The rock breaking mechanism analysis of rotary percussive cutting by single PDC cutter

Rotary percussive drilling technology can solve the problems of low efficiency and high cost in deep hard formation drilling effectively; it can improve drilling efficiency and reduce stick-slip vibration in order to improve transmission efficiency of WOB (weight of bit). However, the rock breaking and ROP rising (rate of penetration) mechanism are not clear enough to some extent. This paper established three-dimensional finite element model of rotary percussive cutting by single PDC cutter. The crack propagation, chip formation, damage evolution, mechanical specific energy (MSE), and other problems are discussed. The results show that the hard rock is more prone to occur brittle failure under rotary percussive cutting, the rotary percussive drilling technology can improve the stress state of the PDC cutter, better to protect the cutter and improve the drilling efficiency; the magnitude of impact amplitude should not be too large when it reaches the threshold to break rock, the impact frequency has significant influence on MSE; rotary percussive drilling technology is not suitable for soft formations. The field applications show that the use of high-frequency impactor can bring obvious ROP rising in the hard formation drilling. The results obtained in this paper can enhance the understanding of rotary percussive drilling technology and provide theoretical basis for the design of impactor.