Fluid Flow in a Skewed Annulus

Abstract

A novel, realistic treatment of annular flow in an oil well is developed. The fluid flow in an annuuls with an inclined or S-shaped inner pipe is considered. The model covers laminar and turbulent flow regimes and the results are experimentally verified. The study predicts axial and angular velocities and frictional pressure losses. The frictional pressure losses are shown to be higher than in the corresponding concentric annulus when the inner pipe is severely S-shaped. However, for typical drilling well geometries, the frictional pressure losses are found to approach the eccentric annular predictions asymptotically. Thus, the study finds the average eccentricity of a vertical or near vertical well, which is a difficult parameter for the engineer to estimate. The results of the study are of practical importance where high annular frictional pressure losses are encountered, such as in slim holes and coiled tubing operations. The frictional pressure losses in complex annular geometries are presented in an easily usable form.