气体钻井条件下钟摆钻具组合运动规律模拟实验研究

Simulated Experiment of Dynamic Characteristics of Pendulum Bottom-hole assembly under gas drilling conditions

为保证井下安全,气体钻井常常不使用或少使用稳定器,此时钻具组合更易发生弯曲而引起井斜。底部钻具组合(BHA)的动力学行为是气体钻井时发生井斜的主要原因。本文通过室内模拟实验,模拟研究气体钻井条件和不同钻进参数下BHA的运动状态及规律。研究结果表明,钻进参数、井壁摩擦系数等对BHA运动状态影响显著:钻压一定,转速低于门限转速时,BHA稳定正向涡动或规则摆动;转速在门限转速附近时,BHA无规则运动,运动状态不稳定;转速高于门限转速时,BHA稳定反向涡动。钻压一定时,提高转速使BHA反向涡动,有利于防斜打直;当转速一定时,提高钻压不利于防斜打直。在进行空气钻井时,可考虑在钻柱上应用滑套式扶正器(或滑套机构)并采用必要的技术措施减小摩擦系数,以减轻钻柱的振动,使BHA沿井壁较稳定地反向涡动,有助于提高防斜打直效果。

Stabilizer is not used or used seldom in gas drilling to ensure the downhole safety.At this time, bottom-hole assembly bends easily resulted in well deviation.One of the main reasons of the well deviation in the gas drilling is dynamic characteristics of the bottom-hole assembly （BHA）.Through laboratory experi- ment,the dynamic characteristics of the BHA were simulated under the conditions of the gas drilling and various drilling parameters.And its influence on the well deviation was analyzed.The result shows that drilling parameters,wall friction factors and others have significant effect on motion state of BHA.Under certain WOB,when the rotation speed is lower than the critical rotation speed,the BHA may be at stable forward whirling or regular oscillation.When the rotation speed is near the critical rotation speed ,sympathetic vibration occurs and the BHA may move irregularly or whirl reversely.When the rotation speed is higher than the critical rotation speed,the BHA may be at stable backward whirling.The backward whirling is favorable for deviation control.The increased WOB is not good for deviation control.Some necessary measures should be taken for reducing fiction factor and alleviating drill string vibration during the gas drilling.It makes BHA whirl backward stably along with the borehole wall,which will improve the effect of borehole deviation control.