Comprehensive insight into cuttings motion characteristics in deviated and horizontal wells considering various factors via CFD simulation

In extended-reach and directional drilling, cuttings transport is a key issue associated with the efficiency of hole-cleaning and drilling operation. If the cuttings cannot be returned to the surface in time, many technical difficulties may arise such as excessive torque and drag, stuck pipe, and loss of well control. In this study, a computational fluid dynamics (CFD) approach with Eulerian–Eulerian (EE) multiphase model was employed to comprehensively understand and analyze the effect of several drilling operation parameters, mud rheological properties, and specularity coefficient (representing various wellbore wall conditions) on the cuttings transport performance. A commercial CFD software (ANSYS FLUENT™ 19.1) was used to implement all simulations, and a sensitivity analysis was executed with an error of less than 5%. Furthermore, the motion patterns of cuttings were observed and analyzed under various factors. The results show that the cuttings transport performance is sensitive to the wellbore wall condition. In the lower side of annuli, the volume fraction of cuttings increases significantly by 28% with increasing specularity coefficients. Additionally, the combined influence of critical shear rate and flow rate on the cuttings distribution was investigated. The relative reduction rate of cuttings concentration decreased by 30% with increasing critical shear rate at the fluid velocity of 0.4 m/s, while that didn't change so obviously at the fluid velocity of 0.8 m/s.