Abstract: In hydrajet fracturing on U-shape coal bed methane (CBM) well,the abrasive perforating sand is difficult to return to the ground and may cause sand sticking.To solve this problem,design of the tool was modified on the basis of horizontal well hydrajet fracturing techniques.First,the centralizer channel was changed from direct to spiral and the nozzle was changed from built-up ceramic to monolithic alloy.Second,operation process was modified,in which both the perforation sand and flowback fluid return to the ground from the vertical well.Finally,the optimized nozzle diameter of 6 mm and optimum tubing displacement of 2.0 m3/min were determined.Field test showed that the modified tools and techniques could effectively avoid sand sticking.4 stage fracturing treatments were finished in the well successfully by using the optimized parameters,with slick water injection of 1 932 m3,sand of 90 m3,and the highest sand ratio reached 23%.After dewatering and depressurization for 3 months,the well started to produce with stable production of 500 m3 per day and the accumulated gas of about 75 000 m3.With the modified tools,techniques and optimized parameters,the problem in the U-shape CBM well fracturing had been addressed and it would provide a reference for subsequent U-shape CBM well fracturing.