Abstract

Phase 1 of the Mooring Integrity JIP, as reported at OTC 2005 [2], highlighted a number of important mooring integrity challenges for the offshore industry. To address these challenges phase 2 was launched, which has attracted the support of 38 international participating organisations including Oil Companies, Operators, Design Contractors, Equipment Suppliers, Consultancies and Regulatory Authorities.

This paper presents a summary of some of the finding from the Phase 2 JIP, which has focused on testing, data gathering and improving design guidance. This paper covers the following areas:

  • Formulation of a practical method to estimate wear/corrosion based on calibration with field measurements

  • Feedback on the break testing of worn mooring components

  • The influence of proof load on fatigue endurance

  • Material compatibility guidance

  • Review of the effects of Microbiologically Influenced Corrosion (MIC)

  • Guidance on how to monitor station keeping performance and what to do with the data received

  • Summary of mooring line failure detection options

  • Inspection guidance for ROV operators

Phase 2 has continued to bring to the fore the importance of mooring integrity which has led to improved offshore inspection and condition monitoring. This paper presents the steps which have been put in place to improve mooring durability both in terms of design and integrity management, based on the operational experience. This information is thus fed back to designers to improve future systems.

Introduction

Phase 1 of the Noble Denton managed Mooring Integrity JIP highlighted the susceptibility of the moorings on even custom designed Floating Production Systems (FPS's) to a number of degradation mechanisms [1] and [2]. This led to the launching of our phase 2 JIP to try to tackle some of the most pressing issues. Phase 2 has been well received by the industry and the number of participating organisations has increased from 23 in phase 1 to 38 in phase 2.

During the course of the phase 2 JIP a number of high profile mooring failures have continued to take place, see for example [3] and [4]. These problems have illustrated the continuing difficulties of achieving mooring integrity while also, in certain cases, providing vital forensic evidence as to the possible cause of some of the failures. The main subjects that have been studied in phase 2 are outlined in the bullet points in the abstract. It is appreciated that these represent a fairly varied collection of topics, but this was judged to be necessary to tackle the key priority areas of mooring integrity as quickly as possible. It should be noted that at the time of writing the JIP programme is still underway, so this paper represents work in progress to date.

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