Particle transport and resuspension mechanisms in rotating annular flows for enhanced wellbore cleaning

This is the authors' abstract. We don't add key points for this paper.

During drilling in extended-reach and highly inclined wells, cuttings migrate toward the lower side of the annulus and form stable beds, increasing drillpipe torque and reducing the rate of penetration (ROP). This behavior is governed by flow asymmetry, rotational shear, particle inertia, and drilling fluid rheology. In this study, particle transport and wellbore cleaning in rotating annular flows are investigated using a three-dimensional computational fluid dynamics (CFD) framework. A V-shaped helical-blade cuttings bed remover is introduced to enhance particle resuspension and axial transport by modifying near-wall flow structures. The effects of tool geometry, flow rate, drillpipe rotation, eccentricity, ROP, wellbore size, and fluid rheology are systematically analyzed. Results show that cleaning performance is controlled by the competition among gravitational settling, shear-induced resuspension, rotational mixing, and axial transport. Higher flow rate, drillpipe rotation, moderate eccentricity, and stronger low-shear rheology improve particle suspension and cuttings removal, whereas higher ROP and larger wellbore diameter promote cuttings accumulation by increasing solid loading or reducing effective transport capacity. Based on these mechanisms, a unified cleaning factor (UCF) is developed through dimensional analysis and multivariate nonlinear regression to quantify coupled hydraulic, rheological, operational, and structural effects. The UCF correlation agrees well with CFD results and provides a physically interpretable tool for predicting wellbore cleaning performance, identifying feasible operating windows, and guiding wellbore cleaning design in complex well geometries.