A novel multifunction fracturing fluid compounding of nano-emulsion and viscous slickwater for unconventional gas and oil

Visous slickwater formed by high viscous friction reducer (HVFR) has been a great success in replacing conventional slickwater in unconventional reservoir. In order to further extend the function of the slickwater to achieve the purpose of multi-effect of one recipe, a new fracturing fluid system composed of nano-emulsion and HVFR was introduced. It combines the functions of nano-emulsion and HVFR to form a new multi-functional fracturing fluid system: it can not only combine the advantages of conventional slickwater and guar gum fracturing fluid, but also avoid their disadvantages. At the same time, it has the effect of spontaneous imbibition oil displacement to enhance oil recovery, realizing the goal of combination of hydraulic fracturing and EOR. Whether the FR-900 drag reducing agent solution meets the fracturing fluid index is studied through the tests of rheological properties, drag reduction properties and sand carrying performance; CND is studied through the tests of wetting angle, demulsification rate, interfacial tension and spontaneous imbibition experiment. The synergistic effect of CND and FR-900 was analyzed by microscopic test at last. The result shown that: 1) CND can enhance the rheological properties and sand-carrying performance of FR-900 solution. After adding CND, the viscosity and viscoelasticity of FR-900 solution were improved, and the single particle sand-carrying performance and dynamic sand-carrying performance of FR-900 solution were also enhanced. The addition of CND has no effect on the friction reduction performance of FR-900. 2) the main component of CND is surfactant oil for imbibition oil displacement. The mixture of CND and FR-900 has the effect of wettability, reducing oil–water interfacial tension and fast demulsification. The experimental results of imbibition oil displacement show that 0.10 wt% CND can improve the oil recovery of FR-900 solution by 12.79%. The mixed solution of CND and FR-900 has the properties of easy breaking and low residue. 3) the field application results show that the new multifunctional fracturing fluid system has the advantages of low operation pressure, high sand-carrying performance and stimulation effects.