Analysis of the nonlinear dynamics of a horizontal drillstring
Abstract
This work aims to analyze the nonlinear dynamics of a drillstring in horizontal configuration. A computational model, which uses a nonlinear beam theory with rotatory inertia and shear deformation of the beam cross section, as well as the coupling between longitudinal, transverse, and torsional vibrations is proposed. This model also takes into account the effects of friction and shock, induced by the lateral impacts between the drillstring and the borehole wall. The model equations are discretized using the Galerkin/finite element method, and then projected in vector space of low dimension to reduced the computational cost of the simulation. The initial value problem that results from the discretization is integrated using the Newmark method. The simulation results show that the lateral shock induces geometrical configurations "close" to flexural modes of higher order. It is also noted that the geometric nonlinearity induces a coupling between the mechanisms of longitudinal and transverse vibration, so that the system responds longitudinally despite not being excited in this direction.
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