Modelling of Pressure Drop and Cuttings Concentration in Eccentric Narrow Horizontal Wellbore with Rotating Drillpipe

In drilling operations, estimation of pressure drop and cuttings concentration in the annulus is veiy complex due to the combination of interacting drilling parameters. Over the years, many investigators have developed empirical correlations to determine these parameters, however, the use of these correlations are limited to their experimental data range and setup and cannot be applicable to all cases. Computational Fluid Dynamics (CFD) method has been widely accepted as the best technique, not only due to its ability to handle complex multiphase flow problems but also its ability to handle unlimited number of physical and operational conditions. The present study examines the effects of annular diameter ratio, flow rate (fluid velocity), drillpipe rotation and fluid type on pressure drop and cuttings concentration in eccentric horizontal wellbore using CFD method. The annular diameter ratio varies from 0.64-0.90 with the drillpipe positioned at eccentricity of 0.623 and rotating about its own axis at 80 and 120 rpm. The drilling fluids were modelled using Newtonian and Power-Law fluids. Results show that at diameter ratio of 0.90, pressure drop is very dramatic yet, the amount of cuttings transported remained almost constant for all fluid velocities. Experimental pressure drop and cuttings concentration data compared favourably with simulation data with mean percentage error of 0.84 and 12%, respectively, confirming the validity of the current model.