Composite Fracturing Fluid Thickeners And Their Production Technology Research

The thickeners are the main additives of water-base fracturing liquids. The single systems of thickeners commonly used in oilfields, natural polymers or synthesized polymers, have such disadvantages as heavy harms to stratra. Therefore it is necessary to research and develop more complex thickeners with higher performance-price ratio.A complex thickener can be acchieved with the chemical-modified products of both artemisia glue and acylamine copolymer with average molecular weight less than 10 million. The carboxymethylized modification method was employed for artemisia glue's modicication. The optimal reaction conditions were: Temperature 55℃, the dosage of NaOH 1.6%, the volume ration of water to ethanol 2.5:20, the dosage of chloroacetic acid 0.8%, the alkalization reaction time length 30 mins, and the etherification time length 3~4 hours. On the other hand, the Mannich modification method was employed for acylamine copolymer's modification. And the optimal reaction conditions were: the concentration of acyamine copolymer 3%, the volume ratio of formaldyde to dimethylamine 1:2, the volume ratio of the mixture of formaldyhyde and dimethylamine to the copolymer's resolution(3~9): 100, reaction temperature 50℃, time length 2 hours.The results of performance evaluation shew that the insoluble substance of the modified product of artemisia glue could be less than 4%, and that the apparent viscosity of its glue could increase by two times. When used as aid agent for modified copolymer, the modified artemisia glue could behave cooperatively in the complex system. The gel fracturing liquids of the complex thickener cross-linked by Potassium aluminium sulfate in slightly acidic conditions behaved good temperature tolorance and shear resistance, and could indure temperature as high as over 90℃. Used as gel-breaking agent, ammonium persulfate could break the gel at room teperature or higher. The apparent viscosity of liquids after gel-breaking could drop below 0.01 Pa ? s, and the residue content was between 20~180 mg/L.Based on the achievements of the experiments, the process was put forward for producing complex thickeners consisting of modified artemisia glue and modified copolymer. This process was proved economically feasible, and the products could reduce the harms to stratra when used in fracturing liquids and therefore the products can be substitute to the general polymers for fracturing. However, the complex thickener still had such disadvantage as weak salt resistance. In the future, further researches on the cross-linking mechanism and macro performances of complex thickeners should be carried out.