Abstract
In the continuous liquid distribution process, the emulsion drag-reducing agent has poor viscosity-increasing ability and a low solid content, resulting in a high concentration and high cost. To solve this problem, a nanosuspension agent with a "shelf structure," a dispersion accelerator, and a density regulator were used as auxiliary agents to realize the stable suspension of a polymer dry powder in an oil phase. The results show that the molecular weight of the synthesized polymer powder could reach nearly 28 million when the mass ratio of acrylamide (AM) to acrylic acid (AA) was 80:20 and a chain extender was added. The synthesized polymer powder was dissolved in tap water and 2% brine separately, and the viscosity of the solutions was measured. The dissolution rate of up to 90% was reached at 30 °C, and the viscosity was 33 and 23 mPa s in tap water and in 2% brine, respectively. A stable suspension can be obtained without obvious stratification in one week and with good dispersion after 6 months by using the following composition: 37% oil phase + 1% nanosuspension agent + 10% dispersion accelerator + 50% polymer dry powder + 2% density regulator. The drag-reduction performance is good, remaining close to 73% with increasing time. The viscosity of the suspension solution is 21 mPa s in 50% standard brine, and the salt resistance is good. The rate at which the suspension fracturing fluid damages the formation is 7.56%, and the reservoir damage is unsubstantial. Its performance in field applications illustrated that its sand-carrying capacity, referring to the capacity of the fracturing fluid to carry proppants into the fracture and place them in a predetermined position, reaches 10%. The results show that the fracturing fluid can be used as a pre-fluid to break the formation, form fractures, and expand fracture networks under low-viscosity conditions and can be used as a sand-carrying fluid to carry proppants into the formation under high-viscosity conditions. Additionally, the fracturing fluid can directly realize the fast conversion between high and low viscosities and allow for multiple uses of one agent.