Optimization of rate of penetration through improved bit durability and extended directional nozzle

The enhanced drilling parameters and custom-designed polycrystalline diamond compact (PDC) bits have greatly improved both rate of penetration (ROP) and footage. Then how to further improve the bit’s ROP and how to deal with the side effects caused by the enhanced drilling parameters remain a challenge. In this work, the single-cutter rock-cutting tests and full-sized bit drilling tests were conducted to investigate the effects of rock types, drilling parameters, and bit designs on ROP. The results showed that in the easy-to-drill formations, the enhanced drilling parameters had a more pronounced effect on improving the bit’s ROP than the optimizations of bit designs such as changing the cutter shape and size. On the other hand, in the hard-to-drill formations, smaller-sized and shaped PDC cutters combined with high-torque tools offered a promising approach to increase ROP. To further improve ROP and footage, two innovative approaches were introduced: improving the bit durability without compromising ROP to ensure one-trip drilling, and using extended directional nozzles together with enhanced hydraulic parameters. The bit durability was improved by optimizing the cutter shape and diamond materials, which helped complete the single-run footage of 2986 m in the field trial of Shengli Oilfield. It was also found that the extended directional nozzle was less effective under conventional hydraulic parameters, but increased the ROP by 32.1% under enhanced hydraulic parameters because of improving jet impact performance through reduced jet diffusion. The findings provided insights for ROP improvement in the oil and gas drilling operations.