A study on the flow behavior inside fluidic oscillation tools for friction-reduction in extended reach well

Abstract

The drilling distance of extended-reach wells is limited by mechanical friction between the drill string and the borehole wall. The fluidic oscillator axial vibratory tools (AVTs) can effectively reduce friction and increase the weight on bit, thereby extending the reach of horizontal wells. However, few studies have delved into the evolutionary mechanism of the internal flow field of fluidic oscillator AVTs. In this paper, two types of fluidic oscillators with different flow path are presented. One is the reverse-feedback oscillator, and the other is sweeping-chamber oscillator. Through computational fluid dynamics method, the internal flow field of these two fluidic oscillator AVTs were analyzed, and the frequency and pressure drop were verified by experiments. The results show that the LES turbulence model provides more accurate simulations, showing an error range of less than 9%. The pressure drop and vibration frequency of the two tools are linearly related to the flow rate. The pressure drop of the reverse feedback oscillation tool is in the range of 0.1–1 MPa, and the vibration frequency is between 13 and 50 Hz. The sweeping-chamber oscillator can reduce vibration frequency to below 15 Hz. The results also show that it is crucial to consider the lag in pressure signals when designing and analyzing fluid oscillator systems, as it can affect the timing and behavior of the system. This research provides profound insights for understanding and optimizing fluidic oscillator systems.