The Research And Application In Daqing Oil Field Of A New Polymer Fracturing Fluid

We have developed a new polymer fracturing fluid for stimulating the fracturing production of peripheral low permeability reservoir in Daqing oil field. The new fracturing fluid is mainly comprised of synthetic polymer thickener JR200, acidic cross linking agent JA60 (pH2⁴), and gel breaker. Besides, three additives are mixed into it, such as clay stabilizer, demulsifier and water recovery aid. The thickener is a kind of hydrophobically associating water-soluble polymers. Its molecular weight is about 300 million. There is no water insoluble matter, aqueous solution shows neutral and instant. Cross-linking gel is non-Newtonian fluid, has excellent resistance to temperature and shear. The researches show that the fracturing fluid is used for 50¹70℃, its ability of temperature-to-resistance shearing is better than hydroxypropy metformin glue fracturing fluid. It is less harmful to strata and fracture flow capacity with low viscosity of breaking gel liquid and less content of scraps.The formula of the new polymer fracturing fluid is 0.18%⁰.60% thickener+1.0% clay stabilizer+0.2%water recovery aid+0.15%prevent emulsifier+0.1%-0.2% gel breaker, the concentration of cross linker is 0.03%⁰.08%, the portion of polymer thickener to cross linker is 40:1. At 50, 90, 120, 170℃, the initial viscosity of fracturing fluid glue ranges from 200mPa·s to 500mPa·s /170s-1, after shearing 50⁹0min, the retain viscosity is more than 65, 135, 205, 108 mPa·s at the corresponding temperature, and can recover after sheared. After 8h gel breaking experiment, the viscosity of gel breaker is less than 5mPa·s. The residue is little, for example, after the fracturing fluid containing 0.5% thickener breaking, the amount of residue is only 5.28mg/L. The amount of gel breaking agent decreases with temperature. Besides, the new fracturing fluid with good prop pant carrying capacity, low filtration, less core damage, excellent petrophysics compatibility, high flow back rate, and not easy to deteriorate, can satisfy the fracturing techniques, such as fracture initiation, transporting and fast flowback, and can use with sorts of fracturing technology. The new polymer fracturing fluid applies to 7 Wells in different blocks. Analysis results show that the stimulating effect in low permeability reservoir(permeability is greater than 2.0×10^-3μm²) is good, for extremely low permeability reservoirs (permeability in 0.05¹.50×10^-3μm²), the effect is not obvious. So, it is suitable for extremely low permeability reservoir (permeability is greater than 2.0×10^-3μm²).