Formation and Propagation of Gel Aggregates Using Partially Hydrolyzed Polyacrylamide and Aluminum Citrate

Abstract

Abstract A comprehensive study of the formation of gel aggregates in systems containing partially hydrolyzed polyacrylamide and aluminum citrate was completed. Under certain conditions, this system forms gel aggregates, commonly referred to as colloidal dispersion gels. Systems that formed aggregates on the exit screen of a screen viscometer also developed flow resistance when displaced through slim tubes and sand packs. A gel system containing 1000 ppm polymer and 33.3 ppm aluminum citrate was studied in sand packs 2ft and 4ft long. In the 2ft sandpack, the gelant showed no significant difference in the flow resistance when compared to polymer injection when 8.7 pore volumes were injected with at residence time 0.83 hours after mixing the gelant inline prior to injection. However, a high flow resistance developed after the sandpack was shut in for 31.4 hours. Viscosity measurements indicate that solution viscosity increases about 15 hours after mixing the solutions but a visible gel structure is not formed. In the 4ft sandpack, gelant was injected at a slow rate so that the residence time was 19.2 hours. A high flow resistance developed across the entire length of the sandpack demonstrating the formation and retention of gel aggregates in the sandpack. Our experimental data demonstrate that gel aggregates can be formed by reaction of partially hydrolyzed polyacrylamide with aluminum citrate and propagated through sandpacks. Permeability to brine following the gelant treatment was reduced by a factor of about 9000. In-depth treatment of a porous matrix by this process is limited because retention of gel aggregates causes the permeability to decrease leading to reduction in flowrate.