管土作用下的钢悬链线立管动力响应及其疲劳分析

钢悬链线立管的疲劳分析得到越来越多的重视,尤其是其与海床土体相互作用引起的疲劳。本文根据Aubeny提出的管土作用模型以及Bridge提出的土体吸力模型,采用有限元方法,在考虑其与海床土体相互作用的基础上,分析了钢悬链线立管在不同载况作用下的动力响应及疲劳损伤。分析发现,钢悬链线立管上触地点和悬挂点处的疲劳损伤更为显著;洋流载荷对立管疲劳损伤的影响随着水深的增加而减弱;土体吸力的存在,会增大触地段尤其是触地点附近的疲劳损伤;立管触地点附近的疲劳损伤与土体刚度呈正相关。     

管土作用下的钢悬链线立管动力响应及其疲劳分析

钢悬链线立管的疲劳分析得到越来越多的重视,尤其是其与海床土体相互作用引起的疲劳。本文根据 Aubeny提出的管土作用模型以及 Bridge提出的土体吸力模型,采用有限元方法,在考虑其与海床土体相互作用的基础上,分析了钢悬链线立管在不同载况作用下的动力响应及疲劳损伤。分析发现,钢悬链线立管上触地点和悬挂点处的疲劳损伤更为显著;洋流载荷对立管疲劳损伤的影响随着水深的增加而减弱;土体吸力的存在,会增大触地段尤其是触地点附近的疲劳损伤;立管触地点附近的疲劳损伤与土体刚度呈正相关。     

钢悬链线立管延长使用寿命方案研究

通过对南海某在位半潜平台钢悬链线立管的疲劳分析,确定了触泥点和平台悬挂点为立管疲劳损伤的关键区域,在此基础上提出了半潜平台移位、改变立管长度和增加立管浮力3种立管延寿方案。对这3种方案进行了强度和疲劳分析。结果表明,3种方案均可将立管疲劳寿命延长一倍,并同时满足极限海况下的强度要求。对3种方案进行敏感性分析,得出了各方案的有效性和适用性,可为深水钢悬链线立管延寿方案设计提供参考。     

深海钢悬链线立管（SCR）安装强度分析

在研究深水钢悬链立管（SCR）安装方法基础上,结合实际工程安装经验,提出了深水SCR在J-lay这种铺管方式下的安装方案,应用专业立管安装分析软件Orcaflex对各个安装过程进行实例分析,对安装过程中立管的安装强度进行校核。     

深水钢悬链立管安装设计分析

钢悬链立管在墨西哥海域、西非等地深海油气田开发中,得到了广泛的应用。基于钢悬链立管的S型铺设,将钢悬链立管的整个安装过程分成三个不同阶段:立管铺设阶段、立管提升阶段以及立管移管阶段。结合实际深水工程案例,应用Orcaflex对钢悬链立管整个安装过程做动态分析,校核钢悬链立管在整个安装过程中的强度。     

钢悬链线立管监测预警系统研究

为了实时监测钢悬链线立管关键位置的运动、应变,对深水钢悬链线立管(SCR)实时监测预警系统进行研究.该系统主要包括数据处理中心的开发及水下传感器的研制,能够在运营期有效评估其疲劳寿命及剩余强度,进而及时预警其运营风险,指导现场操作人员的检测和维修,有助于深水SCR监测预警系统的国产化.     

深水钢悬链立管J型铺设研究

J型铺管法具有先天的深水适应性,已广泛应用于深海水域的管道铺设作业,而我国对深水管道J型铺设的研究仍处于起步阶段。本文以作为深水开发首选立管形式的钢悬链立管为研究对象,应用Orcaflex软件对立管J型铺设过程做动态分析,校核内容包括最大弯曲应力、最大等效应力及有效张力。将铺管过程分3个阶段进行立管J型铺设强度分析,得到立管受力最大铺设阶段。针对受力最大阶段,进行立管作业窗口分析,得到满足立管使用条件的环境参数。本文所开展的深水钢悬链立管J型铺设研究对推进我国深水铺管技术的发展具有实际工程意义。     

深水钢悬链立管弃管回收技术研究

阐述深水钢悬链立管安装中的弃管回收工艺,采用理论分析和数值分析相结合的方法,对深水钢悬链立管安装中的弃管回收进行分析.基于经典悬链线理论,编制钢悬链立管弃管回收分析软件SCRCOV,针对1500m水深和10 in SCR制定弃管回收方案,经商业软件ORCAFLEX验证,自编软件计算结果是准确的.     

