Study On The Impact Of Single Line Failure For The Mooring Assisted Dynamic Positioning System

The higher demand of oil and gas has led to their exploitation and exploration in hasher and deeper waters.The capability to keep position with high accuracy of floating structures has been more and more concerned.Mooring assisted dynamic positioning(PM)system is a new positioning system combining mooring system with dynamic positioning(DP)system.It has a great potential for application with the advantages of high safety,high positioning accuracy and low power consumption.Time domain simulation is an effective method to investigate the mooring assisted dynamic positioning system,it can preliminarily evaluate the positioning ability,positioning accuracy and power consumption of the system.It's of great significance to formulate a precise time domain simulation program for mooring assisted dynamic positioning system.Meantime,the PM system may have failure modes,such as mooring line break,which will lead to serious position loss and power saturation,or even dangers to the workers' life.Therefore,relative analysis should be conducted with the PM system when the most loaded line breakage occurs.With a PM system for a certain deep water semi-submersible drilling platform as the subject,this paper is dedicated to conduct a time domain simulation and a single line breakage analysis under working condition.Main work includes:(1)Formulation of the time domain simulation program for PM system.Treat the mooring system as a static model and the effectiveness of the program is validated(2)Time domain simulation of the PM system when the most loaded line breakage occurs,variation of the positioning accuracy and power consumption(3)Model test of mooring assisted dynamic positioning for a semi-submersible platform is conducted to validated the numerical resultsThis paper combines the self-programming and hydrodynamic software,and do some research on the positioning accuracy and power consumption of the PM system.The situation when the most loaded line breaks is also accounted for,finally an iterative solution is suggested to solve the coupled problem between mooring system and dynamic positioning system,and some conclusions have been draw,which may be of great help to the development of the calculation of mooring assisted dynamic positioning system.