含缺陷连续油管的疲劳寿命研究

发布时间：2018-01-08 08:00

本文关键词：含缺陷连续油管的疲劳寿命研究　出处：《长江大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着石油产业的飞速发展,在油气田的作业中,连续油管作业设备被普遍应用,施展着越来越重要的作用。在作业时,连续油管于滚筒上反复卷绕和拉直的过程中会产生低周疲劳,因为连续油管滚筒和鹅颈导向器的曲率半径远远小于连续油管的弹性极限半径,所以每次弯曲拉直时都会发生塑性变形,当塑性应变累积到一定程度会导致连续油管的疲劳破坏。如果连续油管带有缺陷,在缺陷处会产生应变集中,则会加速连续油管的疲劳损伤累积,疲劳寿命就会加速缩短。如果将这些有缺陷的连续油管再次下入井内,很有可能作业不了几次就发生连续油管的穿孔或者断裂事故。连续油管的缺陷十分常见,为了预防在作业过程中突然断裂而导致安全事故,对含缺陷连油续管的疲劳寿命要有一定的预测,快要达到寿命极限时,应立即停止或放弃连续油管的作业。为了估算含不同形状下的不同尺寸的缺陷的连续油管疲劳寿命以及研究缺陷对连续油管疲劳寿命的影响,本文用有限元方法分别模拟含不同尺寸椭球形缺陷、方形缺陷、球形缺陷以及圆柱形缺陷四种最常见的缺陷的连续油管在卷绕矫直过程中的变形和疲劳,并分别用等效应变法和临界面法估算出相应的疲劳寿命,绘制成相应图表。其中椭球形缺陷和方形缺陷的尺寸包括其余方向上尺寸不变情况下的不同长度、不同深度、不同宽度。缺陷尺寸变化,疲劳寿命也会相应变化,其中长度方向尺寸变化对连续油管疲劳寿命的影响是大于深度方向和宽度方向的影响的;在其余方向上的尺寸不变的情况下,轴向的长度越短,径向的深度越深,环向的宽度越宽,连续油管疲劳寿命就越短。对于球形缺陷的尺寸只是半径的变化,连续油管的疲劳寿命并不随着半径尺寸的变化而单调变化,而是出现波动。圆柱形缺陷对连续油管的疲劳寿命的影响和方形缺陷对连续油管的疲劳寿命的影响是基本上类似的和相通的。综合起来看,四种类型缺陷对连续油管疲劳寿命的影响从大到小依次为:方形缺陷、圆柱形缺陷、球形缺陷、椭球形缺陷。缺陷曲率半径越小的地方,应变集中越明显,应变越集中,对连续油管的疲劳破坏来说,累积塑性就越快,从而疲劳寿命就越短。连续油管在卷绕矫直的过程中,在缺陷处的受力可以看做是轴向的拉伸或压缩,缺陷尺寸在轴向缩短和在环向或者径向增长会降低连续油管的疲劳寿命,反之亦然。
[Abstract]:With the rapid development of petroleum industry, oil and gas fields in the operation, the coiled tubing equipment is widely used, play an increasingly important role. In operation, the process of coiled tubing in the drum repeatedly winding and straightening will produce low cycle fatigue, because the elastic limit radius of curvature radius of coiled tubing and gooseneck guide roller is far less than the coiled tubing, so each bending straightened will occur when the plastic deformation, when the plastic strain accumulated to a certain extent can cause fatigue failure of coiled tubing. If the coiled tubing with defects, defects will be produced in the strain concentration will accelerate the fatigue damage accumulation of coiled tubing, the fatigue life will shorten the. If these defective coiled tubing again into the wells, is likely to work a few times on continuous tubing perforation or rupture of the coiled tubing. The defect is very common, in order to prevent sudden rupture during operation and cause accidents, even of the defective oil continued to have a certain fatigue life prediction, reaching the limit of life, should immediately stop or give up the coiled tubing homework. In order to influence fatigue life of coiled tubing in different sizes with different shapes under estimation of defects the research and the defects on the fatigue life of coiled tubing, using the finite element method is simulated respectively with different sizes of ellipsoidal defects, square defects, spherical and cylindrical defect defect of four kinds of the most common defects of coiled tubing in the winding process of straightening deformation and fatigue, and respectively with the equivalent strain and critical plane method estimate the corresponding fatigue life, drawing into the corresponding chart. The ellipsoid defects and square defects including the size of the other direction sizes of different lengths under the condition of, Different depth, different width of defect size changes, fatigue life will change accordingly, which influence the length size on the fatigue life of coiled tubing is greater than the impact of the depth and width; in the other direction the size unchanged, the axial length and radial depth of the ring. The width is, the shorter fatigue life of coiled tubing. The spherical defect size is the change of radius, fatigue life of coiled tubing does not change with the size of the radius increases monotonically, but fluctuate. Influence of fatigue life on fatigue life of cylindrical defects of coiled tubing and coiled tubing defects on the square is basically similar and interlinked. Taken together, effects of four types of defects on the fatigue life of coiled tubing from large to small is as follows: square defects, cylindrical ball defects. Ellipsoidal shape defects, defect defect. The smaller the radius of curvature, strain and strain concentration is more obvious, more concentrated, the fatigue of coiled tubing failure, accumulated plastic faster, thus the fatigue life is short. The process of coiled tubing in the winding straightening, the stress at the defect can be seen as axial tension or compression, defect size reduce the fatigue life of the coiled tubing, or to radial growth in axial shortening in the ring and vice versa.

【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE931.2

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