考虑海底接触的钢悬链式立管强度以及疲劳损伤分析

发布时间：2018-03-28 21:23

本文选题：钢悬链式立管　切入点：海底接触　出处：《西南石油大学》2017年硕士论文

【摘要】：立管是深水开发中关键设备之一,起到连接海面浮体与海底井口、运送油气资源的作用。钢悬链式立管(Steel Catenary Riser,SCR)是近年来发展起来的一种新型立管。与张紧式立管(Top Tension Riser,TTR)相比,SCR无需张紧力补偿,且对上端浮体运动的敏感性小。与柔性立管(Flexible Riser)相比,SCR能够承受更为恶劣的环境荷载,特别是在高温高压条件下。由于SCR存在诸多优点,SCR逐渐成为深水油气开发中的首选立管形式。但由于SCR在工作状态下受到浮体以及水动力载荷的联合作用,故对其进行可靠的强度校核和疲劳损伤评估是一项充满挑战性的研究工作,同时,这项研究具有重要的理论意义和实际工程价值。钢悬链式立管由悬垂段和流线段组成,触地点是SCR悬垂段与流线段的连接点。悬垂段悬浮于海水中,主要承受波浪以及海流等环境载荷的作用;流线段与海床相互接触,在浮体运动以及环境载荷的联合作用下,与海床反复相互作用。本文基于考虑海底接触的SCR的结构特性,通过建立SCR的有限元数值模型,对SCR整体进行了静力分析和强度校核;对SCR触地点处的浪致疲劳损伤进行了分析;对SCR涡激振动疲劳损伤进行了分析。对钢悬链式立管触地段管土相互作用过程以及数学模型进行了介绍。明确管土相互作用的过程和机理,掌握管土相互作用的定量数学描述,为本文后续数值建模中海床土体参数的合理选择打下坚实的基础。同时,介绍了目前管土相互作用分析的三种方法,综合考虑,采用有限元弹簧来模拟立管触地段的管土相互作用。建立考虑海底接触的钢悬链式立管的数值模型,并进行数值模型的对比验证。选取一典型的与半潜式平台相连的SCR为计算模型,模型考虑立管触地区域与土壤的接触特性,采用等效弹簧来模拟海床土体。对模型进行模态分析,得到SCR的固有特性参数,将固有特性参数进行对比,验证了数值模型的可靠性。首先将不考虑接触的SCR固有特性的理论与数值计算结果进行了对比,然后将不考虑接触以及考虑接触的SCR固有特性的数值计算结果进行了对比,在一定程度上验证了考虑接触的SCR数值模型的可靠性。基于考虑海底接触的钢悬链式立管数值模型,采用考虑管土相互分离的线性截断模型来对P-y曲线进行描述。通过在SCR顶端施加固定的强迫位移来模拟上端浮体的运动,研究了浮体不同方向的运动对立管位移响应以及等效应力的影响,并对该浮体运动下SCR的强度进行了校核。基于考虑海底接触的钢悬链式立管触地点处的结构特性,分别采用了考虑管土分离的线性截断模型以及包含土体吸力效应的帽盖模型来描述P-y曲线。通过改变上端浮体的垂荡运动幅度、土体吸力系数以及海床刚度,对SCR触地点处的动力响应以及疲劳损伤特性进行了分析。分析结果表明:SCR触地点的垂向位移、弯矩、等效应力以及疲劳损伤均随着浮体垂荡运动幅度的增加而呈上升趋势。SCR触地点的垂向位移随着土体吸力系数的增大由高幅低频响应转变为低幅高频响应。SCR触地点的疲劳损伤随着海床刚度的增加呈现先稳定再增加再稳定的趋势。对考虑海底接触的钢悬链式立管涡激振动疲劳损伤特性进行了研究。先对考虑海底接触的立管的固有特性进行了研究,再基于立管固有特性使用模态叠加法对立管的涡激振动疲劳损伤进行了研究。研究过程中,通过改变立管的结构参数以及立管周围的流场参数,对立管的涡激振动疲劳损伤展开了参数研究。研究结果表明:立管疲劳损伤随着立管外径以及立管壁厚的增加呈现下降趋势,而随着海流速度的增加呈现上升趋势;立管最大疲劳损伤出现的位置为接近触地点的流线段区域,且出现最大疲劳损伤的位置随着立管外径以及立管壁厚的增加,逐渐远离触地点。
[Abstract]:Riser is one of the key equipment in the development of deep water, connected to the sea floating body and subsea wellhead of oil and gas resources, transport role. Steel catenary riser (Steel Catenary, Riser, SCR) is a model developed in recent years. And the tension riser (Top Tension, Riser, TTR) compared to SCR without tension compensation, and sensitivity to the upper end of the floating body motion. Small and flexible riser (Flexible Riser), SCR can withstand more severe environmental loads, especially under high temperature and high pressure. Because SCR has so many advantages, SCR has gradually become the first choice in deepwater oil and gas exploration the riser form. But because the SCR by the floating body and hydrodynamic load combination in working condition, so to check its strength and fatigue damage assessment of reliability is a challenging research work, at the same time, this study has important theoretical significance and practical engineering Cheng. The value of steel catenary riser is composed of overhanging section and flow line, contact location is the connection point SCR and flow line. The hanging section hanging section is suspended in the water, waves, currents and other major under the environment load; flow line and seabed contact, the floating body movement and the combined effects of environmental load under the seabed and repeated interaction. This paper is based on the structural characteristics of submarine contact SCR, by establishing a finite element numerical model SCR, the whole SCR was analyzed by static analysis and strength check of SCR; touchdown point of the wave induced fatigue damage were analyzed; SCR on VIV induced fatigue damage were analyzed the steel catenary riser soil interaction process and mathematical model of contact area of pipe are introduced. The process and mechanism of clear pipe soil interaction, grasp mathematical quantitative description of soil interaction, for the following number of Zhi Jianmo Lay a solid