The Effect of Polymer Mixing Time on the Strength of HPAM-Cr(III) Gels

Abstract

The dissolution of hydrolyzed polyacrylamide, commonly used in gel treatments for enhanced oil recovery, takes between 2‒3 to over 24 h at 20‒25 °C. The duration is influenced by factors such as polymer molecular weight and brine salinity. In injection/production wells, gel treatments often involve injecting 50‒150 m3 of polymer solution within 1‒2 days, resulting in the injection of partially dissolved polymer. This raises concerns about the stability and strength of gels containing partially dissolved polymer particles. This study demonstrates that when undissolved polymer particles are kept suspended during the gelation process, there is no significant visual distinction between gels obtained from 30 min or 12 h of polymer mixing. Additionally, viscometer measurements reveal that gels formed with shorter polymer mixing times exhibit higher resistance to shearing. This observation supports the concept that undissolved polymer particles act as a composite material, improving the gel strength. This paper does not advocate for the use of partially dissolved polymer gelants. Undissolved polymer particles cannot effectively penetrate porous media. Gelants containing such particles are primarily suited for addressing fracture conformance issues. Therefore, future research will focus on examining the impact of polymer mixing time on gel syneresis and resistance to washout from fractures.