Preparation and solution properties of polyacrylamide-based silica nanocomposites for drag reduction application

Drag reducers (DRs) have a significant effect on shale hydraulic fracturing. Hence, it is very essential to develop excellent DRs for engineering applications. In this work, a novel nanocomposite drag reducer (PASD-SiO2) was synthesized using acrylamide (AM), sodium 4-styrenesulfonate (SSS), dimethylhexadeylallylammonium bromide (DMAAB) and modified nanosilica by redox free radical copolymerization. Fourier transform infrared spectroscopy (FT-IR), 13C nuclear magnetic resonance spectroscopy (13C NMR), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), elemental analysis, dynamic light scattering spectrophotometer (DLS) and scanning electron microscopy (SEM) were utilized to characterize the copolymer. Then its solution properties were evaluated. The results showed that the nanocomposite exhibited better performances of temperature resistance, salt tolerance, shear resistance and viscoelasticity than those of a pure polymer. The indoor drag reduction measurements were carried out in a closed loop flow system. The maximum drag reduction efficiency of PASD-3%SiO2 was 59.2%, which was 9.7% higher than that of a neat polymer. These improvements in desirable properties were mainly attributed to the dispersion of silica nanoparticles in the polymer matrix. Nanosilica acted as a cross-linker and enhanced the strength of the network structures, which improved the structural stability. In addition, the polymer containing silica nanoparticles exhibited improved structural rigidity. Therefore, the polymer molecules showed more persistent and effective restriction towards vortices under turbulent flows. This novel drag reducer showed good potential for slickwater fracturing applications.