Evaluation of the Influence of Adding Clay in Polymeric Hydrogels Based on Phpa and Aluminum Citrate

Abstract

In situ formation of polymeric hydrogels has been studied to ascertain their ability to block regions with high permeability in reservoirs and enhance oil recovery. The difficulties of applying these gel systems are related, among other factors, to their fragility in the conditions of high temperature and salinity typically found in reservoirs. In this context, various options for modification of gelling systems have been studied, such as addition of reinforcement loads, for preparation of nanocomposite hydrogels with improved mechanical and thermal properties. Thus, the objective of this study was to assess the properties of hydrogels based on partially hydrolyzed polyacrylamide (PHPA), 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 ppm of total dissolved solids (TDS). 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 delta 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 SEM micrographs showed the presence of clay particles adhered in the polymer chain, improving the thermal resistance of the system.