Suppression of Drill-String Stick-Slip Vibration

MATEC Web of Conferences, Jan 2018

We investigate experimentally and numerically suppression of drill-string torsional vibration while drilling by using a sliding mode control. The experiments are conducted on the novel experimental drilling rig developed at the University of Aberdeen [1] and using PDC commercial drill-bits and real rock-samples. A mathematical model of the experimental setup which takes into account the dynamics of the drill-string and the driving motor, is proposed. Then a sliding mode control method is employed to suppress stick-slip oscillations. The experimental and numerical results considering a time delay of the actuator are in a close agreement. Stick-slip vibration is eliminated and significant reduction in vibration amplitude has been observed when using the controller.

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Suppression of Drill-String Stick-Slip Vibration

MATEC Web of Conferences Suppression of Drill-String Stick-Slip Vibration Vahid Vaziri 0 Marcin Kapitaniak 0 Marian Wiercigroch 0 0 Centre for Applied Dynamic Research, University of Aberdeen , UK We investigate experimentally and numerically suppression of drill-string torsional vibration while drilling by using a sliding mode control. The experiments are conducted on the novel experimental drilling rig developed at the University of Aberdeen [1] and using PDC commercial drill-bits and real rock-samples. A mathematical model of the experimental setup which takes into account the dynamics of the drill-string and the driving motor, is proposed. Then a sliding mode control method is employed to suppress stick-slip oscillations. The experimental and numerical results considering a time delay of the actuator are in a close agreement. Stick-slip vibration is eliminated and significant reduction in vibration amplitude has been observed when using the controller. 1 Introduction During a downhole drilling process excessive vibrations can occur, which in most cases have a negative impact on the effectiveness of the process and the drilling equipment [ 2 ]. Such vibration may lead to an accelerated wear and premature damage of the expensive drilling equipment. Often different dynamic effects such as bit-bounce, stick–slip, forward and backward whirls may appear in the drilling process. Recently several attempts have been made to replicate these vibrations in academic laboratories. However, in most studies the cutting process is simulated by a friction between two disks [ 3 ]. In this work we focus on suppression of stick-slip phenomenon while drilling, which nature is still not well understood and can lead to a catastrophic failure of the drill-stings. Therefore, firstly, a 2-DOF lumped mass model is developed using the torque-on-bit curves, which capture both the frictional and cutting components of the drill-bit rock interactions [ 4 ]. Then, a sliding surface is defined and consequently a sliding mode controller is developed which accommodates the parameters uncertainties. The experimental and numerical results demonstrate the predictive capabilities of the mathematical models and the power of the controller to eliminate the stick-slip vibrations in the given conditions. 2 Drill-String Experimental Stand A novel experimental drilling facility has been designed and built at the University of Aberdeen, capable of reproducing all major types of drill-string vibration [ 4–7 ]. It allows to investigate nonlinear behaviour between the drillbit and the formation and to introduce different control methods of vibration suppression. Unlike typical other research experimental academic facilities, our rig is configured in such a way that the cutting process is undertaken using real commercial drill-bits and rock samples. The rig shown in Fig.1 is equipped with a variety of different sensors and transducers. Angular positions are measured by two quadrature encoders having 500 pulse per revolution, where axial motion of the drill-bit is captured by a P1010 position transducer attached to the Bottom Hole Assembly. Horizontal and vertical forces as well as torque coming from the bit to the rock are measured by a 4-component Kistler dynamometer placed under the rock sample. All the voltage signals are sent to a NI PCIe-6321 data acquisition card which has multiple analogue input (16-Bit, 250 kS/s) and output (900 kS/s) channels and four 32bit counters/timers. Accessing to 4 counters, allows us to precisely synchronise two encoders. This is important as then the drill-pipe twist can be calculated accurately. Furthermore, the card high performance allows high frequency data sampling up to 30 kHz. This card is controlled by a LabVIEW programme with custom built graphical interface allowing to monitor responses of the system and to present time histories of variables and phase portraits in real-time. This program also sends the command to the top AC motor through the NI card and the ABB frequency convertor. This convertor can work in speed or torque control modes which control the velocity or torque provided by the motor. Different speed or torque nonlinear control methods can be implemented in the LabVIEW program such as a sliding mode control in Fig.1. (a) l o tr n o c e u q tr o Labview program trr o e v n o c y c n e u q e r f ace top speed f re lateral displacement it n axial dispalacement bit speed torque and weight on bit 0 17.5 0 17.5 t[s] 27.5 Jt Tt ct θt c, k θb motor & gearing drill-pipe BHA drill-bit t[s] 27.5 Tb 3 Mathematical Model and Sliding Model Control The most used class of models for capturing uncoupled torsional vibration consists of several parallel disks, rotating around their common axis and connected to each other by torsional spring and damper. Top disk in all these models represents the rotary table and the bottom disk represents the drill-bit. The bit-rock interaction is modeled by th (...truncated)


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Vahid Vaziri, Marcin Kapitaniak, Marian Wiercigroch. Suppression of Drill-String Stick-Slip Vibration, MATEC Web of Conferences, 2018, pp. 16008, 148, DOI: 10.1051/matecconf/201814816008