Hull Performance Assessment and Comparison of Ship-Shaped and Cylindrical FPSOs With Regards To: Stability, Sea-Keeping, Mooring and Riser Loads In Shallow Water

Floating, Production, Storage and Offloading “FPSO” have become a popular choice since 1980s for marginal and fast-track developments where subsea pipeline is not an economic or feasible solution for export. Field development usually starts with a concept selection procedure which is constituted from a sequence of multi-disciplinary decision making tasks. As limited data is available in the early phase of the development, operators require a robust and rational decision making process to reduce the drawback of immature information. The Multi-Criteria Decision Making (MCDM) process which is used in this paper is an industrial approved and accepted decision making process that can resolve this requirement. This method is commonly used as a decision making method for multiple attributes problems.
The main objective of this study is to illustrate the application of this method for concept selection for shallow water fields. Here the problem is reduced to a selection among two common FPSO concepts: ship-shaped and cylindrical by assessing their performances for the same location. The primary attributes which have been used for performance assessment includes: stability, motions and accelerations, riser stresses and mooring line tensions under both intact and damaged conditions. To simplify the problem, the same topside weight and tank capacity are considered and response comparison is limited to the linear responses induced by wave under full loaded conditions. For both FPSOs spread mooring system with steep-s flexible riser system are considered.
For the given environmental conditions, cylindrical FPSO shows better motion characteristics which leads to smaller mooring and riser loads. This method should be generalized for other shallow water production system by including all the attributes used in the shallow water field development concept selection