The dynamic characteristics of PDC cutter-rock interaction considering mixed fragmentation mode and dynamic rock strength

PDC bit is already an important bit for improving the rate of penetration in deep and ultra-deep oil and gas wells. However, the dynamic rock fragmentation characteristics of PDC bits are still unclear. A coupled fragmentation mechanics model of PDC cutter-rock interaction is established considering the mixed fragmentation mode and dynamic strength. The coupling influence law of cutter angle, cutting depth, strength ratio, horizontal force coefficient (HFC) and vertical force coefficient (VFC) is analysed. The coupling influence law of cutting depth, strain rate, specific energy is analysed. The dynamic HFC and VFC have the same changing law. With the increase of the cutter inclination angle, the dynamic HFC changes into two modes. The definition of the model depends on the dynamic strength ratio. With the cut depth increases, the horizontal force and vertical force will increase, but the increasing trend will be divided into three stages. When the input-energy increases, the drilling speed is divided into three stages. The results have important guiding significance for the PDC bit to increase the rate of penetration and the efficiency of exploration and development.