Overview: Bit Technology (December 2005)

Drilling programs have become more challenging, regarding depths, well profiles, and formation drillability—in terms of hardness and/or abrasiveness. This situation places a lot of pressure on drill-bit manufacturers because they are expected to develop products that drill faster and/or longer in these harsher environments. To achieve this goal, drill-bit technology must outpace the industry’s performance needs. In addition, engineering services and tools, which enable overall evaluation of a drilling program’s objectives, must be developed. Traditionally, hard- and/or abrasive-rock drilling have been reserved for impregnated and roller-cone bits. R&D efforts, focusing on these bit types, continue to improve the rate of penetration and durability of impregnated and roller-cone bits, respectively. At the same time, polycrystalline-diamond-compact (PDC) bits also have experienced accelerated technology developments. As a result, the performances of PDC bits, especially in hard and/or abrasive formations, have become effective and highly consistent. In most applications around the world, PDC bits continue to replace impregnated and roller-cone bits—they are drilling faster and longer. The PDC-bit design process has improved greatly through the use of sophisticated design tools. With these tools, cutting structures can be developed to minimize damaging bit vibrations and/or PDC-cutter wear. Currently, PDC-cutter development also has reached a new level. Impact resistance does not have to be compromised to gain abrasion resistance. Technologies continue to be developed that enable both impact and abrasion resistances to be maximized. In addition, specialized-application tools, which aid in the bit-selection and -evaluation processes, also have been developed. Shortfalls in bit performance, which may seem insignificant in terms of cost, have drastic effects on overall well costs. Considering the technological advancements that continue to be made in bit development, selecting the right bit has become a very critical investment. Available from the SPE eLibrary: www.spe.org SPE 94798 “Drill-Bit Catalog and Bit Index: A New Method for Bit-Performance Evaluation,” by P. Macini, SPE, U. of Bologna, et al. SPE 91782 “Optimization of PDC-Drill-Bit Performance Utilizing High-Speed Real-Time Downhole Data Acquired Under a Cooperative Research and Development Agreement,” by T.S. Roberts, ReedHycalog, et al. SPE 93910 “The Trouble With Bits—A Holistic Approach to Drilling Optimization,” by D. Hamer, Halliburton Sperry-Sun, et al.