Working mechanism and rock-breaking performance study of new core drill bit with negative pressure absorption effect

Abstract

ABSTRACT In order to improve the ROP (rate of penetration) of complex structure and deep wells and reduce the energy consumption of rock breaking during the drilling process, a core drill bit with negative pressure adsorption effect is developed. Rock-breaking energy consumption, ROP, negative pressure effect and rock carrying capacity of new drill bit are studied. Numerical example is conducted to analyze the relationship between the characteristic parameters of drill bit and cutting velocity and experimental tests are carried out to verify the theoretical model and the results of calculation examples. The calculation results indicate that with the increase in the cutting velocity, the axial and tangential forces and the ROP increase and the power consumption of drill bit decreases. The nozzle equivalent size of the new drill bit can be designed as 0.03 mm. According to the experimental results, as the flow rate of fluid increases, the power consumption of new drill bit decreases and the ROP increases. Compared with the conventional bit, the reduced ratio of power consumption of new drill bit is between 8% and 25%, and the ROP is increased by more than 45% in some sections, which show the rock breaking effect of new drill bit is better. The new drill bit can be used in the exploitation of oil and gas well drilling technology with new conditions, and also can provide technical support for improving rock breaking efficiency and ROP in the drilling process.