【作者】 乔东生；

【导师】 欧进萍；

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

【摘要】 目前,我国的海洋油气资源开采主要集中在渤海海域,而占我国领海面积3/4比例的南海海域,油气资源开发近乎空白。据初步估计,整个南海海域的石油地质储量大约在230亿~300亿吨之间,约占我国总资源量的1/3,属于世界四大海洋油气聚集中心区域之一,具有“第二个波斯湾”的美称。我国油气资源开发目前主要集中在200m水深以下的近海海域,油气开发的最大钻探水深为500多米,最大作业水深仅为300多米,深水油气开发技术储备严重不足,与国外海洋工程技术水平差距明显。令人遗憾的是,在我国南海和周围国家有所争议的海域,越南和菲律宾等国家已经率先开始在这些争议海域开始了石油开采,加快南海区域海洋油气开采的步伐已经迫在眉睫。深海采油平台一般均需要通过锚泊定位系统来保持其在一个相对固定的位置,所以锚泊定位系统设计是海上浮式结构物整体设计过程中绝不可忽视的重要环节。锚泊定位系统性能主要取决于海洋环境条件、浮式结构物和锚泊线所受的环境荷载作用、锚泊线的材料及其动力性能、锚泊线布置形式、海水水深等因素的影响。建立合适的数值计算模型和相应的分析技术可从机理上研究锚泊定位系统的动力特性、预测锚泊定位性能,并能够进一步的指导设计及施工。锚泊定位系统的分析主要包括两部分内容:锚泊线自身的性能研究和对浮式结构物的作用。锚泊线自身的性能研究包括其静动力性能、疲劳性能、锚泊基础性能三部分。对浮式结构物的作用主要表现在:锚泊阻尼的影响、与浮式结构物的耦合作用。这些问题的解决途径仍然是数值模拟与模型试验两种方法,但在具体的实施过程中仍然存在很多的问题需要解决。本文主要研究工作包括以下几部分内容:1.利用分段外推法进行锚泊系统静力特性分析,计算中考虑竖向位移对复合锚泊线回复力特性的影响;采用非线性有限元方法进行锚泊线动力响应计算;对复合锚泊线自振频率和刚度等动力特性进行比较分析,其中对聚酯纤维锚泊线的材料特性进行了总结。2.采用非线性有限元时域方法针对深水锚泊线为浮式平台的阻尼贡献进行计算;针对不同参数的影响进行研究并得到一些规律性认识,并对这些规律性认识分别进行统一化的公式拟合;对复合锚泊线的锚泊阻尼特性进行比较。3.针对HYSY-981半潜式平台,在哈尔滨工业大学大气边界层风洞及波浪模拟水槽中进行物理模型试验;基于静力等效设计等效水深截断锚泊系统;获得半潜式平台及其锚泊系统的运动响应试验数据;根据模型试验与数值模拟的比较结果,提出利用粘滞阻尼器补偿截断锚泊线和全水深锚泊线动力性能差别的新概念;对具有粘滞阻尼器补偿截断锚泊系统的半潜式平台运动响应及锚泊张力进行数值计算,并与原计算结果进行比较。4.对DDMS平台及其锚泊系统进行各短期海况下的运动响应计算,计算分别采用钢链-钢索-钢链系统和钢链-聚酯纤维系缆-钢链系统两种具有相同静回复力特性的锚泊系统;采用雨流计数法对锚泊线顶端张力时程进行统计得到疲劳载荷谱;采用基于S-N曲线的Palsren-Miner线性累计损伤理论对这两种锚泊线在长期海况下的疲劳寿命进行比较计算。5.采用ABAQUS建立拖曳锚极限抗拔力分析的数值计算模型及具体计算流程;研究埋深、锚胫和锚爪夹角以及锚泊力作用角度对静极限抗拔力的影响;研究埋深、荷载循环次数对循环极限抗拔力的影响,并与静极限抗拔力进行比较。更多还原

