自升式钻井平台桩靴结构强度分析

桩靴是钻井平台的重要支撑构件,其结构强度对整个钻井平台的安全起着至关重要的作用。以某自升式钻井平台桩靴为研究对象,根据ABS(美国船级社)规范要求,建立桩靴结构强度的力学模型,并合理简化,分析了预压载和自存两种工况下的设计载荷。利用有限元软件MSC.Patran/Nastran对两种工况下桩靴的强度进行分析,研究得到桩靴强度工程化分析流程以及结构强度特性,分析结果为自升式钻井平台的桩靴设计提供参考。     

系列自升式钻井平台桩靴设计与强度评估

自升式平台桩靴的设计形式和结构强度关系到整个平台性能和安全。针对所设计的400ft水深自升式平台两种桩靴结构形式,应用MSC/NASTRAN软件建立有限元模型,依据ABS规范要求并根据实际环境设计结构强度评估工况,对两种桩靴结构进行强度校核,同时计算桩靴各部分质量,分析计算结果最终得出一种较优的桩靴结构形式。     

多种自升式海洋平台桩靴上拔过程仿真分析

本文以自升式海洋平台桩靴为主要研究对象,运用Ansys Workbench中的Design Modeler建立桩靴与土的模型,通过LS-DYNA来模拟桩靴上拔过程,并计算了3种桩靴形式的拔桩力和研究了3种桩靴的上拔过程土体的变形,并将桩靴上拔阻力的理论计算值与数值模拟计算的结果进行比较分析。本文对未来海洋平台的发展有一定的工程意义。     

自升式钻井平台桩靴裂纹修理分析

自升式钻井平台的桩靴和桩腿大量采用如ASTM A517GR.Q、EQ56等低合金高强度的钢材料制造而成,其焊接质量的好坏直接关系着平台的运行安全。文章分析了ASTM A517GR.Q齿条钢的可焊性,介绍了海洋石油941、海洋石油935桩靴裂纹修理工艺以及施工过程,总结了自升式钻井平台桩靴裂纹修理的难点。     

自升式平台插桩物理模型实验及分析

研究自升式平台插桩过程的土体运动滑移以及土体变形规律,对合理评价自升式平台桩腿及桩靴的稳定性有重要的意义。以自升式平台插拔桩为工程背景,基于自主研发的＂流固土多项耦合六自由度单双向静动态加载仪＂,对砂性土海床进行比尺实验,利用物理手段研究平台插桩过程中土体与桩靴耦合作用机理。实验中给出了海床插桩入泥深度与地基承载力的曲线,并且推导出砂土力学性质随桩靴深度变化公式。实验的破坏特征与海洋砂土地基实际破坏一致,说明了模型试验的正确性,同时也为层状穿刺试验提供了实验基础。     

关于自升式海洋平台插桩特性的分析研究

采用通用程序语言VBA,结合工程技术人员对相关规范和理论的理解和实际工程经验,开发出适用于自升式平台桩靴插桩计算分析的程序,实现计算的相对标准化,针对300ft、400ft自升式海洋平台桁架式桩腿结构形式在中国南通海域插桩特性分析研究,阐述了同类海洋平台的插桩深度预测分析过程及方法,该方法和思路的应用对海洋平台的结构安全评估有重要意义。     

圆柱型桩腿的自升式平台风暴站位分析

以四圆柱桩腿自升式气体压缩平台为例,利用SACS软件对圆柱型桩腿的自升式平台风暴站位工况进行分析,根据AISC规范校核桩腿强度,依据计算结果校核提升系统能力、桩靴承载能力、平台抗倾覆能力等。对圆柱型桩腿的自升式平台设计具有一定的参考价值。     

自升式服务平台桩靴结构优化设计

桩靴作为自升式平台的重要结构之一，在整个平台的就位和作业等方面发挥着重要作用。针对350ft自升式多功能服务平台的2种桩靴结构形式，应用MSC Patran和Nastran建立有限元模型，依据美国船级社相关规范对不同工况下2种不同形式桩靴的强度进行评估，并分别对2种桩靴的质量进行统计。对计算结果进行分析比较，并提出一些可行性建议。     

自升式海洋平台桩靴进水监测报警系统研制

本文介绍了一种自升式海洋平台桩靴破损或者桩靴上人孔盖松动,导致桩靴进水而发生声光报警系统。该系统还应用无线电微波技术,将桩靴内部的视频传到控制室监视器。该成果已经应用到一座海洋石油平台,监测及报警效果非常好,提高了平台的安全性。     

海上吊物六自由度系统动力学特性分析

自升式风电安装平台由于作业臂长度的限制,在进行海上钻井和维修作业时会紧靠导管架平台。风电安装平台桩靴插桩过程中会排开大量土体,对临近平台桩基产生很大的挤压荷载。以某自升式风电安装平台和其临近固定平台为研究对象,探讨了风电安装平台桩靴入泥带来的挤土荷载与环境荷载的耦合作用对平台桩基强度的影响。分析结果表明,在靠近泥面一定范围之内,在进行导管架钢桩设计时必须考虑挤土荷载与环境荷载的耦合作用,以满足导管架平台桩基强度要求。     

Advances in the prediction of spudcan punch-through in double-layered soils

Punch-through failure of jack-up spudcan foundations occurs in active oil and gas drilling exploration regions, where relatively stiff soil overlies soft marine layer. Therefore, installation of spudcan foundations in such seabed formations threatens the stability of the jack-up rig. A site-specific assessment of the potential and severity of failure must be completed before the commencement of the installation. However, the accuracy of the prediction is limited by the validity of the design method currently in use. This paper presents advances in the prediction of punch-through failure of jack-up platforms in sand/stiff clay over soft clay soils. New analytical models for spudcan installation in double-layered soils are reviewed and compared to the existing methods in the ISO 19905-1 standard and SNAME standard. The capabilities and limitations of each method are summarised and recommendations are drawn for the theoretical predictions of spudcan punch-through in double-layered soils.     

