Multi-body Hydrodynamic Analysis Of FPSO Offloading System

FPSO tandem offloading is a mainstream way for offshore oil offloading, due to the harsh environmental conditions at sea, when the FPSO and shuttle tanker offloading oil, there are obvious effect of hydrodynamic interaction between the two hulls and relative motion will become complex. Under certain sea conditions, collision risk of FPSO and tanker is higher and stable transportation becomes more difficult. In order to ensure safe operation and avoid a collision, it is necessary to connect a tug to the tanker for positioning. This paper analysis hydrodynamic properties, motion response, mooring cable and hawser tension for FPSO and the offloading system with DNV software SESAM.Based on the potential theory, this paper calculated hydrodynamic properties for FPSO and multiple floating-body system under different conditions with SESAM/HydroD module. I got added mass coefficient, potential damping, motion response, the first-order wave force and second-order wave force transfer function.This paper uses catenary equation for the FPSO mooring system design, calculating dynamic response of FPSO and forces of mooring lines under working conditions and extreme conditions. The effect of pre-tension and stiffness of mooring cable to the motion of FPSO and mooring system is considered. Studies have shown that increasing the stiffness of the mooring line could suppress motion of FPSO. In storm conditions, reducing the pre-tension appropriately will help ensure safety of mooring system.The main failure mode of FPSO offloading system is excess surge, fishtailing motion and break of hawser. In this paper, relative surge motion, heading angle between FPSO and tanker and tension of haswer under different loading condition are calculated with SESAM/DeepC module. Some of the key parameters affecting the offloading system, such as the distance between the two ships, hawser stiffness, wave peak period, the wind and breaking mooring are calculated and analyzed. The risk FPSO-tanker dual floating system is significantly reduced by connecting a tugboat to the tanker. Optimizing the offloading system to get the best arrangement. The results have certain reference value for the design of offloading system.