Effect of inorganic salts on viscosifying behavior of a thermoassociative water‐soluble terpolymer based on 2‐acrylamido‐methylpropane sulfonic acid

Abstract

The effect of different inorganic salts on aqueous solution viscosifying behavior of a thermoassociative water-soluble terpolymer, poly(acrylamide-co-2-acrylamido-2-methylpropane sulfonic acid)-g-poly[acrylamideco-N-(1,1-dimethyl-3-oxobutyl)acrylamide] (PADAS) was examined in comparison with a nonthermoassociative sulfonated copolymer, poly(acrylamide-co-2-acrylamido-2methylpropane sulfonic acid) (PAMS). With increasing salt concentration, thermoviscosifying ability of PADAS was clearly evidenced and the magnitude of thermoviscosifying effect was largely enhanced. The ability of cations and anions to enhance the viscosity of PADAS aqueous solution follows the orders Na þ > K þ > Mg 2þ > Ca 2þ and SO 4 2À > Cl À > Br -> NO 3 À , respectively. Under the same conditions, PAMS shows only thermothinning behavior and viscosity loss. The thermoviscosifying capability of PADAS is relevant to the change in the polarity of aqueous solution and the electrostatic shield effect of counterion for the repulsion between the sulfonate anions on the polymer, and depends mainly on the competition of these two effects. Cryo-TEM observation demonstrates that the microstructure changes of polymers in the electrolyte solution lead to the changes of the viscosifying behavior. V C 2012Wiley Periodicals, Inc. J Appl Polym Sci 125: 4041-4048, 2012

Review on Polymer Flooding: Rheology, Adsorption, Stability, and Field Applications of Various Polymer Systems

“…158 A thermo-viscosifying terpolymer, poly (acrylamide-co-2-acrylamido-2-methylpropane sulfonic acid)-g-poly acrylamide-co-N-(1,1-dimethyl-3-oxobutyl) acrylamide (PADAS) was synthesized. 159 Terpolymer viscosity was enhanced with increasing salt concentration. Among the investigated cations and anions Na + was more effective in enhancing the thermo-viscosifying effect while NO 3 − was the least effective.…”

“…For example, the LCST of the TVP decreased from 48 • C to 32 • C on increasing polymer concentration from 0.4% to 1%. Similarly, on increasing NaCl concentration from 0 to 0.85M, LCST decreased from 50 • C to 44 • C. 159 As most oil reservoirs have temperature greater than 50 • C, therefore, high viscosity can be achieved at reservoir temperatures. TVP may have another advantage of easy injection as viscosity is low below LCST.…”

Rheological Properties of Thermoviscosifying Polymers in High‐temperature and High‐salinity Environments

“…At 0.1 mol/L NaCl concentration, again thermo‐thinning behaviour was observed and viscosity at all temperatures was lower than the viscosity in DW. This reduction in the viscosity is due to a charge shielding mechanism . The viscosity of the SP system in an 0.5 mol/L NaCl solution was lower than the viscosity in DW at temperatures up to 60 °C.…”

“…Based on the data obtained from rheological results of the surfactant‐free polymer, salinity and temperature were found to be the two important parameters that affect the performance of the TVP. Salts have a strong influence on aqueous solution properties of the polymer, due to their impact on the free interaction of energy between water and the polymer . Therefore, the selected SP system was evaluated at a fixed TVP concentration (0.5 %) and fixed surfactant concentration (0.05 %) by varying the salinity of water.…”

“…Firstly, at low salinity, due to the charge screening effect, the polymer chain may become flexible and the viscosity may be reduced. Secondly, beyond a certain salinity chains coil up and intermolecular association can happen, which may result in increase in the viscosity . Also, thermally induced inter‐molecular association and formation of physical junctions enhance the viscosity.…”