CFD-DEM modeling of cuttings transport in underbalanced drilling considering aerated mud effects and downhole conditions

This paper presents a developed CFD (Computational fluid dynamics)-DEM (Discrete elements method) model to study the cuttings transportation in aerated mud drilling process for inclined annuli at downhole conditions. The model is conducted to determine the effects of liquid flow rate, air injection rate, annulus inclination angle, elevated temperature and pressure on the cuttings transport efficiency. The motion of the fluid is computed using CFD based approach with gas-liquid interface capturing provided by the volume-of-fluid (VOF) method. The dynamics of cutting phase is studied by DEM using soft sphere approach in order to take into account the particle collision phenomenon. The continuum and dispersed phases are strongly coupled via the interaction forces such as drag force, lift force and pressure gradient force, which are considered in the developed CFD-DEM model. In addition, the real gas law governs the dynamics of injected air and the gas-liquid viscosity is assumed to be temperature dependant. The predicted results have been compared with the experimental data and fair agreement has been established. The results have indicated that in addition to the liquid flow rate, the cuttings transport efficiency is affected by gas-liquid ratio, ambient temperature and injection pressure.