钻柱动力学研究进展及发展趋势

Research advances and development trend of drill string dynamics

钻柱动力学是安全、高效钻井的基础,许多研究人员对此进行了深入研究,成果累累。然而,钻柱具有超大长细比,工作环境恶劣,非线性特征显著,使得钻柱的安全性面临严峻挑战,这在超万米特深井中尤为突出。因此,把握钻柱动力学研究历程,提炼钻柱动力学核心关键问题十分必要。本文在简要回顾3种基本钻柱振动形式的研究进展基础上,重点阐述了这3种基本振动的耦合振动的研究进展,详细讨论了粘滑和涡动这2种复杂振动的危害、形成机制、研究方法、测量技术和控制方法,并对近十年来备受关注的高频扭转振动(HFTO)的研究进展进行了归纳。现有研究成果表明,涡动是井下钻柱最易出现的一种复杂振动形式,包括向前、向后规则涡动和不规则涡动形式,且大都体现为不规则涡动。其中,反向涡动对钻柱的危害很大,不但会加剧钻具的疲劳破坏,而且会降低钻头的机械钻速。粘滑振动是另一种危害极大的复杂振动形式,其形成机制在于钻头与岩石之间的相互作用,并可用速度弱化效应进行很好描述;粘滑振动与涡动密切相关,粘滑振动中的滑脱阶段的最大转速可能达到地面转速的3倍以上,并伴随着剧烈的涡动。而振动频率远高于涡动和粘滑振动的高频扭转振动的危害不容忽视,但相关机理远未探明,迫切需要攻关研究。

Drillstring dynamics is the basis of safe and efficient drilling,and many researchers have made in-depth research on it with fruitful results.However,the safety of drill string is faced with severe challenges due to its extremely large slenderness ratio,harsh working environment and significant nonlinear characteristics,especially in extra-deep wells exceeding 10,000 meters.Therefore,it is essential to grasp the research process of drill string dynamics and extract the core key issues.Based on a brief review of the research progress of the three basic drill string vibration forms,this paper focused on the research progress of the coupled vibration of these three basic vibration forms,and discussed in detail the harm,formation mechanism,research methods,measurement techniques and control methods of two complex vibrations:stick-slip and whirl.In particular,the research of high frequency torsional oscillation(HFTO),which has attracted much attention in recent ten years,was summarized.Finally,preliminary conclusions and prospects were provided,aiming to offer useful references for the innovative development of drill string dynamics mechanisms and control methods.The existing research results showed that the whirl is the most complex vibra-tion form of downhole drill string,including forward and backward regular whirl and irregular whirl motion,and most of them are irregular whirl motion.Among all the whirl modes,backward regular whirl is more harmful to the drill string,which will not only increase the fatigue damage of the drill tool,but also reduce the mechanical penetration rate of the bit.Stick-slip vibration is another highly harmful and complex form of vibration,which is induced by the interaction between the drill bit and the rock and can be well described by the velocity weakening effect.Stick-slip vibration is closely related to whirl motion.The maximum rotational speed in the slip stage of stick-slip vibration may reach 6-8 times of the ground rotational speed,accompanied with violent whirl motion.The high frequency torsional oscillation,whose vibration frequency is much higher than that of eddy and stick-slip vibration,is even more harmful,and the related mechanism is far from clear and is urgent to explore.