As potential offshore oil fields shift from shallow water to deeper ocean, floating production, storage and offloading (FPSO) systems become more attractive than conventional huge fixed type platforms. Recently we have successfully completed conversion works of two FPSO's from old 280,000 DWT VLCC's and they will be towed and installed at Campos Basin, offshore Brazil. During this project elaborate hydrodynamic and structural analyses were performed to ensure proper function as an FPSO and to convince safety during conversion and towing stage. This paper summarizes general arrangement and typical results of the analyses. Introduction As potential offshore oil fields shift from shallow water to deeper ocean, floating type production platforms such as floating production. storage and offloading (FPSO) systems become more attractive than conventional huge fixed type platforms. The FPSO system is known as economical alternatives to fixed type platforms for deep water applications. Since FPSO has integrated function of production, storage and offloading, its conceptual design is very important to ensure the full performances or these multifunctions. Especially, mooring system has a unique device called turret. Turret enables the FPSO to weathervane with minimum environmental mooring force. A multi-path fluid swivel acts an essential role for oil transfer without leakage during weathervaning. In order to reduce operational cost mooring scheme without thruster-assistance is preferred in spite of quite deep water of around 1,000 meters. Recently Hyundai Heavy Industries has successfully completed conversion works of two FPSO's for Petrobras. Henrique Dias and Jose Bonifacio, from old 280.000 DWT VLCC's and they will be towed and installed at Campos Basin, offshore Brazil. During this project, elaborate Analyses1 were performed to ensure proper function as an FPSO and to convince safety during conversion and towing stage. It covers naval architectural calculations. stability. motion mooring, and fatigue analysis for in-place condition and/or towing condition. Also various global and local structural analyses were performed for floating construction, towing and in-place conditions. During the structural analysis, special attention was paid to consider highly corroded areas arisen from the previous usage as a VLCC. This paper summarizes general arrangement and typical results of the analyses for the Jose Bonifacio. General Arrangement Basically, the hull is converted from 280.000 DWT VLCC that is 17 years old. The general arrangement and principal particulars of FPSO are shown in Figure 1 and Table J respectively. It is claimed that the locations of a flare boom a turret and accommodations are important factors for general arrangement. Generally, the location of accommodation is arranged at stem part as it was for converted hull case. Therefore, the location of the flare boom is at bow which is far from accommodation to prevent the hazardous condition. in spite of forward direction against wind direction. Turret opening may be either at the midship or bow. To ensure the good weathervaning, bow is preferred in our case. However, midship may be chosen in cooperation with thruster-assisted mooring to improve the heave motion characteristics. On the forward part of main deck, a turret and a flare boom are installed.
In these days energy demand is dramatically increasing on the developed and developing countries. Even though the electric power efficiency is gradually improved, the limited energy resources and the shortage of land to construct generations have been existed for long time ago and the environmental limitation like the Kyoto-Protocol is originated. To overcome these obstacles, there is one solution through the cooperation on the national-wide. That is, we should meet the energy problem with having strong relationship among nations. The technological and systemic cooperation on electric power system is much more important than before. It is sure that there are economical and systemic advantages over the limitations when interregional power systems are operated well. Simply, power system interconnection gives the eco-friendly energy' applications and the flexible operating power system. In this paper, the first is focused on the algorithms on the power system and the other is based on the economic side. It is mainly to discuss the tertiary control illustrated over each first and secondary controls existing on two control areas.
A spectral fatigue analysis method is most popularly applied for the detailed design of FPSOs. As the environmental loads at the installation site are directly calculated in the spectral analysis, this method gives the most reliable results although it needs much time-consuming works to fully reflect the environmental loads. As the technology of wave measurements advances, the measured wave data increase. Also their spectral models are very complicated because these include many wave components such as swells and wind seas. Since much time and effort are needed to treat these enormous and complicated wave data for the spectral fatigue analysis, a rational idealization of wave data is definitely required. In this paper, wave scatter diagram at Offshore Nigeria was reviewed and their idealization method was proposed. The influence level of each sea state of the wave scatter diagram was identified considering the fatigue damage levels estimated from the significant wave heights and dominant fatigue load RAOs. The sea states giving small fatigue damages were lumped symmetrically by merging or disregarding while those giving large fatigue damages were kept as original. For the validation of this method, the comparisons of dominant fatigue loads and representative fatigue damages were presented for the idealized wave scatter diagram and the original one. From these comparison works, it was confirmed that the idealized wave scatter diagram gives reliable results with reduced amount of calculation work.
Gas explosion accidents have been recognized as a major hazard of offshore facilities in oil & gas industries. Due to the nature of offshore topside structures, even a single collapse of structural members or equipments may lead to enormous economic and environmental losses. Therefore, such potential hazards that cause the accidental collapse need to be evaluated closely. Gas explosion has been categorized as an important issue of the design of offshore structures regarding the severity of the accident. This paper presents practical considerations for the nonlinear dynamic structural analysis of offshore structures under blast loadings from gas explosion accidents. Numerical investigations including modeling of blast loads and idealization of structural materials and members have been conducted for the overall topside structures. As a design step for offshore structures under blast loadings, an applicable guidance on the finite element analysis (FEA) is described in this study.
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