Modeling of the Critical Deposition Velocity of Cuttings in an Inclined-Slimhole Annulus

Abstract

Summary A coupled computational-fluid-dynamics/discrete-element-method (CFD/DEM) theory is developed to simulate the transportation of cuttings in an inclined-slimhole annulus. In this theory, the liquid phase is governed by the Eulerian continuum equation and the Navier-Stokes momentum-conservation equation. The collisions between particle and wall, between particle and drillstring, and among particles are treated as the spring-damping system, and the particle-contact model is then established. The particle-governing equation based on Newton's second law is established by analyzing the forces on the particles. The CFD/DEM theory is developed by analyzing the forces on the dispersed particles per unit volume, which is the source term in the coupling. Using this CFD/DEM coupling algorithm, cuttings transportation in slimhole drilling is investigated, and the particle velocity and distributions are calculated. The calculated annular cuttings concentration is in good agreement with experimental data from the literature (Kim et al. 2014). The effects of the annular-fluid velocity, angle of inclination, cuttings concentration in feeding, and rotation speed of the drillstring on the annular cuttings concentration are also investigated. A correlation of critical deposition velocity has been proposed by use of dimensional analysis and nonlinear regression analysis. The correlation of annular cuttings concentration is also concluded. The new method proposed in this work is of great significance to hole-cleaning calculation and hydraulic-parameter design in slimhole drilling.