VES压裂液的性能研究与循环使用

Performance research and recycling of VES fracturing fluid

采用阳离子双子黏弹性表面活性剂和KCl制备了一种清洁压裂液VES,并采用5%(w)的煤油对该压裂液进行破胶,破胶液用盐酸纯化析出,过滤得到其中的表面活性剂再次进行配液回收循环使用。采用FTIR和SEM方法对回收前后的VES压裂液结构进行表征。对回收前后VES压裂液的黏弹性、流变性、携砂性等性能进行研究,并进行了岩心伤害实验和破胶实验。表征结果显示,回收前后的表面活性剂结构未发生变化,且回收循环试样依旧具有清晰的胶束层结构,VES压裂液可重复使用。实验结果表明,回收前后VES压裂液仍具有良好的弹性性质,而黏度几乎没有差别,在60 min内各试样黏度缓慢下降至约50 m Pa·s;VES压裂液原样岩心伤害率为4.88%,远小于瓜尔胶体系;经5次回收循环后岩心伤害率为9.22%;VES压裂液具有优良的携砂性能;回收循环后的VES压裂液试样在2 h之内均可彻底破胶,破胶后的试样黏度均小于5 m Pa·s,且无残渣。

The clean fracturing fluid VES was prepared from a cationic gemini viscoelastic surfactant and KCl,and 5%（w） kerosene was used to break the fracturing fluid. The broken fluid was purified and precipitated with hydrochloric acid,and the surfactant was separated by filtering for recycling in fluid preparation. The structures of the VES fracturing fluid before and after recovery were characterized by FTIR and SEM. The properties such as viscoelasticity,rheological property,sand carrying property and the like of the VES fracturing fluid before and after recovery were investigated,and a core damage experiment and agel breaking experiment were performed. The results showed that the surfactant had no change in structure before and after recovery,and the recycled samples still had clear miceller layer structure,reflecting the reusability of the VES fracturing fluid. The VES fracturing fluid fracturing fluid had good elastic properties and almost no difference in viscosity before and after recovery,and the viscosity of each sample was slowly decreased to about 50 m Pa·s within 60 min. Moreover,the core damage rate of the original sample of the VES fracturing fluid was 4.88%,which was far less than that of the guar gum system. Additionally,the core damage rate was 9.22% after 5 times of recycling. The VES fracturing fluid also had good sand-carrying capability. The recycled VES fracturing fluid samples could all be completely broken within 2 h,and the viscosities of the broken samples were all less than 5 m Pa·s with no residue.