Hydraulic Forces Induced by Drillstring Whirling and Rotation Dynamics: A Numerical Investigation in 2D and 3D Domains

Abstract In drilling, the coupling between drillstring dynamics and drilling fluid hydraulics is instrumental to the excitation of vibrations in the drilling system and the applicable boundary conditions for such excitation. However, most of the existing drillstring models fail to capture the dynamic-hydraulic interactions and their impact on drilling performance. To address these challenges, comprehensive computational fluid dynamics (CFD) simulations were conducted with the finite volume method (FVM) to estimate the hydraulic forces on drillstrings under diverse conditions. Coupled lateral-torsional movements of a drill pipe were reconstructed and approximated as the moving boundaries of the CFD model. With the hybrid/dynamic mesh, the proposed CFD model can effectively calculate the real-time annulus fluid velocity field and hydraulic forces with improved accuracy. The simulations span a wide range of drilling scenarios, exploring different drillstring whirling and rotational frequencies, with varying flow rates of Newtonian and non-Newtonian fluids in 2D and 3D domains. The analysis results provide a detailed view of how the drillstring dynamics can affect the drilling fluid hydraulics and can be utilized to guide and improve drilling operations in the field.