. Weber, Marc L. Buursink, Mingzhe Zhu, Alexander C. Ihle, Devin Hencmann, Andrew M. Smith, Katey M. Walter Anthony, and Vasilii V. PetrenkoReferencesKazemi, R., Schlageter, W., Hmiel, B., Weber, T.S., Murray, L.T., Petrenko, V.V., 2021. Investigating methane emissions from geologic microseepage in Western New York State, United States. Elem. Sci. Anthr. 9, 00066. https://doi.org/10.1525/elementa.2020.00066