Flow of drilling fluids in eccentric annuli

The effect of pipe eccentricity on the flow of well bore fluids in annuli is investigated both analytically and experimentally. The expression for azimuthal velocity as a function of the eccentricity ratio and rheological parameters of the fluid was obtained analytically using a linear fluidity model. Velocity profiles were measured for a Newtonian glycerol/water mixture and a non-Newtonian oil field spacer fluid in eccentric annuli using the stroboscopic flow visualization method. Measured velocity profiles in the eccentric annulus compare well to analytical predictions.