Abstract: The problems of deep well reservoir, such as deep burial depth, tight lithology, high fracture pressure and fracture extension pressure, lead to high pressure and difficulty in fracturing, and low density of conventional fracturing fluid, which cannot guarantee the construction safety and effect of measures. In order to solve the above problems, a kind of organoboron crosslinking agent YGB-1 was synthesized in this paper, and the crosslinking ratio and the amount of regulator were optimized by the determination of crosslinking time. The thickening agent, weighting agent and other additives were optimized to form a fracturing fluid formula with density of 1.35 g/cm³, adjustable delay crosslinking time within 3～17 min, and suitable for 160℃ reservoir. Various properties of the fracturing fluid were measured through the temperature and shear resistance test, suspended sand test, resistance reduction test and demulsification test. The results showed that the enhanced guanidine gel fracturing fluid had excellent properties. The viscosity remained above 150 mPa·s after 2 h shear at 160℃ and 170 s^-1. At 90℃, when the sand ratio is 25%, the ceramsite (20～40 meshes) was suspended for 0.5 h without settlement. When the test line is 6 mm and displacement is 3.5 m³/h, the drag reduction rate of the weighted fracturing fluid is 61%. The surface tension of the broken glue solution was 24.8 mN/m, and the residue content was 398.2 mg/L. The anti-swelling rate of broken glue solution was 91%.

Key words: weighted fracturing fluid, organoboron crosslinking agent, additive optimization, delayed crosslinking, performance evaluation