foundation for the reasonable selection of parameters of sea bed soil. At the same time, introduces the three methods of pipe soil interaction analysis, comprehensive consideration, using finite element to simulate the interaction of vertical spring tube contact lots of pipe soil contact. Considering the bottom of steel catenary riser tube numerical model, comparison and verification the numerical model. The selection of a typical semi submersible platform is connected with the SCR model, model considering vertical contact characteristics of regional soil and ground tube, using equivalent spring to simulate seabed. The modal analysis of the model, get the inherent characteristic parameters of SCR, comparing the inherent characteristic parameters, verify the reliability numerical model. The first will not consider the theoretical and numerical results of SCR inherent characteristics of contact were compared, and then will not consider numerical contact and considering the inherent characteristics of the contact calculation SCR The results are compared to a certain extent, considering the reliability of the numerical model of SCR contact is verified. Considering seabed contact of steel catenary riser numerical model based on the linear truncated model separated pipe soil considered to describe the P-y curve. Through the top of the SCR is applied to simulate the forced displacement of fixed floating top body motion, motion on the opposite direction of the floating body effect of different pipe displacement and equivalent stress, and the motion of SCR strength is checked. Considering seabed contact of steel catenary vertical structure characteristics of touchdown point based on the linear truncated model of pipe soil separation the effect of soil suction and contains the cap model to describe the P-y curve. By changing the upper end of the floating body heave motion amplitude, soil suction coefficient and stiffness of seabed, power of SCR at TDP response And the fatigue damage characteristics were analyzed. Analysis results show that the displacement, bending moment SCR touch location vertical, equivalent stress and fatigue damage increased with the floating body heave amplitude increased.SCR vertical displacement of contact points with the increase of soil suction coefficient by the high amplitude low-frequency response to low amplitude the high frequency fatigue response.SCR contact site damage with the increase of stiffness of seabed stability showed the first increase to a stable trend. To consider the submarine contact steel catenary riser fatigue damage characteristics of vortex induced vibration is studied. Then the inherent characteristics of the contact tube considering seabed are studied, then the vortex induced vibration fatigue the inherent characteristics of damage riser riser using the modal superposition method based on a research process, by changing the structure parameters of vertical pipe and vertical pipe flow parameters around the vortex induced vibration of riser. Dynamic fatigue damage parameter expansion research. Research results show that the riser fatigue damage with the outer diameter and riser wall thickness increasing decreasing riser, with increasing the current velocity increase; maximum riser fatigue damage location for the flow line region near the contact points, and the maximum fatigue damage with the increasing diameter position and vertical tube wall thickness of the riser, gradually away from the contact points.

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE95

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