Finite Element Analysis of Dynamic Buckling Evolution and Failure Risk in Tubular Strings under Impact Loading

Abstract

As oil and gas exploration progressively extends into deeper and structurally complex reservoirs, dynamic buckling of down-hole tubular strings under impact loading has emerged as a critical issue, posing significant risks to drilling and completion integrity. This paper presents a fully coupled three-dimensional finite element framework that integrates a Cowper–Symonds rate-dependent plasticity model and an Arbitrary Lagrangian–Eulerian (ALE) formulation to capture both strain-rate sensitivity and fluid–structure interaction—two key aspects that have been largely overlooked in prior tubular string buckling analyses. The model incorporates tubular, casing, and fluid domains under representative down-hole conditions and is validated through systematic mesh convergence and energy balance checks. Simulation results indicate that impact loading produces intense stress concentration and abrupt displacement at the tubular string bottom. Axial deformation alternates periodically between compression and tension, reaching a maximum axial displacement of 0.437 cm and exhibiting pronounced hysteretic energy dissipation. Spatially, the response is non-uniform: severe velocity oscillations (peak 9.07 m/s) occur at the bottom, whereas packer-induced constraints attenuate the top velocity by 75.6%. Axial acceleration dominates the response (peak 460.44 m/s2), far exceeding radial components. The numerical analysis further identifies two critical vulnerability zones: the maximum equivalent stress (519.52 MPa) occurs at the top due to wavereflection superposition, while the initial impact creates a local stress hotspot of 434.35 MPa at the bottom—both locations representing key sites for buckling initiation and subsequent fatigue damage. By quantifying the spatiotemporal evolution of deformation, motion, and stress fields, this study reveals how axial dynamics interact with boundary constraints to trigger dynamic buckling. The findings provide a theoretical basis for the optimum design and safe deployment of deep-well tubular strings, while demonstrating the predictive capability of advanced finite element modeling for complex downhole impact scenarios where experimental data are limited.

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