Innovative Non-Planar Face PDC Cutters Demonstrate 21% Drilling Efficiency Improvement in Interbedded Shales and Sand

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Abstract
Traditional polycrystalline diamond cutter (PDC) technology has made tremendous gains over the past decade with corresponding footage and rate of penetration (ROP) improvements in drilling performance. The remaining challenge is managing interbedded formations with competent stringers while maintaining drilling efficiency and the highest ROP potential, such as those present in the 6 to 6⅛-in. Pinedale Anticline production hole and the 12¼-in. Cana intermediate section. By modifying the standard planar PDC cutter face geometry with novel shallow recessed features, a demonstrated improvement in drilling efficiency was observed in these applications and an increase in attained footage. Extensive analysis in Pinedale runs indicated this cutter design benefits a lower mechanical specific energy (MSE) in the shale and sand, shorter day curves, and higher average ROP per unit of motor horsepower. Initial runs in the Tonkawa sands of the Cana intermediate have started to show similar trends. The successful field runs have been supported by in-depth analysis and study of cutting efficiency including, single-point cutter testing in a pressurized vessel, atmospheric vertical turret lathe testing, and full-scale PDC bit laboratory testing in a state-of-the-art downhole drilling simulator. The results of this work improved the understanding of the thermo-mechanical behavior of cuttings formed by the drilling action of a PDC cutter in these applications. This study is part of an innovative approach to manage rock cuttings, cutting efficiency, and thermal loads as it applies to PDC durability in state-of-the-art drill bit designs. The design changes have improved cutting efficiency and aggressivity, which has improved the ROP of bits in abrasive sand and in the shale sections. This paper provides documentation and visual demonstrations of the features and benefits seen in the single-point test apparatus, the downhole simulator in the laboratory and in the field with case studies compared to offsets of standard bits with planar PDC cutters.

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