海底管道边界条件类型及其对走管行为的影响

Types of submarine pipeline boundary conditions and implications for pipeline walking behaviour

针对深海海底管道两端通常与井口、悬链线立管、器管收集器等相连,管道端部边界条件复杂的情况,为了探究不同的管道边界条件对走管行为的影响,将海底管道端部边界条件简化为3种类型,即类型Ⅰ两端水平力、类型Ⅱ一端水平力一端倾斜力和类型Ⅲ一端弹性边界一端水平力,建立不同边界条件下海底管道走管数值模型,对比分析不同类型边界条件下海底管道走管行为。结果表明:类型Ⅱ边界条件与类型Ⅰ相比,随着管道端部拉力倾角增加,管道轴向拉力减小,走管量也减小,管道拉力倾角从0°增至60°,最大轴向拉力减小6.73%,走管率减小50%,这意味着悬链线立管形态改变,使得作用于海底管道的拉力方向改变,相应的海底管道走管量也随之改变;类型Ⅲ与类型Ⅰ边界条件相比,类型Ⅰ边界条件下海底管道走管率为恒值,随着升降温循环次数的增加,海底管道走管量近似线性增长;类型Ⅲ边界条件下海底管道走管率受器管收集器弹性刚度影响,弹性刚度越大,第1次升降温循环走管率越大;随着升降温循环次数增加,管道走管率快速衰减,直至为0,类型Ⅲ边界条件下多次升降温循环最终走管量通常小于类型Ⅰ。3类边界条件下海底管道走管行为差异很大,可为实际工程中分析海底管道端部边界条件类型、选定合适的边界条件提供参考。

The ends of deep-sea submarine pipelines are usually connected to wellheads,suspended chain line risers,pipeline end manifolds,etc.,and the boundary conditions at the end of the pipelines are complicated.In order to investigate the influence of different pipeline boundary conditions on pipeline walking behaviour,the boundary conditions at the end of the submarine pipelines were simplified into three types:typeⅠis horizontal force at both ends,type Ⅱ is horizontal force at one end and inclined force at the other end,and Type Ⅲ is elastic boundary at one end and horizontal force at the other end;Numerical models of submarine pipeline walking were set up with different boundary conditions,and the behaviour of submarine pipeline walking was comparatively analyzed with the different types of boundary conditions.The results indicate that:compared with type Ⅰ,with the increase of pipeline end tension inclination angle,the pipeline axial tension decreases,and the amount of pipeline walking also decreases in type Ⅱ boundary conditions;With the pipeline tension inclination angle increased from 0°to 60°,the maximum axial tension decreases by 6.73%,and the pipeline walking rate decreases by 50%.This means that the change of the riser shape of the suspension chain line leads to the direction of the tension force acting on the submarine pipeline changes,and the amount of submarine pipeline walking also corresponding change.The comparison between type Ⅲ and type Ⅰ boundary conditions shows that the submarine pipeline walking rate under type Ⅰ boundary conditions is a constant value,with the number of heating and cooling cycles increase,the submarine pipeline walking rate is approximately linear growth;the submarine pipeline walking rate under type Ⅲ boundary conditions is influenced by the pipeline end manifolds elastic stiffness,the greater the elastic stiffness,the greater the walking rate of the pipe line in the first temperature cycle;with the number of heating and cooling cycles increase,the walking rate decreases rapidly until it reaches 0.The amount of pipeline walking under type Ⅲ boundary conditions is usually smaller than that of type Ⅰ.The walking behaviour of submarine pipelines varies greatly under the three types of boundary conditions,which provides some reference for analyzing the types of boundary conditions at the end of submarine pipelines and selecting appropriate boundary condition in actual project.