The dynamics of the horizontal drill string considering frictional forces between the column and the borehole is investigated. A model of longitudinal vibrations of columns proposed in T.G. Ritto et al. is considered. The investigated model has a nonlinear character, and is modelled by the lumped parameters method. The drill-string is discretized with 100 nodes of lumped masses. Displacement of the bit, bit speed and also the ratio between the output power (obtained from the bit-rock interaction) and the input power is defined by the authors. The frictional force between the column and the borehole is relevant and uncertain. The frictional coefficient is modelled as a random field with exponential autocorrelation function. The obtained results are qualitatively and quantitatively consistent with the results of Ritto, where the dynamic model calculations are carried out by the finite element method.
The paper is dedicated to applied problems of dynamic stability of deformable systems. Dynamics of boring columns for shallow drilling (up to 500 m) applied in oil-gas extractive industry is considered. The purpose is investigation of influence of the drill rod's material properties of amplitude-frequency characteristic and stability of movement. Deformation of the drill rod is assumed finite. A model of a compressed-torsioned drill rod is considered within the nonlinear theory of finite deformations of V.V. Novozhilov. Dynamic of elastic movement for steel and dural drill rods applied in the extractive industry, resonant vibration modes and instability zone are investigated. The resonant vibrations of drill rods on the basic and higher (third) frequencies and their stability are calculated.
The purpose of the paper is modeling of nonlinear vibrations and stability of movement of boring columns at finite deformations. Movement of boring columns for shallow drilling (up to 500 m) applied in oil-gas extractive industry is considered. Nonlinear models of movement of acompressed-torsioned drill rod within the nonlinear theory of finite deformations of V.V. Novozhilov are constructed. A method for its analysis and criterion of dynamic stability are offered. The numerical analysis of its elastic dislocations and instability zones of the basic resonance is carried out, which confirm the efficiency of the offered nonlinear dynamic model of rod elements and techniques for their calculation.
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