Theoretical and Experimental Studies of Impact Energy and Rock-Drilling Efficiency in Vibro-Impact Drilling

Abstract Vibro-impact drilling has been proven to be a viable technique for enhancing the rate of penetration (ROP) in deep and ultra-deep well drilling. It is essential to study the effects of impact parameters on impact energy and rock-drilling efficiency for impact tool design and operating parameter optimization. In this paper, the influences of impact parameters including impact frequency, dynamic loading amplitude, and loading on impact energy were analyzed by a theoretical method. Then, a full-scale drilling experiment was conducted to study the rock-drilling efficiency. The results are as follows: the optimal frequency is higher than the resonance frequency of the rock. The impact energy increases with the dynamic loading amplitude. The penetration rate at dynamic loading amplitude of 4 kN (0.13137 mm/s) is 38.7% higher than that of 2 kN (0.09473 mm/s). When the impact frequency is lower than 150 Hz, the rock-drilling efficiency increases with the impact frequency and dynamic loading amplitude. The penetration rate is 0.1051 mm/s at impact frequency of 150 Hz, which is 29.8% higher than that of 10 Hz. The impact energy and penetration rate at square loading waveform are the largest. The impact energy per second at loading waveform of square, sine, and triangle is 19.6 J, 12 J, and 7.91 J, respectively, when the impact frequency is set to optimal frequency of impact energy. This study provides a theoretical guidance for the optimization design of vibro-impact drilling technology.