CFD–DEM approach to investigate the effect of drill pipe rotation on cuttings transport behavior

Abstract Increasing cuttings bed height is a serious concern during extended-reach well drilling. In order to predict and prevent cuttings bed height increase, it is essential to study how the critical parameters influence the cuttings transport, especially the drill pipe rotation effects on the cuttings transport process. In conventional models for cuttings transport, the dynamic behavior of particles due to drill pipe rotation is neglected or empirically simplified. This paper presents a coupled Computational Fluid Dynamics and Discrete Element Method (CFD–DEM) approach to simulate the cuttings transport considering the dynamic collision process. The fluid phase is treated as an Eulerian continuum and described by CFD method. The cutting phase is modeled by DEM using a soft sphere approach for the particle collision dynamic. The continuum and dispersed phases are strongly coupled via the interaction forces such as the drag force, lift force and pressure gradient force, which is taken into account in the developed CFD–DEM model. The model takes into account the collisions of cutting–cutting, cutting–drill pipe and cutting–wall. Simulations are carried out for a number of laboratory-scale configurations, showing good agreement with experiment data reported in literature. The numerical simulations show that the drill pipe rotation builds cuttings presented in non-symmetric distribution along the hole and significantly decreases the cutting volume concentration at the medium and high fluid inlet velocities and lower range of drill pipe speeds. There is no additional contribution of drill pipe rotation after reaching a critical speed at high fluid inlet velocities. At low fluid inlet velocities, increasing the drill pipe rotation from 0 to 80 rpm dose not significantly affect the cuttings concentration; although an increase in drill pipe rotation speed from 100 to 120 rpm provided a remarkable improvement. Furthermore, at low inlet fluid velocities and horizontal inclinations up to 40°, drill pipe rotation can significantly decrease the cuttings concentration. The effect of drill pipe rotation on decreasing the cuttings concentration is almost negligible at high inlet fluid velocities for any inclination.