Gassco delivers plan for UK North Sea Knarr pipeline removal

Norwegian gas trunklines operator Gassco has submitted a decommissioning program to the UK Secretary of State for the 11.6-km section of the Knarr Gas Pipeline (KGP) within UK waters, on behalf of Knarr developer Norske Shell and its partners.

This section extends from the UK-Norway median line to the Knarr Tee structure tie-in spool flange.

Decommissioning of the KGP in the UK sector is taking place in two phases. Phase 1 followed the cessation of production on the Knarr Field on May 1, 2022, and was executed under the terms of the preparatory works request submitted by Gassco a year earlier.

It involved isolation of the KGP at the Knarr tee and the PLEM from downstream infrastructure, installation of a pigging spread at the PLEM, and cleaning and flushing of the KGP back to the Knarr FPSO. Phase 1 activities were completed on May 18, 2022.

The current submission relates to Phase 2, under which a minor section of spool #7 will be cut and disconnected from the PLEM, retrieved and transported to shore in Norway. The work will probably take place during the third and/or fourth quarter of this year, with the remaining spool sections and the KGP to be abandoned in place, cleaned and buried under rock cover.

Due to the proximity of the Knarr tee and PLEM to the UK’s subsea Far North Liquids and Associated Gas System (FLAGS) gas pipeline, removal of those structures will be deferred until the point when the FLAGS gas pipeline enters cessation of production, sometime within the next 25-30 years. This should eliminate risks connected with removal works near live, hydrocarbon-containing infrastructure.

The eventual removal of the structures will be subject to another decommissioning program.

Norway’s Ministry of Petroleum and Energy has approved a separate submission for the sections of pipeline within the Norwegian Continental Shelf, and there has been dialogue between the UK and Norwegian authorities to ensure alignment in the decommissioning work.

The Knarr oil and gas field is in Block 34/3 in the northern Norwegian North Sea, 50 km northeast of the Snorre Field and 50-60 km from the UK-Norway median line in 410 m water depth.

Shell developed the field via two subsea well templates connected to an FSPO, which will be reconditioned for Equinor’s Rosebank oilfield development west of Shetland.

Knarr’s rich gas was exported to the Norwegian sector to the UK via the KGP system, which connects to the FLAGS pipeline.

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