Performance of the reproducible polyvinyl alcohol fracturing fluid system

Abstract

A novel organic boron cross-linker for the polyvinyl alcohol fracturing fluid system was synthesized. The formulas of the fracturing fluid system operating at 50 and 70°C were developed. The performance of the polyvinyl alcohol fracturing fluid system at 70°C was comprehensively evaluated and compared with that of the conventional fracturing fluid. The results show that the polyvinyl alcohol fracturing fluid is mainly elastic in the range 0.01–10 Hz, and the final gel viscosity of the polyvinyl alcohol fracturing fluid is above 50 mPa s under the conditions of continuous shearing for 120 min at a shear rate of 170 s–1 at 70°C. Thus, the fracturing fluid exhibits good temperature–shear resistance. The sedimentation rate of 60 to 80 mesh quartz sand in polyvinyl alcohol fracturing fluid is lower compared to that in the gum fracturing fluid, i.e., the sand-carrying performance is good. The polyvinyl alcohol fracturing fluid system also exhibits other favorable characteristics such as low filtration coefficient, low residue, low fluid loss, easy and thorough gel breaking, low gel-breaking liquid surface tension, and reduced damage to the stratum. Thus, polyvinyl alcohol can replace guar and its derivatives used in fracturing fluid at low temperature. The regenerative experiment with polyvinyl alcohol fracturing fluid shows that the viscoelastic characteristics, temperature–shear resistance, fracture-making ability, and sand-carrying performance decline upon regeneration.