Bulk and rheological properties of polyacrylamide hydrogels for water shutoff treatment

Presenting an optimal hydrogel for water shutoff, based on the bulk and rheological properties, was the main purpose of this research. To determine gelation time, a bottle test was conducted using central composite design method with two factors, AN125VLM and Cr(OAc)(3), as copolymer and crosslinker, respectively. To select hydrogel with high strength network, crosslinking density and consistency modulus were also measured. Hence, a hydrogel with 26,340 ppm concentration of copolymer, 0.12 ratio of crosslinker/copolymer, maximum value of crosslinking density (1,950) and consistency modulus (31,900 Pa) was selected as the optimal one. To study the gelation time among different factors in porous media, rheological experiments were carried out by Plackett-Burman design to screen the eight factors (NaCl, CaCl2, KCl and MgCl2 concentrations, temperature, pH, sodium lactate and nanoclay). Accordingly, temperature was the most effective factor controlling the gelation time, while pH and other factors had negligible effect on the gelation time of the optimal hydrogel.