大位移井套管轴向力对套管挠度的影响

摘要

大位移井套管在重力效应作用下使套管偏心并产生挠曲变形，大幅降低水泥浆的顶替效率，影响固井质量，现场一般采用安装扶正器的方法改善套管的偏心；而两扶正器间的套管在井斜的影响下，套管自重会在轴向上产生一定的分力，井斜角越大其分力越大，对套管的挠度产生的影响也越大。采用纵横弯曲梁理论建立了套管挠度计算模型，并定义了挠度影响因子的概念，在此基础上研究了挠度影响因子随轴向力的变化规律及轴向力对套管挠度的影响。研究结果表明：在轴向力对套管挠度的影响方面存在1个临界力，小于临界力时轴向力对套管挠度的影响可以忽略，大于临界力时轴向力对套管挠度的影响显著；临界力的大小与扶正器间距、套管的弹性模量以及套管截面的轴惯性矩的相关性可以忽略。研究结果间接证明：大位移井中下套管作业时，现场利用套管的自重使套管下入预定深度的正确性，可以有效地减小两扶正器间套管的挠曲变形，并对大位移井扶正器的优化设计具有一定的指导意义。%Because of the gravitational effect,the casing of extended-reach well will engender eccen-tric and bending deformation,which will greatly reduce the cement slurry displacement efficiency and influence cementing quality.Centralizers are usually used to improve casing eccentricity on site.Under the influence of well deviation on casing between two adjacent centralizers,the casing dead weight will produce a certain component force in the axial direction,and the greater of the well deviation,the greater of the load component force,and the greater of the influence on casing bending deflection.Based on the vertical and horizontal bending beam theory,the casing deflection calculation model is established,deflection impact factor is defined,and the relationship between axial force and the deflection impact factor are studied and the casing deflection well as.It is shown that there is a critical force that when the axial force is greater than it,the impact of axial force on the deflection can be ignored,on the contrary,the influence of the axial force on the cas-ing deflection is remarkable.And the relativity between critical force and centralizer spacing,the Young′s modulus,the moment of inertia can be ignored.It shows that,using the dead weight of the casing to run casing can effectively reduce the casing bending deformation between two adja-cent centralizers,and it has a guiding significance to the optimization design of centralizer spacing in extended-reach well.