Numerical Study on Rock-Breaking Mechanisms of Triangular-Shaped PDC Cutter

ABSTRACT Conventional PDC cutter usually gets broken when drilling into deep formations due to high hardness and strong abrasion. To help solve such a problem, triangular-shaped PDC cutters have been developed and utilized in the design of hybrid-cutters PDC bit, which have achieved enhanced rate of penetration and high life cycle. Nevertheless, few researches have focused on the rock-breaking mechanisms of triangular-shaped PDC cutter. This research carries out a series of numerical simulations to reveal the rock-breaking mechanisms of the triangular-shaped PDC cutter. Parametrical analysis has also been conducted to reveal effects of cutting parameters, rock strength, and cutter structural parameters on the rock breaking performances of the triangular-shaped PDC cutter. Numerical analysis results show that the triangular PDC cutter is more easily to crush the rock than the conventional PDC cutter by predominantly decreasing the cutting force. Given the same cutting depth and the cutting angle, the triangular-shaped PDC cutter can exhibit higher rock-breaking performances than that of the conventional PDC cutter. Also, optimal analysis should be done for the design of the triangular-shaped PDC cutter. These research findings help the readers understand the rock-breaking mechanisms and the further application of the triangular-shaped PDC cutter in deep hard formations. INTRODUCTION Along with the development of PDC bit technologies, PDC bits have accounted for more than 90% drilling footage around the world(Dan & Scott, 2015). Meanwhile, given increasing demand on energy consumption, the exploitation depth gradually shifts into deep and ultradeep formations beyond 6000 m, which are usually distinguished by high hardness and abrasion. In those formations, conventional PDC cutters usually get broken in the drilling process due to high impact, large vibration, and strong abrasion, leading to low rate of penetration (ROP), long drilling duration, and unnecessary non-productive time(NPT) (Durrand et al., 2010; J. Liu et al., 2019; Shahrul Amar et al., 2020; Shi et al., 2018; Zhu et al., 2019). To improve the drilling performances, by modifying the planar cutting surface into 3D cutting structure, innovative kinds of PDC cutters have been proposed to enhance the resistance of PDC bits to high impact and strong wear, such as the conical PDC cutter, the axe-shaped PDC cutter, and the triangular-shaped PDC cutter. In detail, the cutting structures of conical, axe-shaped, and triangular-shaped PDC cutters are respectively a conical, ridged, and trustum of pyramid cutting element. Following the available literature findings, many of the non-planar PDC cutters have exhibited better rock-breaking performances than that of the conventional planar PDC cutter.