氟碳表面活性剂的合成及其降压增注体系研究

Synthesis of fluorocarbon surfactant and development of its compound surfactant system for depressurization and increasing injection

关键词:  低渗透油藏  降压增注  氟碳表面活性剂  界面张力  润湿性能

Key words:  low permeability reservoir  depressurization and increasing injection  fluorocarbon surfactant  interfacial tension  wettability

摘要:

目的 针对致密储层注水压力高的问题,开展适宜于低矿化水驱的低界面张力的防膨降压增注体系研究。方法 以聚乙二醇和低碳数含氟烷酸为原料合成了氟碳表面活性剂(FEC),并对其结构进行了表征。研究了氟碳表面活性剂与Gemini表面活性剂和有机铵盐防膨剂的复配性能,探讨了复配表面活性剂中FEC含量对防膨性能、界面性能及润湿性能的影响,确定了表面活性剂増注体系,评价了降压增注性能。结果 实验结果表明,氟碳表面活性剂(FEC)和Gemini表面活性剂(GC)的复配可有效提高防膨效果。FEC/GC复配体系中加入0.8%(w)铵盐防膨剂可以使界面张力降到10-3 mN/m；在m(FEC∶GC)为(1∶1)~(3∶2)时,岩心接触角增加到54°~59°之间,可有效降低水在矿物表面的黏附功。优化出的复配増注体系具有很好的耐冲刷性能,经过10次蒸馏水冲洗后防膨率达75.24%。结论 岩心实验表明,注入复配体系1 PV后,压力下降34.7%；3口井的现场试验表明,该体系具有较好的降压增注效果,达到了降低致密油藏注水压力的目的,对低渗储层的降压增注具有指导性意义。 

Abstract:

Objective Aiming at the problem of high injection pressure in tight reservoir, a depressurization and augmented injection system with low interfacial tension suitable for low mineralized water flooding was developed. Methods Fluorocarbon surfactant FEC was synthesized from polyethylene glycol and fluoroalkanoic acid with low carbon number, and its structure was characterized by IR. The compounding properties of fluorocarbon surfactant with Gemini surfactant and organic ammonium salt anti swelling agent were studied. The influences of FEC content in the compound surfactant on anti swelling performance, interface performance and wettability were discussed. The surfactant increasing injection system was developed and its depressurization and increasing injection performance were evaluated. Results The combination of fluorocarbon surfactant FEC and Gemini surfactant can effectively improve the anti swelling effect. Adding 0.8% ammonium salt anti swelling agent into FEC/GC composite system can reduce the interfacial tension to 10-3 mN/m, For the system with the FEC/GC mass ratio of 1∶1-3∶2, and the core contact angle increases to 54°-59 °, which can effectively reduce the adhesion work of water on the mineral surface. The optimized compound injection system has good erosion resistance, and the anti swelling rate reaches 75.24% after 10 times of distilled water washing. Conclusion The core experiment shows that the pressure decreases by 34.7% after injecting the compound system 1 PV. The field test of three wells shows that the system has good effect of depressurization and increasing injection, and has achieved the goal of reducing water injection pressure in tight reservoirs, which is instructive for depressurization and increasing injection in low permeability reservoirs.