Gao Feng,Shi Huaizhong,Huang Zhongwei,et al.Numerical simulation on impact crushing of hard rock by PDC bit based on cohesive element[J].China Petroleum Machinery,2025,53(10):109-114.
Gao Feng,Shi Huaizhong,Huang Zhongwei,et al.Numerical simulation on impact crushing of hard rock by PDC bit based on cohesive element[J].China Petroleum Machinery,2025,53(10):109-114.DOI: 10.12473/CPM.202501001.
Numerical Simulation on Impact Crushing of Hard Rock by PDC Bit Based on Cohesive Element
The rock of deep oil and gas reservoir has high hardness, and the drilling efficiency of PDC bit is low under conventional drilling mode. Impact drilling performs well in crushing hard rock, but the damage mechanism of PDC bit crushing hard rock under impact is still unclear. To address this issue, a numerical model for impact rock breaking of PDC bit was established based on cohesive element, common model parameters were set, the crack evolution and stress distribution characteristics of rock under impact were simulated and analyzed, and rock damage data were quantitatively extracted for research. The research results show that the axial impact rock breaking of PDC bit exhibits obvious stage nature. Initially, multiple independent damage zones are formed, which eventually merge into a networked damage area with the accumulation of impact energy, thereby further enhancing rock breaking efficiency. During this process, the stress is mainly concentrated beneath the cutter and propagates outward in an arc shape. Different axial impact frequencies have a significant influence on the rock damage mode: low-frequency impact (10 and 20 Hz) leads to a higher proportion of tensile damage, promotes the growth of crack volume, and ultimately forms more extensive destruction; high-frequency impact (30 and 40 Hz) leads to a faster growth of initial crack, but affected by stress wave attenuation, crack propagation is constrained, and even crack closure may occur. It is ultimately found that the 20 Hz impact frequency yields the highest proportion of tensile damage, indicating that this frequency corresponds to the optimal rock breaking mode. The research results provide reference for the optimization of impact rock breaking parameters of PDC bit.
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