【作者】 彭朋；

【导师】 陈国明；

【作者基本信息】 中国石油大学 ， 机械设计及理论， 2009， 博士

【摘要】 本论文结合国家高技术研究发展(863)计划海洋技术领域重大项目“深水钻完井关键技术”部分内容展开,对深水钻井隔水管系统寿命管理技术作了较系统的研究,采用理论分析、数值计算和计算机仿真等方法,在深水钻井隔水管失效模式识别和损伤评估、寿命管理方法研究、监测和检测方法与技术分析、寿命管理体系应用等方面取得一定的研究进展。主要研究进展总结如下:1.深水钻井隔水管失效模式识别和损伤评估深水钻井隔水管系统作业环境和载荷复杂多变,面临多种失效可能,首先对腐蚀、疲劳和磨损三种主要失效模式分别进行机理分析和定量损伤评估,这是寿命预测和管理的基础。采用许用应力法进行腐蚀缺陷评估;考虑腐蚀缺陷造成的管壁应力集中,在计算系统疲劳寿命时引入应力集中系数,给出一种综合评估两种损伤的可行方法。疲劳损伤评估从波致疲劳和涡激疲劳两方面展开,波致疲劳针对每一种典型海况分别讨论然后加权累积,无缺陷单根和有缺陷单根的损伤评估分别采用S-N曲线法和裂纹扩展理论;涡激疲劳评估则是基于隔水管系统的模态分析,根据流剖面和振动能量筛选出对疲劳损伤贡献最大的响应模态,确定其应力幅和应力范围用于损伤计算。磨损评估中采用偏心圆筒模型模拟隔水管磨损,以管壁磨损最深处内壁的环向应力达到某种强度极限作为失效判断条件,进行磨损剩余强度计算。2.深水钻井隔水管寿命管理方法研究提出了隔水管系统在一个钻井作业周期内的寿命管理策略,包括系统损伤和寿命预测、单根适用性评价、作业过程监测、作业后检测、建立隔水管信息数据库等部分。含缺陷单根的使用寿命取决于缺陷临界尺寸和损伤发展速率两方面:首先按照缺陷类型分析单根的临界缺陷尺寸,裂纹型缺陷的临界深度取为隔水管壁厚或更小尺寸,腐蚀和磨损缺陷的临界尺寸根据管壁缺陷位置的应力强度准则确定;则临界尺寸与缺陷发展速率的比值为隔水管寿命的预测值。定义了一个5,000ft钻井隔水管系统,以其为目标进行作业周期寿命管理,并根据寿命预测值对疲劳、腐蚀和磨损三种损伤模式划分损伤等级,损伤等级高的管段应在作业过程之中和之后给与重点监测和检测。对于使用含缺陷单根的实际隔水管系统,缺陷单根应布置在损伤预测最低的位置以获得最大系统可靠性。借鉴完整性管理理论初步建立单根寿命管理策略,在缺陷类型识别和失效机理评价的基础上分析失效概率和失效后果,由此确定单根的失效风险,风险评价值是检测和维修决策的重要依据。对隔水管单根进行疲劳、腐蚀和磨损可靠性分析:疲劳可靠性分析分为无缺陷单根和含裂纹型缺陷单根两种情况,分别由损伤关系和裂纹扩展寿命关系建立极限状态方程;最大腐蚀深度认为服从I型极大值分布,根据腐蚀深度准则计算可靠度;磨损可靠度则为磨损值低于临界磨损量的概率。认为隔水管属于串联系统,但单根之间具有一定相关性,采用区间估计法对目标隔水管系统进行了系统可靠度计算。3.隔水管系统监测和检测方法与技术分析通过对运动/应变监测方法以及单机/实时监测系统的分析,综合考虑监测成本、安装情况、线路可靠性等因素,确定采用分布式单机运动监测系统进行深水钻井隔水管监测,并对所需传感器数量、监测覆盖范围以及传感器最佳安装位置进行了分析。提出了一种深水隔水管VIV监测位置优化方法:基于隔水管有限元模型进行模态分析,识别对VIV疲劳贡献最大的模态作为监测对象;对于每一阶主要模态,考虑隔水管倾斜和重力影响,寻找使响应加速度幅值达到最大的所有位置;从中确定最佳位置安装监测装置,使该位置处的其他模态响应为最小。4.深水钻井隔水管寿命管理体系应用深水隔水管系统的悬挂模式需给于足够重视,在悬挂固有频率、轴向动力放大系数和轴向响应分析的基础上,对目标隔水管系统的硬悬挂模式进行案例讨论。起下作业过程中,要求在每个单根下放或回收之后整个隔水管柱均满足无压缩和轴向载荷条件。悬挂分析中讨论有/无防喷器组两种情况,根据无压缩准则确定最大允许加速度,计算此时的悬挂系统轴向载荷,若载荷值大于支撑装置承载能力应考虑采用软悬挂方式,或回收一定数量单根直至轴向载荷满足条件。结合目标系统讨论了隔水管损伤减缓措施,对于隔水管涡激疲劳采用改变顶张力和内部泥浆密度以及交错布置浮力单根的方法;对于隔水管磨损,通过调整钻井船偏移和顶张力减小隔水管弯曲角度,从而降低管壁磨损。初步建立隔水管作业信息数据库和单根检测数据库,前者是对隔水管系统的描述和管理过程记录,涵盖隔水管作业过程中涉及的环境信息、钻井船和作业信息、隔水管系统的配置和组成、作业过程监测数据以及对隔水管的操作等内容;后者包括单根检测结果以及单根评估记录,是单根适用性评价和检测计划更新的依据。更多还原

