等曲率井眼中钻柱与井壁问接触力分析

建立了等曲率井眼中考虑轴向力和重力的钻柱平衡方程式，采用理论和非线性有限元的方法分析了等曲率井眼中钻柱与井壁之间的接触力。采用牛顿一拉普森方法对非线性有限元方程进行了迭代求解。要保证理论分析的精度，同样需要考虑边界条件。计算结果表明，由于外力的作用，钻柱紧贴于井壁的一侧时，钻柱的刚度对钻柱与井壁间的接触力无影响，此时，井眼曲率越大，钻柱与井壁之间的接触力越大。当外力不足以使钻柱紧贴于井壁的一侧时，钻柱的刚度对钻柱与井壁之间的接触力有影响。与理论分析相比，非线性有限元方法应用范围更广，解的精度更高。

Study of contact force between drill string and borehole wall in constant-curvature wellbores

The equilibrium equations of drill string considering weight and axial force in constant-curvature wellbore were derived, The contact force between drill string and borehole wall was analyzed using nonlinear finite element and theory analysis method, Nonlinear finite element equilibriums were solved by Newton-Raphson method. Boundary conditions were considered to make the result accuracy. The results show that the stiffness of drill string is irrelative with the contact force when the force can contact drill string with one side of the borehole wall, and the more curvature of hole, the more the contact force is. When the force can not contact drill string with one side of the borehole wall, the stiffness of drill string can influence the contact force. Compared with theory analysis, nonlinear finite element can be used widely, and the precision is higher.