Aircraft-based mass balance estimate of methane emissions from offshore gas facilities in the Southern North Sea

• Main Authors: Pühl, Magdalena, Roiger, Anke, Fiehn, Alina, Gorchov Negron, Alan, M, Kort, Eric, A, Schwietzke, Stefan, Pisso, Ignacio, Foulds, Amy, Lee, James, France, James, L, Jones, Anna, E, Lowry, Dave, Fisher, Rebecca, E, Huang, Langwen, Shaw, Jacob, Bateson, Prudence, Andrews, Stephen, Young, Stuart, Dominutti, Pamela, Lachlan-Cope, Tom, Weiss, Alexandra, Allen, Grant
• Other Authors: Deutsches Zentrum für Luft- und Raumfahrt Oberpfaffenhofen-Wessling (DLR), University of Michigan Ann Arbor, University of Michigan System, Royal Holloway University of London (RHUL), British Antarctic Survey (BAS), Natural Environment Research Council (NERC), Norwegian Institute for Air Research (NILU), Department of Earth and Environmental Sciences Manchester (EES), University of Manchester Manchester, National Centre for Atmospheric Science York (NCAS), University of York York, UK, University of Oxford, Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Norwegian Sea
• Online Access: https://hal.science/hal-04405415; https://hal.science/hal-04405415/document; https://hal.science/hal-04405415/file/acp-2022-826.pdf; https://doi.org/10.5194/acp-2022-826

International audience Atmospheric methane (CH4) concentrations have more than doubled since the beginning of the industrial age, making CH4 the second most important anthropogenic greenhouse gas after carbon dioxide (CO2). The oil and gas sector represent one of the major anthropogenic CH4 emitters as it is estimated to account for 22% of global anthropogenic CH4 emissions. An airborne field campaign was conducted in April-May 2019 to study CH4 emissions from offshore gas facilities in the Southern North Sea with the aim to derive emission estimates using a top-down (measurement-led) approach. We present CH4 fluxes for six UK and five Dutch offshore platforms/platform complexes using the well-established mass balance flux method. We identify specific gas production emissions and emission processes (venting/fugitive or flaring/combustion) using observations of co-emitted ethane (C2H6) and CO2. We compare our top-down estimated fluxes with a ship-based top-down study in the Dutch sector and with bottom-up estimates from a globally gridded annual inventory, UK national annual pointsource inventories, and with operator-based reporting for individual Dutch facilities. In this study, we find that all inventories, except for the operator-based facility-level reporting, underestimate measured emissions, with the largest discrepancy observed with the globally gridded inventory. Individual facility reporting, as available for Dutch sites for the specific survey date, shows better agreement with our measurement-based estimates. For all sampled Dutch installations together, we find that our estimated flux of (122.7 ± 9.7) kg h-1 deviates by a factor 0.7 (0.35-12) from reported values (183.1 kg h-1). Comparisons with aircraft observations in two other offshore regions (Norwegian Sea and Gulf of Mexico) show that measured, absolute facilitylevel emission rates agree with the general distribution found in other offshore basins despite different production types (oil, gas) and gas production rates, which vary by two orders ...