EXPERIMENTAL STUDY ON THE PROMOTING EFFECT OF SURFACTANTS ON THE FRACTURING FLUID FLOWBACK IN SHALE GAS WELLS

Shale reservoirs generally have extremely low porosity and permeability, and the capillary pressure is high, so the backflow of the fracturing fluid is very difficult, which in turn causes damage to the reservoir. In this paper, the effect of different types of surfactants on the fracturing fluid flowback of shale gas wells was studied based on conventional self-priming damage and displacement damage evaluation. The results show that the surfactant effectively reduces the interfacial tension of the fracturing fluid, and the Gemini surfactant GS-1 can reduce the interfacial tension to 0.075 mN/m. The surfactant solution can significantly improve the hydrophilicity of the reservoir at a specific concentration, and the GS 1 at a concentration of 0.1% can increase the contact angle of the shale surface to 94.1 degrees. Core dehydration experiments show that the bi- and amphoteric surfactants have a significant effect on the fracturing fluid, and the core dehydration rate can reach 59.15% and 30.15%, respectively, which is much higher than 16.48% when no surfactant is added. The results of core backflow experiments show that the final return efficiency of the test solution with the addition of Gemini surfactant can reach 80.18%, and the recovery rate of permeability reaches 80.67%. The study shows that surfactants can effectively promote the backflow of fracturing fluids in shale wells and can control the liquid phase damage caused by fracturing fluid retention on shale reservoirs.