偏心钻头钻进时的底部钻柱力学分析

Mechanical Analysis of Bottom Drilling Strings while Using Eccentric Bits

采用静力分析的方法,建立了偏心钻头底部钻具组合的力学模型,并完成了对力学模型的求解。应用数值计算方法,分析了偏心钻头底部钻具组合的受力和变形特性。通过对切点位置、钻头侧向力、井斜角及钻压分配比的分析发现:使用偏心钻头时钻柱与井壁的切点位置要比没有偏心时低得多;在倾斜井眼中,钻头偏心块在上方时,随钻压的增加钻具的降斜趋势减弱,增斜趋势增强;当偏心块在下方时,随钻压的增加钻具的降斜趋势增强;钻压分配比对钻头侧向力的变化趋势有重大影响。

A mechanical model of bottom hole assembly (BHA) with eccentric bits is established and the solution of this model was given by means of numerical method. The mechanical properties and the deformation characteristics of the BHA with the eccentric bit are analyzed. Through the analysis of tangential point position, the lateral force acting on the bit, inclination and the distribution of bit weight, a few conclusions are put forward as following: the tangential point position while using the eccentric bit is much lower than using a conventional bit. Meanwhile, in deviated holes, the location of the eccentric pad on the bit will influence the hole deviation and the distribution of bit weight has a great effect on the lateral force on bit.