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

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Don Field Decommissioning ProgrammeDON-BP-001A typical casing programme was as follows:(1) After setting a 30in conductor and a 20in casing in a vertical hole at 1600ft TVDSS,a 17 1/2in hole was drilled (deviated as necessary) to circa 5000ft TVDSS, where a13 3/8in casing was set in the Palaeocene.(2) A 12 1/4in hole was then drilled to 9500ft TVDSS where a 9 5/8in casing was set inthe Shetland Group.(3) Finally, an 8 1/2in hole was drilled through the Brent target and into the Dunlin, to atarget depth of 11,700ft TVDSS, and a 7in liner run as the completion string.(In some instances the well could be deepened another 300ft to penetratethe Statfjord.)The effective reservoir is a 150 to 180ft thick (vertical) section of sandstone. For bothproducers and injectors, this section was perforated uniformly from top to bottom.13 chrome steel was recommended for the completion tubulars and related equipment.The final programme for plugging and abandoning the wells will be produced in liaisonwith the chosen wells contractor. Work will be performed under the Design andConstruction Regulations (DCR) Part IV (Wells) [4.4].2.2 Subsea Equipment2.2.1 WellheadsNational Oilwell xmas trees (refer to Figure 4.5) are installed on the seven wells.Figure 4.5 Typical National Oilwell Xmas TreeDescriptions of Items to be DecommissionedMay 2011 4-7
DON-BP-001Don Field Decommissioning ProgrammeEach xmas tree incorporates the following main elements: Xmas tree block and valve assembly Retrievable valve package Completion equipment Associated flowlines and fittings Subsea choke Debris capThe Subsea Control Module (SCM) is supplied separately, but forms part of theretrievable valve package that is cantilevered off the main xmas tree frame.Xmas tree physical data is as follows: Weight – 34.5 tonnes Height above seabed – 5029mm Footprint – 2565mm x 2565mm Construction – Carbon steel2.2.2 Don ManifoldThe Don manifold (refer to Figure 4.6) was designed in 1988 by John Brown Engineers &Constructors Ltd and built by Peterhead Engineering Company Ltd. The manifold wasdesigned as a compact structure, capable of being installed and retrieved from either aMobile Offshore Drilling Unit (MODU) (via the moonpool) or by crane on a conventionalDiving Support Vessel (DSV).The Don manifold, which is secured to the seabed by two 20in steel piles to a depth ofapproximately 10m, was the connecting point between the Don Field and Thistle for: Collecting oil from the wells into the 8in production pipeline Distributing water from the 8in water injection pipeline to the water injection wells Distributing chemicals to the production wells Receiving and distributing control signals from Thistle to the wells Receiving and distributing data signals from the wells to ThistleInfield flowline and umbilical jumpers connected the manifold to individual wells. AnSCM was mounted on each xmas tree to control its valves (some SCMs have sincebeen removed). Manifold valves were controlled from an SCM mounted on the wellPN01 xmas tree.The manifold structure provides protection for the following items: Control umbilical termination box Chemical injection umbilical termination box Valves and associated pipework InstrumentationDescriptions of Items to be Decommissioned4-8 May 2011
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Don Field Decommissioning Programme (pdf, 7.8MB) null - BP

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