特深层强塑性地层PDC钻头高效破岩数值模拟OA

In oil and gas drilling of ultra and extra-deep formations,the fluid column pressure is very higher,and the rock at the bottom of the well is more compacted and ductile,which can cause extremely prominent problems on rock-breaking using the traditional PDC drill bits.In this study,downhole core samples from a well at a depth of 8078 m in Xinjiang South Rim block and seven different geometrical shapes of PDC teeth were used as testing materials for indoor rock-breaking experi-ments.Numerical simulation was also conducted to explore the rock cutting mechanisms of the special-shaped PDC teeth un-der the conditions of ultra-high bottom hole pressure in ultra-deep formation.The effects of cutting force,mechanical specific energy and aggressiveness of the PDC teeth were considered in order to analyze the influence of tooth structure on the rock-breaking performance of PDC drill bits.The results show that,under the condition of high confining pressure in ultra-deep formation,the difficulty of rock-breaking increases significantly,which is manifested in a significant increase of the cutting force and mechanical specific energy,and a significant decrease of the aggressiveness of the PDC tooth.Under a high confi-ning pressure of 140 MPa,planar PDC teeth have larger cutting force than that of three-ribbed ridge PDC teeth.In terms of mechanical specific energy and aggressiveness,the performance of three-ribbed ridge PDC teeth is better than that of planar PDC teeth.Comprehensively considering cutting force,mechanical specific energy and aggressiveness,the three-ribbed ridge PDC teeth have a more balanced performance,which is suitable for drilling operations in ultra-deep,high pressure and strongly ductile formation.