Determination of Viscosity and Wall Slip Behavior of a Polymer-Gel Used for Leakage Control From Couette Viscometry Data

Abstract

Polymer-gel, as a rheological complex fluid, is vulnerable to slip at solid walls. If wall slip occurs, the accuracy of viscosity measurements that are based on the no-slip boundary condition assumption is affected. This paper presents a general numerical procedure based on Tikhonov regularization for correcting Couette viscometry data in the presence of wall slip. This procedure needs only two-measurement viscosity data from two different annular gap sizes. Using the presented procedure, we determined the viscosity and wall slip behavior of a special polymer-gel used for leakage control. The results show that, the polymer-gel ZND-2 does not always exhibit significant wall slip, until the polymer content reaches a critical level of 0.3–0.5% by mass. An empirical correlation was proposed in power law form to describe the relationship between wall slip velocity and wall shear stress. It indicates that there is a minimum wall shear stress that needs to be overcome for a given polymer-gel sample manifesting wall slip phenomenon. The critical minimum wall shear stress and the gel structure strength increase drastically when the polymer content increases beyond a certain value, which is 1.0% by mass for ZND-2. When wall slip occurs, the difference is remarkable between the slip-corrected and apparent rheological parameters for different annular gap sizes. The slip-corrected rheological properties indicate that the polymer-gel ZND-2 used for leakage control behaves as a yield plastic fluid and has good shear thinning capability.