Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering ConferenceShanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Deepwater Mooring Monitoring and Early Warning System Development
Xueping Bai 1, Xiaoyong He1, Yongjun Chen 2, Da Li1,4, Yongfeng Wu 3
1
CNOOC Research Institute, Beijing, China
2
DMAR Engineering, Inc., Houston, Texas, USA3
CNOOC Hainan, Haikou, Hainan, China
4

College of Shipbuilding Engineering, Harbin Engineering University, Harbin, Heilongjiang, China

multiple mooring line failure of Gryphon Alpha FPSO in UKCS wascaused by the severe weather (Christou, 2012 & Bhardwaj, 2017).

ABSTRACT
For deep-water floating structures, mooring system is essential for thesafe operation of the facility. Historical accidents show that mooring
failures can put serious threats to the environments, asset, and evenhuman lives. First, detailed numerical analysis is performed for themooring system of a deep-water platform. Then, the response
characteristics and effects of mooring failure on platform performanceare studied. Finally, a mooring monitoring and early warning system
are proposed based on the numerical analysis results.

Based on the historical accident data, the main reasons for the mooring
failure include 1) several environments, 2) component failure due tomanufacturing defects, corrosion, fatigue, etc., and 3) human error
during installation and operation.
Mooring system failure will reduce the floating structure’s stationkeeping capability, and may cause progressive failure of neighboringlines, and thus results in large offset and even riser rupture, production
shutdown.

KEY WORDS: Deep Water; Mooring System; Monitoring System;
Early Warning System;

Lingshui 17-2 Semisubmersible is China’s first deep-water floatingproduction platform and its spread mooring system is China’s firstpolyester mooring system, which create significant challenges to its
operator (Jia, 2018). In order to assist the operator to know the realtime performance of the mooring system, and improve the safe
operation and maintenance experience, an integrated mooring
monitoring and early warning system is developed and installed on theplatform.

INTRODUCTION
Mooring system is an indispensable component of deep-water floating
structure, which responsible for station-keeping under extreme weatherconditions. Mooring system affects not only the rigid body motions of
the floating structure, but also the performance of riser system.
A mooring system normally comprises mooring lines, anchors andconnectors. A mooring line connects the floating structure to an anchor
on the seafloor. The typical materials employed for mooring line
include chain, wire, synthetic fiber rope, or a combination of the three.
Water depth and environmental condition determine which materials
make up the mooring system. Due to its lightweight, low cost, and highhorizontal restoring efficiency, polyester rope becomes more and more
popular for the permanent mooring system of deep-water floating
structures (Chen, 2013).

NUMERICAL ANALYSIS FOR MOORING SYSTEM
In order to develop a fit-for-purpose monitoring and early warning
system, the system global performance under design environmental
conditions should be studied. Meanwhile, the impact of single line
failure on the system performance and the associated recovery
approaches should be investigated.
Design Parameters

During the past two decades, there are numerous mooring incidents
around the world for offshore oil and gas industry. In 2008, themooring incident for Kikeh Spar in Southeast Asia was due to its
improper heat treatment of the shackle (Gordon, 2014). In 2011, theTake a deep-draft semisubmersible production platform as example,
detailed numerical analysis is performed. The mooring system consistsof 16 mooring lines with 4 on each column. The angular space between

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