Local instability of rotation of a drill string
UDC
534.1Abstract
Stability of a flexible drill string rotating in a curved oil well is studied. The string is considered as an elastic Cosserat bar, general equations are derived and the cases allowing for the closed form solution are analyzed. The rotation with constant angular velocity is shown to be feasible only for a straight shaft. In all other cases the rotation is unstable and for some relations between the parameters it is accompanied by quasi-static transition to a new configuration. The instability is caused by the energy exchange between the torsional and bending modes. The increasing torque on the end of the shaft improves the rotational stability at expenses of the increasing stresses in the drill string.
Keywords:
drill string, Cosserat curve, local instabilityFunding information
Работа выполнена при поддержке РФФИ р2006_юг (проект 06-01-96641).
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Copyright (c) 2008 Беляев А.К.
This work is licensed under a Creative Commons Attribution 4.0 International License.
