| With the increasing demand for energy, the global exploitation of deepwater oiland gas is continuously improved. The drilling and production platforms are floatingplatforms such as tension leg platform (TLP), semi-submersibles (Semi-sub),floating production storage&offloading (FPSO) and Spar. The TLPs have bothsemi-fixed and semi-compliant features, which are used in oil drilling andproduction abroad extensively because of its excellent motion performance.However, so far there is no TLP to be built in our country China. For a long time,many scholars at home and abroad have done considerable research on TLP. One ofthe most core problems is hydrodynamic properties and dynamic responses of TLP.This research aims to master performances of TLP, develop new type of TLP, andincrease Chinese technical reserve on oil and gas exploitation in deep sea. In theintroduction, the source, significance and main contents of this thesis are illustrated.The most commonly used types of floating platforms in the exploration anddevelopment of deepwater oil and gas and its characteristic are summarizedespecially TLP, such as its development history, research status, main types andcharacteristics, the current research status and directions of development. Based onthe reviews of introduction, the main contents in this thesis are as follows:(1) The main contents of general design, relevant codes, operation regulationsand interaction design methods are introduced for TLP. The methods and the path ininnovating a new-type TLP are summarized. Then an innovative deep-driftmulti-column extended tension leg platform (DME TLP) is global designed underthe environmental conditions of South China Sea according to relational criterions.The analytical solutions of TLP’s nonlinear motion based on the corner are deducedaccording to the quasi-static analysis method. It is used to study the global motionresponse of TLP considering the main parameters. The influence of TLP’s tension,cross-sections, lengths and hull’s cross-section upon the global motion response ofTLP is analyzed.(2) The theory of potential flow and diffraction&radiation are used tocalculate the wave frequency responses of TLPs in frequency domain and theinfluences of tendon additional stiffness are considered. Four TLPs with commonforms and the innovative DME TLPs are chosen as research models, the motionRAOs of platform, additional mass and radiation damping in different conditions areobtained. The results show that the additional stiffness from tendons to platformreduced the motion RAOs of TLP in the energy focus range of wave period. Thenatural periods of surge, sway and yaw are longer, and heave is shorter. The patulous mooring system and optimization of waterline plane may reduce the hydrostaticstiffness matrix of platform, and RAOs of changed platform may be increased. Theinnovative DME TLPs have good performance on wave frequency response; itsmain parameters are diameter of column, spacing and draught.(3) The whole coupled response model composed of platform, risers andtension legs is built to simulate the motion response of different types of TLPs andDME2TLP in time domain considering the hydrodynamic parameters and thecombined action of wind, current and wave. The results show that surge and sway ofTLP, which are mainly composed by low frequency motion, are conspicuous andmotions of TLP in other direction are inconspicuous. Roll and pitch are mainlycomposed by high frequency motion. Yaw is mainly composed by low frequency.Because surge and sway can bring on heave, heave has many low frequencyelements. The effect of risers is to increase heave and its low-frequency contents.DME2has more excellent performance than CTLP in each direction.(4) The vibratory response analysis model of tendon is made based upon thetheory of string vibration. In addition, the nonlinear partial differential equations ofvibratory response of tendon are deduced. Afterwards an even more complex modelfor VIV of tendon is built considering the influences of platform motions and bothof wave and current loads. Moreover, the finite element method is used to analysisthe motion response of tendon. The results show that the motions of platformprovoked resonance of tendon in more frequencies. The tendon would have VIV, andit may be in a state of divergence.(5) The studies on performance improvement of TLP are completed to makeTLP apply to deeper waters or severe sea condition. A mixed mooring system of TLP,which is composed by catenary cables and vertical parallel tendons, is advanced toimprove the motion response performances of TLP, and the motion performance ofTLP in Extreme Sea Environments can be improved by adding pontoon on eachtendon. The analysis model of additional pontoon TLP is built. The hydrodynamicparameters of platform and additional pontoon are calculated by using thediffraction/radiation wave theory. In addition, the coupled dynamic responsebetween the platform and additional pontoon on the effect of wind, wave and currentloads is analyzed according to multi-module cooperative solving analysis andconsidering different pontoon dimension and emplacement water depth. |
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