【Abstract】 At present, the exploitation of offshore oil and gas resources is concentrated in the Bohai sea area of China territorial waters. While South China Sea as three fourths of our territorial water, the gas and oil resources development is nearly empty. According to preliminary estimate, the oil reserves in the South China Sea approaches 23 billion to 30 billion tons, accounting for one third of China’s total amount of resources. As the center of the world’s four major offshore oil and gas accumulation, this area gets high reputation of“The Second Persian Gulf”. In China, gas and oil resources exploitation is primarily in the 200m water depth. The development of maximum drilling depth comes near 500 meters and maximum operating depth comes up to 300 meters. Compared with foreign ocean engineering technology, there is still a gap between theirs and our deepwater oil and gas development. Unfortunately, Vietnam, Philippines and other neighboring countries have begun their exploitation in advance in the disputed areas of South China Sea. Therefore, it’s momentous to accelerate the pace of oil exploitation in South China Sea.Deepwater oil platforms are generally required by mooring positioning system to maintain it at a relatively fixed position, so the design of mooring positioning system plays an overwhelming role in the overall design process of floating structure. Mooring positioning system performance depends mainly on the ocean environmental conditions, the environmental loads acting on floating structure and mooring lines, the material and dynamic performance of mooring line, the arrangement of mooring lines, water depth and other factors. Establishing an appropriate model and obtaining corresponding numerical analysis techniques can help study from the mechanism of the dynamic characteristics of mooring positioning system, predict mooring positioning performance, and further guide the design and construction.The research on mooring positioning system analysis mainly consists of two parts: performance investigation of mooring system and influence to floating structure. Performance investigation of mooring system mainly includes: static and dynamic characteristic, fatigue and anchor system. Influence to floating structure mainly includes: influence of mooring damping and coupled effect with floating structure. The two methods of solving these problems are still based on numerical simulation and model test, but there are many other new problems in the procedure. The main works of this dissertation are as follows:1. The piecewise extrapolating method is employed to the static characteristic analysis of mooring system, and the influence of vertical displacement to restoring force of hybrid mooring line is also estimated. The dynamic response analysis of mooring line is conducted through nonlinear finite element method. Then the analysis of natural frequency and stiffness of hybrid mooring line are compared, and the material characteristics of polyester mooring line are summarized2. The damping contribution of mooring line to floating platform is calculated by the nonlinear finite element method in time domain. The influences of various parameters to mooring damping are studied and the results show some regularity. The regularity is respectively fitted by uniform formula. The mooring damping characteristic of hybrid mooring line is compared.3. The model tests of HYSY-981 semi-submersible platform are conducted in the Joint Laboratory of Wind Tunnel & Wave Flume at Harbin Institute of Technology. A truncated mooring system is designed based on the static equivalent principle. Then the motion responses of semi-submersible platform and its mooring system are obtained from experimental results. Base on the comparative results of model test and numerical simulation, the viscous damper compensated system in truncated mooring lines is proposed in the paper. The numerical simulations for truncated model tests of semi-submersible platform with viscous damper compensated system in mooring lines are conducted and the motion responses of semi-submersible and its mooring line are compared with the primary results.4. The motion responses of DDMS platform and its mooring system are calculated under each short-term sea state, and the results are based two mooring systems which have the same static restoring force characteristic. The two mooring systems respectively consist of chain-wire-chain and chain-polyester-chain. The Rain Flow counting method is employed to obtain the fatigue load spectrum in each short-term sea state based on the time series of mooring line tension. The Palsren-Miner linear cumulative law model is used to compare the fatigue damage of the hybrid mooring lines in long-term sea state.5. The numerical model and specified calculation flow for ultimate pullout load of drag embedment anchor are established by ABAQUS. The influence of depth, fluke/shank angle and mooring angle to static ultimate pullout load of drag embedment anchor are studied. The influence of depth and load cycle times to dynamic ultimate pullout load of drag embedment anchor are studied and the results are compared with static ultimate pullout load.更多还原