Study On High Temperature Viscoelastic Surfactant Fracturing Fluid And Its Rheological Properties

In order to develop high temperature viscoelastic surfactant fracturing fluid, a new type of high temperature resistance viscosifier, long carbon chain alkyl amide amine oxide (LQ-FJ), was studied in this paper and the related factors were also investigated. The corresponding system performances and micelle aggregation microstructures were researched. The rheological properties of viscoelastic fluid made from long carbon chain alkyl amide amine oxide were studied. A new mixed fracturing fluid system formed by a low concentration of long carbon chain alkyl amide amine oxide (1%LQ-FJ) and hydrophobic amphoteric cellulose FAG-500 was obtained. Properties of other five kinds of viscoelastic surfactant fracturing fluids were also studied. Main conclusions were acquired as follows:1) The long chain amine such as oleic acid amide propyl dimethyl tertiary amine and erucic acid amide propyl dimethyl tertiary amine, hydrogen peroxide were taken as raw materials. The long carbon chain alkyl amide amine oxide was obtained by a batch method. The factors such as mole ratio of tertiary amines, mole ratio of mixed tertiary amine and hydrogen peroxide, solvent species, reaction temperature, reaction time, pH on the performances of viscoelastic surfactant fracturing fluid were confirmed. The optimum synthetic conditions were found.2) When long carbon chain alkyl amide amine oxide was dissolved into water, the system could be self-thickened to viscoelastic fracturing fluid without any salts or additives. Viscoelastic fluid LQ-FJ possessed a network structure, which was demonstrated by TEM and SEM. The high temperature viscoelastic surfactant system 2%LQ-FJ which could be stable at 110℃ was obtained, and the system viscosity still retained 55.64mPa·s at 110℃.3) The rheological research results showed that viscoelastic fluid made form LQ-FJ had obvious viscoelasticity, hysteresis loop and shear thinning properties.The high temperature viscoelastic surfactant fracturing fluid 2%LQ-FJ had heated-thickening and heated-thinning properties. Viscoelastic fluid LQ-FJ flow curves could be well stimulated by non-linear co-rational Jeffreys model.4) Synergistic thickening action was observed between low concentration surfactant solution 1%LQ-FJ and hydrophobic amphoteric cellulose FAG-500. The mixed fracturing fluid 1%LQ-FJ+0.2%FAG-500 could be stable at 80℃ and the system viscosity still retained 47.5mPa-s.5) Through studying other five kinds of viscoelastic surfactant fracturing fluid performances, other two kinds of high temperature viscoelastic surfactant fracturing fluid were obtained, namely 2% erucic amide propyl dimethyl betaine and 2% long carbon chain amine oxide+3% sodium salicylate, which could be stable at 100℃ or above.