TY - GEN
T1 - The influence of drillstring-borehole interaction on backward whirl
AU - Vijayan, K.
AU - Vlajic, N.
AU - Friswell, M. I.
PY - 2014
Y1 - 2014
N2 - A major concern within the oil drilling industry remains the high risk associated with the drilling bit and tool failure from the build-up of damaging vibrations. Effective understanding of the drillstring dynamics is essential for efficient drilling operation. Complex dynamic behaviour is often observed in the drillstring due to friction, impact, unbalance eccentricity and energy exchange between different modes of vibrations. The interaction between the drillstring and borehole wall involves nonlinearities in the form of friction and contact. A two disk model is used to study the behaviour of the system. The effects of impact, friction and mass unbalance are included in the model. The drillstring borehole interaction induces whirling behaviour of the drillstring causing forward whirl, backward whirl or intermittent bouncing behaviour depending on the system parameters. A critical steady state behaviour within the system is the backward whirling of the drillstring, which reduces the fatigue life of the drillstring. The theoretical model analyses the influence of different parameters, such as the eccentricity and rotational speed, on the induced backward whirl within the system. The influence of rotor speed on the system dynamics is explored using a run up and run down and is analysed using a two dimensional waterfall plot. The waterfall plot indicated the frequency of maximum response for each rotor speed. Depending on the whirling behaviour the dominant frequency was observed at the natural frequency, the rotational speed or the backward whirl frequency. The behaviour of the system by varying the eccentricity and coupling stiffness was analysed. The results from the study indicated that depending on the eccentric mass and the coupling stiffness the backward whirl could be localized to a single rotor.
AB - A major concern within the oil drilling industry remains the high risk associated with the drilling bit and tool failure from the build-up of damaging vibrations. Effective understanding of the drillstring dynamics is essential for efficient drilling operation. Complex dynamic behaviour is often observed in the drillstring due to friction, impact, unbalance eccentricity and energy exchange between different modes of vibrations. The interaction between the drillstring and borehole wall involves nonlinearities in the form of friction and contact. A two disk model is used to study the behaviour of the system. The effects of impact, friction and mass unbalance are included in the model. The drillstring borehole interaction induces whirling behaviour of the drillstring causing forward whirl, backward whirl or intermittent bouncing behaviour depending on the system parameters. A critical steady state behaviour within the system is the backward whirling of the drillstring, which reduces the fatigue life of the drillstring. The theoretical model analyses the influence of different parameters, such as the eccentricity and rotational speed, on the induced backward whirl within the system. The influence of rotor speed on the system dynamics is explored using a run up and run down and is analysed using a two dimensional waterfall plot. The waterfall plot indicated the frequency of maximum response for each rotor speed. Depending on the whirling behaviour the dominant frequency was observed at the natural frequency, the rotational speed or the backward whirl frequency. The behaviour of the system by varying the eccentricity and coupling stiffness was analysed. The results from the study indicated that depending on the eccentric mass and the coupling stiffness the backward whirl could be localized to a single rotor.
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M3 - Conference contribution
AN - SCOPUS:84913614464
T3 - Proceedings of ISMA 2014 - International Conference on Noise and Vibration Engineering and USD 2014 - International Conference on Uncertainty in Structural Dynamics
SP - 1267
EP - 1280
BT - Proceedings of ISMA 2014 - International Conference on Noise and Vibration Engineering and USD 2014 - International Conference on Uncertainty in Structural Dynamics
A2 - Sas, P.
A2 - Moens, D.
A2 - Denayer, H.
PB - KU Leuven
T2 - 26th International Conference on Noise and Vibration Engineering, ISMA 2014, Including the 5th International Conference on Uncertainty in Structural Dynamics, USD 2014
Y2 - 15 September 2014 through 17 September 2014
ER -