全井钻柱系统多体动力学模型

采用绝对节点坐标法建立了三维井眼全井钻柱系统多体动力学模型,将大长细比全井钻柱离散为绝对节点坐标梁单元,讨论了梁单元格式,并研究了井口、钻头处边界以及钻柱与井壁的接触/摩擦模型,给出了包含绝对节点坐标梁单元的钻柱系统运动方程。采用向后差分法求解微分-代数方程组,全面计算分析了全井钻柱系统的受力变形、摩阻扭矩、耦合振动、涡动、动力屈曲等力学特性,可在钻柱动力学研究和工程应用中发挥作用。

A multibody dynamical model of full-hole drillstring system

It is necessary for improving drilling efficiency and safety to investigate drillstring dynamics. A multibody dynamical model for 3D full-hole drillstring system was proposed based on the absolute nodal coordinate formulation (ANCF). The large fineness ratio of full-hole drillstring could be discretized into ANCF beam elements with the model and the format of beam elements was discussed. The absolute nodal coordinate formulation of beam elements and boundary conditions at wellhead and bit, as well as a contact/friction model between drillstring and wellbore were also investigated. A dynamic governing equation set for the full-hole drillstring system that contain ANCF was given and solved with the backward differentiation formulation (BDF) for differential algebraic equations (DAEs). The analysis of deformation, drag and torque, coupled vibration, whirling and dynamic buckling of the full-hole drillstring system was carried out, and the results showed that it can play an active role in drillstring dynamics researches and engineering applications.