Drag Bit Wear Model

A performance model for polycrystalline-diamond-compact (PDC) bits was modified to include the wear prediction of individual cutters. Wear predictions are based on the geometry of each cutter, the rock type, the forces acting on the cutter, cutter velocity,and cutter temperature. The results of predicted and actual cutter wear for different 8 1/2-in. (21.6-cm) field-worn PDC bit designs are shown. The worn geometry of each cutter was measured and compared with the model's prediction. Laboratory performance tests were also conducted with similar bit designs to quantify the effect of bit imbalance. Reduced rate of penetration (ROP), drilling an overgauge hole, and increased cutter wear and breakage can result from bit imbalance.