【作者】 王伟；

【导师】 张来斌； 帅健；

【作者基本信息】 中国石油大学(北京) ， 安全科学与工程， 2024， 博士

【摘要】 随着海洋油气资源的开发,海底管道铺设里程日益增长。海底管道作为海洋油气资源输送的重要设施,长期遭受恶劣海洋环境的侵害。海底管道泄漏事件极易升级为灾难性事故,造成巨大的财产损失和环境污染。评估海底管道失效风险是预防灾害发生的重要手段,因此,对海底管道进行风险评估势在必行。为保障海底管道在复杂的海洋环境中高效运行,本文以锦州湾JZ25-1S混输管道为研究对象,根据管道惯性测量中心线坐标,识别海底管道弯曲应变,考虑海底环境下腐蚀现象频发,针对高应变区域管道可能存在复杂载荷与悬空段的特征,分别开展悬空管道力学响应分析与复杂载荷下的群腐蚀缺陷间相互作用分析,结合悬空管道动态响应规律与含腐蚀缺陷管道应力应变分析结果,提出了基于贝叶斯网络的海底管道失效动态风险评估方法。主要成果如下:(1)基于三次B样条插值曲线和五点三次平滑拟合曲线建立了海底管道中心线数学描述方法,对比了插值方法与拟合方法评价海底管道弯曲应变结果的准确性。结果表明三次B样条插值曲线对数据的精度具有较强的依赖性,能够较好地根据惯性测量单元采集的数据点还原海底管道走势,当采集的坐标数据信噪比较小时,描述结果波动性强,导致弯曲应变结果偏大;复杂的海底环境对惯性测量单元检测精度存在影响,五点三次平滑拟合曲线在一定程度上可以抑制数据中的噪声,其结果更为平滑,更适合评估海底管道弯曲变形情况。(2)根据锦州湾JZ25-1S混输管道所处海域及管道规格,考虑内压、海流、波浪载荷及非线性管-土相互作用,建立了海底悬空管道力学分析模型,研究了土壤性质、海流方向以及悬空长度对海底悬空管道应力分布及动态响应的影响,揭示了土壤作用下悬空管道的振动特性,基于动态失效原则确定了该海域的极限悬空长度为20m,结合雨流计数方法与疲劳寿命曲线评估了波浪和海流联合作用下悬空管道的疲劳寿命。悬空管道静力与动力分析结果表明,悬空长度小于20m的管道,悬空中心应力响应最为显著,其累积疲劳损伤最高,对于悬空长度超出20m的管道,悬空段与埋土段连接处位置应力波动最为剧烈,该区域极易引发管道的疲劳失效。(3)构建了轴力与内压作用下轴向排列与环向排列双缺陷管道有限元模型,揭示了轴力、缺陷间距及缺陷尺寸对缺陷间应力相互作用的影响。当管道承受轴向拉伸载荷时,轴向排列缺陷间相互作用随缺陷间距增加非线性减弱,当载荷转为压缩载荷,缺陷间相互作用随缺陷间距增加而逐渐增强,对于环向排列缺陷,当管道承受轴力与内压共同作用,缺陷间相互作用随缺陷间距增加先增强后减弱,且在环向间距为0.1πD时对管道失效压力影响最强。(4)以腐蚀、疲劳、第三方破坏、管材缺陷及自然灾害作为海底管道失效因素,建立了海底管道失效风险判识模型。基于贝叶斯网络,设置海底管道运行参数、悬空长度、缺陷参数及海上第三方活动为证据节点,提出了可以实时评估海底管道失效风险的方法,为解决海底管道运行中的不确定性因素提供了技术思路。更多还原