深水钢悬链线立管(SCR)安装分析研究

海管(立管)是海底生产系统和浮武装置之间的关键连接.随着海洋油气开发水深的不断增加,对海管(立管)自身以及辅助施工设备的性能都提出了更高要求,施工及正常作业的安全保证愈加重要.基于立管分析软件Orcaflex,针对项目中的SCR立管进行了安装分析,并依据规范进行应力、应变校核,可为深水安装分析及方案的确定提供一定的技术参考和理论支持.     

钢悬链线立管整体干涉分析研究

深水海洋立管具有柔性,特别是极端海况条件下,相邻立管之间可能发生互相干涉而增大立管的应力,从而影响其疲劳寿命.钢悬链线立管相比顶张力立管,有效张力较小,对环境载荷作用更加敏感,更容易发生碰撞.基于动力学分析软件OrcaFlex建立有限元模型,从允许碰撞的角度出发,对串列布置于张力腿平台上的两根钢悬链线立管进行整体碰撞分析,研究立管间距、尾流模型、拖曳力系数、海流流速和柔性接头刚度对立管碰撞的影响,阐述对碰撞范围、上下游立管相对运动速度、最大碰撞速度和最大碰撞能量的影响规律,为实际工程中立管的空间布置和结构优化设计提供参考.     

深水SCR立管触地区域管土作用研究进展(英文)

钢悬链线立管作为一种全新的深水立管系统已经在国外多个项目中应用,总结了有关深水钢悬链线立管触地区域管土相互作用的研究进展,主要包括STRIDE和CAluSIMA工业合作计划的研究数据和其他的相关论文,能够为国内深水钢悬链线立管的研究提供参考.     

考虑内流和海床作用的柔性立管和钢悬链线立管非线性分析(英文)

Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flows, is critical to ensure personnel and asset safety. In this study, a special global coordinate-based FEM rod model was adopted to identify and quantify the effects of internal flow and hydrostatic pressure on both flexible and deepwater steel catenary risers, with emphasis on the latter. By incorporating internal flow induced forces into the model, it was found that the internal flow contributes a new term to the effective tension expression. For flexible risers in shallow water, internal flow and hydrostatic pressure made virtually no change to effective tension by merely altering the riser wall tension. In deep water the internal pressure wielded a dominant role in governing the riser effective tension and furthering the static configuration, while the effect of inflow velocity was negligible. With respect to the riser seabed interaction, both the seabed support and friction effect were considered, with the former modeled by a nonlinear quadratic spring, allowing for a consistent derivation of the tangent stiffness matrix. The presented application examples show that the nonlinear quadratic spring is, when using the catenary solution as an initial static profile, an efficient way to model the quasi-Winkler-type elastic seabed foundation in this finite element scheme.     

Influence of seabed trench formation on fatigue performance of steel catenary risers in touchdown zone

The subsea survey results using remote operating vehicles (ROV) show that trenches with a depth of several riser diameters can be developed underneath the steel catenary risers (SCR). Therefore, an important question in respect of the riser–seabed interaction is, how the trench formation beneath the riser affects the riser fatigue performance in the touchdown zone. A common methodology reported in literature to study the impact of trench formation on riser fatigue life is the insertion of an artificial mathematical expression of the riser profile into the seabed. This study shows that such methodology can be inconsistent and leading to contradictory results. The current paper has employed ABAQUS finite element software and coded a non-linear soil hysteretic model to automatically simulate the variable seabed stiffness and the gradual trench development through the touchdown zone. In this method, the seabed model parameters are initially adjusted to extreme values allowing trench with desired depth to be developed over a moderate number of displacement cycles of the SCR. The design wave scatter diagram is then applied, simulating a generic Spar system, after switching the model parameters to values with normal range. The paper presents the impact of trenches of different depths on the fatigue performance of SCRs in the touchdown zone.     

深水钢悬链线立管顺流向非线性动力分析

深水钢悬链线立管在外部流体作用下的动力响应在立管的性能优化设计中是非常重要的.文章考虑了深水钢悬链线立管轴向大应变的特性以及弯曲刚度和内流的影响,利用Hamilton原理和拉格朗日应变理论建立了立管的二维动力学模型.将外部流体的非线性作用力用Morison方程表示,通过Hermite插值函数对动力学方程进行离散,采用平均加速度法求解立管的动力响应.探讨了外部流体的非线性作用力对海洋立管顺流向动力响应的影响以及不同流速和拖曳力系数与海洋立管共振响应幅值的关系.     

