定向井杆管接触状态的有限元仿真模型

A finite element simulation model of the rod-tubing contact state in directional wells

将定向井抽油杆柱离散为空间梁单元,通过在所有节点构造双向弹簧元模拟抽油杆柱与油管的接触状态,考虑双向弹簧元弹簧刚度系数对单元刚度矩阵与总刚度矩阵的影响,建立了抽油杆柱与油管接触状态的有限元仿真分析模型。仿真结果表明,弹簧元能够准确模拟杆管接触状态,确定杆柱与油管内壁接触状态、杆管接触压力以及扶正器与油管接触压力;抽油杆柱与油管柱接触受实际井眼轨道的影响,井眼造斜段、局部狗腿度较大的井段,杆管接触压力较大;在定向井抽油杆柱安装扶正器可以明显减小或消除杆体与油管的接触压力以及接箍与油管的接触压力。

The rod string of the directional well was discretized as the space beam unit and the node where it was located was used to construct the bi-directional spring element to simulate the contact state between the pumping rod and the tubing.Considering the effect of the spring rigidity coefficient of the bi-directional spring element on the unit rigidity matrix and total rigidity matrix,the finite element simulation analysis model of the rod-tubing contact state was established.The simulation result indicates that the spring element could exactly simulate the rod-tubing contact condition and determine the contact condition between the rod string and the inner wall of the tubing as well as the contact pressure of the rod string and the contact pressure between the centralizer and the tubing.The contact between the rod string and the tubing string was subject to the effect of the orbit of the actual hole.The rod-tubing contact pressure was great in deflection sections and sections with great local dog-leg severity.The installment of the centralizer in the rod string of the directional well could remarkably reduce or remove the contact pressure between the rod and the tubing as well as the contact pressure between the collar and the tubing.