Don Field Decommissioning Programme (pdf, 7.8MB) null - BP

DON-BP-001Don Field Decommissioning Programme2.1.2 Leave In Situ with Trenching at Selected SectionsSelective trenching would be used to secure sections of pipelines or umbilicals thatmight present a snagging hazard, eg span or exposed sections, or sections susceptibleto spanning or exposure due to currents and wave action.Trenching would be achieved by ploughing, mechanical cutting or water jetting,depending on the type of soil and the required trench depth. The trench would theneither be backfilled with the sediment removed during trenching, or left to backfillnaturally as a result of currents and wave action.2.1.3 Leave In Situ with Selective RemovalPartial removal of pipeline and umbilical sections may be considered as an option inconjunction with leaving the majority of a pipeline or umbilical in situ.Sections of pipelines or umbilicals that emerge out of the seabed or have inadequateburial would be cut out and recovered. Cut ends would be removed back to stable buriedpipe so that there is no possibility of a snagging hazard.2.2 Options for Full Recovery2.2.1 Full Recovery by Reverse ReelingThis process is shown in Figure 10.1.Figure 10.1 Reverse Reel MethodReverse reeling offers the simplest form of pipeline and umbilical recovery. Dependingon the line diameter, a purpose-built reel ship can carry several kilometres of eitherflexible or rigid pipeline, and offers rapid recovery of small-diameter line in particular.Pipelines10-2 May 2011