Study on rheological behavior and salt-thickening mechanism of a synthesized twin-tailed hydrophobically modified polyacrylamide

Hydrophobically modified polyacrylamide (HMPAM) is widely used in petroleum development, whereas it still confronts challenges in high salinity reservoirs. In this work, a twin-tailed modified polyacrylamide was introduced and characterized by FT-IR, H-1 NMR and TGA. The rheological properties and thickening mechanism were investigated by viscosimetry, rheology, macroscopic appearance, dynamic light scattering, fluorescence spectroscopy and beta-cyclodextrin inclusion. The results revealed that by increasing NaCI from 0 to 50 g/L, the critical association concentration declined and solutions transformed from a transparent fluid of 115 mPa.s to viscoelastic fluid of 2040 mPa.s. Eventually, the viscosity decreased with white precipitation at 200 g/L NaCl. The salinity conduced to the aggregate of hydrophobic groups, while excessive aggregate decreased the hydrodynamic volume, which in turn caused a reduction of macroscopic viscosity. Higher polymer concentrations were conducive to better salt-thickening property. This copolymer showed great salt resistance and prospects for application in high salinity reservoirs. (C) 2019 Elsevier B.V. All rights reserved.