Sean Gas Field Tender

Location UKCS Block 4925a Southern North SeaScope The Sean gas field which is located 94km east of the UK coast in the southern North Sea will be decommissioned by 2029. The Sean gas field which was discovered in 1969 and has been producing since 1986 will be decommissioned as it is nearing the end of its productive life. Located in Block 4925a within the Southern North Sea SNS gas province on the UK continental shelf UKCS the Sean gas field was discovered in 1969. One-Dyas UK a subsidiary of Dutch exploration and production company One-Dyas holds 50 interest in the field and is the operator while the remaining interest is held by Rockrose UKCS15 formerly known as SSE EP UK. The application for the cessation of production submitted by One-Dyas UK was approved by the Oil and Gas Authority OGA. The company also submitted an application for the fields decommissioning in October 2021. The cessation of production is expected in 2025 while the decommissioning activities are scheduled to be completed by 2029.Located approximately 94km east of the UK coast at a water depth of 30m the Sean gas field comprises three separate fields namely East Sean North Sean and South Sean. The field was developed with three platforms of which a wellhead and compression platform PD and a production and accommodation platform PP were interconnected through a bridge forming the Sean Papa infrastructure. The third platform is a not permanently attended installation NPAI called Sean Romeo RD. Sean RD and Sean PP are connected through PL310 a 20in-diameter gas export pipeline. The infrastructure also includes an electrical cable between Sean PP and Sean RD. Sean PD features ten well slots of which eight are producing while Sean RD has six slots of which two are in production.The gas produced from the Sean field is transported to Shell UKs Bacton Terminal in North Norfolk UK via a 106.5km-long and 30in-diameter gas export pipeline named PL311 which has a subsea isolation valve SSIV at 250m from Sean PP. Sean gas field decommissioning details The programme includes decommissioning of the three fixed steel platforms associated subsea infrastructure and related pipelines at the field. The topsides and substructures of the three platforms namely Sean PP Sean PD and Sean RD will be completely removed and transported onshore for dismantling and either recycling or disposal. The substructure piles will be cut 3m below the seabed before removal. The PL310 pipeline and the onshore section of the PL311 pipeline will be decommissioned at the site. The rock placed around the PL311 SSIV structure is planned to be excavated and then filled back into the hole. The structure piles will be cut 3m below the seabed removed and returned to shore for dismantling re-use and recycling. The two mooring buoys comprising surface buoys anchored through concrete blocks on the seabed will be completely removed and returned to