Assessing appropriate stiffness levels for spudcan foundations on dense sand

Before a jack-up can operate at a given location, a site-specific assessment of its ability to withstand a design storm during operation must be performed. During this assessment, the complex state of stress and strain under a spudcan is usually simplified to a value of foundation stiffness that is integrated as a boundary condition into the structural analysis. Soil stiffness is a critical parameter affecting the foundation and structural load distribution and displacements, and the jack-up natural period and dynamic response. The level of spudcan stiffness is an area of intense interest and debate. This paper assesses appropriate stiffness levels for numerical simulation. Utilising results from a detailed “pushover” experiment of a three-legged model jack-up on dense sand, the paper compares the experimental pushover loads and displacements on the hull and spudcans to numerical simulations using different assumptions of spudcan stiffness. These include pinned and encastré footings, linear springs and a force-resultant model based on displacement-hardening plasticity theory. Constant stiffness levels are shown to be inadequate in simulating the experimental pushover test. The non-linear degradation of stiffness associated with the latter force-resultant model is critical.     

自升式钻井平台桩靴裂纹分析、处理及修复研究

桩靴是自升式平台的重要组成部分,主要作用是支撑整个平台,将平台所受的载荷传递到海床.一旦桩靴失效,将导致桩腿下沉,平台无法保持水平.文章利用有限元方法研究了自升式平台桩靴在出现裂纹后的应力水平,并研究相关的应对措施与修复方法.     

Controlled installation of spudcan foundations on loose sand overlying weak clay

Offshore jack-up rigs are often used for site exploration and oil well drilling. The footings of jack-up rigs are known as spudcan foundations. The risk of rapid uncontrolled penetration of spudcan in seabed (“punch-through”) exposes jack-ups to significant risk during installation in strong over weak layered seabeds. An example for this is a thin loose sand layer overlying a weaker stratum of clay. To prevent spudcans from “punch-through”, an in-situ measurement concept is suggested in this paper to control the installation process of spudcan foundations. First, three-dimensional finite element studies using a Coupled Eulerian–Lagrangian method are carried out to simulate the penetration process. The numerical results have been validated with existing analytical solutions and centrifuge model test data. Furthermore, parametric studies are carried out to quantify the influences of the sand thickness and shear strength of the clay on the bearing capacity of spudcans. Based on the numerical studies an idea for the development of an in-situ measurement concept is suggested to control the spudcan penetration process in-situ.     

自升式平台桩靴/地基承载力的数值分析

桩靴/地基承载力的准确预报是确保自升式平台进行海上插桩作业安全性的重要前提,常规的规范算法在处理复杂地基条件时存在困难。基于非线性数值分析方法,在对加载点位置、网格尺寸、地基边界等关键技术进行研究的基础上,以某400ft水深自升式平台为例,分别对海底均质土和成层土的承载力进行了研究。同时,对各土层参数的影响进行了详细分析,为探索插桩过程中地基破坏原理和承载力计算提供了一些参考。     

The undrained bearing capacity of a spudcan foundation under combined loading in soft clay

Mobile jack-up drilling rigs are typically supported by individual, large diameter spudcan foundations. Before deployment, the suitability of a jack-up to a location must be shown in a site-specific assessment under loads associated with a 50-year return period storm, which ultimately need to be resisted by the foundations. The capacity of the spudcans under combined vertical, horizontal and moment loading is therefore integral to the overall site-specific assessment of the jack-up.In soft clays, spudcans can penetrate deeply into the seabed, sometimes up to several footing diameters, with soil flowing around the downward penetrating footing, sealing the cavity. Although this is generally believed to provide some additional bearing capacity to the footing, no detailed study or formal guidance is available to date. This study, therefore, investigates the influence of soil back-flow on the failure mechanisms and quantifies the effect on the capacity of a spudcan under general loading through finite element analyses. A closed-form analytical expression is developed that describes the capacity envelope under combined loading, applicable to embedment depths ranging from shallow to deep.     

自升式平台层状地基条件下插桩过程数值模拟研究

对于采用独立式桩靴结构的自升式平台,桩靴的入泥深度是保障平台安全作业的关键问题之一。采用ABAQUS软件的Explicit求解器,以位移增量步方式计算地基极限承载力;在施加初始地应力场的前提下,引入无限元边界处理方法,考虑了土壤无限大边界条件的影响,并使用ALE自适应网格技术有效地解决了土壤模型的大变形问题;最后,将有限元计算与经验公式计算进行比对分析。结果表明,在一定预压载荷条件下,有限元计算结果能较全面精确地反映插桩结果,弥补经验公式考虑参数单一、无法解决层状土承载力之间不连续问题以及无法动态模拟插桩过程的不足。     

自升式平台上下分体探讨

提出上下分体的自升式平台结构形式及其作业方式,通过提高平台支撑结构刚度,减小平台上部结构尺度、重量及所受外荷作用,降低自升式平台造价,以减缓自升式平台造价随作业水深增加而急剧上升的趋势.