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通过有限元分析方法，建立了带偏轴接头下部钻具组合的动力学方程，在处理相应的边界条件后，对带偏轴接头的下部钻具组合的钻头侧向力随时间变化的趋势和钻具任意截面的运动轨迹进行了全面的动态仿真研究，讨论了钻具的结构参数（偏轴距）、钻井参数（钻压、转速）对钻头侧向力和下部钻具在井内运动形态的影响，根据仿真结果判断带偏轴接头下部钻具组合的防斜效果，并提出为达到好的防斜效果所需的钻具结构参数和钻井参数。计算结果表明，由于偏轴接头的存在，带偏轴接头下部钻具组合的公转趋势增强，钻头无稳定的指向，这是偏轴钻柱能够防斜的重要原因。偏轴接头偏轴距的大小、转盘转速对偏轴钻柱防斜效果的影响较大，而钻压对防斜效果影响较小，因而可以通过增加钻压来提高机械钻速，达到既防斜又提高机械钻速的目的。

DYNAMIC ANALYSIS OF BOTTOM HOLE ASSEMBLY WITH ECCENTRIC SUB AND ITS MOTION SIMULATION RESEARCH

Through setting up the dynamic equations of bottom hole assembly (BHA) with eccentric sub by use of finite element analysis method,a full dynamic simulation research on the bit side force change-with-time of BHA with eccentric sub and the motion trail of arbitrary drillstem section was carried out after having treated the relevant boundary conditions;the effects of the drillstem construction parameter (eccentric distance) and drilling parameters (WOB,rotary speed) on the bit side force and the motion shape of BHA in borehole were analyzed;the efficiency of deviation control of BHA with eccentric sub was identified according to the simulation results;and the drillstem construction parameter and drilling parameters necessary for obtaining good efficiency of deviation control were put forward.The simulation results indicated that,because of the existence of eccentric sub,the revolution trend of BHA would be enhanced and the bit would cut borehole at arbitrary direction (this was the important reason why the BHA with eccentric sub could control hole deviation);and the magnitude of eccentric distance and the rotary speed had great effects on deviation control but WOB had a little effect,thus being able to raise ROP by increasing WOB to attain the goals of both controlling well deviation and enhancing ROP.Such a study has provided a theoretical basis for applying reasonably BHA with eccentric sub.