Mechanism and Experimental Study of a Novel Chord-Edge Cutter for Stick-Slip Mitigating

Summary To address severe stick/slip vibration and low drilling efficiency of polycrystalline diamond compact (PDC) bits in deep hard-plastic formations, a novel chord-edge cutter is proposed to optimize cutter/rock contact and mitigate stick/slip at its source. Based on the analysis of cutter-induced dynamic load behavior, static pressing simulations, single-cutter cutting tests, and bit/drillstring system experiments were conducted to evaluate the chord-edge cutter’s performance. Simulations show that the chord-edge cutter induces a wider, more uniform strain field during rock penetration, resulting in a smoother fracture process. Single-cutter tests reveal that its mean and fluctuation of axial and cutting forces are lower within a rake angle of 10° or less, with cleaner groove and more efficient chip evacuation. Bit/Drillstring Experiment A, conducted in sandstone and limestone, benchmarks the chord-edge cutter bit against a conventional cutter bit. Under identical rate of penetration (ROP), the chord-edge bit provides lower stick/slip vibration intensity (SSVI), lower mean torque on bit (TOB), and reduced TOB fluctuation. In limestone at a weight on bit (WOB) of 4800 N, these three indicators are 36.31%, 84.68%, and 29.3% of those of the conventional bit. Experiment B, in a comparison with an axe-shaped cutter bit, shows that in granite, the chord-edge bit trades a 19% ROP reduction for a 44% lower SSVI at 4800 N WOB, whereas in shale, it achieves a substantial SSVI reduction together with 15–25% lower TOB at comparable ROP. These results confirm that the chord-edge bit effectively broadens the stable operating window, enabling high WOB, low rotation per minute (RPM) drilling while enhancing efficiency and mitigating stick/slip.