Preparation and performance evaluation of nanoparticle modified clean fracturing fluid

Abstract

A new cationic trimer surfactant bis[2-hydroxy-3-(N,N-dimethyl-N- cetyl) propyl] dipropylammonium chloride was sythesized by two steps. Analysis results of FTIR and 1H NMR show the synthesized cationic trimer surfactant is target product. Two kinds of clean fracturing fluids VES-W without nano-TiO2 and VES-N with nano-TiO2were prepared using the cationic trimer surfactant as the main agent. The morphology, temperature resistance, shear resistance, apparent viscosity, viscoelasticity, sand carrying properties, gel breaking properties and core damage rate of the VES-N, compared with the crosponding clean fracturing fluid without nanoparticles (VES-W), were systematically studied in this paper. Cryo-TEM indicated that, the worm micelles were formed in VES-W and VES-N fracturing fluid systems, and after adding nano-TiO2, the strength of VES-N is higher than that of corresponding VES-W.The temperature resistance of VES-N and VES-W systems were 100 ℃ and 81 ℃ respectively, and the nano-TiO2 particles can effectively improve the viscoelasticity of VES-N. The proppant in VES-N system had lower settling rate than VES-W, demonstrating that the addition of nano-TiO2 can effectively improve the sand carrying capacity of the system. When the amount of kerosene was more than 1.0 wt%, the VES-N and VES-W systems were completely broken, and nano-TiO2 almost had no effect on the gel breaking properties. The filtration coefficients of VES-N and VES-W systems were 4.247 × 10−4 m/min1/2 and 7.378 × 10−4 m/min1/2, respectively. The residual rate of VES-N in rock core is slightly higher than that of VES-W, and the core damage is slightly higher than that of VES-W, but VES-N had good complexed properties, so the oilfield fracturing results show that the effect of VES-N fracturing fluid is very good in fracturing stimulation of low permeability reservoirs.