钻柱屈曲特性模拟与分析

发布时间：2018-06-01 02:33

本文选题：钻柱屈曲 + 临界屈曲载荷　；参考：《西南石油大学》2015年硕士论文

【摘要】：受井眼约束钻柱的屈曲行为,对钻井诸多方面都有不良影响,会引起钻柱摩阻和扭矩的显著增加,甚至使管柱“锁死”,导致钻压传递困难、钻柱疲劳破坏等井下复杂情况。特别是随着水平井、大位移井、多分支井的推广应用,受井眼约束的钻柱屈曲问题研究的重要性更加突出,钻柱屈曲研究已成为的钻柱优化设计的热点问题。本文基于弹性力学力学理论,考虑钻柱自重和井眼弯曲的影响,建立了不同井段(垂直段、斜直段、增斜段、降斜段)钻柱屈曲力学分析模型,推导了钻柱正弦屈曲临界载荷和螺旋屈曲临界载荷计算模型,计算了管柱屈曲后井壁接触载荷。针对不同尺寸钻柱,分析了井斜角、井眼曲率对钻柱屈曲临界载荷和接触力的影响。在斜直井段,钻柱临界屈曲载荷与井斜角成正比,水平段中钻柱躺在井眼低边,稳定性要高于斜直井段钻柱；弯曲井段影响钻柱屈曲最重要的因素为井眼曲率,增斜井段造斜率与钻柱临界屈曲载荷成正比,降斜井段则相反；随着轴向力的增大,钻柱与井壁的接触力也逐渐增大。本文采用非线性大变形理论,建立了钻柱几何非线性和接触非线性的有限元钻柱屈曲分析模型,模拟了不同井段钻柱屈曲变形演化过程及其对应的接触力矢量图。由于自重作用,斜直井段钻柱处于井眼低边,随着轴向载荷的增大会使钻柱沿井眼低边屈曲成正弦状,钻柱发生正弦屈曲后,随着轴向载荷的进一步增加会使钻柱由正弦屈曲向螺线屈曲演化,当载荷达到临界值时,管柱的屈曲形状会从正弦屈曲变成螺旋屈曲,从正弦屈曲到螺旋屈曲是一个瞬态的过程,当钻柱发生螺旋屈曲后,轴向力继续增大,会使钻柱与井壁的接触力激增；增斜井段随着井眼曲率的增加,临界屈曲载荷增加,屈曲从钻柱底部开始；降斜井段则相反,轴向载荷先将部分钻柱推向井眼高侧,然后从底端开始发生屈曲,随后顶端也开始发生屈曲,钻柱中部最后发生屈曲,并且降斜井段很容易发生屈曲。论文对比分析了钻柱屈曲解析解和有限元模拟结果的差异,模拟结果与理论计算值相对变化在15%以内,证明采用有限元分析方法确定钻柱屈曲临界载荷的方法是可行的。
[Abstract]:The buckling behavior of drill string restrained by borehole has a bad effect on many aspects of drilling, which will cause obvious increase of friction and torque of drill string, and even make string "lock", resulting in difficult transmission of drilling pressure, fatigue failure of drill string and other complicated downhole conditions. Especially, with the popularization and application of horizontal well, extended reach well and multi-branch well, the research on the buckling of drill string constrained by borehole becomes more and more important. The buckling of drill string has become a hot issue in the optimum design of drill string. Based on the theory of elasticity, considering the influence of drill string weight and borehole bending, different well sections (vertical section, oblique straight section, increment section) are established in this paper. The critical load of sinusoidal buckling and spiral buckling of drill string is derived, and the contact load of shaft wall after string buckling is calculated. The effects of inclined angle and borehole curvature on the critical load and contact force of drill string buckling are analyzed. The critical buckling load of the drill string is proportional to the angle of the well, and the drill string lies on the low side of the hole in the horizontal section, and the stability of the drill string is higher than that of the drill string in the oblique straight section, and the most important factor affecting the buckling of the drill string in the curved section is the borehole curvature. The slope rate of the increased slope section is directly proportional to the critical buckling load of the drill string, while the downslope section is opposite, and the contact force between the drill string and the shaft wall increases gradually with the increase of axial force. The nonlinear large deformation theory is used in this paper. The finite element buckling analysis model of drill string with geometric nonlinearity and contact nonlinearity is established, and the evolution process of drill string buckling and its corresponding contact force vector diagram are simulated. Due to self-gravity, the drill string in the oblique straight section is on the low side of the hole. With the increase of axial load, the drill string will buckle into a sinusoidal shape along the low side of the hole, and the drill string will buckle after sinusoidal buckling. With the further increase of axial load, the drill string evolves from sinusoidal buckling to helical buckling. When the load reaches the critical value, the buckling shape of the string changes from sinusoidal buckling to spiral buckling. It is a transient process from sinusoidal buckling to helical buckling. When the screw buckling occurs, the axial force continues to increase, which will make the contact force between the drill string and the shaft wall surge, and the critical buckling load increases with the increase of borehole curvature. The buckling begins at the bottom of the drill string, whereas in the downhill section, the axial load first pushes part of the drill string to the high side of the hole, then begins to buckle from the bottom, and then the top also begins to buckle, and the central part of the drill string finally buckles. The difference between the analytical solution of drill string buckling and the result of finite element simulation is analyzed, and the relative change between the simulation result and the theoretical value is less than 15%. It is proved that the finite element analysis method is feasible to determine the critical buckling load of drill string.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE921.2

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