19 Jan 2023
19 Jan 2023
Status: this preprint is currently under review for the journal ACP.

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

Magdalena Pühl1, Anke Roiger1, Alina Fiehn1, Alan M. Gorchov Negron2, Eric A. Kort2, Stefan Schwietzke3, Ignacio Pisso4, Amy Foulds5, James Lee6, James L. France3,7,8, Anna E. Jones7, Dave Lowry8, Rebecca E. Fisher8, Langwen Huang5, Jacob Shaw5, Prudence Bateson5, Stephen Andrews6, Stuart Young6, Pamela Dominutti9, Tom Lachlan-Cope7, Alexandra Weiss7, and Grant Allen5 Magdalena Pühl et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 2Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA
  • 3Environmental Defense Fund, Berlin, Germany
  • 4Norwegian Institute for Air Research (NILU), Kjeller, Norway
  • 5Department of Earth and Environmental Science, University of Manchester, Manchester, M13 9PL, UK
  • 6National Centre for Atmospheric Science, University of York, York, YO10 5DQ, UK
  • 7British Antarctic Survey, Natural Environment Research Council, Cambridge CB3 0ET, UK
  • 8Department of Earth Sciences, Royal Holloway, University of London, Egham TW20 0EX, UK
  • 9Université Grenoble Alpes, UMR 5001, CNRS, IRD, Grenoble, 38000, France

Abstract. 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 point-source 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 facility-level 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 of magnitude. Therefore, mitigation is warranted equally across geographies.

Magdalena Pühl et al.

Status: open (until 02 Mar 2023)

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Magdalena Pühl et al.

Magdalena Pühl et al.


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Short summary
In April–May 2019 we carried out an airborne field campaign in the Southern North Sea with the aim to study methane emissions of offshore gas installations. We determine methane emissions from elevated methane measured downstream of the sampled installations. We compare our measured methane emissions with estimated methane emissions from national and global annual inventories. As a result, we find inconsistencies of inventories and large discrepancies between measurements and inventories.