In 1987, the IADC adopted an improved Rock Bit Dull Grading System. Although it was modeled after the previously used T-B-G System, it was expanded to provide a much clearer "mental picture" of a dull bit. This paper documents the changes from the 1987 version to the 1992 IADC Dull Grading System. Since the changes are minor, they are listed at the beginning of the paper. Additionally, for those needing more detail, the entire 1992 IADC Dull Grading System is presented. CHANGES FROM 1987 * Outer Cutting Structure: Definition will change to "All cutting elements that touch the side of the hole".*Reasons Pulled Add: "LIH" - for "Left in Hole"*Bearing Grade Add: "N" - for "Not Able to Grade"*Location: "G" represents gage area, replacing "H".*IADC bit topics also updated in 1992 include IADC Classification and Fixed Cutter Dull Grading. Introduction The use of dull bit evaluation methods represents a key step in the advance of rock bit technology. Historically, a driller would learn through experience how to examine a "dull" to determine what type of bit to run next, and how it should be run (WOB, RPM, etc.). This was part of the art that separated the best drillers from the rest. An industry wide effort began years ago to teach the art of bit wear analysis to a broader range of personnel so that dull bit evaluation would become an integral part of daily drilling practice. General guidelines were established in the mid-1950's for relating typical bit wear patterns to the possible causes and remedies. This approach was helpful but limited by the lack of a common vocabulary for describing bit wear and documenting the dull condition in drilling reports. Meanwhile, basic bit performance studies produced a greater appreciation for the economic impact of bit wear and its close relationship to bit selection and operating practices. An industry standard for reporting bit wear was clearly needed. The Weight/Speed/Penetration Sub-Committee of the American Association of Drilling Contractors (AAODC) established the first dull grading standard in 1961. P. 819^

Controversy exists regarding the optimum nozzle configuration for rolling cutter bits. Frequently, this confusion is compounded by tests which compare an experimental configuration to only the standard nondirected, three nozzle design. Additionally, field data can cloud comparisons because of the lack of control and repeatability of formation and drilling conditions. The strategy of this paper is to describe the use of controlled laboratory conditions to best isolate the true benefit of various hydraulic configurations. Tests were conducted in a pressurized drilling environment using 9-7/8 tooth and insert bits in Mancos shale. Hydraulic configurations include combinations of standard and directed nozzle bits with center jets, long extended nozzles, and short extended nozzles. Results indicate that directed nozzles provide substantially better bit cleaning and rate of penetration (ROP) than the standard and short extended nozzle configurations and slightly faster rate of penetration than long extended nozzle configurations. Introduction The evolution of bit technology has shown substantial increases in durability and penetration rates. A key area of focus for improving rate of penetration has been bit hydraulics. The first advancement was to change from regular circulation bits to today's standard jet bit with three non-directed replaceable nozzles. Subsequent work by several researchers has established the importance of optimizing system hydraulics to maximize hydraulic cleaning at the bit. Adding to that success others have proposed alternate nozzle configurations to boost rate of penetration. The two basic strategies applied in alternate nozzle configurations are to place the nozzle closer to the formation and to direct nozzles so that they clean cutters and reduce balling. The alternate nozzle configurations evaluated in this work are discussed below. The authors acknowledge nozzle blanking and asymmetric nozzles as candidates for future study.

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Controversy exists regarding the optimum nozzle design for rolling-cutter bits. This paper describes the use of controlled laboratory conditions to isolate the true benefit of various hydraulic designs. Tests were conducted in a pressurized drilling environment with 9Ys-in. [2S1-mm] tooth and insert bits in Mancos shale. Hydraulic designs include combinations of standard-and directed-nozzle bits with center jets and long and short extended-nozzle bits. Results indicate that directed nozzles provide substantially better bit cleaning and rate of penetration (ROP) than the standard-and short extended-nozzle designs and a slightly faster ROP than long extended-nozzle designs.

This paper provides documentation of six cases in which Thermally Stable Diamond (TSD) bits were used in combination with downhole motors yielding economically successful results in the Permian Basin. In addition, a detailed discussion of the TSD cutting element and TSD bit design is presented. This discussion compares the TSD to natural diamonds and polycrystalline diamond compacts (PDC's) and explains why TSD bits are superior in some applications.