Rheologic Properties of a Water-Soluble Terpolymer with Vinyl Biphenyl

A water-soluble acrylamide-modified terpolymer (PAAP) with sodium 2-acrylamido-2-methylpropane sulfonate and vinyl biphenyl as the hydrophobic monomer was synthesized to obtain a polymeric thickening agent applied in middle- and low-permeability oil reservoirs. The polymer is expected to possess a low molecular weight and high solution viscosity. The steady-state consecutive shear cycles of PAAP in aqueous and brine solutions were measured, and the viscoelastic properties of PAAP solutions were investigated as a function of polymer, NaCl and sodium dodecylbenzene sulfonate (SDBS) concentrations. The aqueous PAAP solutions exhibits pseudoplastic and thixotropic behavior over the range of shear rate and shear thickening behavior at very low shear rate. The steady-state shear results show that some disrupted associating aggregates at high shear rate can be reformed during the shear reversion process and the suitable shear rate is favorable to the formation of hydrophobically associative structures in the brine solutions. Above 0.05 ga <...dL(-1) PAAP, aqueous PAAP solutions have predominantly elastic character over the range of angular frequency that is strengthened with increasing polymer concentration. The PAAP brine solutions exhibit predominantly elastic behavior only above 3 rada <...s(-1) and a salt-thickening effect. By addition of an optimum amount of SDBS (0.5-0.8 mmola <...L-1), the complex viscosities become much higher than the dynamic viscosities, although the loss tangent values increase owing to the formation of loose associative structures.