| Fracturing fluids is one of the working liquids in fracturing operation. Its performance plays an important role to the effectiveness of fracturing operation. Most of the viscoelastic surfactant-based fracturing fluids consist of a quaternary ammonium salt surfactant, showing low high-temperature stability and high cost.In this thesis, a novel series of viscoelastic surfactants (VES) were prepared by using of vegetale oil and N-aminopropylmorpholine as the hydrophobic and hydrophilic groups, respectively.The composition and distribution of fatty acid in vegetable/animal oil were investigated by GC analysis. A series of fatty acid methyl ester (FAME) samples were systhesized from free fatty acids in the presence of p-toluenesulfonic acid. Vegetable/animal oils were transformed into their corresponding mixed FAMEs. The acid composition and distribution in each of the vegetal/animal oil were obtained through comparison of the mixed FAMEs with individual free fatty acid FAME.Four types of VES, including amide-amine salt, Gemini, betaine and non-ionic VES were prepared from free fatty acids. Main factors that influence the system viscosity, such as concentration of VES, the type and the amount of inorganic salt additives and the type of fatty acids, were investigated. The following results were concluded: (1) Amideamine salt-type, betaine-type and non-ionic surfactant-type VES show satisfactory high-temperature performance, while Gemini-type VES exhibits poor high-temperature stability. (2) The type of fatty acids show considerable effects to the properties of VES fluids. Under the same condition (concentration 5%, molar ratio n(amideamine):n(H2SO4)=2:1, 2 wt% NaCl and 98℃), the viscosity of steric acid series VES reaches upto 173 mPa·s, better than oleic acid and palmitic acid series. For betaine-type VES at concentration of 5% and 98℃, the fluid viscosities are 117 mPa·s, 21 mPa·s and 198 mPa·s, for steric, oleic and palmitic acid series, respectively. Among them palmitic acid series is the best. For non-ionic type VES, the viscosities for the above three acid series are 210 mPa·s, 243 mPa·s and 348 mPa·s, again palmitic acid shows the best results under the same condition.Sterting from vegetable oils, including soybean oil, peanut oil, cotton seed oil, rapeseed oil, palm oil and sunflower oil etc, three types of VES (amide-amine salt, betaine, non-ionic) were prepared. Results show that: (1) Amideamine salts VES made from peanut oil and soybean oil exhibit poor high-temperature performance(lower than 90℃). (2) Betaine-type VES made from peanut oil can be used up to 90℃at concentration of 4%. (3) At concentration of 5% and 95℃, the viscosities for VES fluids, in the order of palm, peanut, cotton, sunflower, soybean ans rapeseed oil, are as follows: 306 mPa·s, 255 mPa·s,219 mPa·s, 198 mPa·s, 90 mPa·s and 78 mPa·s.In addition, as a novel application for waste or used oils, VES from acidified oil and cooked oil were prepared and utilized as fracturing fluid thickening reagents. When mixed with other series VES and certain additives, the fluid system showed satisfactory high-temperature properties. For example, the viscosity for 5% VES fluid from acidified oil and palm oil(1:1) can reach to 180 mPa·s at 95℃, while the number for an acidified oil-palmitic acid-steric acid VES fluid mixture is 171 mPa·s. The viscosity for a cooked oil-palm oil VES mixed system is 102 mPa·s at 95℃. The aforementioned results indicate that both acidified oil and cooked waste oil can be used to make VES for fracturing fluids.
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