Dependence of Polymer Retention on Flow Rate

Abstract

The efficient use of aqueous polymer solutions as mobility control agents demands an understanding of the mechanisms of mobility reduction. Mobility reduction is defined as the ratio of initial brine mobility to polymer solution mobility. Although much work has been directed toward this goal, there have been very few physical insights or conclusive explanations. This study presents experimental results that imply a reasonably consistent physical interpretation and demonstrate that the amount of polymer retained increases with flow rate. In the graphical representation, effluent concentration and mobility reduction profiles are plotted vs. pore volumes injected for a 500-ppm polysaccharide solution with 2% NaCl in a 121-md Berea core 1 in. in diam and 6 in. long. Effluent concentration fractions were determined by measuring efflux times for effluent and inlet samples in a constant-head capillary viscometer. A significant implication of these results is that polymer retention under reservoir conditions will usually be less than values measured in the laboratory, in view of reduced flow rates encountered in the field.