Study On Oil-displacement System Based On Clean Fracturing Gel-breaking Fluid

Aiming at the large volumes,high treatment cost of fracturing flowback fluid,and its harmfulness for environmental safety,a method was estabilished to realize its reutilization in surfactant flooding,based on fundamental properties of viscoelastic surfactant based fracturing gel-breaking fluid.VES fracturing gel-breaking fluid based flooding system was constructed in laboratory.Flooding system formula is: 0.1~0.4wt% fracturing gel-breaking fluid+0.004~0.02wt% AOS.The interface tension for Ansaichang crude oil can reach 7.0×10-4mN/m under the condition of 61℃ and 8.1×104mg/L salinity,which could meet the standard of tertiary recovery.Entirely performance evaluating experiments showed that the applicable temperature range of the surfactant is 50℃~90℃ and the salinity range is 3×104mg/L~21×104mg/L.Under the condition of 61℃,8.1×104mg/L salinity,the flooding system has excellent wettability and emulsifying performances.The static adsorption quantity on the clean sand is 30.25mg/g.The dynamic adsorption is about one third of static adsorption and the retention is about one fourth to one third of dynamic adsorption.The physical model experiments showed that the oil recovery value can be enhanced 12.5% under optimal injection method,which confirmed its excellent performances on enhanced oil recovery after water flooding.The existing form,the starting method and migration mode after injecting surfactant of theresidualoil are explored by CT core-scanning,SEM core-scanning and microscopic simulation model aiming to study the displacement mechanisms of surfactant.