深水悬链复合锚泊线疲劳损伤计算

以某座Spar平台的锚泊系统为研究对象,首先利用三维绕射理论计算Spar平台主体波浪力,得到平台的总体运动响应时程。再建立复合锚泊线的二维非线性有限元动力分析模型,基于DelVecchio(1992)提出的经验公式,采用迭代的方法计算复合锚泊线的刚度。锚泊线和海床之间的接触作用基于刚性海床假定,基于Morrison公式计算锚泊线的惯性力和拖曳力荷载,根据计算得到的平台主体运动响应时程作为锚泊线顶端输入条件,在时域范围内进行复合锚泊线的动力分析。计算得到中国南海某海域各短期海况条件下复合锚泊线应力的时间历程曲线,采用雨流法对其计数得到对应于各短期海况条件下的疲劳载荷谱。最后根据Miner线性累积损伤模型,对复合锚泊线在长期海况条件下的疲劳损伤进行比较计算。     

新型深水多立柱 FDPSO 涡激运动研究进展

平台涡激运动易导致立管及系泊系统疲劳损伤,危害其安全、稳定性。平台由于具有较小的纵横比、显著的刚性特征及特有的系泊系统,其涡激运动显示出与立管等细长体涡激振动截然不同的运动特征。文中介绍了FDPSO常采用的特殊升沉补偿装置、多立柱绕流特性及多立柱海洋平台涡激运动的研究进展。鉴于深水多立柱FDPSO涡激运动及稳定性研究是非常复杂的流固耦合问题,文中给出了研究其涡激运动的基本思路和步骤,介绍新型多立柱FDPSO涡激运动的研究方法及现状,为其涡激运动抑制及抑制装置研制提供理论支撑。     

操作与悬挂工况下的深海立管有限元分析(英文)

近年来,在深海进行油气开发的技术进展日新月异,全世界的海洋工程公司都在用更新的科技手段努力向更深的海域拓展,向深海进军已经成为了整个海洋行油工业的总体趋势.作为连接、平台设备和海底的重要设备,深海海洋立管的设计和使川也越来越趋向标准化.该文以某深海立管为例,从操作工况和悬挂工况两个方面探讨了钻井立管的整体分析中遇到的主要问题并进行了相关的校核.该文的具体上作包括计算了立管在钻探模态下的旋转角度和应力分布,确定了操作半径、浮箱数日等要素,并根据API规范进行了校核.根据计算的结果可以看出,所选的立管在恶劣海况下的操作半径相对较小,而确定的浮箱数略多,相关结论对立管的初步设计具有较好的参考意义.     

Extreme response based reliability analysis of composite risers for applications in deepwater

As current oil reserves start to deplete, companies are looking to exploit deeper deposits. At these greater depths composite risers, with their high strength-to-weight ratio, reduce the effective tensions and bending moments compared to steel risers. However, there is still limited research into their behaviour, with one key missing element being a comparison with traditional riser designs which accounts for variances in material properties and wave loads. This paper therefore conducts a strength-based reliability analysis of composite catenary risers operating between 1,500 m and 4,000 m. A static global catenary model is combined with Classical Laminate Theory to determine the extreme response and its performance is verified against FEA. This response is evaluated with the Tsai-Wu failure criterion to determine first-ply failure. The effect of laminate moisture absorption on the long-term reliability of submerged composite-based risers is also investigated as it can cause a significant reduction in the strength of composite risers. The reliability analysis is conducted using the Monte Carlo Method, revealing that the composite risers perform well at 4000 m. The degradation in performance from moisture absorption becomes increasingly important at greater depths and needs further investigation for these applications.     

Efficient long-term fatigue analysis of deepwater risers in the time domain including wave directionality

Accurate fatigue assessment is a challenging and crucial aspect of riser design. The prediction of the long-term fatigue damage must account for numerous sea states of different wave heights, periods, and directions. Each sea state entails a dynamic analysis, often performed in the time domain owing to the significant nonlinearities. Because of the short-term uncertainties from irregular waves, the simulation duration must be sufficiently long for results to converge. To alleviate the hefty computational cost of long-term fatigue analysis, researchers have proposed efficient methods, but these are not without drawbacks; in particular, wave directionality is commonly neglected. This paper presents an efficient method for long-term fatigue analysis based on time domain simulation, considering wave directionality among other things. The proposed method is based on an enhanced version of control variates to reduce the variance in Monte Carlo simulations (MCS). The control function is constructed by training artificial neural network (ANN) models using existing MCS data. Here, a customized scheme is developed to allow for the situation that the training data and ANN prediction cases have different wave directions. The proposed method is unbiased and provides an error estimate. Simulations are performed on a floating system, and the proposed method is found to improve the efficiency of MCS significantly. Different scenarios such as fixed and random wave directions are compared, confirming that wave directionality is critical and should be included in a long-term fatigue assessment.