Research on Dynamics and Performance of Composite Impact Acceleration Tool

Purpose The deep or hard formation is an important development direction of oil and gas energy resource exploration, and new equipment for accelerating rock breaking is urgently needed. Therefore, a new composite impact acceleration tool is proposed in this paper. Methods Based on the tool, the dynamic theoretical model and differential equation of the drill string system are established. And simulate the rock breaking characteristics of PDC (Polycrystalline Diamond Compact) cutters under composite impact. Results The new tool can change these results from periodic fluctuation to be stable such as the angular velocity of the drill bit, driving and friction torque. Simultaneously, the angular displacement changes from discontinuous to continuous increase. The increase of WOB (Weight on Bit) could enhance PDC invasion depth and improve rock breaking efficiency, but it may cause bouncing of drill bit. The rotational speed of 60 rpm (revolution per minute) is the critical point in the cases. When the rotational speed increases above 60 rpm, the specific energy of rock breaking reduces and the efficiency improves. However, it shows the opposite characteristics when the rotational speed increases below 60 rpm. Conclusions The application of the composite impact acceleration tool can significantly suppress the stick–slip vibration and improves dynamics stability of drill string system. Also, appropriate selection of key parameters such as WOB or rotational speed can improve drilling efficiency.