An alternative characterization of bit-sticking phenomena in a multi-degree-of-freedom controlled drillstring

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    Abstract

    A piecewise-smooth model of three degrees of freedom, which exhibits friction-induced stick-slip oscillations, is considered. This model corresponds to a simplified torsional lumped-parameter model of an oilwell drillstring. An alternative method to characterize the stick-slip motion and other bit-sticking problems in such a drilling system is proposed. This method is based on the study of the relationships between the different types of system equilibria and the existing sliding motion when the bit velocity is zero. It is shown that such a sliding motion plays a key role in the presence of nondesired bit oscillations and transitions. Furthermore, a proportional-integral-type controller is designed in order to drive the rotary velocities to a desired value. The ranges of the controller and the system parameters which lead to a closed-loop system without bit-sticking phenomena are identified. © 2008 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    Pages (from-to)3162-3174
    Number of pages12
    JournalNonlinear Analysis: Real World Applications
    Volume10
    Issue number5
    DOIs
    Publication statusPublished - Oct 2009

    Keywords

    • Control systems
    • Discontinuous equations
    • Dynamical bifurcation
    • Dynamical systems in control
    • Friction
    • Models of real-world systems
    • Periodic solutions
    • Stabilization of systems by feedback

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