【作者】 胡志强；

【导师】 崔维成；

【作者基本信息】 上海交通大学 ， 船舶与海洋结构物设计制造， 2008， 博士

【摘要】 我国南海深海海域油气资源丰富,号称“第二个波斯湾”。我国现已计划在南海海域进行海洋油气勘探开发。已有地质资料表明,南海大部分油气资源蕴藏在水深超过500米的海域。但是,我国海洋油气开发企业目前所拥有的钻井船和钻井平台,仅能在水深小于500米的海域进行钻井作业。因此,中国海洋石油总公司携手国内知名设计单位、船厂和高等院校,正在设计建造我国第一艘3000米水深半潜式钻井平台。国家有关部门对建造深水半潜式钻井平台给予鼎力支持,实施“十一五国家高技术研究发展计划”重大专项“3000米水深半潜式钻井平台关键技术研究”(课题编号:2006AA09A103)。论文的研究内容是在该课题的子课题之一“深水半潜式钻井平台总体性能、定位技术及水池模型试验研究”支持下开展并完成的。此外,本文的部分研究工作也得到了上海市科委重大专项课题“深海单柱式平台关键动力特性的理论与实验研究”(课题编号:05DJ14001)的大力支持。掌握新型深水半潜式钻井平台的设计技术具有重大的意义。目前我国船舶设计单位在新型海洋工程结构物的设计研究方面,与国外先进企业相比,仍然有较为明显的差距。出于短期经济利益的目的,采用直接购买国外设计图纸,或是由国外设计公司提供基本方案的方法,虽然可以满足工期的要求,但是需要花费大量的资金,并难以获得核心的设计方法和设计理念,而且在一定程度上压制了我国设计单位自主创新能力的发展。目前我国设计单位采用的设计理念是建立在改良母型平台基础上的串形设计方法,存在过多依赖母型平台、设计成本高、周期长的不足,不完全适合于新型的深水半潜式钻井平台设计。要加快深海资源开发的步伐,必须创新地提出适合于深水作业设施的设计理念和设计方法。深水半潜式钻井平台是高度复杂的工程系统,涉及学科多,各性能之间耦合性强,设计难度大。多学科设计优化技术(简称MDO)是解决这一难题的可行技术之一。论文的研究目的在于探讨多学科设计优化技术在深水半潜式钻井平台概念设计中的适用性及关键技术。为此,论文在以下几个方面开展了研究工作:(1)论文介绍了多学科设计优化技术的发展历程,以及国内外研究现状。然后重点分析了MDO技术的若干个关键技术,包括数学建模、试验设计和多项式近似模型技术等,这些关键技术是合理应用MDO技术的核心。论文重点描述协同优化过程(简称CO)的原理和工作流程,并以缓冲球鼻首的优化设计为例,分析了协同优化过程在船舶与海洋工程结构物设计中的适用性。研究表明,协同优化过程有较理想的工程应用适用性。(2)论文从半潜式钻井平台的特点出发,对其主要性能做了描述,并确定了半潜式钻井平台概念设计中所应用的学科分类和学科分析方法。论文选取了一个目标平台,选定了六个独立设计变量,及设计变量的变化范围。利用试验设计技术,确定每个设计变量的变化水平。采用均匀设计表,确立了22个试验工况。论文对海洋工程结构物设计中常用的两类重要的学科分析手段——水池模型试验技术和数值分析技术做了详细介绍。水池模型试验技术是半潜式钻井平台获得准确水动力性能的关键技术之一。文中阐述了试验设施、相似率、坐标系、试验仪器、试验布置,以及试验结果。试验结果包括风力载荷、流力载荷、静水率减试验结果、不规则波试验结果,以及测量获得的垂荡运动、横摇运动和气隙性能结果等。并指出这些结果对数值分析起到确定修正参数的作用。数值分析技术是另一个重要的学科分析技术。研究中以SESAM软件作为数值分析主要运用手段。运用这些分析手段,对半潜式钻井平台的水动力性能、稳性、定位性能、结构性能和工程应用性能等开展了全面的学科分析工作。(3)半潜式钻井平台的水动力性能是平台作业者最关心的性能之一。研究中通过建立目标平台的水动力分析模型,结合模型试验结果修正系数,完成水动力分析。获得了目标平台的垂荡运动、横摇运动和气隙性能在22个试验工况中的分析结果,并利用近似模型技术,建立这三个水动力性能指标的近似模型。稳性性能是半潜式钻井平台设计中的重要性能之一。国际海洋工程界和大多数船级社对浮式生产系统的稳性性能都有严格的要求。半潜式钻井平台的稳性性能以系数K来衡量,并以平台的横稳性性能为研究对象。采用简化方法计算倾覆力矩,采用数值分析方法计算回复力矩。依据ABS规范,计算得到稳性性能衡准系数K,并建立目标平台的稳性性能近似模型。半潜式钻井平台的定位性能是影响钻井作业效率的重要因素,包括动力定位性能和锚泊定位性能。动力定位性能学科分析采用数值计算和试验相结合的方法。研究了波浪平均漂移力的成因,重点介绍了Maruo方法和Newman方法的基本原理。总结风力、流力和波浪平均漂移力,得到平台的环境外力图,这是动力定位推进系统选型工作所需要的重要参数。锚泊定位性能学科分析采用时域分析方法,计算得到十年一遇海况条件下的最大水平位移。根据动力定位和锚泊定位计算结果,建立相应的近似模型。针对半潜式钻井平台的结构性能,论文探讨了传统的结构设计流程中存在的一些不足,以及利用多学科设计优化技术,可以在详细结构设计工作之初,就将半潜式钻井平台总体强度的要求体现在具体的结构设计中。采用设计波法开展总强度分析,选定了四个典型波浪设计工况,完成目标平台在设计波作用下的总体结构强度分析。根据结构应力分布,确定半潜式钻井平台箱型甲板的上甲板和立柱间区域为高应力区,并以四个典型波浪工况下结构应力的平均值作为衡量平台总体结构强度性能的指标,建立结构性能的近似模型。论文中采用数学拟合的方法确定半潜式钻井平台的可变载荷性能近似计算公式;采用时域分析法计算极端海况下锚链最大载荷性能;以平台主体钢材重量作为分析对象,建立起重量估算公式,以此估算半潜式钻井平台的造价。完成对工程应用学科和经济性能的学科分析工作。(4)在水池模型试验、学科分析和多学科设计优化技术的研究基础上,利用协同优化过程,完成了针对目标半潜式钻井平台的多学科设计优化过程,获得目标平台的概念设计优化方案。通过调整约束变量对各性能要求的严格程度,一共完成了7次多学科优化分析,并对这7次优化分析结果进行评价,总结出多学科设计优化的一大特点——“折中”。(5)在总结多学科设计优化技术在深水半潜式钻井平台概念设计中应用的基础上,论文最后提出了利用MDO技术,协助设计师获得新型海洋工程结构物概念设计方案的一种新思路和方法——“多学科设计优化专家方法——MDOEXT”。论文对该方法的工作流程进行了详细的描述,说明该方法是一种建立在多学科设计优化基础上的,能够有效地分配并协调顶层设计专家和普通设计人员之间的工作交流,比较适合于开展新型海洋工程结构物概念设计工作的一种新设计理念和设计方法。综上,论文在以下三方面,做出了创新性的研究成果:(1)国内首次提出将多学科设计优化技术引入到海洋平台的概念设计中。论文以深水半潜式钻井平台为研究对象,通过多种先进的学科分析手段,开展了大量的学科分析工作,并利用多学科优化技术,系统地完成了深水半潜式钻井平台的概念设计的优化工作,证明了多学科设计优化技术在该领域的适用性,并且提出了一个掌握半潜式钻井平台整体性能的新方法。(2)提出了在概念设计阶段采用模型试验结果修正数值分析的方法。利用该方法可以在概念设计阶段,通过数值分析方法获得更为准确合理的分析结果。(3)提出了“多学科设计优化专家方法——MDOEXT”。该方法能够合理地安排并协调顶层设计专家和普通设计人员的工作,帮助设计人员获得整体性能最佳的概念设计方案。该方法是一种新的设计理念和设计思路,使更多的设计人员参与到最重要的概念设计过程中来,增加概念设计在整个海洋工程结构物设计中的比重,并减少后续设计工作中的矛盾,节约设计成本。更多还原

