Numerical simulation research on improving cleaning cuttings effectiveness with pulsed jet under confining pressure

The drilling technology with pulsed jet is highly capable of cleaning the cuttings, but its acceleration mechanism remains unknown. By establishing a physical model for bottom hole cleaning cuttings by pulsed jet with single-nozzle under confining pressure, the numerical simulation research was conducted on the whole process of cleaning cuttings by pulsed jet, and the main factors affecting the cleaning cuttings effect by pulsed jet was analyzed. The research finding shows that unsteady state rotational flow is one of the main reasons for improvement of cleaning cuttings effect by pulsed jet. Under the same flow rate, the cleaning cuttings efficiency by pulsed jet is about 1-1.6 times that of continuous jet in average. The efficiency of cleaning cuttings by pulsed jet increases with the increase of nozzle diameter and inlet flowrate. The confining pressure has small effect on the process of cleaning cuttings by pulsed jet. The overall effect of cleaning cuttings by low frequency pulsed jet is good, with the increase of particle sizes, the heterogeneity of cuttings distribution within the impact area at hole bottom is intensified and the efficiency of cleaning cuttings by pulsed jet is reduced. The resulting conclusions provide a theoretical guidance for research on acceleration technique by pulsed jet.