Coupled dynamic analysis of thruster-assisted turret-moored FPSO

Abstract

To reduce large motion responses of a turret-moored Floating, Production, Storage and Offloading (FPSO) unit in harsh environment in deep waters, a thruster-assisted position mooring (POSMOOR) system can be applied. By applying the system, global dynamic responses can be improved in terms of the mooring line/riser top tensions, operational radius of the FPSO, and the top and bottom angle of the production risers. Kalman filtering as an optimum observer and estimator for stochastic disturbances is implemented in the developed control algorithm to filter out wave frequency components. Investigation of the performance of a thruster-assisted turret-moored FPSO was conducted in terms of surge, sway, yaw motions, and tension time series by using a fully coupled hull/mooring/riser dynamic analysis program in time domain. The two cases, motion analysis of an FPSO with thrusters and without thrusters, are extensively compared. The numerical examples illustrate that a thruster-assisted turret-moored FPSO can be an effective solution compared to a conventional turret-moored FPSO for deepwater production.