Abstract:According to the fractal theory,a fractal model for consuming energy on rock fragmentation is provided through energy consumption analysis of rock fragmentation in rotary drilling. The factors,such as size distribution of rock cuttings and energy consumption in the process of drilling are taken into account and the factors affecting energy consumption of rock fragmentation on the bit are considered. The model shows that the energy consumption on rock fragmentation is not only related to the drilling parameters such as weight on bit and rotational speed,but also the size of rock cuttings and the fractal dimension of size distribution. The model can be used to determine the necessary energy consumed on rock fragmentation and it can also be inversely used to optimize drilling parameters with the energy consumption on the rock fragmentation. In addition,the three classical formulas of the crushing work ratio theory can be obtained by properly simplifying the model,hence,the general applycation of the model is proved.