## 1 Introduction  
China has successfully tapped its domestic shallow oil and gas reservoirs and is now shifting its focus toward the development of unconventional oil and gas resources, which will be the primary area of exploration and production in the future. According to a comprehensive survey and study, China holds the second-largest reserves of unconventional oil and gas resources globally. However, the country's heavy reliance on external sources for oil and natural gas stands at approximately 73% and 43%, respectively. Therefore, there is an urgent need to intensify the exploration and exploitation of unconventional oil and gas resources [1]. However, unconventional oil and gas resources are located in complex formations and are difficult to extract [2], which puts higher requirements on the performance of drill bits. It is well known that PDC (Polycrystalline Diamond Compact) bits have higher wear resistance and efficiency compared with roller cone bits, especially in hard formations [3, 4], leading to a higher market share of PDC bits, which was investigated to be as high as 75-80% in 2018 [5, 6]. Nevertheless, the prevailing PDC bits utilized in drilling operations predominantly rely on the shearing action provided by the mounted cutters. This shearing action, however, exhibits limited aggressiveness, making it challenging to penetrate hard rocks such as granite. As a result, PDC cutters are required to repeatedly rub against the rock surface and await the accumulation of sufficient energy from the drill string to effectively break the rock. Consequently, this approach significantly diminishes the drill bit's lifespan and efficiency, escalating drilling costs. Therefore, there is a pressing need to enhance the performance of PDC bits, with the structure of the PDC cutter playing a crucial role in determining their overall performance. Investigating and optimizing the performance of PDC cutters with diverse structures is a proven approach to enhancing drill bits' overall lifespan and efficiency [7]. As a result, numerous researchers have devoted significant efforts to exploring the rock-breaking characteristics of PDC cutters with various structures and assessing their suitability for specific formations, with particular emphasis on non-planar cutters [8]. [PERSON] et al. [9] conducted a study on the rock-breaking characteristics and efficiency of circular cutters, axes-shaped cutters, wedge-shaped cutters, and triangular prism cutters through experiments combined with numerical simulation methods. Their results showed that the axe cutters have better drilling ability in hard formations and are suitable for the front row of the cutter blade of the PDC bit, while the angled cutters are more suitable for auxiliary rock breaking and should be installed in the back row of the cutter blade of the PDC bit. Conical PDC cutters are mostly used for auxiliary rock breaking in PDC bits [10; 11]. [PERSON] et al. [12] used the finite element method to numerically simulate the rock-breaking process of conventional PDC cutters, conical PDC cutters, and the overall rock-breaking process of the drill bit, and the results of the study showed that the conical cutters as auxiliary cutting structures could well produce pre-breaking of rocks at 100 MPa compressive strength, thus improving the overall drilling ability of the bit in hard rocks, while this approach was not effective for rocks with 50 MPa compressive strength. The axe PDC cutter not only has the characteristics of a conventional cutter's shear breaking in the rock-breaking process but also has a crushing effect on the rock, which can significantly improve the ROP and mechanical specific energy (MSE) of the drill bit [13; 14]. The distinctive ridged structure of the axe PDC cutter not only reduces the weight of the drill bit but also optimizes rock-breaking efficiency.