FPSOs are becoming extremely important economically. Many nations/organizations are using them to supplement the conventional oil rig/floating platform especially due to the refinery capability they exhibit in situ in the drilling environment. However many of the multinational oil and gas companies are drifting towards the conversion of VLCCs to FPSOs. It is against this backdrop that a work of this nature considered an optimized method of converting an FPSO from a VLCC. The various methods of producing such a vessel were looked at taking two FPSOs: BONGA (New Build) and MYSTRAS (Converted) operating in West African Waters as case studies. A number of vivid and valid ship construction parameters were taken into consideration using a computerized model. Analysis reveal that the block coefficient (CB) yields an important result that if put in place during the design phases of FPSOs – be it new build or converted will go a long way to enhance the conversion process. The CP of the new build FPSO was found to be 0.7202 while the converted one was 0.690 with sponsons and 0.818 excluding sponsons. The CP equally further supports the increased deck space which the modification provided with the strength analysis. Bending Moments and Shear Force distribution along the longitudinal axis (i.e. length) of the vessels with sponson fitted were determined and the section moduli of important/critical sections calculated. Stability analysis was carried out to cover the most critical modes and condition of the vessel’s operation. Righting levers was computed at prescribed loading conditions in the various operating regimes. Results obtained from the analysis showed that incorporating sponsons provided sufficient rigidity and good stability characteristics of the hull under all operating conditions. Finally, on the economic trend, the use of converted FPSO is favoured to those of new build due to the reduced lead-time.

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