考虑残余应变的连续油管螺旋屈曲载荷新公式

在假设连续油管初始形态为正弦形态,受外载发生屈曲后由正弦形态变成螺旋屈曲形态的基础上,推导得出在斜直井中考虑残余应变的连续油管螺旋屈曲载荷计算新公式。利用新公式进行的实例计算和分析表明,当井斜角小于2°时,连续油管螺旋屈曲载荷随着初始幅值角的增大而增大,但井斜角大于2°后,螺旋屈曲载荷随初始幅值角的增大而减小,且随着井斜角的增大,减小的幅度变大;井斜角的增大,使连续油管的螺旋屈曲载荷增大。

A new calculating formula for helical buckling load of coiled tubing with residual strain

Based on assumptions of buckling behaviors of coiled tubing in straight deviated wells, the formula of bending stain energy, the formula of work done by the external force and the formula of work done by the weight component have been derived from the basic mechanical theories. According to the principle of minimal potential energy and the principle of conservation of energy, the helical buckling equilibrium equations have been established and done integral of the three formulas-bending stain energy including smartly using the Euler formula of complex number and series of complex number to lay out the transcendental trigonometric function to the polynomial of ordinary trigonometric function. A new calculating formula of coiled tubing helical buckling forces which consider the effect of the coiled tubing residual strain in the straight deviated well has been derived and verified by the calculating cases. The new formula derived can be simplified to accord with the former formulas derived by Wu and Lubinski et al and it is correct.