The FPSO is a floating, production, storage and offloading ship-shaped vessel. Production facilities are mounted on raised supports above the vessel deck. Reservoir fluids pass from subsea production wells, via flowlines and risers, up into the turret and then to the production facilities. Produced oil is stored in the vessel cargo tanks and periodically offloaded onto a shuttle tanker via a loading hose.
(Courtesy Internet Reference 91)
FPSO design has shown a fast evolution in recent years. The concept is more and more frequently used for deepwater solutions and in addition new design concepts are being considered. (reference)
FPSO concepts have frequently been based on converted tankers. Shipbuilding standards could be directly applied and the hull design could be covered with existing ship Rules. However, specific operational tanker design criteria are no longer applicable to FPSOs as the hull now becomes a floater with storage capacity rather than a sailing tanker. Therefore it is justified to raise the question whether a new build FPSO is to be considered as an offshore structure or that traditional maritime principles are still applicable.
An FPSO, being a permanent offshore installation based on a tanker-like vessel, carries design aspects in it from two design cultures, i.e. shipbuilding and offshore. A typical tank arrangement of a converted single hull tanker consists of two side ballast tanks in the cargo tank area and generally provides sufficient ballast capacity for FPSO operation. For a new build FPSO it is beneficial to arrange ballast tanks such that initial and operational costs are minimized. A possibility is to design the side tanks as void spaces, and dedicate one large central tank in the cargo block to be used as ballast tank or kept void in loaded condition. Separate trim and heeling tanks are arranged in fore and aft ship. Such an optimum ballast system can only be achieved if riser loads and process modules are evenly distributed.
A ship structure is relatively flexible. Topsides modules must therefore be supported such that they are compliant with the hull girder. Also the topsides designer has to set his dimensions and support arrangement in line with the ship structure.
Adapted from Cathodic Protection Strategies for FPSO's Jim Britton
See also: Fouling,FPSO, Ions in seawater,DO in seawater, Seawater scaling, Anti-fouling coatings
FPSO Design and Conversion: A Designer's Approach by T. Terpstra, IHC Gusto Engineering; B.B. d'Hautefeuille, Single Buoy Moorings; A. A. MacMillan, Det Norske Veritas (Courtesy Internet Reference 93)
FSU : Floating Storage Unit
FPU : Floating Production Unit
FPSU : Floating Production & Storage Unit
FSO : Floating Storage & Offloading
FDPSO : Floating Drilling Production Storage & Offloading
FSG : Floating Storage of Gas
FGSO : Floating Gas Storage Offloading
FPSG : Floating Production Storage of Gas