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

Don Field Decommissioning ProgrammeDON-BP-001 Phase 2Potential abandonment of the reservoir and upper plugs by a LWIV, and final rigpreparatory work (setting of barriers). Phase 3Subsea xmas tree removal by a construction vessel. Phase 4Rig workscope, pulling tubing and placement of remaining reservoir abandonment andany intermediate plugs. Phase 5Batch swat final cement plugs by a construction vessel or a LWIV, followed by batchwellhead removal and seabed clearance.The techniques listed in Table 7.2 have been identified for use in Donabandonment operations.TechniqueBullheading throughtubingConventionalabandonmentCoiled tubingCutting of theconductorThrough tubingabandonmentCommentThis technique will be considered for suitable wells whereisolation is required between reservoir sands (currentlyapplicable to well PN06 only). Wireline perforating gunswould be used to provide communication between tubingand annuli, and cement would be bullheaded or circulatedin place.Involves a full workover, plugging wells, removing thesubsea xmas tree and utilising BOPs.Through tubing technology, using conventional coiled tubingto accurately place cement. This technique has previouslybeen utilised for a number of well abandonments wheretubing integrity has been lost. Coiled tubing will not be usedfor the primary abandonment unless, on investigation, it isfound that there is a lack of integrity in the tubing.The preferred method will be to use abrasive cutting toolsto sever and recover each string 3m below the mud line.The guide base will be recovered with the 30in stringif bonded.If it is not possible to abrasive cut and recover the guidebase at this time, the contingency explosive charge may beused, if a permit is granted.This technique involves the placement of cement throughthe existing tubing. This option is being evaluated as aLWIV option and could be used for placement of thereservoir and some intermediate plugs.Table 7.2 Don Wells Abandonment TechniquesSelected Removal and Disposal OptionsMay 2011 7-3