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。
本文利用ANSYS有限元软件,对承受外压套管的承载能力和变形损坏进行了仿真,主要做了如下工作:
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压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,外压达到临界值以前,套管的变形很小,而当外压达到临界值之后,套管所能承受的外压急剧降低,变形显著增加。而且通过计算得知,在非均匀外压作用下,套管的临界外压远低于均匀外压作用下套管的临界外压,即在非均匀外压作用下套管的承载能力会大大降低。这是导致套管大量损坏的主要原因。
2.建立了偏心套管的有限元模型,分析了偏心套管在均匀外压作用下的应力场和位移场。通过计算发现,偏心度会降低套管的承载能力,随着偏心度的增加,套管的失稳外压随之下降。
3.建立了椭圆套管的有限元模型,分析了椭圆套管在均匀外压作用下的应力场和位移场。通过计算可知,椭圆度会使套管的承载能力降低,随着椭圆度的增加,套管的失稳外压随之下降。
本文的研究对指导石油套管的设计及套损的防治具有重要的理论意义和实际价值。?
Tubular collapses are already international general problems and tubular collapses speed is increasing with years. For many years, domestic and foreign oilfield, scientific institution, colleges and universities have done masses of work on tubular collapse mechanism, and have summarized some tubular collapse mechanism scientific payoffs. But there are still a lot of problems to solve.
In this paper, the sustainability and deformation of external pressure on tubulars are analyzed and imitated by using the finite element software ANSYS. The main work of this paper are as follows.
1. Finite element model of ideal tubular is established, stress field and displacement field of ideal tubular under uniform pressure or non-uniform pressure are analyzed. By observing displacement-load curve, we can see that the deformation increases slowly at the beginning until the maximum pressure (collapse pressure) is reached, and then a decrease in the pressure is observed with a large increase in the deformation. Tubular’s collapse pressure under non-uniform pressure is much lower than its collapse pressure under uniform pressure. That is why so many tubulars are destroyed.
2. Finite element model of eccentric tubular is established, stress field and displacement field of eccentric tubular under uniform pressure are analyzed. By observing displacement-load curve, significant reduction in the collapse pressure of a tubular occurs when a small eccentricity is introduced. Eccentricity increases while tubular collapse pressure decreases.
3. Finite element model of ellipse tubular is established, stress field and displacement field of ellipse tubular under uniform pressure are analyzed. By observing displacement-load curve, significant reduction in the collapse pressure of a tubular occurs when a small ovality is introduced. Ovality increases while tubular collapse pressure decreases.
This work proved to have important academic merit and practical value on directing tubular designs and protection of tubular collapse.?
引文
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