A rheological investigation of a high temperature organic gel used for water shut-off treatments

Polyacrylamide-based gels are used in many water shut-off treatments. In this study, a copolymer of polyacrylamide/tert-butyl acrylate (PAtBA) is cross-linked with polyethyleneimine (PEI). The kinetics parameters of the gelation reactions were determined using steady shear viscometry at temperatures of 80 to 130 °C. The addition of salts to the mixing water was found to increase the gelation time. On the other hand, higher polymer and cross-linker concentrations reduced the gelation time. The activation energy was found to be 118 kJ/mol in distilled water and decreased to 93 kJ/mol in seawater. The reaction orders were found to be first order with respect to both PAtBA and PEI. The effects of initial pH and contamination with iron(III) on the gelation time were also examined in detail. Recommendations for field application of this gelling system are given.