Viscoelastic properties of a high temperature cross-linked water shut-off polymeric gel

This is the first published study that investigates the viscoelastic properties of an organically cross-linked polymeric gel used in water shut-off treatments. A copolymer of acrylamide and t-butyl acrylate was cross-linked with polyethylene imine. The effects of various parameters on the rheological properties of the gel were addressed. Experimental results indicated that the storage modulus of the gel decreases with the increase in the salinity of mixing water. Also, higher gel elastic modulus was obtained at higher cross-linker concentrations. A highest elastic modulus of 3.4 kPa was obtained for a gel with a composition of 7 wt.% polymer and 1.2 wt.% cross-linker. However, syneresis was observed in gel samples with 1.2 wt.% cross-linker concentration. The gel lost 53% of its elastic modulus after 1 month of ageing at 150 °C. Based on the trends noted with the elastic modulus, two different mechanisms for gel formation were identified below and above 100 °C.