Experimental Study of Laminar Displacement Flows in Narrow Horizontal Eccentric Annuli

Wells with poor cement jobs are prone to develop paths where the hydrocarbons might leak to the surface. Such events cause environmental risks and costly repairs. Even though horizontal wells have been drilled since the 1980s, studies on the dynamics of the fluid-fluid displacement under this configuration are scarce. In this work, we present experiments on the displacement of two Newtonian fluids in laminar regime in a horizontal uniform annulus. The minimum non-dimensional parameters required to describe the flow under such conditions include a buoyancy number (b), viscosity ratio (μ2/μ1) and eccentricity (e). We have designed and built a flow loop that mimics the annular displacement under controlled and dimensionlessly comparable conditions found in field. Within this apparatus we can set key process parameters: flow rate, eccentricity, fluid rheology and density. Data acquisition is through imaging with high sensitivity cameras and partially automated instrumentation. Preliminary results of the experiments show that there is a subtle balance between eccentricity and buoyancy. Sufficiently high values of |b| will end up in stratification of the fluids. The secondary flows created in an eccentric annulus compete against a positive buoyancy, driving the flow to the wide side (top) at moderate values of b. The effect of the viscosity ratio is most relevant at small values of b. The experimental data from this work can be compared against both mathematical model predictions and computational simulations used in the design of primary cementing jobs.