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Vibration of drillstring is the most important factor of its destruction and reduction in drilling operations efficiency. One of the main causes of excessive vibration of drillstring is drillstring-wellbore contact, therefore drillstring-wellbore contact has been studied in several researches. Indeed the contact behavior of drillstring and wellbore is of great concern to drilling companies in the oil and gas exploration industries. In this research, dynamic behavior and vibration of non-linear finite element model of a drillstring in contact with wellbore, has been investigated. By considering total length of drillstring, a three-dimensional timoshenko beam element is employed. In addition the geometric stiffening effect including nonlinear terms, the added fluid mass and the contact between drillstring and borehole wall has been considered using improved contact model with a more complete model than previous studies, that the stiffeness of contact determined form energy balance relations. The equation of motion of drillstring obtained using energy approach and lagrange’s equations and full order equations are used to drive the results. Coupling between various vibrations has been tested and the effect of recent model in analysis of dynamic behavior and vibration of drillstring have been evaluated.

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In this research, dynamic behavior of non-linear finite element model of a drillstring is investigated. By considering total length of drillstring, a three-dimensional timoshenko beam element is employed. In addition the geometric stiffening effect, the added fluid mass and the contact between different parts of the drillstring and the borehole wall has been considered, with a complete model the effects of these factors have been analyzed separately. The equation of motion obtained and full order equations are used to drive the results. For the first time, a domain of drillstring that contact more possibility to occur in this domain is identified. The natural frequencies of the drillstring are evaluated and compared with the available commercial software results and recorded results for the actual drillstring. Coupling of vibrations of model is tested and the effect of linear and non-linear model in analysis of dynamic behavior and vibration of drillstring, especially in contact with the borehole wall and the effect of weight on bit change on the contact at stabilizers are analyzed and for the first time the contact time in each of stabilizers have been evaluated.