【Abstract】 With the development of marine oil and gas resources,the mileage of submarine pipeline construction has been increasing.As important facilities for the transportation of marine oil and gas,submarine pipelines suffer from the harsh marine environment for a long-term period of time.Submarine pipeline leakage accidents are extremely easy to escalate into catastrophic events,causing huge loss of property and environmental pollution.Therefore,risk assessment of submarine pipelines is imperative.In order to ensure the efficient operation of submarine pipelines in complex marine environments,this paper takes the JZ25-1S mixing pipeline in Jinzhou Bay as the research object.The bending strain of submarine pipelines is identified according to the pipeline IMU centerline coordinates.For the characteristics of the pipeline in the high strain where the complex loading and suspended pipe may exist,the mechanical response analysis of suspended pipelines and the interaction of cluster corrosion defects under complex loads are carried out respectively by considering the frequent corrosion phenomena in the seabed environment.Combined with the dynamic responseof suspended pipelines and the stress and strain analysis of pipelines containing corrosion defects,a dynamic risk assessment method for submarine pipeline failure based on Bayesian network is proposed.The main results are as follows:(1)A mathematical description method for the centerline of submarine pipelines has been developed using cubic B-spline interpolation and five-point cubic smoothing fitting.The accuracy of the interpolation and fitting methods in evaluating the bending strain results of submarine pipelines compared.The results show that the cubic B-spline interpolation has a strong dependence on the accuracy of the data.It can better restore the trend of submarine pipeline according to the data points collected by the inertial measurement unit.The description results show strong fluctuation when the signal-to-noise ratio of the collected coordinate data is small,which leads to the large bending strain result.However,the complex submarine environment has an impact on the detection accuracy of the inertial measurement unit.The five-point cubic smoothing fitting curve can suppress the noise in the data,and the results provide smoother results,which are more suitable for assessing the bending deformation of submarine pipelines.(2)According to the sea enviornment and pipeline specification of JZ25-1S mixed transportation pipeline in Jinzhou Bay,the mechanical analysis model of submarine suspended pipeline was developed by considering the internal pressure,currents,wave and nonlinear pipe-soil interaction.The effects of soil properties,current direction and suspension length on the stress distribution and dynamic response of the submarine suspended pipeline were investigated.The vibration characteristics of the suspended pipeline under the influence of soil were revealed.The critical suspended length of 20m in Bohai Sea was determined according to the dynamic failure principle.In addition,the fatigue life of the suspended pipeline under the joint application of wave and sea current was determined by combining the rainfall counting method with the S-N curve.The results of static and dynamic analysis of the suspended pipeline show that for the pipeline with the suspended length less than 20m,the stress response of the suspended center shows the most significant,and accordingly the accumulated fatigue damage reaches the highest.When the length of the suspended pipe exceeds 20m,the stress fluctuation at the connection between the suspended section and the buried section shall be the most intense,and the fatigue failure of the pipeline could be triggered very easily in this region.(3)A finite element model of a pipeline containing double defects subjected to axial force and internal pressure was constructed,with the defects arranged in axial and circumferential arrangements,respectively.The effects of axial force,spacing and geometries of defects on the interaction between defects were revealed.When the pipe is exposed to axial tensile load,the interaction between the axially arranged defects decreases nonlinearly with the increase of the defect spacing.As the tensile load turns to compressive load,the interaction between defects gradually enhances with the increase of defect spacing.for the pipeline containing circumferentially arranged defects and exposed the joint loads of axial force and internal pressure,the interaction between the defects intensifies and then diminishes by increasing the defect spacing.The impact on the failure pressure of pipes occurs most strongly at a circumferential spacing of 0.1πD.(4)An identification model for failure risk of submarine pipelines was developed with corrosion,fatigue,third party damage,intrinsic defects and natural disasters as the causal factors of submarine pipeline failure.The approach that can assess the failure risk of submarine pipelines in real time was proposed based on the Bayesian network.The dynamic Bayesian network incorporates submarine pipeline operating parameters,suspended lengths,defect parameters,and offshore third-party activities as evidence nodes.The dynamical risk assessment method can provide an excellent way of thought for solving the uncertainties in the operation of submarine pipelines.更多还原