Objective In view of the tight gas reservoir reconstruction in Sichuan and Chongqing area, volume fracturing is mainly used to make long fractures, and high-strength sand addition puts forward higher requirements for sand carrying and resistance reducing performance of fracturing fluid. A hydrophobic association polymer is developed as a resistance reducing agent.

Methods Hydrophobic intramolecular association of hydrophobic association polymer is used to achieve excellent viscosity increasing effect. At the same time, the resistance reducing agent and metal cross-linking agent can form a stable cross-linking system, further improve the viscosity of fracturing fluid, thus forming a variable viscosity fracturing fluid system suitable for tight gas reservoir development.

Results The fracturing fluid system has been used for 12 wells in tight gas reservoirs in Qiulin, Jinhua, Zhongtai and other areas. The results show that the sand strength is 5-6 t/m, the maximum sand concentration is 480 kg/m³, the viscosity range of variable viscosity fracturing fluid is 3-30 mPa·s, and the drag reduction rate is more than 70%, which can meet the requirements of construction design.

Conclusions The fracturing fluid system can be adjusted in real time in the viscosity range of 2-100 mPa·s, and the drag reduction rate is more than 70% in low to medium viscosity range. In the case of cross-linking, the drag reduction rate is 55%-60%, and the core damage rate is less than 15%. The sand suspension performance is good and the field use is simple and convenient.