Evaluation of the influence of adding clay in polymeric hydrogels based on partially hydrolyzed polyacrylamide and aluminum citrate

Polymeric hydrogels have been evaluated for their ability to block high‐permeability regions of heterogeneous reservoirs, distributing the injected fluids to low‐permeability regions, aiming to improve oil recovery. However, the stability of these hydrogels can be reduced under conditions of high temperature and salinity typical of reservoirs. Thus, the objective of this study was to assess the properties of hydrogels based on partially hydrolyzed polyacrylamide, with different molar masses, crosslinked with aluminum citrate, in the presence or absence of bentonite clay. We call these systems composite hydrogels or conventional hydrogels, respectively, and prepared them in synthetic brine containing 29,940 mg/L of total dissolved solids. The selected hydrogels were submitted to rheology tests and scanning electron microscopy for assignment of gel strength codes. The results showed it was possible to obtain composite hydrogels with enhanced thermal properties in comparison with conventional hydrogels, mainly at a temperature of 85°C. The rheological tests, by determining the viscous modulus (G"), elastic modulus (G'), and the ratio between the two (G"/G'), along with the tan δ factor, indicated competition in the interaction between the clay and crosslinker, due to the latter's positive charges in relation to the negative charges present in the polymer chains. The scanning electron microscopy micrographs showed the presence of clay particles adhered in the polymer chain, improving the thermal resistance of the system.