基于水/辛酸异戊酯-白油反相乳液体系合成压裂液增稠剂及性能

Properties of a fracturing fluid thickener synthesized by inverse emulsion polymerization based on water/isoamyl octanoate-white oil

反相乳液聚合过程中通常采用饱和烷烃的混合物白油作为分散介质,但是白油在使用过程中会存在污染环境的问题。本文以可降解化合物辛酸异戊酯替代了部分白油作为混合油相,丙烯酰胺(AM)和丙烯酰氧乙基三甲基氯化铵(DAC)为单体,通过反相乳液聚合法合成了W/O型聚丙烯酰胺-丙烯酰氧乙基三甲基氯化铵(P(AM-DAC)),通过~1H NMR、FT-IR和SEM对其结构进行表征。考察了乳化剂用量和辛酸异戊酯用量对预乳液稳定性、黏度和油-水界面张力的影响,引发剂用量和反应温度对P(AM-DAC)水溶液黏度的影响。结果表明:当乳化剂用量为10%,辛酸异戊酯用量为50%时,引发剂用量为0.8%,反应温度为38℃时,P(AM-DAC)水溶液黏度达到最大值,为129 mPa·s。考察了P(AM-DAC)与以白油作为油相合成的聚丙烯酰胺-丙烯酰氧乙基三甲基氯化铵(P(AM-DAC)-W)的性能对比,P(AM-DAC)和P(AM-DAC)-W的粘均分子量分别为5.019×10~6和5.045×10~6;质量分数为1%的水溶液黏度分别为129和132 mPa·s;当Na^(+)质量浓度为3000 mg/L时,1%的水溶液黏度分别为65和67 mPa·s;在90℃,170 s^(-1)剪切速率下持续剪切45 min后,1%的水溶液黏度分别为36.9和43.1 mPa·s;陶粒在1%的水溶液中的沉降速度分别为0.049和0.053 mm/s;破胶液表面张力分别为27.8和28.9 mN/m;残渣含量分别为1.63和1.76 mg/L。该研究表明辛酸异戊酯代替部分白油制备压裂液用增稠剂是可行的,不仅不影响增稠性能,而且对耐盐、耐温耐剪切、携砂、破胶和残渣含量等性能没有造成明显的影响。

In the process of inverse emulsion polymerization,white oil,which is a mixture of saturated paraffins,is usually used as the oil phase,but white oil will pollute the environment during the process of use.In this work,W/O-type poly(acrylamide-acryloxyethyl trimethyl ammonium chloride)(P(AM-DAC))was synthesized by inverse emulsion polymerization.A biodegradable compound,isoamyl octanoate,was used to replace part of the white oil as mixed oil phase,and acrylamide(AM)and acryloxyethyl trimethyl ammonium chloride(DAC)were monomers.The structureof P(AM-DAC)was characterized by~1H NMR,FT-IR and SEM.The effects of the dosages of emulsifier and isoamyl octanoate on the stability,viscosity and interfacial tension of the pre-emulsion were studied,and the effects of initiator dosage and reaction temperature on the viscosity of aqueous P(AM-DAC)solution were investigated.The results showed that,when the dosage of emulsifier was 10%,the dosage of isoamyl octanoate was 50%,the initiator dosage was0.8%,and the reaction temperature was 38℃,the viscosity of aqueous P(AM-DAC)solution reached the maximum value of 129 mPa·s.The properties of P(AM-DAC)were compared with that of poly(acrylamide-acryloxyethyl trimethylammonium chloride)synthesized by using white oil as oil phase(P(AM-DAC)-W).The viscosityaverage molecular weights of P(AM-DAC)and P(AM-DAC)-W were 5.019×10~6 and 5.045×10~6,respectively.The viscosities of 1%aqueous solutions were 129 and 132 mPa·s,respectively.When the mass concentration of Na~+was3000 mg/L,the viscosities of 1%aqueous solutions were 65 and 67 mPa·s,respectively.After continuous shear at 90℃and 170 s~(-1)for 45 min,the viscosities of 1%aqueous solutions were 36.9 and 43.1 mPa·s,respectively.The settling velocities of ceramsite in 1%aqueous solutions were 0.049 and 0.053 mm/s,respectively.The surface tension of the gel-breaking fluids was 27.8 and 28.9 mN/m,respectively.The residue contents were 1.63 and 1.76 mg/L,respectively.Therefore,partial substitution of white oil by isoamyl octanoate in the preparation of the thickening agent for fracturing fluid is feasible,without any negative influence on the thickening performance,salt resistance,temperature resistance,shear resistance,sand carrying,gel breaking and residue content.