Development and application of hobbing-cone hybrid PDC bit

In order to solve the problems of low ROP and short service life of the bit drilling in deep and hard formation, a new technology of hobbing-cone hybrid PDC bit which has combined the advantages of conventional PDC bit and the hobbing-cone is proposed in this paper. The bit is developed and applied on basis of the structure design and the contrast experiment between the hobbing-cone bit and the conventional roller-cone hybrid PDC bit. The indoor drilling experiments show that the hobbing-cone hybrid PDC bit can form groove-shaped crushing pits in the bottom-hole. The teeth on the roller have high circumferential coverage on bottom-hole rock and an obvious pre-fracture effect on the rock. The experiment result shows that ROP of the hobbing-cone hybrid PDC bit is 20–30% lower in soft rock but 15–20% higher in hard rock, indicating that the bit is more suitable for hard rock drilling. Moreover, in the field application, average ROP of the hobbing-cone hybrid PDC bit is 126.1% higher and the footage is 89.6% longer than the comparisons, while wear status of the bit after drilling is quite good. Field application results show that the hobbing-cone hybrid PDC bit has good drilling effect in directional and hard formations, which can be well adapted to the drilling of applied wells (blocks) and directional sections with good steering performance, making it an optimization to improve the working performance in complex and hard-to-drill formations.