Research On Mechanism Analysis And Suppression Of Stick-slip Vibration Of Drill String

In oil drilling operations,due to the friction between the drilling equipment and the rock at the bottom of the well wall,various kinds of vibration will be generated,which can be divided into lateral vibration,longitudinal vibration and torsional vibration.Torsional vibration is the most harmful to drilling operations,while stick-slip vibration of drill string belongs to torsional vibration.Stick-slip vibration is a reciprocating vibration form of bit sticking,sliding,re-sticking,and re-sliding.If it is not suppressed,it will cause serious drilling accidents.For example,stick-slip vibration of drill string will lead to accelerated wear of drilling equipment,decreased drilling safety,decreased drilling efficiency,prolonged drilling cycle and other adverse effects.Therefore,it is very important to study the suppression of stick-slip vibration of drill string.In order to suppress stick-slip vibration of drill string,a torsional model of drill string system with four degrees of freedom including rotary table,drill rod,BHA and drill bit is established.The model takes into account highly nonlinear friction such as torsional degrees of freedom,drill string damping and rock-drill bit interaction.The system model is simulated by mathematical software MATLAB and Simulink simulation modules.The experiment restores the phenomenon of stick-slip vibration in actual drilling process and analyzes the influence of drilling parameters on stick-slip vibration.In order to suppress stick-slip vibration of drill string,a fractional-order PI?D?(FOPID)controller is designed.In order to highlight the control effect of the fractional-order PI?D? controller,an integer-order PID controller is added for comparison.After adding the fractional-order PI?D?controller and the integer-order PID controller to the model,simulation experiments are carried out again.The results show that the fractional-order PI?D? controller can stabilize the system rapidly.Moreover,the inhibition effect on stick-slip vibration of drill string system is obviously better than that of integer-order PID controller,which makes the stability time of the system advance by 100 s,and can react quickly to sudden changes of parameters in the system,thus making the system stable quickly.The research conclusion has important guiding significance for the suppression of stick-slip vibration of drill string in engineering practice.