【Abstract】 There exist large amount of oil and gas reserves in South China Sea, and someone calls it The Second Persian Gulf. China has started the projects of drilling and exploiting the oil and gas reserves in that area. Current geologic material demonstrates that most of the oil and gas reserves locate at the site with water depth more than 500 meters. However, present drilling units owned by Chinese enterprises can only operate at the site with water depth less than 500 meters. Cooperating with the famous domestic design institutes, the shipyards and the universities, CNOOC is now organizing a process of designing and building the first semi-submersible drilling unit, which can operate at the site with water depth of 3,000 meters. The government provides a powerful support. A National High Technology Research and Development Program of China (Grant No.2006AA09A103) has been set up, and its aim is to support the research on the techniques for the semi-submersible drilling unit operating in 3,000 meter water depth. The research included in this dissertation is supported by one of its sub-programs, whose aim is to develop techniques in the research for global performance, position capability and model test. Besides, part of the content in the dissertation is also supported by a project founded by Science and Technology Commission of Shanghai Municipality (Grant No.05DJ14001).It is of great importance to master the design skill for semi-submersible drilling unit. Presently, Chinese design facilities are lagged behind the foreign design enterprises, on the capability of designing advanced ocean engineering units. Although purchasing ready-made drawings or fundamental design projects directly from foreign enterprises can shorten the design phase, it would cost large amount of capital. Furthermore, it will be difficult to obtain the core techniques from the foreign enterprises, and the purchase deeds will tamper the innovative tendency of Chinese design facilities. The prevailing design process in China is the series process, based on the purpose to improve the parent unit. This design process has the shortages of relying too much on the parent unit, high design cost and long design period. It is not suitable well for designing the advanced ocean engineering units. New design concept and design technique should be invented to meet the requirements for the operation in deep water depth area. The semi-submersible drilling unit is a high complicated system with many disciplines involved, and many coupling effects exist between the disciplines. The design work is a challenge job. Multidisciplinary Design Optimization, simplified as MDO, is one of the feasible techniques to solve this problem. The research in this dissertation is focused on the application of MDO technique to the design of semi-submersible drilling unit operating in large water depth, and following research work has been finished.(1) The development history of MDO technique and its current research condition are introduced in the dissertation. Several key techniques of MDO are then described thoroughly, including mathematic modeling, design of experiment and polynomial approximation model technique. The fundamental principle and flow chart of Collaborative Optimization are introduced, and its feasibility of application in the marine and ocean engineering is verified by a soft bow design example. It is indicated that the Collaborative Optimization can hand with the marine and ocean engineering operation.