Experimental-numerical method for evaluation of energy consumption in percussive drilling of granite

Abstract

Most geothermal energy is found in hot and dry rock (HDR), and the total resources distributed at depths of 3-10 km are 20.9×106 EJ. Most HDR projects are developed in granite formations and understanding and control of the energy consumption in percussive drilling of granite is essential. Thus, the impact energy is dissipated in various processes including fracture of the granite, kinetic energy of the particles, and heat. This study presents a numerical-experimental method to evaluate the energy consumption in percussive drilling process. The method uses particle flow code (PFC2D) and experiments using a modified Hopkinson pressure bar system. Optical high-speed and infrared cameras were used to record the impact process during the dynamic drilling process. The velocity of fragments was estimated by the high-speed images and the instantaneous temperature change during the impact was observed from infrared images. Preliminary results are given in this study indicating that the proposed numerical and experimental methodologies can be used to investigate the energy consumption during percussive drilling. The preliminary results presented in this paper are part of a larger work in progress, and more work needs be carried out to obtain the energy consumption of the drilling process under different loading and boundary conditions.