| With the oil exploitation gradually developing towards deep water, the relative problems about the ocean floating platforms as fundamental facilities have become the research hotspots. At present, there are three kinds of ocean platforms all over the world, which include Tension leg platform (TLP), Semi-submersible platform and Spar platform. Although these platforms have played an important role in offshore petroleum industry, the deficiencies of them still exist. For instance, TLP platform is highly sensitive to water depth. Furthermore, the Semi-submersible platform and Spar platform are greatly subject to the carrying capacity and sole function. Therefore, the ocean platform begins to present the trend of multifunctional integration. As the successful instance, FPSO (floating production storage and offloading system) and FDPSO (floating drilling production storage and offloading system) have become more and more popular among the ocean industry.By analyzing and comparing the performance of various floating platforms, this paper proposes an innovative sandglass-type floating body and a novel concept of sandglass-type floating drilling production storage and offloading system and the preliminary design of the main body, which can not only maintain the advantages of ship-type and cylindrical FDPSO but also withstand the severe sea conditions. The new concept includes sandglass-type floating body and relative functional modules, in order to provide a completely new engineering equipment and solution method for oil exploration. The main works of this dissertation are as follow:For the new sandglass-type floating body, by using the hydrodynaminc analysis software AQ WA, the influences of downward inclination, water-plane radius and displacement volume on wave load and motion response amplitude operators (RAOs) are qualitatively analyzed.On this basis, the viscous damping and nonlinear stiffness are considered. Then by means of potential theory and engineering method, the approximation formulas of heave F-K force, diffraction force and the frequency versus minimum RAO are deduced. Furthermore, according to the definition of stability and geometrical relationship of floating body, the calculation expression of initial stability can be achieved. Finally, the design scheme of sandglass-type floating body is summarized and formulated.Based on the scheme, a sandglass-type floating body with the same functions as the Sevan cylinder-type FPSO and CNOOC octagonal type FPSO has been introduced as a case study. The results show that the shape design of sandglass-type concept can obviously improve the stability and various hydrodynamic performances (heave and pitch motion, green water and steady drift force, etc.).In order to better verify the advantages of sandglass-type concept, the accuracy of the theoretical analysis method,and the feasibility of dsign scheme for the main body, a model experiment of water tank has been performed, which mainly includes natural period of pitch and roll motion, viscous damping coefficient, heave and pitch motion RAO, and motion response under random waves, etc. The results demonstrate the advantages of the sandglass-type concept, and provide the basis for following research.Furthermore, the effects of the moon-pool's shape and size on the hydrodynamic performance of sandglass-type floating body are analyzed. Then the scheme of sandglass-type FDPSO is obtained. Compared with a ship-type FDPSO, a cylindrical FDPSO and a semi-submersible platform, the advantages of sandglass-type FDPSO about heave and pitch hydrodynamic performance are validated. Moreover, the influences of COG height and inertia moment on its hydrodynamic performance are further studied to provide theoretical evidence and design principle for the follow-up design.A deep-water taut mooring system has been presented for the sandglass-type FDPSO. Firstly, the effects of different parameters have been analyzed respectively, which include low-frequency surge damping, wind and current coefficient, hydrodynamic coefficients of mooring line, fairlead position and hang angle, and so on. Then according to standard requirement, the strength and station keeping performance of taut mooring system are checked. Next, in the fatigue analysis, the dynamic stiffness of fiber rope has been introduced into the fatigue calculation. Finally, some instructive conclusions on engineering practice are made to provide an economical and reliable deep-water mooring system. |
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