Partially hydrolyzed polyacrylamide (HPAM) is the water-soluble polymer most often used in flooding applications in the petroleum industry. However, in aqueous solutions at high temperatures, HPAM undergoes hydrolysis of the lateral amide groups, and the presence of salts in the solution can lead to precipitation of this polymer. Therefore, a method was developed to monitor the thermal stability of HPAM solutions in different saline environments and varying temperatures. The proposed test method involved measurements of intrinsic viscosity as a function of time and determination of the degree of hydrolysis of the HPAM by elemental analysis. The results obtained indicated that the presence of divalent cations (Ca +2 and Mg +2 ) negatively influenced the intrinsic viscosity of the solutions and in some systems led to precocious precipitation of the polymer in environments with higher concentrations of these cations. The hydrolysis reaction of the amide groups to the acrylate groups of the HPAM chain was significantly affected by rising temperature: at 50 C, hydrolysis occurred, but not as significantly as at 70, 85, 90, and 95 C. Hydrolysis up to 84% was observed for solutions processed at 90 C. The results also indicated limits of hardness for the brine at some temperatures: 1353 ppm for 95 C and 2867 ppm for 70 C. For brine containing 13,610 ppm or more of divalent cations, hydrolysis and precipitation of the polymer were not observed at 50 C.

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Asphaltenes are considered the main agents responsible for stabilizing petroleum emulsions. However, due to the complex chemical nature of crude oil, it is necessary to extract these molecules and prepare model solutions to investigate the effects of the various asphaltenes separately. In this study, the demulsification efficiency of oil‐in‐water (O/W) nanoemulsions based on silicone polyethers was evaluated using asphaltene model emulsions. The interfacial properties of the model emulsions were evaluated, with and without the presence of the nanoemulsions, by interfacial tension and inerfacial rheology measurements and correlating them with the ability and/or speed of diffusion to the interface. Dispersion/flocculation tests of the asphaltenes were performed to assess whether the nanoemulsions were modifying the aggregation state of the asphaltenes during the process of destabilizing the model emulsions. Through the interfacial rheology tests of the model asphaltene/saltwater system, with or without addition of the systems used in the demulsification tests, it was possible to determine the influence of the nanoemulsions on the mechanical properties of the interfacial film. The results of the water/oil gravitational separation tests showed that the nanoemulsions had separation efficiency between 80 and 95%, depending on the composition of the water/surfactant/oil/asphaltene system. The nanoemulsions containing xylene as the oil phase destabilized the emulsions the fastest. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44174.