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

Abstract:

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.