Modeling of yield-power-law fluid flow in an eccentric annulus with fixed horizontal cuttings bed

Abstract

ABSTRACT Inclination and horizontal wells are commonly used to develop petroleum and natural gas reservoirs. Cuttings bed buildup is inevitable in an eccentric annulus because of the high inclination angle (>60°), which affects the drag and torque as well as the downhole pressure. To accurately and conveniently predict the pressure gradient in an eccentric annulus with fixed horizontal cuttings bed, a simplified model was established in this study to predict the pressure gradient by using the effective hydraulic diameter. In addition, simulation experiments were carried out to investigate the pressure gradient in the eccentric annulus with a cuttings bed using the computational fluid dynamics (CFD) software ANSYS Fluent. The simplified model was validated by comparing the results with those obtained from CFD simulations. The results show that the average shear stress of the cuttings bed wall first decreases and then increases with increasing cuttings bed height. The simplified is in good agreement with the results of existing numerical and CFD simulations (within an error of ±10%). The proposed simplified model provides a shortcut for the prediction of the pressure gradient in an eccentric annulus with a cuttings bed.