Photo: Transocean Arctic rig on Dvalin; Source: Wintershall Dea

Wintershall Dea curbs Dvalin gas flows over mercury issues

Oil and gas company Wintershall Dea has decided to postpone the commercial gas production and curtail output from its Dvalin field located offshore Norway due to a high level of mercury in the gas flow.

Dvalin field - Wintershall Dea
Dvalin field; Source: Wintershall Dea

Dvalin is a subsea tieback in the Haltenbanken area of the Norwegian Sea linking an underwater template to the nearby Heidrun platform.

Wintershall Dea informed on Thursday that, during the production flow test of the Dvalin production wells, measurements showed that the gas flow contained a level of mercury which exceeded the maximum amount allowed in the system.

Consequently, the field’s commercial gas production will be delayed.

The drilling of the Dvalin production wells started in August 2019 and was finalised in the third quarter last year.

In total, Wintershall Dea drilled 18,203 metres on the field, delivering the four new wells from the Transocean Arctic rig.

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Wintershall Dea received consent from Norwegian authorities for the start-up of the Dvalin field in October 2020.

As planned, the system start-up was successful, the offshore infrastructure was functioning as expected and the first gas flow was achieved in late 2020, Wintershall Dea said on Thursday.

During the production flow test, the measured mercury levels were higher than in the exploration phase ten years ago.

However, the Dvalin wells proved good reservoir quality and confirmed the reserves as stated in the PDO. The field reserves, therefore, remain unaffected by the mercury issue.

Wintershall Dea together with its project partners has started studies to identify a technical solution to enable full production, including the application of established industry mercury removal solutions.

Until an appropriate remediation solution is implemented, the gas flow from the field will be curtailed, the company concluded.

The gas from Dvalin will be transported to Heidrun via a 14.9-kilometre pipeline.

From there, it will be sent to the Polarled trunk line via a 7.5-kilometre pipeline before it will be further processed to dry gas spec at the Nyhamna onshore gas terminal.