Impact of CO2 leakage through North Sea wells

Researchers are investigating the limits and possibilities of the submarine storage of CO2

14.05.2019 / Kiel. Realistic estimates show that global warming can only be kept below 1.5 or 2 degrees Celsius if carbon dioxide is actively removed from the atmosphere. Storage beneath the seafloor is an option that has been investigated intensively by an international team of scientists led by the GEOMAR Helmholtz Centre for Ocean Research Kiel. An assessment of opportunities and risks has now been published in the journal International Journal of Greenhouse Gas Control.

It is possible to reduce anthropogenic COemissions by separating COfrom flue gases and storing the captured CO2in geological formations. Negative emissions can be achieved by coupling biogas production with COseparation and storage. Assessments by the IPCC show that these approaches are essential parts of the technology mix that is needed to limit global warming to less than 2°C. In Europe the largest potential to store COis located offshore in deep saline aquifers and other sub-seabed geological formations of the North Sea. However, more than 10 000 wells have been drilled into the seabed of the North Sea over the last decades to find and produce oil and gas. At many of these wells, methane gas from shallow biogenic deposits is leaking into the environment because the surrounding sediments were mechanically disturbed and weakened during the drilling process. COthat is stored in the vicinity of these wells may leave the storage formation, leak into the North Sea and ultimately return into the atmosphere. 

“We have performed a release experiment in the Norwegian sector of the North Sea to determine the footprint and consequences of such a leak”, explains Dr. Lisa Vielstädte from GEOMAR Helmholtz Centre for Ocean Research Kiel. She is lead author of the study which has now been published in the scientific journalInternational Journal of Greenhouse Gas Control.COgas was released at the seabed in 82 m water depth at a rate of 31 t yr-1which is at the upper end of the range of methane emissions observed at leaky wells. The released COwas tracked and traced using a remotely operated vehicle (ROV) equipped with chemical and acoustic sensors and additional measurements on board of Research Vessel Celtic Explorer. The experiment was conducted by GEOMAR as a contribution to the European project ECO2(http://www.eco2-project.eu/). 

“Our data show that COgas bubbles were completely dissolved close to the seafloor”, Dr. Vielstädte points out. The pH value of ambient bottom waters was lowered from a background value of 8.0 to a more acidic value of 7.0 at the release site as a consequence of the dissolution process. “This bottom water acidification has detrimental effects on organisms living at the seabed”, Prof. Dr. Klaus Wallmann, from GEOMAR and lead scientist of the ECO2 project points out. “However, strong bottom currents induced a rapid dispersion of the dissolved COsuch that the area at the seabed where potentially harmful effects can occur is small”, according to Prof. Wallmann. The area where the pH lowering exceeds 0.2 units has a size of about 50 m2.

“In conclusion, we can say that observations and accompanying modeling confirmed that leakage through wells may affect local ecosystems in the immediate vicinity of the well but has no detrimental large-scale effects on the North Sea ecosystem. Thus, we tentatively conclude that it is possible to store COsafely in sub-seabed formations if the storage site is located in an area with a small number of leaky wells” Prof. Wallmann summarizes. 

This month a second release experiment is conducted in the North Sea by the European project STEMM-CCS (https://www.stemm-ccs.eu/). Advanced sensors and monitoring devices will be used to track and trace the released COand study the environmental effects. These additional data will help us to further validate the performance of prospective storage sites in the North Sea and their potential contribution to climate change mitigation. 



Vielstädte, L., Linke, P., Schmidt, M., Sommer, S., Haeckel, M., Braack, M. and Wallmann, K. (2019) Footprint and detectability of a well leaking COin the Central North Sea: Implications from a field experiment and numerical modelling. International Journal of Greenhouse Gas Control84, 190-203. https://doi.org/10.1016/j.ijggc.2019.03.012


High-res images

The research vessel POSEIDON (foreground) and the British research vessel RRS JAMES COOK (background) at the Goldeneye gas production platform off Scotland during the current release experiment. Photo: Peter Linke/GEOMAR

Picture showing the setup of the gas release experiment with the Ocean Elevator lander (with yellow syntactic foam blocks) and mounted equipment (CO2 and Krypton gas bottles, battery packs, control unit and gas release head) deployed at  ~80 m water depth in the vicinity of the Sleipner CO2 storage site. Photo: ROV-Team/GEOMAR.

The usage of the image material provided with this press release is free for editorial purposes in conjunction with the content of this press release. The image source must be named.



Dr. Andreas Villwock (GEOMAR, Communication & Media), Phone: +49 431 600-2802, presse(at)geomar.de

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