Research On Design Of Obround FPSO

In the exploitation of offshore oil resources, Floating Production Storage and Offloading,referred to as "FPSO",is most widely used. A complete offshore oil exploitation and production system contains FPSO, which is an integrated marine floating device capable of the production process, storage and transportation of oil, a subsea production system and the shuttle tanker. Current FPSO is basically in ship-shaped or cylinder-shaped, the advantages and disadvantages of which are summarized here while an FPSO in obround, combining the dominant scale advantages of the ship and cylinder shaps, is proposed and designed in this paper, whose subdivision and mooring scheme designs are studied.Based on the advantages and disadvantages of the existing traditional FPSO, an obround FPSO is designed. Finite element analysis on ship-shaped, cylinder-shaped and obround FPSO indicates a strong comprehensive adaptability of the obround FPSO on hydrodynamic performance. Also, qualitative analysis of the advantages of structure design, stability and general arrangements support the good comprehensive performance of the obround FPSO.In order to reduce the hydrostatic bending moment of the obround FPSO, the subdivision of the obround FPSO is studied. But there are a lot of performance that is affected by the subdivision, which involves the stability, the effective capacity and many other aspects, so this is a multi-objective optimization. Combined with the regular experimental design method,numerical simulation and the approximate model technique, multi-objective optimization software Isight, calling Matlab assembly, is used to establish the framework of multi-objective optimization, with the hydrostatic bending moment, the area of the used steel plate and the effective capacity selected as the objective function; the width of side tank, the width of central ballast tank, the number of longitudinal compartments and the length of each compartment selected as design variables; intact stability, damage stability and specification requirements as the constraint conditions. Proper search strategies are applied in the solution of the multi-objective optimization of subdivision of the obround FPSO, resulting in the Pareto frontier solution set between every objective. By comparing the result with the sample points, it is known that no values of objective function of sample points are all better than that of Pareto solutions, validating the feasibility of subdivision multi-objective optimization framework.The study on the mooring system of obround FPSO is conducted. Based on the AQWA-LINEJDRIFT module in AQWA, tension type single point mooring system of the obround FPSO is analyzed couple-dynamically, and the movement performance and mooring force of mooring system under the wind and wave are further calculated. The effect of position of inner turret, distribution form of mooring lines and the number of mooring lines on FPSO mooring system performance is discussed, based on which, an optimized mooring scheme is proposed, where the distance between the turret and the stem is 10% of the length between perpendiculars and a 3 × 3 root/group three-step cable arrangement is used.