Influences Of Polymer Solution Properties On Flow In Porous Media
Authors: Wang Fred H.L. 
Published: December 2007

This paper presents the results of a systematic study of factors influencing the flow of polymer solutions in porous media. Effects of inertia, shear-thinning viscosity, visoelasticity, and molecule-wall interactions on the flow in porous media are demonstrated by correlations of the appropriate dimensionless parameters. Packed beds of glass beads with different parameters. Packed beds of glass beads with different particle sizes are used. The polymer solutions investigated particle sizes are used. The polymer solutions investigated include sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), xanthan gum (XG), sodium cellulose sulfate ester (CSE), polyethylene oxide (PEO), and partially hydrolyzed polyacrylamide (PAM). Fluid property variables in the dimensional analysis include power-law parameters, relaxation time, and molecular size of the polymer solution. Power-law parameters and relaxation time of the solutions Power-law parameters and relaxation time of the solutions were determined from a cone-and-plate steady-shearing experiment. The hydrodynamic size of the polymer molecules is characterized by coupling intrinsic viscosity measurements with gel permeation chromatography. The polymers, which are cellulose derivatives or fermentation polysaccharides such as CMS, HEC, CSE, and XG, show flow resistance in porous media that can be correlated simply with the shear-thinning bulk viscosity. Polymers with magnitude than can be attributed to bulk viscosity alone. This excess resistance is due to the visoelastic effect. However, the Deborah number does not correlate the observed excess flow resistance between different types and concentrations of polymer solutions. Permeability reduction corresponding to monolayer adsorption also is observed. The permeability reduction associated with polymer adsorption is permanent, and the initial permeability cannot be restored even with thorough flushing with a polymer-free solution. The velocity dependence of both the permeability reduction and residual permeability reduction suggests that the permanently adsorbed monolayer is deformable under the shear fields.

Introduction

High-molecular-weight water-soluble polymers are being used today to control mobility and enhance sweep efficiency in waterflooding oil-recovery process. Laboratory and field studies (along with numerical simulation of polymer flooding) have clearly demonstrated that polymer additives of a few hundred parts per million can increase oil recovery.

The flow of polymer solutions in natural porous media is a complicated process. In addition to the complex solution, rheological properties and porous media structure, mechanical entrapment, and inaccessible pore volume, and other phenomena such as degradation gel formation, and plugging also can occur. Although much useful information plugging also can occur. Although much useful information on the performance of polymer solutions in oil reservoirs has been presented, the experimental conditions were so variable that difficulties arose in correlating the numerical data. Thus, a systematic laboratory study of the factors influencing the performance of polymer flooding is conducted to isolate and understand each mechanism.

A dimensional analysis method is used to design the experiments. Effects of fluid inertia, shear-thinning viscosity, viscoelasticity, and molecule-wall interactions are demonstrated by correlations of the characteristic dimensionless parameter. Uniform packed beds of glass beads with different particles sizes are used to avoid undesired complications. Polymer solutions under investigation include sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), xanthan gum (XG), sodium cellulose sulfate ester (CSE), polyethylene oxide (PEO), and partially hydrolyzed polyacrylamide (PAM). polyacrylamide (PAM).Theoretical analyses that are available for predicting the velocity and pressure gradient relationship in porous media almost universally have been developed by coupling a structural model of the porous media with a rheological model of the fluid. The correlations based on the capillary model are summarized below since they will be referred to in later sections.