Abstract: In Northeast Oil and Gas Field, the dispending fluid of fracturing fluid is deficient and formation water cannot be recycled easily.To solve these problems, the characteristics of formation water in Northeast Oil and Gas Field were analyzed and the reusable fracturing fluid was investigated.It is indicated from formation water characteristic analysis and formation water based fracturing fluid optimization experiments that the formation water in several blocks (e.g.Sujiatun) is characterized by weak alkaline, strong bioactivity and high contents of Ca²⁺ and Mg²⁺.As a result, the conventional thickener swells slowly and even precipitates, the stability of prepared based fluid is poor, crosslinking is uncontrollable and the temperature resistance of crosslinked fluid is poor.Ultimately, the BCS molecular self-association fracturing fluid based on formation water was adopted and its 130 ℃ formula is 0.55% thickener BC-S+0.45% thickening synergist BL-S+0.3% metallic ion stabilizer BCG-5+0.2% high temperature stabilizer B-13+0.3% efficient antiprecipitant BC-3.Its performance was evaluated.It is indicated that after BCS fracturing fluid is sheared for 120 min at 170 s^-1 under 130 ℃, its viscosity is high than 35 mPa·s.Its temperature resistance and shear resistance are good.Its proppant carrying capacity is better than that of HPGfracturing fluid.Its gel breaking is complete with the content of gel breaker residue only 1.5 mg/L.Its surface tension is 24.32mN/m.After the flowback fracturing fluid is diluted with 60% tap water, the BCS fracturing fluid can satisfy the criterion of original 130 ℃formula, and thus the formation water can be recycled many times.