Research on the rock-breaking mechanism and key factors influencing ROP enhancement during marble cutting with special-shaped PDC cutters

To improve the understanding of key drilling parameters affecting the efficiency of the shaped polycrystalline diamond compact (PDC) bits during drilling operations in marble formations, this study conducted experimental investigations to explore the correlations between weight on bit (WOB), rotational speed and other key drilling parameters with rate of penetration (ROP). Using marble as the research object, this study aims to deepen the understanding of novel special-shaped PDC (SPDC) cutter’s rock-breaking mechanisms and provide technical reference for the selection and application of SPDC cutters in stratigraphic formation. The results demonstrate that: (1) The cutting angle, serving as a critical structural parameter of PDC bits, significantly impacts vibration reduce, service life prolongation, and cutter penetration capacity, thereby directly affecting the bit’s rock-breaking efficiency. Experimental verification indicates that when drilling medium hard rocks (e.g., marble), the optimal cutting angle of PDC bits with different shaped cutter falls within 10°–15°; (2) WOB exerts direct influence on ROP, with medium-hard formations exhibiting statistically significant linear correlations between WOB and ROP at medium–high rotational speeds; (3) Rotational speed positively correlates with ROP enhancement. The optimal rotational speed range for marble drilling is determined to be 400–600 rpm, representing the optimal rock-breaking phase. These findings establish a theoretical foundation for bit optimization and operational parameter rationalization in efficient rock fragmentation.