Hydrodynamic aspects of turret-moored FPSOs

Abstract

As oil and gas exploration moves toward deeper, harsher waters, and marginal fields, the issues concerning the associated floating production storage and offloading ships (FPSOs) get more complex. Traditionally, at the early stage of the design of FPSOs, subsystem design is individually taken up and subsystem interactions are accounted for through an uncoupled approach, as against a more rigorous fully coupled approach. In fully coupled approach, the system components and mutual interactions are coupled concurrently. Issues related to mooring system of FPSOs are some of the key aspects needing close attention. Approaches for determining the peak behavior belonging to turret-moored FPSOs to random wind, seawater flow, and wave forces for a specified life are still evolving. In the case of weathervaning FPSOs, special consideration is essential for the representation of realistic non-collinear environments. Also, choice of location of turret inside hull is an important design decision, as turret position influences motions. Similarly, another aspect requiring attention is the development of resonant sloshing due to excitation owing to external waves. Also combined piston modes happen within the turret and in the volume between turret and moon pool walls, which is an important hydrodynamic phenomenon. The flow parting via chain table openings heavily damps the piston mode. The paper reviews the literature on some of these hydrodynamic aspects concerning motion response of turret-moored FPSOs.