(2) The characters of semi-submersible are described in detail, and the disciplines in the conceptual design and their analyzing techniques are decided. An object semi-submersible drilling unit is chosen. Six design variables are selected out and their varying ranges are determined. The varying levels of design variables are made by the theory of Design of Experiment, and 22 loadcases are determined by Uniform Tables.The two key analysis ways, model test and numerical analysis, are described in detail. Accurate hydrodynamic characters of the drilling unit can be obtained by model test technique. Some key points of using model test technique are introduced in the dissertation, including facilities and instruments, law of similarity, coordinate system, environment modeling, and test results. The results include wind-force, current-force, decay result, irregular wave test results, and the results of heave, roll and air-gap. The test results would be used as the correction coefficients to the numerical simulation results. Numerical simulation is another important discipline analyzing technique. The characters of hydrodynamics, stability, positioning capability, structural performance, and engineering operation are obtained with numerical simulation techniques.(3) The hydrodynamic character of the drilling unit is one of the characters concerned mostly by the operators. The hydrodynamic discipline analysis is finished with the hydrodynamic model and the correction coefficients. The characters of heave motion, roll motion and air-gap of the 22 loadcases are obtained, and the approximation models of the three characters are built up.The stability character of the drilling unit is one of the most important characters in the design. Most classification societies and the international organizations all make strict requirements on the stability check. Coefficient K is used here to check the stability of the drilling unit. The stability in beam-sea is selected out to be checked in the research. The overturning moment is calculated by the simplified method, and the righting moment is carried out by numerical simulation method. According to the ABS rule, the coefficient K is obtained, and the approximation model of stability is built up.The positioning capability is one of the important factors influencing the drilling operation. The positioning capability consists of the dynamic positioning and the mooring positioning. The numerical simulation method and the model test technique are used together to finish the discipline analysis of the dynamic positioning. The cause of mean wave force is introduced, and the fundamental theories of Maruo method and Newman method are described. The environmental resistance figures are drawn, based on the conclusion of the mean wave force, the wind force and the current force, and it is a key factor in the determination of dynamic positioning operation machines. Time domain analysis method is used to finish the discipline analysis of the mooring positioning. The maximal horizontal displacement of the drilling unit is carried out. The approximation models are built based on the discipline analysis results of the dynamic positioning and the mooring positioning.Concerning the