扩张式封隔器胶筒力学行为数值模拟研究及改进

发布时间：2018-03-27 19:13

本文选题：扩张式封隔器　切入点：胶筒　出处：《西安石油大学》2017年硕士论文

【摘要】：在工况复杂的油气井井下工作时,封隔器胶筒的密封性能和强度还不能很好的满足需求,从而本文先对扩张式封隔器胶筒进行力学行为数值模拟研究,分析各个阶段受力时所反映出的问题,然后从结构和材料对胶筒进行了研究,并对单一式密封元件和组合式密封元件的密封性能进行了比较分析。本文以常用的K344封隔器为对象,运用弹性理论以及大变形理论知识对封隔器胶筒分两个阶段进行了受力分析,第一个阶段是胶筒扩张后且与套管接触前,第二个阶段是与套管接触后,得到了每个阶段受力的特点。然后用有限元软件建立了K344含胶筒在内的局部有限元模型(包括中心管,上下胶筒座,套管),模拟它的工作过程,得到了它各个阶段的受力云图。结果表明,当封隔器处于内压20.0 MPa工作状态时,上、下胶筒座与中心管联接部分的应力水平最高,其最大Mises应力为66.19MPa。在胶筒中,中间部分的应力变化趋于平缓,而靠近两端处应力可达18.05MPa,且肩部变形最大,剪应变达到0.8。针对胶筒在坐封时所反映出的受力特征,在建模时对胶筒结构进行了改进,在改变封隔器胶筒结构和材料参数(厚度,高度,摩擦系数,肩部倾斜角,加钢丝连线)后用有限元进行了分析,对比分析后得出在同等外部条件下,胶筒的接触应力随着胶筒厚度的增加而减小,密封性能也随之减小。胶筒长度太短会产生应力集中现象,因此胶筒的长度不能太短,本文建议选择大于125mm的长度。为了保持密封元件的完整性和工作的可持续性,必须有稳定的接触应力为了同时保持足够的摩擦力使胶筒在工作时不滑动,本文建议选用0.28的摩擦系数。随着封隔器胶筒肩部角度的变化,胶筒上的最大应力差异不大,而且倾角为15°时的最大应力反而要高于30°和45°时的应力,所以建议肩部倾角取15°,此时既有利于减弱肩部突出的程度,也能满足强度需求。在建模时对胶筒材料进行了改进,分别在胶筒中添加1-3层钢丝帘线,对其坐封过程进行有限元分析后,对比得出了材料补强措施。本文对单一密封元件与组合式密封元件的密封性能进行了比较分析,通过数据对比可以看出采用组合式密封元件,不仅降低了封隔器的坐封力,且承压能力要比采用单一式密封元件高,密封效果也更好。
[Abstract]:When working under oil and gas wells with complex working conditions, the sealing performance and strength of the Packer rubber barrel can not meet the requirements well. So the numerical simulation of the mechanical behavior of the expanded Packer cylinder is carried out in this paper. The problems reflected in the stress of each stage are analyzed, and then the structure and materials of the rubber tube are studied. The sealing performance of single seal element and combined seal element is compared and analyzed. In this paper, the commonly used K344 Packer is used as the object. Using the theory of elasticity and the theory of large deformation, the stress of the Packer rubber cylinder is analyzed in two stages: the first stage is after the cylinder is expanded and the casing is in contact with the casing, the second stage is after the contact with the casing. Then the local finite element model (including central tube, upper and lower rubber tube, casing, etc.) is established by using finite element software, and its working process is simulated. The results show that when the Packer is in the working state of 20.0 MPa, the stress level of the connecting part of the lower rubber tube and the central tube is the highest, and the maximum Mises stress is 66.19 MPA in the rubber tube. The stress variation of the middle part tends to be gentle, while the stress near the two ends can reach 18.05 MPA, and the shoulder deformation is the largest, and the shear strain reaches 0.8. In view of the stress characteristics of the rubber cylinder when it is seated and sealed, the structure of the plastic tube is improved when modeling. After changing the structure and material parameters (thickness, height, friction coefficient, shoulder angle, wire connection) of the Packer cylinder, the finite element method is used to analyze the structure and material parameters. The contact stress of the cylinder decreases with the increase of the thickness of the cylinder, and the sealing performance also decreases. If the length of the cylinder is too short, the stress concentration will occur, so the length of the cylinder should not be too short. This paper suggests choosing a length greater than 125mm. In order to maintain the integrity of the sealing element and the sustainability of the work, there must be a stable contact stress in order to maintain sufficient friction at the same time so that the cylinder does not slide while working. The friction coefficient of 0.28 is suggested in this paper. With the change of shoulder angle of the Packer cylinder, the maximum stress on the Packer cylinder has little difference, and the maximum stress at the angle of 15 掳is higher than that at 30 掳and 45 掳. Therefore, it is suggested that the shoulder inclination angle should be 15 掳, which can not only reduce the degree of shoulder protruding, but also meet the demand of strength. In modeling, the plastic tube material is improved, and 1-3 layers of steel cord are added to the rubber tube, respectively. After finite element analysis, the material reinforcement measures are obtained. The sealing performance of single seal element and combined seal element is compared and analyzed in this paper. Through the comparison of data, it can be seen that the combined seal element is adopted. It not only reduces the sealing force of the Packer, but also has a higher pressure bearing capacity and better sealing effect than that of a single seal element.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE931.2

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