Drilling Performance of Self-propelled Straight-Rotary Mixing Nozzle

In order to improve the application results of hydraulic radial drilling technology in hydrate exploitation and reservoir stimulation,numerical simulation method was used to study the drilling performance of self-propelled nozzle,which is the core component of hydraulic radial drilling.The drilling performances of three commonly used self-propelled nozzles were compared and analyzed in terms of the propulsion performance and rock-breaking effect.The results show that the jet core length of the straight-rotary mixing jet nozzle is 1.18 times that of the rotary jet nozzle,which enables to eliminate the low-speed zone in the center of the rotary jet.And the tangential velocity and radial velocity of the jet are larger,which enable better shear rock breaking effect.The straight-rotary mixing jet nozzle has obviously larger effective rock-breaking area than that of the straight jet nozzle and it helps to produce larger holes.In addition,there is an optimal operating pressure range for the best drilling performance of the straight-rotary mixing jet nozzle.The study shows that the straight-rotary mixing jet nozzle has good drilling performance with the rock-breaking advantages of both straight jet and rotary jet.The results provide reference for efficient exploitation of marine natural gas hydrate and reservoir stimulation.