New insights of further enhanced tight oil recovery after hydraulic fracturing by VES fracturing fluid

In the process of fracturing in tight reservoirs, viscoelastic surfactant (VES) fracturing fluid has many advantages that can significantly increase the recovery of tight oil. However, there is a risk of formation blockage due to heavy emulsification in the formation. In this study, a VES microemulsion (VES-M) system with low reservoir damage and high oil displacement efficiency is constructed using VES fracturing fluid and polyhydroxy alcohol. The average particle size in the fluid is only 3%-10% of the average pore size of the tight reservoir, and the formation damage is 16.00%. The new fluid can achieve ultra-low interfacial tension (IFT) with Winsor type III microemulsion. Compared with slickwater fracturing fluid and formation water, the new fluid can filtrate deeper into the matrix and increase the oil recovery by 7.20%-11.32% during the flowback process. This study provides a possibility for the field application of VES fracturing fluid in tight reservoirs and new insights into the effects and rules of employing the VES-M system to enhance tight oil recovery.