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

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DON-BP-001Don Field Decommissioning ProgrammeA tie-in tee-piece, located 13.1km from Thistle, was installed for a proposed future tie-in.The tie-in tee-piece is protected by grout formwork and a protective frame attached tothe pipeline.3.9.3 3in Chemical Injection Umbilical (PL600)When the chemical injection umbilical was installed, and at certain times during itsoperation, flexiweight mattresses, grout formworks, grout bags and rock dump havebeen used to stabilise the umbilical as shown in Figure 10.18.Figure 10.18 3in Chemical Injection Umbilical Stabilisation FeaturesApproximately 2km from the Don manifold, the chemical injection umbilical crossesover the NLGP using flexiweight mattresses, grout formworks and rock dump. Refer toParagraph 3.6 for further details.3.9.4 4in Control UmbilicalWhen the control umbilical was installed, and at certain times during its operation,flexiweight mattresses, grout formworks and rock dump have been used to stabilise theumbilical as shown in Figure 10.19.Figure 10.19 4in Control Umbilical Stabilisation FeaturesApproximately 2km from the Don manifold, the control umbilical crosses over the NLGPusing flexiweight mattresses, grout formworks and rock dump. Refer to Paragraph 3.6for further details.Pipelines10-16 May 2011
Don Field Decommissioning ProgrammeDON-BP-0014 Scope of Decommissioning Works4.1 GeneralThe Don pipelines and umbilicals decommissioning scope of work is as follows: Flowline jumpers, and chemical injection and control umbilical jumpers between theDon manifold and individual wells The 8in production pipeline from the double spoolpiece flange at the Don manifoldto the Thistle 500m zone The 8in water injection pipeline from the double spoolpiece flange at the Donmanifold to the Thistle 500m zone The 4in control umbilical between the Don manifold and the Thistle 500m zone The 3in chemical injection umbilical between the Don manifold and the Thistle500m zoneNote: Decommissioning of the materials within the Thistle 500m zone will be deferreduntil the Thistle is decommissioned. The NLGP crossing will also be deferred untilNLGP decommissioning.4.2 Pipeline, Umbilical, Flowline and Jumper CleaningThe 8in production pipeline (PL598) and the 8in water injection pipeline (PL599) havebeen cleaned by pigging and flushing with inhibited water to a cleanliness of 10ppmOiW. Both pipelines are disconnected from any process plant topsides on theThistle Installation.Four hydraulic cores of the 4in control umbilical held oceanic HW540, a water-basedhydraulic fluid totalling approximately 6900 litres. The Environmental Impact Assessmentreviewed options and recommended no cleaning for the control umbilical which will beleft in situ (refer to Section 9 for further details). Eventual gradual discharge of thecontained fluid will pose little or no risk to the marine environment, or even if it weredischarged in the unlikely event of a one-off occurrence.The contents of the 3in chemical injection umbilical (PL600) included Surflo SI662scale/corrosion inhibitor (1800 litres), Surflo 6442 scale/corrosion inhibitor (1250 litres),Surflo H356 scale inhibitor (1100 litres) and methanol (1250 litres). As a result of coreblockage and uncertain integrity, it is not feasible to clean the umbilical. It is proposed toleave the chemical umbilical in situ with no cleaning. This option has been deemed ashaving the least impact on the surrounding marine environment. BP will apply for thenecessary permits to discharge these chemicals.All flowlines contain either raw or inhibited seawater and are disconnected at oneend or both.PipelinesMay 2011 10-17
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Executive SummaryMay 2011 2-5Table
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Descriptions of Items to be Decommi
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Don Field Decommissioning Programme (pdf, 7.8MB) null - BP

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