【作者】 李彬彬；

【导师】 欧进萍；

【作者基本信息】 哈尔滨工业大学 ， 防灾减灾工程与防护工程， 2011， 博士

【摘要】 近年来,随着全球化发展对能源需求的加剧,深水油气开发得到了快速的发展。浮式平台作为深海水域重要的钻井采油装备,其相关问题成为国内外研究的热点。目前,国际上广泛应用的浮式平台类型有:半潜式平台、张力腿TLP平台和Spar平台等。尽管这些平台已经在深水油气田的开发中扮演了重要的角色,但同时也存在着一些不足,例如:传统半潜式平台的水动力性能较一般、TLP平台造价和建造难度对水深敏感以及Spar平台特征尺寸大对船坞要求高等。因此,开发新型深水浮式平台,进一步的改进或改良其性能具有重要的现实意义。此外,对于深水浮式平台,作为其最关键的科学问题之一——水动力与运动性能仍需要进一步的研究。本文在对各类深水浮式平台进行总结、分析和比较的基础上,提出了一种新型的浮式平台概念——Deep Draft Multi-Spar(DDMS),为深水油气开发装备提供了一种新的解决方案。论文对DDMS平台进行了概念设计、频域内水动力与运动响应分析、时域内主体、系泊索和立管全耦合的运动响应分析、垂荡和纵摇耦合的马修不稳定性分析以及DDMS平台物理缩尺模型实验等。主要内容包括以下几个方面:(1)采用交互式的方法概念设计了一座工作水深1500m,排水量近7万吨的DDMS平台。概念设计主要包括平台的总体布置、主体尺寸估计、系泊系统布置、立管系统布置、平台重量控制、稳定性验算和运动性能验算等。另外,分析和获得了平台结构特征参数与平台稳性、水动力及运动性能之间的相互关系。(2)在频域求解了DDMS平台和Truss Spar的一阶水动力信息,并比较了两种平台的耐波性。在运动响应计算中采用了数值迭代的方法来处理粘滞阻尼等非线性项,并着重分析了垂荡板和平台主体产生的粘滞阻尼对浮式平台运动性能的影响。分析结果表明垂荡板能非常有效地降低平台垂荡响应;平台主体产生的粘滞阻尼对于纵荡低频动力响应有明显的抑制作用。由于自然周期增大,DDMS平台的垂荡运动性能进一步提升,明显优于Truss Spar平台,适用于多种不同海况条件。(3)建立了时域内平台主体、系泊系统和立管系统全耦合的数值预报模型。对非耦合、系泊索耦合和全耦合三种不同的数值模型进行了自由衰减测试和风浪流联合作用测试。通过这些测试,比较和分析了系泊索和立管对浮式平台总体响应的影响及其耦合效应。研究结果清楚地显示来自垂荡板和系泊索的阻尼能够减小平台垂荡方向的动力响应特别是纵荡方向的低频运动。在考虑系泊索动力响应的全耦合分析中,波频部分的系泊索张力占主要部分;对于考虑系泊索静力的非耦合分析中,低频部分的张力起到了控制作用。(4)建立了垂荡和纵摇耦合的运动方程,严格考虑了平台水线面积、稳性高度和排水体积随平台运动的变化关系。在规则波和随机波作用下分析了DDMS平台的马修不稳定性并着重讨论了阻尼对不稳定的发生起到的抑制作用。分析结果显示,垂荡板和系泊索对于抵抗马修不稳定的发生扮演了重要的角色。数值模拟的结果还很清晰地说明马修不稳定的发生来源于耦合运动之间能量的相互传递和转化。(5)在波浪水槽中进行了物理缩尺模型实验,获得了DDMS平台水动力和运动响应的实验室数据。模型实验中还特别包含了6种不同模型工况,用以考察垂荡板和开孔的龙骨立管导向板等薄板对平台水动力与运动性能的影响。实验结果揭示了对于垂荡响应,低频响应与波频响应是可比的,当波浪控制周期远离垂荡自然周期时,低频部分响应甚至大于波频部分。在包括中国南海千年一遇的6种不同海况下,DDMS平台都显示了良好的耐波性能,垂荡响应极值均不超过2.5m。更多还原

