Primary Cementing Of Horizontal Wells. Displacement Flows In Eccentric Horizontal Annuli. Part 1. Experiments

We present results of approximate to 300 miscible Newtonian displacement flow experiments carried out in a dimensionally scaled laboratory set-up. Annulus eccentricity, density difference and viscosity of the fluids are varied, over a wide range of laminar Reynolds numbers. Comparisons with predictions from the two-dimensional gap-averaged (2DGA) model of Carrasco-Teja et al. (J. Fluid Mech., vol. 605, 2008, pp. 293-327) show excellent agreement in predicting the underlying competition between buoyancy and eccentricity, which results in either top side or slumping flows. Other features of the experiments are not predicted as well. The main discrepancy results from a variety of dispersive effects that are not present in the 2DGA model, e.g. dispersion within the annular gap and due to azimuthal secondary flows. We find that dispersive effects dominate to the extent that the slumping flows are best described by bulk diffusive spreading of the height-averaged concentrations, relative to the mean flow. A variety of flow structures and wave-like instabilities are discussed. The study is relevant to the oilfield process of primary cementing of horizontal wells.