钻柱-钻头-岩石系统动力学特性研究

摘要

钻头、钻柱和岩石系统作为一个整体,其动力学特性相互耦合,相互影响,而现有文献的研究中大都忽略了整个系统这种动力学耦合.鉴于此,考虑下部钻具纵横扭动力耦合、钻头与岩石非线性接触,建立了钻柱-钻头-岩石系统动力学模型.采用有限元法模拟了三牙轮钻头破岩钻进的动态过程.研究结果表明:在三牙轮钻头破岩钻进过程中,钻头与岩石互作用以及由此引起下部钻具振动均具有明显的非线性和随机性;由于牙轮钻头破岩方式以纵向冲击为主,钻具纵向振动强于横向,动钻压平均振幅达到静钻压的40％以上;扭转振动可能引起负扭矩现象.研究结果为牙轮钻头破岩机理及井下钻具非线性动力学特性的研究提供了新思路.%Drill bit,drill string and rock system as a whole,has coupled and interacted dynamic characteristics,which is neglected in most of researches.In view of this,considering the coupling of axial and lateral torsion of the lower drilling tool and the non-linear contact between the drill bit and the rock,a dynamics model of drill string-bit-rock system has been established.By using the finite element method,the dynamic process of rock drilling by tricone bit has been simulated.The results showed that,the interaction between the drill bit and the rock and the consequent vibration of the lower drilling tool were obviously nonlinear and random in the process of rock drilling by tricone bit.Because the axial impact is dominant in tricone bit drilling rock,and the axial vibration is greater than lateral vibration,the average amplitude of the dynamic weight on bit is 40％ more than that of the static weight on bit.Torsional vibration may cause negative torque.The results provide a new idea for the study of the rock breaking mechanism of cone bit and the nonlinear dynamic characteristics of the downhole drilling tool.