Overview: Bit Technology (December 2006)

Abstract

Drilling activity has increased in the last couple of years, with wells being drilled deeper and into harder and more-abrasive formations. These drilling environments present serious challenges for drill bits in terms of rate of penetration (ROP) and bit durability. The high drilling-activity level and increased demand led to increased rig rates. To reduce drilling costs, drilling engineers have had to re-evaluate bottomhole-assembly designs, drilling processes, drilling fluids, and applications. Drill bits, although insignificant in terms of price, have huge effects on operational costs. To improve drilling performance, considering the challenges, drill bits must drill faster and last longer. These targets are what drilling engineers have come to expect and what bit companies are delivering to the industry. Several types of drill bits are available for different applications and drilling challenges—polycrystalline-diamond-compact (PDC), impregnated, and roller-cone bits. To reduce drilling costs substantially in the current environment, technology development must expand and permeate into all the different bit types. For PDC bits, new modeling tools and bit designs are being developed on a continuous basis. Bit-behavior analysis, especially the characterization of the different vibration modes, has become a standard in the bit-design process. New PDC cutters with very high abrasion-resistance properties continue to be developed. These cutters stay sharper for longer periods of time, thus improving ROP and durability. Substantial ROP and durability improvements are also being seen with impregnated bits. These improvements resulted from detailed evaluations that focused on the effects of drive tools (rotation speed and power regime), down-hole-pressure environment, and depth of cut on impregnated-bit development and performance. For roller-cone bits, new technologies are improving seal reliability and cutting-structure durability. In addition, new developments in metal-seal-bearing technology have drastically increased the on-bottom drilling time of roller-cone bits, especially in directional wells. Drill-bit companies have accepted the challenges, and they do not plan on slowing down. Bit Technology additional reading available at the SPE eLibrary: www.spe.org SPE 102182 "Coupling of Downhole-Dynamics Recorder Enhances System-Matched Approach to Drill-Bit Design and Application With a Specific Rotary-Steerable System" by S. Barton, SPE, ReedHycalog, et al. SPE 102134 "Vibration Analysis, Model Prediction, and Avoidance: A Case History" by G. Robello Samuel, Halliburton Drilling, Evaluation, and Digital Solutions, et al. SPE 99193 "Real-Time Downhole Torsional Vibration Monitor for Improving Tool Performance and Bit Design" by D.C.-K. Chen, Halliburton Sperry Drilling Services, et al.