Experiments and 3D Numerical Simulation Study on the Vibration Characteristics of PDC Bits During Rock Breaking

During oil and gas drilling, the harmful vibration of the drill string greatly reduces drilling efficiency. The interaction between the drill bit and the formation is one of the main sources of drill string vibration. Studying the vibration characteristics of the drill bit during rock breaking is the basis for controlling the vibration of the drill string and improving drilling efficiency. This article uses a self-designed three-dimensional rock breaking test system to conduct rock breaking tests under different drilling parameters, and combines the discrete element method to study the vibration characteristics of the drill bit. Research has shown that the values and vibration amplitude of weight on bit(WOB), and fluctuation amplitude of rotational speed all increase with the increase of the rate of penetration(ROP); At the same ROP, the higher the rock strength, the greater the WOB; The vibration frequency of WOB is more complex than the vibration frequency of rotational speed. The vibration frequency of WOB changes with the increase of drilling pressure, and the vibration frequency of rotational speed is independent of the magnitude of WOB, basically equal to the first-order torsional natural frequency of the system; As the drilling pressure increases, the vibration frequency of the WOB gradually approaches the vibration frequency of the rotational speed. The research results deepen the understanding of the vibration characteristics of drill bits and have practical guiding significance for studying the movement of drill strings.