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Reliability analysis of FPSO mooring systems and the interaction with risers

Book ·
OSTI ID:455481
;  [1];  [2];  [3]
  1. Noble Denton Europe, London (United Kingdom)
  2. BCD Offshore, Basingstoke (United Kingdom)
  3. BP Exploration, Sunbury-on-Thames (United Kingdom)
Turret moored Floating Production Storage and Offloading (FPSO) systems are considered suitable for a wide range of environmental conditions but experience of designing moorings for these units in harsh environments is limited. Furthermore, each floating production system has its own requirements as to the way the riser system is operated because of its dependence on both reservoir and site specific conditions. The current mooring codes do not have a consistent set of requirements; for example, the intact mooring system safety factors range from 1.5 to 2.3. Such vastly differing requirements result in wide variability in the intrinsic safety, reliability and cost. This paper describes a reliability analysis carried out for the first North Atlantic FPSO (Foinaven), to address the acceptance criteria for moorings by returning to the fundamentals. Although the analysis deals with FPSO`s, the approach is applicable to any catenary moored unit. One primary purpose of the mooring system is to maintain the integrity of the riser system. Level 2 reliability analysis techniques have been used to compute the interacting probability of line tension failure and exceedance of riser design excursions. These studies have shown that it is possible to gain safety and cost advantages by integrating the analysis of moorings and risers using carefully determined target reliability levels obtained from calibration analysis and/or industry norms. The paper also sheds further light on the magnitude of the safety factors needed to achieve the desired reliability levels.
OSTI ID:
455481
Report Number(s):
CONF-9606279--; ISBN 0-7918-1491-2
Country of Publication:
United States
Language:
English

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