A New Design of Ultrahigh Pressure Flow Channel for Common PDC Bit

In order to overcome the limitation that downhole supercharger could only support special PDC bit,a new design of ultrahigh pressure flow channel for common PDC bit was developed.Based on calculation of pressure loss in high-pressure pipe,a new shunt mechanism was designed and the diameter and length of diverter hose were determined.Through analysis of ultrahigh pressure water jet,the nozzle was optimized in structure,contraction angle of cone and its size.By laboratory testing,the sealing performance of all parts and connections under different pressures was verified.Theoretical analysis showed that lower limit of wall thickness at top of the shunt mechanism was 3.1 mm.Considering flow rate and pressure in operation,diameter of ultrahigh pressure pipe was designed as 8 mm,matching 400 mm-long high pressure hose;shrinkage angle of high-pressure water jet nozzle at maximum flow coefficient was designed as 13°;length of cylindrical outlet section of the high-pressure nozzle was defined 2-4 times that of the outlet diameter.Field test demonstrated the new design allowed average ROP to increase by 71.95%.Therefore,shunt device,diverting device and ultrahigh pressure nozzle of the ultrahigh pressure system with direct-connect dual-flow channels meet the requirements in field operation.The downhole supercharger integrating with common PDC bit can broaden its scope of application.