关键词: 三维弯曲井眼, 非线性问题, 元胞自动机, 非线性方程, 钻柱力学, 有限元法, 求解方法

Abstract:

The problem of multidirectional contact of drill string with borehole wall is usually studied by using penalty function method, gap-element method, formal stiffness method and loosing constraint method. But these methods have slow calculation speed and are difficult to meet the requirements of engineering application. A new solution for nonlinear finite element equations of multidirectional contact of drill string with wall of borehole was proposed by establishing three-dimensional finite element model of drill string in the curved well bore and definite condition of the contact between drill string and borehole wall on the basis of cellular automata. This solution method is suitable for solving the nonlinear contact problem of drill string in the three-dimensional curved well bore and has the advantages of simple programming and convergence speed. It can be used to solve the complex boundary conditions of collision in three-dimensional curved borehole.

Key words: three-dimensional curved well bore, nonlinear problem, cellular automata, nonlinear equation, drill string mechanics, finite element method, solution method