Characteristics of Conicl Diamond Tooth for Breaking Hard Rock Under Vibratory Percussion

ABSTRACT The application of conicl PDC teeth to vibratory percussion drilling technology is expected to break deep hard rock efficiently and improve drilling efficiency. In this paper, the characteristics of conicl diamond tooth cutting and hard rock under percussion are investigated. Firstly, experiments on percussion compression of conicl diamond tooth into the broken rock were carried out to analyse the percussion energy and the characteristics of rock crushing pits. Secondly, a numerical model of the cutting process of conicl diamond tooth under the vibratory percussion was established. Three stages of rock-breaking by conical tooth cutting under high frequency number percussion are analyzed. Stress peaks with percussion of 6 times increased by 36.8% and 25.5% compared with percussion of 0 times and percussion of 3 times. There is the highest point of rock-breaking efficiency between percussion of 3 times and 4 times. Cutting force with percussion amplitude of 1.5mm increased by 42.7% compared with percussion amplitude of 0mm. The rock-breaking specific energy with percussion amplitude of 1.5 mm increased by 32.4% compared with percussion amplitude of 0 mm. This study provides a theoretical basis for the use of conical tooth in PDC drill bits under percussion. INTRODUCTION In the oil and gas exploration and development industry, drilling cost accounts for a large proportion of the overall development cost. The application of efficient drilling technology directly affects the final benefit(Wang, 2003)i. The exploration and development of deep and ultra-deep wells has become the focus of current attention(Meiling et al., 2014)ii and conventional drilling methods are increasingly unable to meet the needs of efficient drilling. As the well depth increases, the hardness and plasticity of the rock increases and the drillability decreases, which also increases the difficulty of drilling in deep hard formations. How to improve ROP has become one of the key issues in drilling engineering technology research. Previous studies have shown that vibratory percussion drilling can significantly improve rock breaking efficiency in hard rock(Hustrulid, 1971;Li et al.,2020;Pavlovskaia et al.,2015)iii.