Combined simulation of whirl and stick-slip phenomena using a nonlinear finite element model
- Baker Hughes INTEQ GmbH, Celle (Germany)
- Technical Univ. Braunschweig (Germany)
A time domain drillstring dynamics model allows the prediction of BHA dynamics related to torsional and two plane lateral vibrations. The model considers a nonlinear Finite Element approach that takes into account arbitrarily shaped assemblies during drilling of curved boreholes. Each nodal point represents a stabilizer, a collar connection or a wear knot moving viscously dampled inside open hole or a casing. In the case of wall contact, restitution forces from the formation act on the string and contact velocity dependent friction forces are introduced. The torsional and the lateral degrees of freedom (d.o.f.) are therefore coupled. The authors introduce a nonlinear relationship between the cutting forces at the PDC bit and the angular velocity of the bit. Bit and BHA whirl, rotational Stick-Slip phenomena and normal drilling conditions are solved numerically. Results show that the drilling process is always transient. Commonly used static models only can provide the drilling engineer with rough estimates of the loading. Evaluation of BHA failures sometimes reveal an ultra high dynamic loading of the BHA components that can be analyzed and predicted with this time domain application.
- OSTI ID:
- 485049
- Report Number(s):
- CONF-970146--; ISBN 1-890277-02-9
- Country of Publication:
- United States
- Language:
- English
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