Optimized design and application of a directional reaming-while-drilling polycrystalline diamond compact bit

Abstract

Directional reaming while drilling is mainly used to optimize the casing program, improve cementing quality, and avoid drill pipe sticking caused by hole shrinkage. Under the condition of directional reaming while drilling, polycrystalline diamond compact (PDC) bits often suffer from serious failure modes such as balling, coring, and ring out. Based on the failure mechanism of reaming-while-drilling PDC bits in the Tahe oilfield and actual drilling needs, the optimized design of the reaming structure, crown profile, and cutter distribution of the PDC bit were analyzed, and a directional reaming-while-drilling PDC bit was developed. Specifically, the basic reaming structure is two-stage reaming, with the crown profile of the pilot bit being designed as a slightly raised structure and the cutters being distributed on the basis of the self-balancing principle. Field application in the Tahe oilfield shows that the bit achieves good performance in directional reaming while drilling, with the reaming diameter being larger than the required Φ 170 mm while the dogleg severity reaches 3.3°/10 m, which indicates that both the reaming and deflecting abilities of the bit can satisfy the engineering requirement. Moreover, the average footage of CK306B is 93 m and the rate of penetration of the bit is 1.24 m/h, which are, respectively, 90% and 47.6% higher than values from the first round of field application. The research results demonstrate the feasibility of novel directional reaming while drilling with a PDC bit in deep wells. In addition, the method can meet the requirements of trajectory control and directional reaming. The lateral imbalanced factor, which has a great influence on the reaming and drilling process of a directional reaming-while-drilling PDC bit, could be controlled within 5%, which can improve the stability of the bit as well as reduce bit failure, thus prolonging the life of the bit.