钻柱黏滑振动特性仿真与产生机理分析
Characteristic Simulation and Mechanisms Analysis for Drill-Strings Stick-Slip Vibration

针对钻探作业中产生的钻柱黏滑振动现象,研究了仿真环境下钻柱系统的黏滑振动特性与振动产生机理。基于振动理论,建立了井下钻进系统的双自由度弹性模型,提出了一种模拟钻头-岩石摩擦力矩的算法;构造了钻进系统结构图,模拟了钻柱黏滑振动的变化规律,并通过极限环分析钻柱黏滑振动的产生机理;绘制钻井参数与振动幅值和周期的关系曲线,讨论了钻井参数对钻柱黏滑振动的影响。仿真结果表明,钻柱黏滑振动主要表现为钻头周期性地黏滞和滑动,属于一种由非线性摩擦力引起的自激振动;钻井参数的改变影响钻柱黏滑振动的剧烈程度。
To our best knowledge, there is no paper in the open literature concerning the structural simulation for drill-strings stick-slip vibration. In order to improve both the productivity and the quality of the drilling and, thus, attenuate the intensity of vibration, we commit to analysis the dynamic characteristics and produce mechanism of the drill-strings stick-slip vibration. In the full paper, we explain in detail our simulation research results; in this abstract, we just add some pertinent remarks to the three topics of explanation: (1) dynamic model of the drill-strings drive; (2) the special law of motion of drill-strings stick-slip vibration; (3) the effect of drilling parameters; the subtopics of topic 1 are the double degrees of freedom model (subtopic 1.1), the Karnopp drill-tool friction sub-model (subtopic 1.2), and the structure diagram of the system as shown in Fig.3 in the full paper (subtopic 1.3); under subtopic 1.2, Fig.2 in the full paper avoids the problem of non-unique friction description in the zero-speed region of drilling-tool; under subtopic 1.3, we derive eqs. (7) and (8); under topic 2, we propose a new algorithm to apply the Karnopp friction sub-model to the simulation as shown in Fig.4 in the full paper, the phenomenon of drill-strings stick-slip vibration is simulated by MATLAB as shown in Fig.5 in the full paper, we point out that drill-strings stick-slip vibration exist hysteresis effect as shown in Fig.6 in the full paper, and we analyze the limit cycle of nonlinear drill-strings system which reflect the energy change of the system and the producing mechanism of vibration as shown in Fig.7 in the full paper; under topic 3, Fig.8, Fig.9 and Fig.10 in the full paper show the amplitude and frequency of stick--slip oscillation change curve which abscissa respectively corresponded to drill string-length, driving speed and weight-on-bit (WoB). The simulation results indicate preliminarily that: (1) the undesired drill-strings stick-slip vibration belongs to a self-excited vibration and is caused by the nonlinear friction which gives rise to the imbalance between the kinetic energy and potential energy of both ends of the drill-strings; (2) adjusting drilling parameters can effectively suppress the stick-slip vibration of the drill-strings