铅垂井段钻柱的浑沌运动

Chaotic Motion of a Drillstring in Vertical Section

考虑了钻柱即时构形中轴向力对弯曲变形的影响 ,计及由于钻柱弯曲而产生的轴向附加力 ,得到了铅垂井段钻柱在周期性波动钻压激励下的非线性参数激励振动系统。将非线性动力系统理论用于钻柱动力学的研究 ,用 Melnikov- Holmes方法得到了钻柱可能发生浑沌振动的参数激励的阈值 ,推导了根据钻柱的物理与几何性质计算动力系统参数的公式。作者根据本文提供的计算方法和计算公式编制了相应的程序模块 ,可为钻井现场提供合理的工作参数 ,使钻柱运动远离浑沌区 。

Considering the effect of the axial force on the bending of a drillstring in vertical section and taking the extra axial force caused by lateral deformation into account, this paper studies the nonlinear, parametrically excited system describing the vibration of a vertical drillstring subjected to periodic weight on bit. The theory of non linear dynamic system was used to study the drillstrings nonlinear dynamics. The parameters of the dynamic system were formulated in terms of the physical and geometric characters of the drillstring. The threshold value of the parameter excitation that can trigger chaotic motion of the drillstring was obtained by means of Melniko Holmes method. A computer block was programmed to calculate the parameters of the dynamic system according to the formulae presented in this paper. The block can give out the reasonable operating parameters to keep the motion of the drillstring far from the chaotic region. The trajectory of borehole can then be controlled more effectively.