Pressure drawdown mechanism and design principle of jet pump bit

Reducing the Bottom Hole Dierential Pressure (BHDP) to reduce the cutting hold-down eects can signicantly improve the Rate Of Penetration (ROP). This paper analyzes the pressure drawdown mechanism of the jet pump bit, and then designs a novel annular jet pump bit. Using the hybrid grid method, key factors aecting the pressure drawdown capacity of the bit are discussed. The back ow below the reverse nozzle outlet is the main reason for the pressure drawdown capacity of the jet pump bit being reduced. The design principle of the jet pump bit is given. The axial and radial angles are 150-180and 60-75, respectively, and the bit clearance should be kept below 3 mm, preferably using the vortex-jet ow combination pressure drawdown theory, to reduce the bottom hole pressure. The bit rotation speed should be as large as possible, all of which provides the theoretical guide for its development.