A novel framework for spatiotemporal dynamic modelling of rotary drilling with uniformly alternating full and partial blades

• Developed a dynamic model of drilling with uniformly alternating full/partial blades • Utilized a rock morphology model to accurately capture multiple regenerative effects • Identified the key stable operating parameters to suppress undesired vibration • Revealed the spatiotemporal dynamics characterized by axial-torsional coupling In this article, an integrated model in spatiotemporal domain is developed to study the coupled axial-torsional dynamics of a drill-string. Unlike most models that only consider the interaction between an idealized drill-bit with identical radial blades and rock, this study introduces a drill-bit that aligns to engineering practicability more closely, with a structural configuration of uniformly alternating full and partial blades. According to the cutting geometry at bit-rock interface, the evolution of rock surface morphology (RSM) at well-bottom is formulated through algebraic equations to accurately capture the multiple regenerative effects induced by bit-rock disengagement, i.e., bit-bounce. The entire drill-string structure and rock formation are spatially discretized by using the finite-element (FE) method, and the resultant dynamic model is tested by checking its numerical convergence, showing that the model is robust. Then, a comparative analysis is conducted between the traditional state-dependent-delay (SDD) model and the proposed RSM model. The results demonstrate that the RSM model maintains volume conservation for the total cuttings generated in drilling process while achieving lower computational cost, whereas the SDD model fails to preserve volume conservation. Hence, the proposed RSM model can capture the cutting dynamics of the drill-bit more accurately. Finally, a simulation-driven case study under various drilling conditions is conducted to reveal the nonlinear dynamic characteristics of drill-string system. These findings provide a theoretical framework for subsequent development of model-based active control strategies to suppress detrimental drill-string vibration, specifically targeting stick-slip vibration and bit-bounce.