Bundles and towed installation

Bundles and towed installation

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On marginal, short-term field developments, conventional one-off bundles may not be economically viable. There are two concepts to enable the reuse of bundles. The advantages and disadvantages are discussed: 1. A conventional bundle with a ballast water line could be flooded for long-term stability and emptied during repositioning This has more steel than conventional bundles Pig launchers and receivers for ballast pipe must be built into the towhead 2. A flat-pack bundle (used for deep-water bundles and single lines) with the central core flooded for stability and emptied during repositioning Suitability of the bundle would depend on the particular flowline configuration Future tie-ins to flowlines could be made easier Simple pig launchers and receivers are needed at each end of a central carrier pipe This provides only limited protection to flowlines Re-usable bundles are in the region of 5% to 10% more expensive than conventional bundles, but the cost of repositioning in a similar field is 40% to 50% of the original investment. They can be recovered to an onshore facility for refurbishment and length adjustment, or for decommissioning at the end of their useful life. Major problems are the long-term integrity of the ballast chains and, more particularly, their fabric strap connections, and the re-floating of the towhead structures. Cassandra N˚2 was installed in the North Sea 2007 on a field with a known short life with the intention of future reuse. However, the second use field is yet to be decided. ƒ Components of a bundle that require designing ƒ Flowline pipes ƒ Carrier pipe ƒ Ballast chains ƒ Bulkheads ƒ Spacer units ƒ Tow/trail heads ƒ Added equipment for reuse Any questions? BUNDLEDESIGNSUMMARY BUNDLE DESIGN – SUMMARY

Bundles are constructed from the components listed above. Each of these components has unique considerations for design. The work is generally undertaken by the installation company.