Solid–liquid hydrodynamics in a slim hole drilling annulus

We examine solid–liquid mixture upward hydraulic transport of solid particles in vertical and inclined annuli with a rotating inner cylinder. Lift forces acting on fluidized particles play a central role in many important applications such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, and sediment transport. Annular fluid velocities in our study varied from 0.4 m/s to 1.2 m/s. The effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in a slim hole annulus were measured for fully developed flows of water, and for aqueous solutions of sodium carboxymethyl cellulose (CMC) and bentonite. For higher particle feed concentrations, the hydraulic pressure drop of the mixture flow increased due to friction between the wall and solids, or among solids. Comparing our numerical and experimental results allowed the assessment and further development of existing two-phase numerical models and grid constructions.