Study on rock breaking mechanism of PDC bit with rotating module

Abstract

In view of the problems of low ROP, short bit life and high energy consumption of bits in deep and difficult formations. Basing on the 360°rotating teeth and disc PDC bit, a rotating modular PDC bit is proposed. The rock breaking efficiency of the bit is improved by “cross scraping” of the rotating module element (RME) and fixed cutting teeth. In addition, the rotating module element works alternately, which cools the cutting teeth in time, slowing the wear of the cutting teeth and prolongs bit life. This paper introduces the structural characteristics and working principle of the novel bit, and carries out variable parameter experiments on the rotating module element (side angle, journal angle, and tooth arrangement density, etc.) The experimental results show that the rotating speed of the rotating module element increases with the increase of the side angle, and decreases with the increase of the axial angle. The variation rules of cutting load and MSE of rotating module element under different structural parameters are studied. The indoor test shows that the ROP of rotary modular PDC bit is increased by 15% and the MSE is reduced by 14%, It is implies that the “cross scraping” of the rotary module element and the fixed cutting teeth can reduce the rock breaking specific work, and provide theoretical basis and support for the design of the subsequent rotary modular PDC bit.