The IADC Roller Bit Dull Grading System

Abstract

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^

A Review on Tool Life in Coal Measures Rocks

“…McGehee et al, proposed a new and improved version of the International Association of Drilling Contractors (IADC) on a bit dull grading system 43 . The underlying research carried out by them was appropriated from their published research work between 1986 to 1992.…”

New Industry Standards to Increase the Reliability of Drilling Operations

“…After the end of a bit run, the drill string is pulled from the well. Bit wear is classified using the 8-digit standard proposed by IADC (McGehee, et al, 1992), seen in Fig. 4.…”