腐蚀对导管架海洋平台的强度及可靠性的影响分析

发布时间：2018-03-30 02:34

本文选题：导管架海洋平台　切入点：腐蚀　出处：《中国石油大学(华东)》2014年硕士论文

【摘要】：导管架式海洋平台是目前海上石油开发广泛采用的结构形式,平台的钢结构长期处于盐雾、潮气和海水等恶劣的海洋环境中,受到海洋大气、海水及海生物的侵蚀,产生剧烈的腐蚀,腐蚀类型多种多样。各种类型的腐蚀改变了导管架海洋平台结构材料的力学性能,降低了平台的强度和极限承载能力,从而严重影响了平台的使用寿命和安全,导致海洋平台事故频繁发生。因此,为保证平台结构的安全性和可使役性,科学地研究腐蚀对导管架海洋平台的强度及可靠性的影响十分必要。本文通过查阅文献、理论分析以及利用ANSYS软件进行有限元分析的方法,以CB812井组采油平台为研究对象,进行了以下工作:首先,对导管架海洋平台在海洋环境下的腐蚀进行了全面的描述,包括全面腐蚀和局部腐蚀;其次,建立了无腐蚀损伤平台整体的有限元模型,通过静力分析,得到其应力分布情况,并对平台结构逐级加载,得到其极限承载力;然后,分别考虑均匀腐蚀及局部点蚀,建立含腐蚀损伤平台的有限元整体及局部实体模型,对其进行应力分析,将结果与无腐蚀损伤平台的应力比较,得到两种腐蚀损伤对该导管架海洋平台的强度的影响;最后,采用蒙特卡洛抽样方法,分别计算初始无腐蚀损伤以及服役期内含均匀腐蚀损伤的平台的失效概率及可靠度指标,并进行比较,分析得到腐蚀对平台可靠性的影响。得到了以下结论:第一,在海洋环境下,导管架平台会产生严重的腐蚀,包括全面腐蚀及局部腐蚀,两者都将导致平台应力集中,但是局部点蚀的应力集中更严重,对平台强度的影响更大。第二,当产生点蚀凹坑群时,在一定范围内,凹坑之间会相互影响。第三,当两个点蚀凹坑沿管壁环向分布比其沿轴向分布时,应力集中更严重,最大应力更大,应当重点注意。第四,随着服役期间的延长,由于均匀腐蚀损伤的累积,导管架海洋平台的失效概率逐渐增大,可靠度指标逐渐减小,即均匀腐蚀降低了导管架海洋平台的可靠性。
[Abstract]:The ducted offshore platform is widely used in offshore oil development at present. The steel structure of the platform is in the harsh marine environment such as salt fog, tide and sea water for a long time, and has been eroded by the ocean atmosphere, sea water and marine organisms. Various types of corrosion change the mechanical properties of jacket offshore platform materials and reduce the strength and ultimate bearing capacity of the platform. Therefore, in order to ensure the safety and serviceability of the platform structure, the life and safety of the platform are seriously affected and the accidents of the offshore platform occur frequently. It is necessary to scientifically study the influence of corrosion on the strength and reliability of jacket offshore platform. This paper takes the CB812 well group oil recovery platform as the research object through consulting literature, theoretical analysis and finite element analysis with ANSYS software. The following works have been done: firstly, the corrosion of jacket offshore platform in the marine environment is described comprehensively, including total corrosion and local corrosion; secondly, the finite element model of the whole platform without corrosion damage is established. Through static analysis, the stress distribution is obtained, and the ultimate bearing capacity is obtained by loading the platform structure step by step. Then, considering the uniform corrosion and local pitting respectively, the finite element integral and local solid models of the platform with corrosion damage are established. The stress analysis is carried out, and the results are compared with the stress of the platform without corrosion damage, and the influence of two kinds of corrosion damage on the strength of the jacket offshore platform is obtained. Finally, Monte Carlo sampling method is used. The failure probability and reliability index of the platform with initial no corrosion damage and uniform corrosion damage in the service period are calculated, and the effects of corrosion on the reliability of the platform are analyzed and compared. The following conclusions are obtained: firstly, the failure probability and reliability index of the platform with uniform corrosion damage in the service period are calculated. In marine environment, jacket platform will produce serious corrosion, including total corrosion and local corrosion, both of which will lead to stress concentration of platform, but the stress concentration of local pitting corrosion will be more serious, and the influence on the strength of platform will be greater. When the pitting pit group is produced, there will be interaction between the pits in a certain range. Thirdly, when the two pitting pits are distributed in the circumferential direction along the pipe wall, the stress concentration is more serious and the maximum stress is greater than the axial distribution of the two pitting pits. Fourth, with the extension of service period, due to the accumulation of uniform corrosion damage, the failure probability of jacket offshore platform increases gradually, and the reliability index decreases gradually. That is, uniform corrosion reduces the reliability of jacket offshore platform.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P755.3

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