EXPERIMENTAL STUDY OF DISPLACEMENT FLOWS IN A VERTICAL ECCENTRIC ANNULUS

Primary cementing is an essential part in constructing an oil or gas well. Leakage occurs due to a poor seal of the cement in the annulus, which may be caused either during or after placement. Key in controlling leakage is to ensure the integrity of the surface casing, which is primarily vertical. This paper addresses the underlying fluid mechanics that may affect cement placement in vertical casings. We present results of miscible Newtonian displacement flow experiments carried out in a dimensionally scaled laboratory set-up. The experimental set-up has been described in detail (Renteria and Frigaard, J. Fluid Mech, 905, 2020) [ 1], and used previously in horizontal orientation. We use the same annular flow loop but in vertical configuration. The effects of density difference, viscosity ratio and eccentricity of the annulus have been studied. We find that the eccentricity is always dominant in affecting the displacement, and the narrow side view gives us more detail of residual layers. The buoyancy number and Reynolds number are key factors that affect the stability of the whole process. Large buoyancy number and small Reynolds number lead to stable interface and less dispersion. The residual layer at the narrow side can be removed out to a degree, under significant density difference and at lower flow rates. However, the viscosity ratio appears to play only a secondary role in vertical displacement flows. Our future directions will use the present experiments for comparison with 2D and 3D models, and we then aim to extend the experimental program to shear-thinning non-Newtonian fluids.