Numerical Simulation and Experimental Study of Rock Breaking with Full Single-Roller Polycrystalline Diamond Compact Compound Bit

Abstract A single-cone bit occupies a unique role in small hole drilling applications. To enhance the durability and rock-breaking efficiency of a single-roller bit during deep ultra-deep and small hole drilling operations, a spherical single-roller polycrystalline diamond compact (PDC) compound bit was developed. A numerical simulation model of full-tooth rock breaking was constructed to investigate the rock-breaking mechanism and effectiveness of single-roller PDC compound bit, followed by manufacturing a full-size single-roller PDC compound bit and conducting rock-breaking experiments. Numerical simulation findings reveal that cutting forces from seven PDC cutters emerge during varying time intervals, exhibiting essentially periodic distributions. The alternating slip scraping rock rock-breaking pattern facilitates optimal utilization of PDC cutter breaking features and benefits. Experimental outcomes from rock-breaking tests demonstrate the single-roller PDC compound bit's enhanced rock-breaking efficiency and superior development potential compared to Chen Lian's single-cone bit. During drilling operations in hard limestone, the single-roller PDC compound bit achieves greater energy efficiency at elevated WOB (weight on bit) conditions. Under identical RPM (revolutions per minute) and WOB parameters, the single-roller PDC compound bit's ROP (rate of penetration) surpasses Chen Lian's single-cone bit by 170%–290% in limestone formations; in sandstone formations, the single-roller PDC compound bit's ROP exceeds it by 68%–782%. The single-roller PDC compound bit exhibits lower MSE (mechanical specific energy) compared to Chen Lian's composite single-cone bit, measuring below 44%.