Preparation and viscoelasticity of novel hydrophobic associating polymer with salt stimulation responsiveness by functional monomer modification for fracturing fluids

In this study, a salt-resistant hydrophobic association polymer (PZDY) was synthesized from acrylamide, octadecyl dimethylallyl ammonium chloride, and decane polyoxyethylene ether acrylate by aqueous polymerization. Infrared spectroscopy, fluorescence spectroscopy, scanning electron microscopy, and other characterization methods were used to study its properties and the rheological properties of the PZDY solution were analyzed. The results showed that when concentration of NaCl is less than 5 wt% and that of CaCl 2 is less than 1 wt%, the viscosity of 0.4 wt% PZDY increased with an increase of the salt concentration. When the salt concentration continued to increase, the PZDY viscosity gradually decreased. Investigation of the rheological behaviors showed that the 0.6 wt% PZDY in the 5 wt% NaCl and 1 wt% CaCl 2 solution could withstand temperatures up to 180 °C after being sheared for 2500 s at 170 s −1 and its viscosity exceeded 50 mPa·s. Moreover, the viscosity of the 0.6 wt% PZDY in 5 wt% NaCl increased from 104 to 205 mPa·s and that in 1 wt% CaCl 2 increased from 110 to 157 mPa·s at a shear rate of 170 s –1 , at 180 °C, and a shear time of less than 500 s. Meanwhile, scanning electron microscope (SEM) results showed that the salt addition enhanced the quasi-spatial network structure, with closer clustering of PZDY molecules in the NaCl solution than in the CaCl 2 solution. The storage modulus (G′) and loss modulus (G″) increased with the increase of the PZDY concentration. Therefore, PZDY can be used to improve the heat and shear resistance of fracturing fluids and enhance oil recovery.