structural condition of the drilling unit, some defects in the conventional structure design flow are discussed. It is pointed out that the requirement of the global strength of the drilling unit can be shown at the beginning of the detail structural design, with the employment of MDO technique. The design wave method is used to do the global strength analysis, and four typical design load conditions are chosen. The structural components with the highest stress level at the intersection area between the box-deck and the column is selected out to represent the structural condition. The mean stress level of the four design loadcases is chosen to be the key factor, and the approximation model is built up with it.Polynomial fit method is used to acquire the approximation calculation formula for the payload of the drilling unit. The time-domain analysis method is applied to calculate the maximal mooring force of the mooring lines. The building cost of the drilling unit is calculated out by the estimation formulae for the semi-submersible drilling unit weight. All of the three discipline analyses are finished to reflect the engineering operation character and the economic character.(4) The optimization process for the semi-submersible drilling unit is accomplished by Collaborative Optimization method, on the basis of discipline analysis, model test results and MDO technique. The conceptual design plan is optimized and then obtained. The optimization process runs for seven times, according to different restriction variables. The results of the seven optimization processes are concluded. A character of MDO technique can be summarized as a trade-off process.(5) An innovative process, called MDOEXT process, is brought forward, based on the summary of utilizing MDO technique in the conceptual design of semi-submersible drilling unit. The new process can help the designers to obtain a better design plan. The working flow of the new process and the way how it can adjust the work between the experts and the average engineers are described in detail. The new way is suitable for the conceptual design for ocean engineering units.In summary, three innovative accomplishments have been finished in the dissertation.(1) It is the first time of introducing the Multidisciplinary Design Optimization technique into the floating platform design field in China. The feasibility of applying MDO technique in the ocean engineering field is verified, through the process of conceptual design for a semi-submersible drilling unit. Furthermore, a new way of mastering the global characters of the semi-submersible drilling unit is promoted.(2) A new way of guiding the numerical simulation process to acquire better analysis results with the help of model test technique in the conceptual design phase is promoted.(3) An innovative process, called MDOEXT, is brought forward. The new process has the power of adjust the work between the experts and the average design engineers, and it can help the designer to obtain a better conceptual design plan. This is a prosperous design concept. It acquires more designers joining the conceptual design phase, and it will increase the proportion of conceptual design in the whole design phase, reduce the contradictions in the following design process and save the total design cost.更多还原