椭圆度对套管挤毁强度的影响分析

发布时间：2018-10-19 11:07

【摘要】：套管损坏已经成为一个国际性的普遍问题,并且套损速度有逐年上升的趋势。多年以来,国内外油田、科研机构和高等院校在套损机理研究方面做了大量的工作,研究总结出多项套损机理成果,但仍然有许多问题需要解决,值得深入研究。本文基于ANSYS有限元软件,对承受外压套管的挤毁强度和变形损坏进行了仿真,主完成以下内容：1.建立了理想套管的有限元模型,分析了在均匀和非均匀外载荷作用下理想套管的应力场和位移场。通过观察位移载荷关系曲线发现,外载荷达到临界值以前,套管的变形很小,而当外载荷达到临界值之后,套管所能承受的挤毁压力急剧降低,变形显著增加。而且通过计算得知,在非均匀载荷作用下,套管的挤毁强度远低于均匀载荷作用下套管的挤毁强度,即在非均匀载荷作用下套管的挤毁强度会大大降低。这是导致套管大量损坏的主要原因。2.建立了在有椭圆度的情况下,套管椭圆度与挤毁强度之问的数学模型,套管的挤毁强度随着椭圆度的增加而降低。3.建立了椭圆套管的有限元模型,分析了椭圆套管在均匀载荷作用下的应力场和位移场。通过计算可知,椭圆度会使套管的挤毁强度降低,随着椭圆度的增加,套管的失稳外压随之下降；当套管上作用的是非均匀分布的载荷时,不均度系数越小,椭圆度对套管挤毁强度的影响越小,但套管的挤毁强度变化与椭圆度的变化仍然成反比。4.当非均匀载荷的最大值沿椭圆长轴或短轴方向作用时,椭圆度引起的载荷能力降低并不大,套管承载能力主要受制于载荷非均匀度。
[Abstract]:Casing damage has become an international problem, and the casing failure rate is increasing year by year. Over the years, a great deal of work has been done in the research of casing damage mechanism in oil fields, scientific research institutions and colleges and universities at home and abroad, and many results of casing damage mechanism have been summarized, but there are still many problems to be solved, which are worthy of further study. Based on ANSYS finite element software, the extrusion strength and deformation damage of casing under external pressure are simulated. The main contents are as follows: 1. The finite element model of ideal casing is established, and the stress field and displacement field of ideal casing under uniform and non-uniform external loads are analyzed. By observing the displacement load relation curve, it is found that the casing deformation is very small before the external load reaches the critical value, but when the external load reaches the critical value, the collapsing pressure that the casing can withstand decreases sharply and the deformation increases significantly. The results show that under the action of non-uniform load, the collapsing strength of casing is much lower than that of casing under uniform load, that is, the strength of casing collapsing under the action of non-uniform load will be greatly reduced. This is the main cause of casing damage. 2. A mathematical model of the relationship between casing ellipticity and collapsing strength is established under the condition of ellipticity. The collapsing strength of casing decreases with the increase of ellipticity. The finite element model of elliptical casing is established, and the stress field and displacement field of elliptical casing under uniform load are analyzed. The calculation results show that ellipticity will decrease the collapsing strength of casing, and with the increase of ellipticity, the external pressure of casing instability will decrease, and when the load acting on the casing is non-uniformly distributed, the unevenness coefficient will decrease. The influence of ellipticity on casing collapsing strength is smaller, but the change of casing collapsing strength is still inversely proportional to ellipticity. When the maximum value of non-uniform load acts along the direction of the long or short axis of the ellipse, the load capacity caused by ellipticity is not greatly reduced, and the bearing capacity of the casing is mainly restricted by the load heterogeneity.
【学位授予单位】：西安石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE931.2

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