Experimental Study On The Mechanism Of Infiltration And Replacement Of Composite Fracturing Fluid System

Tight reservoirs are characterized by low porosity and low permeability.Compared with conventional reservoirs,different development methods should be adopted,and fracturing technology is often used in actual production.The natural productivity of low permeability reservoirs is low,and fracturing operations need to be performed early,but often yield low yields and maintain high water injection pressures.Wit h the improvement of fracturing fluid technology,various fracturing fluid technologies are applied in specific reservoirs,and the diversification of fracturing fluid composition is an important basis for satisfying tight reservoir exploitation in the future.Therefore,by combining surfactant with traditional fracturing fluid to form a composite fracturing fluid system,a new idea was proposed for the composite fracturing fluid technology.Through experimental research,the performance analysis of surfactant and new composite system was improved to achieve the purpose of excavating the remaining oil in tight reservoirs and improving the reco very efficiency by combining the corresponding technology.Aiming at the characteristics of low porosity permeability in tight reservoirs,this paper selects the infiltration absorption combined with stimulation and displacement for laboratory experiments to study the mechanism of infiltration absorption and stimulation replacement of composite fracturing fluid system,a nd analyzes the changing rules of factors affecting the oil recovery effect.In this paper,a composite fracturing fluid system is designed and its interfacial t ension and wettability are evaluated.The experimental results show that the concentrat ion of Surfactant in the composite fracturing fluid system increases,and the interfacial tension first decreases and then increases,there is an optimal concentration value,th e temperature can reduce the interfacial tension by changing the viscosity and the sha pe of the oil,and the complex fracturing fluid can reduce the interfacial tension and change the wettability of the core.Static / Dynamic imbibition experiments are design ed.The results show that the necessary condition of imbibition process of oil-wet cor e is wetting reversal,and the effect of static imbibition of water-wet core is good We ttability is the main factor to improve the static imbibition effect,and low interfacial tension is the secondary factor,the static imbibition effect can be improved by increas ing the temperature and decreasing the viscosity of the oil,and the imbibibition rate of the composite fracturing fluid system can be optimized when the dynamic imbibibit ion capacity of the composite fracturing fluid is higher than that of the single fracturing fluid,the dynamic imbibition effect can be improved by using complex fracturing fluid and choosing reasonable injection rate,and the results of imbibition displacement oil production physical model experiment under the action of complex system show t hat core cutting fracture can improve huff and puff oil recovery,fracture is a necessa ry condition for liquid huff and puff oil production in tight reservoir,and the combin ation of imbibition and Huff and puff displacement can improve oil recovery Increasin g reservoir temperature,increasing injection pressure difference and selecting reasonabl e soak time can effectively improve oil recovery in tight reservoir.