Application of foam as drilling fluid for cuttings transport in horizontal and inclined wells: A numerical study using computational fluid dynamics

Abstract

Proper hole-cleaning is an important part of drilling operations. Foam with a low density and a high apparent viscosity could be considered as a good candidate for cuttings lifting and transportability. This paper aims to investigate the potential of foam for drilling cuttings transport in inclined and horizontal wells by performing a simulation study. To this end, a computational fluid dynamics (CFD) approach was used to simulate foam flow for cuttings transport by employing Eulerian multi-phase model. Foam rheology was expressed using a non-Newtonian power law model. A detailed sensitivity analysis including the effect of foam quality, foam injection velocity, well inclination, pipe eccentricity and pipe rotation on the cuttings transport efficiency was presented. The simulation results were also validated by a series of previously reported laboratory-scale experiments. Numerical results showed that by increasing foam quality from 70 to 90% at an injection velocity of 5 ft/s in a horizontal well condition, in-situ cuttings concentration decreased by 1.3 times. Also, increase of the foam injection velocity from 3 to 5 ft/s at a foam quality of 90% exhibited a positive impact on the cuttings transport efficiency. This was mainly due to the foam capability to remove stationary cuttings bed. Numerical results also showed that increase of well inclination led to a formation of a static cuttings bed. As to the results, increase of well inclination angle from vertical position to 30° caused an increase in in-situ cuttings concentration by 3.6 times. Moreover, results revealed that pipe eccentricity led to inefficient cuttings transport and thus resulted in cuttings accumulation in wellbore. However, pipe rotation improved cuttings transport efficiency due to an asymmetric distribution of cuttings bed through the annulus.