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新型深吃水多柱延伸式张力腿平台的概念设计与耦合运动响应分析

Conceptual Design and Coupled Motion Response Analysis of An Innovative Deep-draft Multi-column Extended Tlp

【作者】 闫功伟

【导师】 欧进萍;

【作者基本信息】 哈尔滨工业大学 , 工程力学, 2013, 博士

【摘要】 随着全球能源需求量的不断增加,越来越多的深海油气资源得以勘探和开发,采用的钻采设备主要是不同类型的浮式平台,其中以张力腿平台、半潜式平台、浮式生产储油轮和柱式平台这四种最为常用。张力腿平台,运动性能优良,同时具有半固定和半顺应的特点,已被广泛应用于世界众多深海油气钻采工程当中,但目前在我国尚没有一座在建或投入使用。世界上的很多学者已经对张力腿平台的各方面性能做了大量的研究,其中水动力特性及动力响应性能是张力腿平台最核心的科学问题之一。为了掌握张力腿平台的各方面性能,为我国深海油气资源的开发积累技术储备,本文在综述目前世界深海油气资源勘探开发中常用浮式平台的类型和特点以及张力腿平台的发展历史、不同型式的特性和主要科学问题的研究现状及方向的基础上,主要做了以下几方面的研究工作:(1)介绍了张力腿平台的总体设计内容、相关规范规程、交互式设计方法和基本力学特性,归纳出了深水浮式平台型式创新的方向和原则,提出了一种新型的深吃水多柱延伸式张力腿平台,并根据我国南海特定海域的实际环境条件对它进行了概念设计和选型,得到了此种平台的基本特性,结果表明新型深吃水多柱延伸式张力腿平台所受到的波激力状况要明显优于传统张力腿平台,具有更好的动力响应性能。用拟静力的方法分析了张力腿平台运动对各参数的敏感性,结果表明影响张力腿平台性能的主要参数有平台水线面面积、张力腿的初始预张力和就位长度。(2)应用势流理论及波浪的绕射和辐射理论,考虑系泊系统的附加刚度,建立和求解了张力腿平台上体的波频响应运动方程。以四座常用类型张力腿平台和新型系列深吃水多柱延伸式张力腿平台为对象,建立它们的数值计算模型,分别计算了它们的水动力参数和波频响应,结果表明系泊系统的附加刚度使得波浪能量集中的周期范围内平台各方向的运动幅值响应算子取值均变小,纵、横荡和首摇均呈现出很长的自然周期,垂荡和纵摇的自然周期很短;水线面的减小将同时减小平台的波浪荷载和静水回复刚度,会同时增大平台垂荡和纵摇的幅值响应算子;新型深吃水多柱延伸式张力腿平台具有良好的波频响应特性,立柱的直径、间距和吃水是影响其性能的主要参数。(3)考虑多种环境荷载与平台运动的耦合关系,建立了由平台上体、立管和张力腿系泊系统共同组成的张力腿平台时域耦合运动方程,并给出了方程迭代求解的方法。建立平台全耦合运动系统的数值模型,数值模拟不同工况下四座常用类型张力腿平台和新型深吃水多柱延伸式张力腿平台的时域运动响应,结果表明张力腿平台纵荡将引起垂荡,它们和首摇运动均以低频成分为主,而纵摇就是高频成分占绝对优势的波频响应,立管的主要作用是增加平台主体的沉降和提高垂荡响应的低频成分比例,新型张力腿平台在各方向上的运动性能均要比传统式张力腿平台优良。(4)应用弦振动理论推导了张力腿在流荷载作用下产生卡门涡街时的非线性偏微分振动方程,从而建立了适用于概念设计阶段的平台张力腿动力响应快速预报模型,进一步推导了张力腿在顶端受到平台各方向运动作用时的动力响应计算方法,最后用数值模拟的方法分析了一个张力腿算例在波、流联合作用下在不同方向上和不同工况下的动力响应,其中考虑了张力腿的运动与所受流荷载大小及方向的耦合效应。结果表明波浪荷载的作用很小,平台的运动会激起张力腿在更多频率上的共振响应,在一定条件下张力腿会产生涡激振动并处于发散状态,这将严重危害平台的安全。(5)提出了两种能够使得张力腿平台适用于更深海域或更恶劣海况的方案:混合系泊系统方案和附加浮箱张力腿方案。数值模拟结果表明装备混合系泊系统的张力腿平台各方向的响应幅值均会有显著地减小,在张力腿的一定位置附加浮箱可以显著降低平台的纵荡和垂荡响应极值和平台的慢漂响应,但对纵摇没有明显作用。

【Abstract】 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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