Torque Reduction Mechanism and Test Study of PDC Bit Specially Designed for Coiled Tubing Drilling
Due to small diameter and high flexibility of coiled tubing,frictional self-locking and buckling eas-ily occur during drilling,resulting in difficult WOB application and inefficient ROP accordingly.In order to im-prove the drilling ability of coiled tubing under low WOB,a small-sized PDC bit used for coiled tubing drilling was specially designed.By means of cutting test of single cutter,micro-bit and full-bit rock breaking tests of horizontal well drill string,the torque reduction mechanism of small-sized PDC bit was studied,and the influence of different cutter shapes on rock breaking effect were compared.The study results show that when the rake angle of PDC cutter is small,the average cutting force on wide edge cutter is 10.35%to 24.56%smaller than that on conventional cut-ter when breaking rocks of the same volume.At the same ROP,the torque of a wide edge cutter bit is lower than that of a conventional cutter bit,with a maximum torque reduction of 37.64%.At the same rotary speed and WOB,the maximum torque reduction of a wide edge cutter is 28.58%,and the greater the WOB,the more obvi-ous the torque reduction effect is.The specially designed wide edge cutter PDC bit is more suitable for coiled tub-ing to realize rock breaking with low WOB,low torque and high speed.The study results provide new solutions and theoretical support for improving the adaptability of coiled tubing drilling technology in drilling with low WOB.
万方数据
维普
