三牙轮钻头钻进时钻柱轴向振动的特征

由于三牙轮钻头的特殊几何结构,钻进过程中在岩层顶部容易形成一个三脊状井底,正是这一三脊状井底,当钻头旋转一周时钻柱轴向三次凸凹变化,由此在轴向产生1倍、2倍和3倍及其更高次倍于转盘转速rpm的谐波振动.另外,三牙轮钻头与地层作用破岩时牙轮牙齿产生啮合振动,由于三脊状井底对啮合振动进行幅度调制形成调幅信号,根据调幅信号的频率特征,振动信号在频域表现为具有一定边带的一束谱线,它是钻头工作正常的“健康信号”.本文总结出了三牙轮钻头钻柱轴向振动的一般规律,并通过华北油田固108井实际测量数据分析,这一特征已经得到现场数据的验证.

AXIAL VIBRATION PERFORMANCE OF DRILL STRING WHEN DRILLING WITH THREE-CONE BIT

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.