Study on cuttings transport behavior in annulus and bottom-hole using CFD-DEM

The increased demand for energy has led to the development of innovative drilling methods and technologies in the oil and gas industry. Inefficient transportation of cuttings causes downhole cleanliness issues, which have drawn widespread attention. One way to overcome cuttings transport inefficiency is to use suitable modeling methods to determine capable drilling parameters that will ensure the effective removal of cuttings particles. In this paper, Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) are combined to deeply investigate the impact of various drill parameters on cutting transport. The effects of cuttings particle size, eccentricity, fluid velocity, drill pipe/bit rotation speed, and bit offset angle are analyzed by studying the velocity of cuttings particles and the spatial distribution of particles in the annulus and bottom-hole. The results show that an increase in eccentricity and particle size reduces the velocity of cuttings particles, with the velocity decreasing more significantly when the eccentricity is greater than 0.5 and the particle size exceeds 2 mm. An increase in fluid velocity and speed of drill pipe/bit significantly increases the velocity of cuttings particles, which has a positive feedback effect on the migration of cuttings particles in the downhole. Bit offset angle leads to changes in the bottom-hole spatial structure and reduces the cuttings transport efficiency. These findings provide a useful strategy for improving cuttings migration and downhole cleaning.