FPSO Computational Fluid Dynamics (CFD) analysis in heavy sea storm conditions for the validation of process design

In the last years, the use of FPSOs is becoming a widespread technology because it is a practical and cheap system for the exploitation of small oilfields or deep water oil wells, i.e. oilfields for which the installation of pipelines is too expensive. Recently, growing attention has been devoted to the advanced design of vessels able to operate effectively even when the system is subject to abrupt movements. The study of the behavior of process fluids (gases and liquids) and their mutual interfaces within the FPSO separators is a very challenging task, which can be tackled effectively by means of Computational Fluid Dynamics (CFD) techniques. In this paper, a fluid dynamic model of a FPSO separator is developed using a CFD methodology. This model is able to predict the behavior of the fluid and of their interfaces within the separators to be installed on FPSOs. Several simulations were carried out to study the behavior of the fluids and the efficiency of two vessel types (reboiler and surge vessel). The vessels are subjected to the forcing conditions typical of an ocean storm, i.e. surge, sway, heave accelerations and roll, pitch and yaw rotations, gathered from real historical data. Transient simulations were carried out applying time-varying accelerations to the vessel. The methodology is described in order to give general guidelines for the FPSO simulations. The main technical contributions of this study are: • the understanding of the behavior of the liquid in the separator mounted on FPSOs in different storm conditions; • the validations of FPSO separator design to assure their functionality even during heavy storms; • the development of a numerical methodology to implement complex CFD simulations in the presence of time-varying boundary conditions which models the effect of sea movements on on-board ship devices