| Abstract:The extended reach well drilling technology has provided the possibility of significantly improving the extraction efficiency of unconventional energy such as shale gas. However, during the horizontal drilling process, the high friction between the drill string and the wellbore wall has limited the widespread application of this technology. An effective solution to this challenge is to incorporate jet oscillation tools within the downhole drilling assembly. Nevertheless, such tools commonly face issues like complex operating mechanisms, intricate structural design, and excessively high tool pressures. In light of these issues, this paper introduces a low-pressure, motionless-component feedback-type oscillatory jet pressure pulse reduction tool. Visual experiments and numerical simulations were conducted to investigate this tool. By monitoring the evolution of the internal flow field, the working mechanism of the jet oscillator was elucidated. The results revealed that pressure pulses are generated through a combination of wall-attachment switching of the jet and the growth and dissipation of vortices. Performance studies were conducted, exposing the tool's operational characteristics under varying conditions, such as different flow rates, drilling fluid densities, and viscosities. Structural optimizations were also carried out for situations involving low drilling flow rates, extending the tool's operational range. This paper provides new insights into drag reduction techniques for large displacement well drilling. |
