Abstract: Due to the problems of serious back-pressure, large friction and torque fluctuation in the drilling of build-up section and horizontal section, the rock breaking WOB cannot be effectively applied, which results resulting in low ROP of conventional PDC bit run. By using tools such as hydraulic agitator, compound bit, certain effect on acceleration of ROP cannot be achieved, but well site drilling needs can not be fully met due to limitation of tool size, installation position and downhole safety of compound bit. Therefore, a self-vibration unit of compact structure is designed based on the principle of water hammer impact. A new ϕ215.9 mm self-vibration PDC bit is developed. Through theoretical calculation and CFD numerical simulation technology combined with key parameters such as vibration frequency and vibration force, a new ϕ215.9 mm self-vibration PDC bit is developed, which can produce low-frequency axial impact force directly acting on rock. The field application in well Yun'an X1 shows that the mutation frequency and variation range of the hook load of the new self-vibration PDC bit are significantly lower than those of the compound bit in the same section of the same well, which effectively reduces the friction between the drill string and the borehole wall and further alleviates the back pressure problem. Thus, the average ROP is increased by 32.97% in the same well compared to that of compound bit, and by 74.50% compared to that of the conventional PDC bit in the adjacent well, realizing the speed increase, cost reduction and efficiency increase.

Key words: PDC bit, build-up section, horizontal section, back pressure, self-vibration