Wear Estimation Technique for Poly-Crystalline Diamond Compact (PDC) Bits Under Lab and Field Conditions

Abstract Wear measurements come with their own unique challenges. PDC drill bit cutters are intricate in shape, causing problems in measuring wear flat and examining cutting profile properly under magnification. Between drilling runs, limited time is available to investigate the wear, justifying the need of an improved technique overcoming these problems. The paper provides with techniques and methods to quantify and report the wear recorded both in lab applications of PDC drill bits and their field applications. Technique presented here covers a wide range of bit wear, using visual inspection, HD pictures, volumetric material loss estimations and replication of drill bits. Replication of drill bits at RTV (Room Temperature Vulcanization) using quantum silicones is used. Linear and volumetric shrinkage of replica material, surface tension and edge retention are studied to measure and compare dimensional accuracy of replicas to retain original sample in shape and size only and not texture. Replicas are more convenient to study under microscopes, than drill bits itself and also provide a permanent record of the drill bit at the time of interest, while further use of drill bit can be made, reducing NPT between subsequent drilling runs. Replicas show acceptable levels of shrinkage (both linear and volumetric). Replicas attain the edge and minor edge rounding effect is observed. For lab scale tests, very little weight difference is observed for the PDC drill bits before and after experiments. Wear is reported in the form of “an increase in chamfer width” for cutting profile of PDC cutter and “a decrease in thickness of PDC material”. Slight damage of cutting edge of lab scale PDC bit is observed. For field scale tests, HD pictures and replicas are used to provide a permanent record for wear assessment. IADC dull grading system is used for wear investigation of field-scale PDC drill bit.