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

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DON-BP-001Don Field Decommissioning ProgrammeTotal Exposed LengthYearControlUmbilicalMetreChemicalUmbilicalControlUmbilicalPercentChemicalUmbilical2009 51 219 0.29 1.232002 29.2 – 0.17 –2001 – 218 – 1.232000 79.2 – 0.45 –1999 – – – –1998 32.0 – 0.18 –1997 32.9 – 0.19 –1996 79.0 – 0.44 –1995 31.4 209 0.18 1.181994 78.0 113 0.45 0.661993 – 322 – 1.821992 78.0 1518 0.40 8.631991 17.0 191 0.10 1.07Table 10.6Exposure History of the 4in Control and 3in Chemical Injection(PL600) UmbilicalsSpanSpanning has not been an issue for the 4in control umbilical. No spans were reporteduntil 1996. Single spans were found in 1996 and 1998, two spans were found in 2000and a further two spans were found in 2009. These spans have extremely smalldimensions (5 to 10cm high).Spanning has not been an issue for the 3in chemical injection umbilical. Only three spanshave been reported in the last 10 years. These are located at the tie-in points and haveextremely small dimensions (5cm high).None of the spans on either of the umbilicals has exceeded the FishSafe criteria(10m x 0.8m).6.4 Present Condition6.4.1 GeneralThe control umbilical is not presently functional. The four hydraulic hoses of the controlumbilical contain a water-based hydraulic fluid.Pipelines10-32 May 2011
Don Field Decommissioning ProgrammeDON-BP-001The chemical injection umbilical has not been functional since it became blocked andthen ruptured in 1995. Hoses of the umbilical presently contain various scale/corrosioninhibitors and methanol.6.4.2 Length and Location of Exposures and Spans4in Control UmbilicalThe most recent inspection of the 4in control umbilical in 2009 reported that theumbilical was almost entirely (99.71%) buried with only 51m of exposure. Most of thislength is associated with the NLGP crossing. The reported level of umbilical exposurehas remained consistently low, being between 0.1% and 0.47% of the inspected length.The 2009 GVI survey has confirmed our understanding that the umbilical remains stablein an out of use condition.Two spans were found in the most recent inspection in 2009. The spans have extremelysmall dimensions (5 to 10cm high).3in Chemical Injection Umbilical (PL600)The most recent inspection of the 3in chemical injection umbilical in 2009 reported thatthe umbilical was almost entirely (98.8%) buried with only 219m of exposure. Theseexposures are associated with the Don manifold and Thistle approaches.Three, extremely minor spans were reported by the most recent inspection of the 3inchemical injection umbilical in 2009. The longest span is 94cm long x 2cm high. Spanswere also reported at the Don manifold and Thistle Installation approaches. The umbilicalat the Don manifold approach is to be removed eliminating this span. Removal of theumbilical at the Thistle platform will be deferred until the Thistle platformis decommissioned.6.4.3 Present Burial DepthBurial depth information is available when a visual inspection GVI is performed. Althoughsuch inspections were performed less frequently than sidescan sonar survey, theydemonstrate consistent burial depths.The most recent full-length visual inspection of the 4in control umbilical was performedin 2009. Excluding sections where the umbilical was designed not to be buried and theabove exposures, the typical depth of burial is 0.18m to 0.37m as shown in Figure 10.23.The most recent full-length visual inspection of the 3in chemical injection umbilical wasperformed in 2009. Excluding sections where the umbilical was designed not to beburied and the above exposures, the typical depth of burial is 0.11m to 0.37m as shownin Figure 10.24.Due to the low seabed currents and stiff clay soil in the area, there is no reason tobelieve that these conditions will change in the future as indicated by results from linesin the same vicinity.PipelinesMay 2011 10-33
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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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