【Abstract】 The dissertation focuses on life management technique for deepwater drilling risers, which is a part of the“863”High Technology Research and Development Program of China (No.2006AA09A106-4) of the key technologies of deepwater drilling and completion. Life management technique for deepwater drilling risers is investigated systemically based on theoretical research, numerical calculation and computer simulation, including failure mode identification and damage assessment, comprehensive study on life management method, analysis on monitoring and inspection method and technology, as well as life management system application of deepwater drilling risers. The main works are summarized as follows:1 Failure Mode Identification and Damage Assessment of Deepwater Drilling RisersThe drilling riser system is facing a variety of possible failures with the complicated operating environment and load conditions. First of all, the mechanisms of corrosion, fatigue and wear are analysized respectively, and the damage for each of the three kinds of failure modes is assessed quantitatively. The evaluation of corrosion flaws is based on the Allowable Stress Approach. The effect of the corrosion defects is taken into account multiplying the nominal stresses by stress concentration factors of the riser joints containing corrosion defects. The fatigue analyses are performed considering the wave loads and the vortex-induced vibrations. The wave fatigue is weighted-integrating of fatigue damage of each typical sea state. For ideal joints and joints containing corrosion pits, the fatigue damage is calculated with S-N curve and crack propagation theory. As to the VIV fatigue damage assessment, a modal analysis of the riser is performed and the major response modes are determined according to profile and vibration energy. The stress range of the vibration modes then can be used to compute the fatigue damage. In the wear assessment, the cross section shape of worn riser is analogized as an eccentric cylinder. The rupture capacity of the crescent-shaped wear riser is predicted when the internal circumferential stress reaches to a certain limit.2 Comprehensive Study on Life Management Method of Deepwater Drilling RisersThe life management strategy in a drilling cycle for the drilling riser system is presented in the paper, including the damage and life prediction, applicability evaluation of joints, operation process monitoring, riser inspection, establishment of riser information database, and so on. The life of riser joints containing defects is decided by the critical dimensions of flaws as well as development rate of damage. The critical dimensions are determined in view of different kinds of defects. The critical crack depth is not greater than riser wall thickness, and the critical dimensions of corrosion and wear can be anticipated according to stress intensity criteria. A 5,000ft deepwater drilling riser system is defined as the object of life management during the drilling operation. Damage level of riser is classified based on life prediction results in view of corrosion, fatigue and wear of joints, and the joints with high damage level should be given priority monitoring and inspection. Concerning to real drilling riser system with joints which containing defects, the joints with defects should be arranged where the damage predictions are as small as possible to ensure the reliability of the whole system.The life management strategy for riser joints is proposed using integrity management theory for reference. The probability of failure and consequences of failure are analysized based on failure mode identification and failure mechanism appraisal. Then the risk of failure of joints is decided, which is the foundation of inspection and maintenance. The fatigue, corrosion and wear reliability of riser joints are evaluated respectively. For joints without and with crack defects, the limit state equations are formed according to damage and crack propagation life relationship separately. The maximum depth of corrosion defect is deemed to obey I type maximum value distribution through analysis, and reliability of corrosion is calculated in accordance with corrosion allowance. Reliability of wear is the probability that the wear of riser joint is less than the critical wear. The drilling riser pertains to series system while there is certain correlation among different joints, so the system reliability can be determined by interval estimation method.3 Analysis on Monitoring and Inspection Method and Technology of Deepwater Drilling RisersAfter the analysis of motion and strain monitoring method as well as standalone and real-time monitoring system, the monitoring strategy for deepwater drilling riser is proposed considering monitoring cost, installation, reliability, etc. Using distributed standalone system for motion monitoring, the number and spatial extent of the instrumentation as well as optimum sensor placement are discussed. An optimization approach for VIV monitoring locations is presented based on modal analysis of the riser system. The main modes that have significant contribution to fatigue are firstly identified. For each one of the modes, search for possible locations for installation according to the acceleration in response, considering the riser tilt and gravitational effects. Then the optimum location is that would give a near max-signal for one mode while at the same time being close to a zero-signal location for the other modes.4 Life Management System Applications of Deepwater Drilling RisersThe natural frequency, amplification factor and axial response of the object system are discussed, based on which the hard hangoff of the riser is implemented. During the tripping operation, the stress of whole riser string should meet the criterion of no compressive loading after running or pulling each joint and the axial load is not overload. The hangoff analysis is discussed for riser system with and without BOP. The maximum allowable acceleration is determined by the criterion of no compressive. The axial load of hangoff riser system should not greater than load capacity of drill derrick, otherwise soft hangoff can be taken into account, or a number of joints should be recovered until there is no compressive stress in riser.The damage alleviation for drilling riser system is discussed. As to vortex-induced fatigue, the method of altering top tension and mud density as well as layout of riser joints with staggered buoyancy is discussed. The flexible angle is reduced by adjusting vessel offset and top tension of riser system, and in this way, the riser wear damage can be modified.The information databases for drilling operation and riser joints are preliminary established. The drilling operation information database is the description of drilling riser system and the record of riser management, including environment information, vessel and operation information, drilling riser configuration, monitoring data and operation sequence, etc. The riser joints information database consist of inspection results of joints and evaluation report based on inspection data, which is the reference to applicability evaluation and inspection updating of joints.更多还原