Research On New Type Spin Jet Bit

With the demand for energy and difficulties of drilling increased, the ultrashort radius radial horizontal well is widely used in exploitation of low permeability reservoirs, it also can increase the yield of old well. So the research of the not enlarge aperture to the horizontal well technology and jet bit is of great significance.In this paper, based on the technological requirements of the in casing veer radial horizontal well, design the structure of spin jet bit according to the characteristics of small size hydraulic drilling bit. Spin hydraulic bit has a center nozzle, and two side nozzles. By numerical simulation, analyzing how parameters such as the expanding angle of center nozzle,tilt angle of the side nozzle and eccentricity influence the jet flow field characteristics, and then determine the nozzle form. Analyzing the effects of combination nozzle parameters on drilling through bench experiment.Numerical simulation found that the center nozzle should use laval nozzle, side nozzle should adopt the cone nozzle. The center laval nozzle cavitation’s cavitation effect is obvious,the cavitation effect generated along the side wall, concentrating in the distance which is about two to three times of the nozzle exit diameter. From the exit of centre of nozzle, along the axis of jet bit within a distance, it has a good high and low pressure area distribution, that induce the cavitation, near the the location that S=1Dn, the nozzle reached the maximum negative pressure, and then the pressure rises rapidly. When the outlet angle is 30°, straight column section length is one to two times the entrance diameter, the range of continuous negative pressure is the largest, the cavitation effect is the best. Through the flow field numerical simulation of center of the combination of laval nozzle and side nozzle, it is concluded that combination nozzles’ jet spray coverage diameter can reach more than 60 mm,it works best when the optimal angle of side nozzle is 35°.Based on the results of numerical simulation, develping the spin hydraulic drilling bit,and through indoor rock drilling experiment, analyzing the influence of structure parameters on the drilling effect. When side nozzle has an Angle of 30~35°, the eccentricity e is a center nozzle inlet diameter, the drilling ability of jet is the strongest. Compared with the single nozzle, the diameter of drilled hole and rock fragmentation efficiency of spin jet bit has obviously increased, under the condition of the optimal spraying distance, the biggest rock bore hole diameter can reach more than 50 mm.