Preparation And Fracturing Performance Of Unsaturated Gemini Betaine Surfactant

In the 21st century,China's demand for oil and gas resources is increasing every year.In this conditions,the improvement of fracturing technology has far-reaching significance to improve oil and gas production.Fracturing fluid is the core of fracturing technology.Plant gum,polymer and cellulose are used as thickeners of fracturing fluid.Although these substances have good gelling performance,they have poor dispersion performance,high content of insoluble substances,and high formation damage after gel breaking.However,due to its unique mechanism of gelling and breaking,clean fracturing fluid has low damage to the reservoir and high return rate after gel breaking,which solves this problem.In this paper,gemini steamidopropyl hydroxy sulfobetaine(GSHSB),gemini oleamidopropyl hydroxy sulfobetaine(GOHSB),gemini linoleamidopropyl hydroxy sulfobetaine(GLHSB)and gemini?-linageamidopropyl hydroxy sulfobetaine(GL?HSB)were obtained by amidation reaction,quaternized reaction and gemini reaction.(1)Molecular structure was designed and screened for surfactants.Synthesis of tertiary amine intermediates via amidation reaction using stearic acid(SA),oleic acid(OA),linoleic acid(LA),?-linagenic acid(L?A)and 3-(dimethylamino)-1-propylamine(DMAPA)as raw materials.Quaternary amine intermediates were synthesized by quaternary amination of 3-chloro-2-hydroxypropanesulfonic acid sodium salt(CHPS-Na)with tertiary amine intermediates.The final product series of betaine surfactants were obtained by using isophorone diisocyanate(IPDI)as linking group for the gemini reaction.1H NMR and FT-IR was employed to attest the construction of betaine gemini surfactants and percentage of acid data,amine value and isocyanate content were determined.The synthesis process of GLaHSB amidation reaction was also optimized.When the reaction time was 8 h,the reaction temperature was 160?,the catalyst dosage was 0.5%,and the molar ratio of LaA to DMAPA was 1:1,the conversion rate was 87.9%.The synthesis process of GL?HSB quaternization was optimized and screened.The reaction time was 8 h,the reaction temperature was 80?,and the molar ratio of tertiary amine to CHPS-Na was 1.2:1.The conversion rate reached 74.9%.(2)The basic properties of series of betaine gemini surfactants was showed that the CMC of GSHSB,GOHSB,GLHSB,GL?HSB were 9.68×10-5,8.9×10-5,8.54×10-5,7.69×10-5 mol/L,and the surface tension was 34.51,33.77,32.56,31.07 mN/m,respectively.The interfacial tension test of oil and water was showed that the increase of time will reduce the oil-water interfacial tension.The oil-water interfacial tension of GL?HSB was 0.016 mNm-1 at 30 mintue.UV spectra was showed that the absorption peak was red-shifted in 190?220 nm.The CMC of the series of betaine gemini surfactants were 9.68×10-5,8.9×10-5,8.54×10-5,7.69×10-5 mol/L.The particle size test showed that when the concentration is 1×10-4 mol/L and 1×10-3,the particle size is 6.5?15.7 nm and 141.8?274.4 nm.The wormlike micelles formed by GL?HSB were observed by SEM,and further entangled to form a spatial network structure.With the increase of concentration,the network structure is closer and the diameter is 50?100?m.The foaming ability of the GSHSB was reached 2 cm.With the increase of the number of double bonds,the foaming properties of betaine surfactants was decrease,and the height of the foam was decreased lower.GL?HSB has good emulsifying property,and it takes 300 s to separate 10 mL water.(3)The related fracturing performance of series of betaine gemini surfactants was studied.The viscosity of 2%GL?HSB solution reached 52.7 mPa·s,under pH=4 the viscosity reached 93.5 mPa·s,and the viscosity was changed little in NaCl and CaCl2 solution with salinity of 3000 mg/L.GL?HSB solution was promoted by NaSal at pH=4.The sedimentation rate of proppant in GL?HSB reached 0.1013 mm/s at 80?.It can be seen that GL?HSB entanglement forms a three-dimensional network structure though SEM,and the proppant is wrapped in the three-dimensional network structure.WLMs can not be completely observed in white oil gel breaking,while the gel breaking products of(NH4)2S2O8,NaHSO3 and KMnO4 was showed flake structure.Under the action of(NH4)2S2O8,the breaking temperature was 80?,the breaking time was 3 h,the viscosity was less than 5 mPa-s.The gel breaking of white oil is not complete,and the particle size of the product is about 115?129 nm.The particle size of(NH4)2S2O8,NaHSO3 and KMnO4 gel breaking products is 26?96 nm.The residue was not found after the treatment of(NH4)2S2O8,NaHSO3 and white oil,while the residue was found in the product after KMnO4 gel breaking,and the content was about 10 mg/L.The core matrix damage rate of series of betaine gemini surfactants is in the range of 5%?6%.