Synthetic polymer fracturing fluid weighted by sodium formate enables fracture stimulations in Ultra-High pressure and High-Temperature reservoir

Weighted fracturing fluid was considered to be one of the key technologies to deal with the challenge of abnormally high pressure and ultra-high temperature reservoir stimulation in the case of existing fracturing equipment. In this work, a thickener polymer Pt-Fb that meets the requirements of fracturing fluid weighting by HCOONa was synthesized. And HCOONa- weighted fracturing fluid with delayed crosslinking characteristics and good friction reduction performance was developed based on the polymer Pt-Fb. It is much cheaper than CHKO2-weighted guar gum fracturing fluid. The density of HCOONa-weighted fracturing fluid was up to 1.3 g/cm3. The fracturing fluid proposed in this study meets the temperature resistance and shear resistance requirements of 170 °C and 170 s−1. Besides, a complete gel breaking was obtained by using NaBrO3, and the internal mechanism was investigated from both experimental and theoretical aspects. It was revealed that a mild multi-step oxidation reaction enables NaBrO3 to break the HCOONa-weighted fracturing fluid.