Quantification of methane emissions at abandoned gas wells in the Central North Sea.

Vielstädte, Lisa, Karstens, Jens, Haeckel, Matthias, Schmidt, Mark, Linke, Peter, Reimann, Susan, Liebetrau, Volker, McGinnis, Daniel and Wallmann, Klaus (2015) Quantification of methane emissions at abandoned gas wells in the Central North Sea. Marine and Petroleum Geology, 68 . pp. 848-860. DOI 10.1016/j.marpetgeo.2015.07.030.

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Abstract

As a result of extensive hydrocarbon exploration, the North Sea hosts several thousand abandoned wells; many believed to be leaking methane. However, how much of this greenhouse gas is emitted into the water column and ultimately reaches the atmosphere is not known. Here, we investigate three abandoned wells at 81-93m water depth in the Norwegian sector of the North Sea, all of which show gas seepage into the bottom water. The isotopic signature of the emanating gas points towards a biogenic origin and hence to gas pockets in the sedimentary overburden above the gas reservoirs that the wells were drilled into. Video-analysis of the seeping gas bubbles and direct gas flow measurements resolved initial bubble sizes ranging between 3.2 and 7.4mm in diameter with a total seabed gas flow between 1 and 19 tons of CH4 per year per well. Estimated total annual seabed emissions from all three wells of ~24 tons are similar to the natural seepage rates at Tommeliten, suggesting that leaky abandoned wells represent a significant source of methane into North Sea bottom waters. However, the bubble-driven direct methane transport into the atmosphere was found to be negligible (<2%) due to the small bubble sizes and the water depth at which they are released.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/228344
Additional Information: WOS:000367631900013
Keywords: Abandoned wells; Cold vents; Methane; Seepage; Seismic chimney; ROV Kiel 6000 ; ROV Phoca ; RV Alkor ; AL412 ; CE12010
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R03
OceanRep > The Future Ocean - Cluster of Excellence > FO-R07
OceanRep > The Future Ocean - Cluster of Excellence > FO-R05
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.marpetgeo.2015.07.030
ISSN: 0264-8172
Projects: Eurofleets, ECO2, Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 03 Sep 2015 07:19
Last Modified: 11 Apr 2017 09:41
URI: http://oceanrep.geomar.de/id/eprint/29499

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