Experimental Study on Bit-Drill String Stick-Slip Vibration Based on the Dynamic Load Characteristics of PDC Cutters

In ultra-deep drilling, stick-slip vibration reduces tool life and drilling efficiency, with dynamic load characteristics generated by discontinuous cutting in the tooth-rock contact zone being a key contributing factor. To address this, this study proposes two quantitative indicators: cutting force fluctuation amplitude (CFFA) and torque amplitude (TA). Experiments were conducted on PDC (Polycrystalline Diamond Compact) tooth scraping and micro-bit-drill string stick-slip vibration. The results show that: CFFA is primarily governed by depth of cut(DOC) and rock properties, increasing with rock strength and DOC. When DOC increased from 1 mm to 1.5 mm in sandstone and from 0.15 mm to 0.3 mm in limestone, the sequential growth rates of CFFA reached 67.96% and 150.92%, respectively. Variations in rock-breaking volume revealed overall positive correlations among CFFA, TA, and Stick-Slip Vibration Intensity (SSVI) of the bit-drill string coupled system. When the weight on bit(WOB) in sandstone increased to 3000 N, TA and SSVI rose to 1.78 and 1.42 times their initial values. The experiments verified the generation mechanism of these characteristics and their vibration-inducing principles, elucidating the influence of the law of drilling parameters on system stick-slip vibration. These findings provide technical support for parameter optimization in ultra-deep well drilling.