大位移井振荡射流压力脉冲减阻工具结构设计与性能分析

Structural design and performance analysis of oscillating jet drag reduction tool used in extended reach wells

大位移井钻进技术为大幅提高页岩气等非常规能源的开采效率提供了可能。然而,大位移井钻进过程中钻杆与井壁间的摩阻高,降低了钻进效率。解决当前大位移井或水平井钻井施工过程中摩阻大、托压严重技术难题的有效办法之一是在井下钻具组合中增加可产生振荡功能的减阻工具。但目前此类工具种类少,且普遍存在工作机理复杂、结构设计困难、工具压力过高的问题。因此,本文提出了一种压力低、无运动零部件的逆反馈式振荡射流压力脉冲减阻工具。对该工具开展了可视化实验与数值模拟研究,通过监测工具内部流场的演化阐明了射流振荡器的工作机理,结果显示压力脉冲的产生是由射流的附壁切换、工具内部涡流的生长与消散等共同组成;开展了工具脉冲性能研究,揭示了本工具在不同流量、钻井液密度、粘度等条件下的工作性能。并针对小钻进流量的工况进行了结构优化,拓展了该工具的工作范围。本文可对大位移井钻进工具的设计提供新的参考。

The advancement in the drilling technology of large displacement wells has provided a great potential for significantly improving the efficiency of extracting unconventional energy sources such as shale gas.However,the high friction between the drilling rods and the wellbore during the process of large displacement well drilling reduces the drilling efficiency.One effective solution to address the technical challenges of high friction and severe drag in the current construction process of extended reach wells or horizontal wells is to incorporate drag reduction tools capable of generating oscillations into the downhole drilling tool assembly.However,currently,there are few types of such tools,and they generally suffer from complex working mechanisms,difficulties in structural design,and excessively high tool pressures.Therefore,this paper proposes a reverse feedback oscillating jet pressure pulse drag reduction tool with low pressure and no moving parts.Visual experiments and numerical simulations were conducted on this tool,and the working mechanism of the jet oscillator was elucidated by monitoring the evolution of the internal flow field of the tool.The results showed that the generation of pressure pulses is composed of phenomena such as the wall attachment and detachment of the jet,as well as the growth and dissipation of internal vortices in the tool.Furthermore,the pulsation performance of the tool was studied,revealing its operational performance under different conditions such as flow rate,drilling fluid density,viscosity,etc.Structural optimization was carried out for conditions of low drilling flow rates,expanding the operational range of the tool.This paper can provide new insights for the design of large displacement well drilling tools.