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Technical Paper: Conductor System Design For A Deep Water Jackup in Cantilever Mode Over the ETAP Platforms
Paper 52768
Abstract
Increasingly, field developments in the 0 m - 100 m depth range are utilising deep water, harsh environment jackups in cantilever mode over fixed platforms near to their operating limits. In such water depths, it is possible that there will be substantial relative movements between the jackup and fixed platform, under the action of environmental wind, wave and current loading. Any such relative movements cause very high loadings within the conductor system, in the surface equipment and on the jacket guides; indeed, such loadings are often in excess of those caused by environmental loading on the conductors themselves. Consequently, all of the above loadings must be accounted for in the design process, in appropriate combinations.
The above issues were addressed in the design of conductor systems for two platforms located the United Kingdom Continental Shelf (UKCS) Central North Sea (CNS). The platforms were Marnock and Mungo, which form part of the ETAP development. A thorough understanding of the key issues were developed, and analytical and design solutions prepared to maximise drilling operability. Operating procedures were prepared, to ensure that the conductor systems will remain within acceptable operating envelopes. These procedures are now being used in the field.
The purpose of this paper is to briefly describe the analytical work which was performed for both Marnock and Mungo, summarise the key issues, and outline the operating procedures that were developed (by the ETAP project) to manage the integrity of the conductor systems. Also contained in the paper is an outline of the topics which should be addressed when designing such systems for use from deep water jackups, working in cantilever mode (over fixed platforms).
Though each jackup/conductor/platform combination is unique, the novel techniques described in this paper will be applicable to other projects, where similar systems are being considered.
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