Abstract: To solve the problem that conventional guar gum fracturing fluid is harmful to tight sandstone gas reservoir, a kind of low damage nano-sealing fracturing fluid was developed by means of molecular structure design and orthogonal experiment. During the fracturing of tight gas reservoir, fracturing fluid can be blocked out of the reservoir matrix, and the liquid can be drained back quickly after the fracturing, so as to effectively reduce the retention and adsorption of thickener molecules and the damage of liquid phase. The fracturing fluid is sheared for 120 min at 35$\sim$140℃ and 170 s$^{-1}$, the final viscosity is over 80 mPa$\cdot$s, the gel can be broken thoroughly, the residue content is low, the surface tension of the GEL breaker is 25.91 mN/m, the damage rate to the tight sandstone core is less than 15%, and plugging performance and other comprehensive performance meet the requirements of field construction. Using this fracturing fluid in ZJ125 Well, the fluid performance is good, and the fluid flowing back is quick after the operation, the flowing back rate being as high as 75.94%, 47% higher than adjacent well; the natural gas output is 1.647 5 $\times$10$^4$ m$^3$/d, 2 times of adjacent Well JS316HF, showing that the gas reservoir has a good low retention property in tight sandstone gas reservoirs.

Key words: tight sandstone, gas reservoir, nanometer blocking, low damage, fracturing fluid