【Abstract】 Recently, the exploration of oil and gas in deepwater expands quickly to meet global development and energy needs. The problems related to deepwater floating platform are becoming the research hotspot due to the significant position of deepwater floating platform serving as drilling and production facility in deepwater oil and gas exploitation. At present, three main floating platform types, Semi, TLP and Spar platform, are widely applied in the worldwide deepwater oil and gas exploitation. However some problems are still existing e.g. poor hydrodynamic performance of conventional Semi, water depth sensitivity of TLP platform and the fabrication difficulty of Spar platform. Therefore, developing innovative deepwater floating platform and improving the behavior are significant and necessary. Meanwhile, being one of the essential research issues for deepwater floating platform, the hydrodynamics and motion performance of the platform still need further study. Based on review, analysis and comparison of various floating platform types for deepwater, a novel concept i.e. Deep Draft Multi-spar (DDMS) is proposed to be an alternative solution for deepwater oil&gas exploration. In this dissertation, the conceptual design of DDMS platform, hydrodynamics and motion of DDMS in frequency domain, the motion analysis of DDMS based on the hull/mooring/riser coupled model in time domain, the analysis of the platform Mathieu instability based on heave and pitch coupled equation, and the physical scale model test of DDMS platform are carried out. The main works of this dissertation are as follow:1. In this dissertation, a conceptual design of DDMS platform with 70,000t displacement working in 1500m water area is conducted. The conceptual design procedure includes the general arrangement of the platform, estimation of hull dimensions, arrangement of the mooring system and riser system, platform weight control, stability check, motion performance check and so on. Furthermore, the correlation between the characteristic structure parameters of the platform with the stability, hydrodynamics of the platform are acquired and analyzed.2. In frequency domain analysis, the first-order hydrodynamics of the DDMS platform and Truss Spar are computed and the seakeeping ability of the two platforms is compared. The interactive numerical method is applied in the computation of structure response to handle the nonlinear factors such as viscous damping. Furthermore, the influence of the heave plates and the viscous damping generated by the hull to the motion performance of the floating platform is especially analyzed. The results show that the heave plate can reduce the heave response effectively and the viscous damping contributed by the hull can suppress the low frequency response for surge obviously. The DDMS platform could be applied in more ocean environments than Spar platform due to its much better heave motion performance than the one of Spar platform.3. In time domain simulation, a hull/mooring/riser coupled model is established. The three different numerical models, uncoupled, hull/mooring coupled and hull/mooring/riser coupled model, are subjected to free decay test as well as the wind, wave and current joint action test respectively. Based on the above two tests, the effect of mooring line and riser on the global motion of the floating platform as well as the coupled effect are compared and analyzed. The results clearly show the damping from the heave plates and mooring line is able to reduce the dynamic response for heave and especially the low frequency motion for surge. The mooring line tension of wave frequency is the major contributor in dynamic analysis while the low frequency component is dominator in static analysis.4. Mathieu instability is carefully analyzed upon the establishment of coupled vertical and rotational motion equations which rigorously consider the varieties of water area, metacentric height and displaced volume with floater’s motion. The Mathieu instability of DDMS is studied in regular and random waves, and the damping effects which suppress the occurrence of Mathieu instability are investigated especially. For the Mathieu instability, damping of heave plate and mooring line play an important role in restraining the instability. The results also obviously indicate Mathieu instability is owing to the energy transfer and exchange between the coupled motions.5. The scale model test is executed in wave flume and relevant hydrodynamics as well as global motion are acquired. Six different model cases are employed in the model test to investigate the effect of various horizontal thin plates attached to the model such as heave plate and guide plate at keel with hole on the hydrodynamics and motion performance of platform. The recording heave responses significantly reveal that the low frequency component is comparable with the wave frequency component and even higher when the controlled wave period is far away from the heave natural period. For 6 different extreme environments in model test, even for the extreme environment of South China Sea with 1000-r return period, the DDMS platform exhibits favorable seakeeping ability whose maximal heave response does not exceed 2.5m.更多还原