FPSO Mooring Line Fatigue

Offshore oil and gas FPSO vessels maintain their position in the seas by mooring system. FPSO vessels are made to serve for long operational time in the ocean for example 25 years. Thus, the mooring system which mainly comprise of mooring lines are required to be reliable for its service lifetime. In order to achieve a standard level of reliability, the fatigue property of mooring line is one of the important aspects that was considered.
The non-linear dynamic characteristic of mooring system as a result of the random nature of the ocean waves creates high computation time. Therefore, the objective of this project is to reduce the fatigue damage analysis cases through sensitivity studies. The studied parameters for sensitivity are the mooring configurations, environmental loads, loading condition and riser existence. Effects in fatigue are studied through the utilization of DeepC software for an internal turret-moored FPSO which is located in West Africa. This location is chosen to simplify the environment data collection process by adopting a similar environmental condition as provided in [1]. The FPSO mooring system comprise of 12 mooring lines (4 bundles x 3 lines). Each parameter are applied to investigate its effect towards the fatigue damage of the mooring lines.