Effect of Concentration on HPAM Retention in Porous Media

Abstract

Abstract This paper investigates the effect of HPAM polymer concentration on retention in porous media using both static and dynamic measurements. Consistent results using these two methods show that different polymer retention behaviors exist in dilute, semidilute and concentrated regions. In both the dilute and concentrated regions, polymer retention is basically concentration-independent. In contrast, in the semidilute region, polymer retention is concentration-dependent. If a porous medium is first contacted sufficiently with dilute polymer solution to satisfy the retention, no significant additional retention occurs during exposure to higher HPAM concentrations. Based on the experimental results, a concentration-related retention mechanism is proposed that considers the orientation of the adsorbed polymer molecules and the interaction between molecular coils in solution. Using this model, we explain why polymer retention does not show much dependence on concentration in the dilute and concentrated regimes. Further, in the semidilute region, we explain how moderate coil interactions lead to mixed adsorbed polymer orientation and magnitude on rock surfaces, and retention becomes concentration-dependent. In field applications of polymer and chemical floods, reduced polymer retention may be achieved by first injecting a low-concentration polymer bank.