Effects of degree of hydrolysis and shear on gelation reaction kinetics and gel strength. [Polyacrylamides

Abstract

Gelation tests were conducted to investigate the effect of the degree of hydrolysis on gelation reaction kinetics and gel strength using four low-molecular-weight polyacrylamides (MW = 400,000 daltons), which were 10% (HPAM1-10), 20% (HPAM1-20), 30% (HAPM1-30), and 40% (HPAM-40) hydrolyzed, and Cr-3 (pH = 4.8) and Al-3 (pH = 7.0) crosslinkers. Results showed that for polymer/Cr-3 gel systems, samples prepared with a low-molecular-weight polyacrylamide polymer, which was 20% hydrolyzed, gelled at a faster rate and retained higher gel strength than those prepared with a low-molecular-weight polyacrylamide polymer, which was 10% hydrolyzed. Under the screening condition, no viscosity enhancement was observed in samples prepared with polymers having a degree of hydrolysis equal to or greater than 30%. For polymer/Al-3 gel systems, samples prepared with a low-molecular-weight polyacrylamide polymer, which was 20% hydrolyzed, gelled at the fastest rate and retained the strongest gel strength among the polymer/Al-3 gel systems prepared with four low-molecular-weight polyacrylamide polymers, which were 10, 20, 30, and 40% hydrolyzed, respectively. Gelation tests of gel systems in glass bead packs showed that high shear favored the gelation of a gel system that had a fast rate of gelation, but had an adverse effect on the gelation of three gel systems that had a slow rate of gelation. Weak gels were found to be injectable through porous media. Weak gels were degradable under high shear condition and regained viscosity under low shear conditions. 17 refs., 8 figs., 1 tab.