Research on the Mechanism and Suppression of Stick-Slip Vibration of Drill String

Stick-slip vibration, existing in deep and ultra-deep wells exploration and development, not only causes mechanical drilling speed lowered and drive power wasted, but also speeds up the aging and failure of drilling tools, which seriously threaten the safety of drilling processes. Taking the system of rig rotation ae the research object, a torsional model of the drilling string system with two degrees of freedom including rotary table, BHA (Bottom-Hole Assembly), and the drill bit was established. The method took into account highly nonlinear friction such as torsional degrees of steel, stick damping, and rock-drill bit interaction. The system model was simulated by MATLAB and Simulink simulation modules, and the stick-slip vibration characteristic of the drilling string was analyzed in the actual drilling process. In order to suppress the stick-slip vibration of the drilling string, a control system of double closed-loop based with PID control strategy was designed. The research conclusion has important signification for the suppression of stick-slip vibration of drilling string in engineering practice.