Evaluation of highly stable ultrahigh-molecular-weight partially hydrolyzed polyacrylamide for enhanced oil recovery

Abstract

Polymers used in the polymer flooding technique for enhanced oil recovery (EOR) should improve rheological properties of water phase to improve sweep efficiency so that they are more widely applicable for use in oil fields. This study aimed to determine the molecular weight of a novel polymer, partially hydrolyzed polyacrylamide (HPAM), and to explore the effects of rheological properties of the polymer solution on its performance in EOR. The polymer was synthesized through vinyl polymerization using acrylic acid and acryl amide. To evaluate HPAM, several methods are used in this study. Field flow fractionation revealed that it had ultrahigh molecular weight (UHMW; 7.330x10(6) Da absolute weight-average molecular weight). Results of rheological measurement showed that UHMW HPAM could be applied even at a concentration of 1000 ppm to achieve desired properties. Furthermore, UHMW HPAM showed viscoelastic behavior within a wide range of temperatures and salinities. Polymer flooding with UHMW HPAM recovered 4% more oil because of its high viscosity and molecular weight.