关键词: 钻柱, 纵向振动, 振幅调制, 频谱分析

Abstract: Because of special geometry structure of three-cone bit,the top of formation will form a tri-spine well bottom while drilling with three-cone bit the drill string.It is the tri-spine well bottom that leads to the axial harmonic of vibration when the bit revolves a round and the three concavo-convex heave of bit and formation result in one time(1×rpm),two time(2×rpm),three time(3×rpm) turning table speed.In addition,while the teeth of the tri-cone bit interact with the formation,the drillstring will generate tiny axial vibration.As the vibration is symphonious to the tri-spine well bottom,the vibration signal exhibits amplitude modulation character.This character had been verified by in-site measurement data and numerical simulation.In this paper,the drillstring axial vibration character under drilling with three-cone bit is analyzed.Though in-site test of the well Gu-108 at Huabei Oil Field in China,vibration signal spectrum is also presented.

Key words: drillstring, axial vibration, amplitude modulation, frequency spectrum