A novel experimental setup for axial-torsional coupled vibration impact-assisted PDC drill bit drilling

The geological conditions of hot dry rock (HDR) reservoirs are complex. The geothermal mining of HDR faces major challenges in the drilling and construction of wells, fracturing to create storage, and flowing to extract heat. Vibration impacts help improve the rock-breaking efficiency, where the axial-torsional coupled vibration impact technology can increase the bit penetration depth and reduce the stick-slip effect. To study the feasibility and efficiency of the axial-torsional-coupled vibration impact-assisted Polycrystalline Diamond Compact (PDC) bit to break high-temperature and high-pressure rocks, a new experimental setup was designed. The system includes a drilling fluid circulation system, an axial-torsional coupled impact drilling system, a formation simulation system, and a data acquisition and control system. This setup can produce a rock-breaking torque of 2000 N·m, a drilling speed of 200 rpm, a weight on bit of 100 kN, an axial vibration frequency of 100 Hz, and a torsional vibration frequency of 50 Hz. It can simulate the formation pressure of 70 MPa and the rock temperature of 400 °C. A series of rock-breaking drilling experiments were successfully conducted using this setup. The results show that the axial-torsional coupled vibration-impact assisted PDC bit has a good performance in breaking high-temperature and hard rocks, which can accelerate the application of this new technology in deep formation drilling.