1524 EXPERIMENTAL STUDY ON ROCK BREAKING DIFFERENCE UNDER DIFFERENT PENETRATION PARAMETERS OF DISC-LIKE HYBRID BIT SPHERICAL AND CONICAL INSERTED TEETH UNDER IN-SITU STRESS ENVIRONMENT *Xin Huang1,2,3, Jucai Chang1, Chuanming Li1, Lina Jia4, Dongdong Pang1, Chao Qi1, Lei Fan1 1 School of Mining Engineering, Anhui University of Science and Technology, China (*Presenting author: Xin Huang) 2 Anhui Province Key Laboratory of Intelligent and Green Mining of Deep Coal Resources, Anhui University of Science and Technology, China 3 Anhui Key Laboratory of Mining Construction Engineering, China 4 Inner Mongolia North Heavy Industry Group Co., Ltd, China ABSTRACT To simulate the stress environment of oil and gas drilling and explore the crushing effect of disclike hybrid bit spherical and conical inserted tooth on green sandstone under different penetration speeds and penetration depths, an in-situ stress triaxial tooth penetration rock breaking equipment was developed. To study the rock breaking effect, the tooth shape, penetration depth, and penetration speed were considered rock breaking parameters. The brittleness index was used to evaluate the difficulty of rock breaking by spherical and conical teeth. The energy utilization rate of rock breaking was assessed by specific energy consumption, and the fracture pit morphology during the spherical and conical teeth penetrating rock was quantitatively analyzed using three-dimensional contour scanning. In this study, it was found that the brittleness index and specific energy consumption increased with the increase in penetration speed and penetration depth. It indicates that the penetration depth is too large, which is not conducive to the generation of fragments and requires more energy. For shape differences, the brittleness index of the conical cutter is lower than that of the spherical cutter, while the rock-breaking specific energy consumption of the spherical cutter, the fractal effect is better than that of conical teeth, and the penetration speed and penetration depth have less effect on the area of the crushing pit of conical teeth, but cause the crushing pit area of spherical teeth to decrease rapidly, thus conical teeth are more suitable for pilot penetration, while spherical teeth are favorable for the further penetration to produce cracks and rock fragments. KEYWORDS Oil and gas drilling; Disc-like hybrid bit; Penetration parameters; Inserted tooth; Crushing pit area 1. INTRODUCTION With the continuous growth of global energy demand and the ongoing exploration and development of oil and gas resources, drilling engineering is steadily advancing into deeper and more complex formations. Efficient rock-breaking technology is one of the core challenges for improving drilling efficiency and reducing operational costs. Especially in deep formations, complex geological conditions such as high insitu stress, high hardness, and strong abrasiveness often lead to bottlenecks for traditional single-structure bits (such as pure PDC bits or roller cone bits), including low rate of penetration (ROP), rapid wear, and poor stability(Hu et al., 2021;Zhao et al., 2021). The drill bit is the direct rock-breaking tool and is key to drilling acceleration(Huang et al., 2019;Zhang et al., 2020). Therefore, improving the performance and rock-breaking efficiency of the drill bit—this direct rock-breaking tool—is the most effective direction for solving the problem of low drilling efficiency in hard-to-drill formations. To better address the issues of low ROP and short service life of bits in hard formations and to further enhance the performance of conventional hybrid bits, many scholars have proposed a new hobbing-cone hybrid PDC bit technology that combines the advantages of traditional PDC bits and roller cone bits. For example, Niu et al. proposed a disc-like hybrid bit (DLHB), which achieves an ROP in hard formations that is 30% higher than that of traditional hybrid bits (Niu et al., 2018;Niu et al., 2023), as shown in Figure 1(a). Huang et al. proposed a novel low-torque hybrid bit that can reduce impact vibration on PDC cutters(Huang et al., 2022), see Figure 1(b). Zhang et al.
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