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Description
This paper critically evaluates the use of lumped-parameter models in drill-string dynamics, showing that they fail to accurately reflect the continuous nature of the system. Simulations across various levels of complexity, from basic axial models to fully coupled 3D continuous representations, demonstrate that lumped models often produce misleading results, especially when the Bottom Hole Assembly (BHA) is simplified as a single concentrated mass. Theoretical considerations involving wave reflections further highlight the conceptual flaws in such simplifications. Additionally, the practice of validating these models through laboratory experiments is questioned, as these setups often disregard fundamental similitude requirements. The results indicate that lumped models are not suitable for realistic drill-string analysis, while continuous models provide a far more faithful and robust representation of the system’s dynamics.