An Instantly Dissolving Fracturing Fluid Technology Using Hydrophobic Associating Polymers Based on Swelling-Curing Mechanisms

Due to hydrophobic associating polymers fracturing fluid have problems, such as poor dispersing performance, a long swelling time and which was unsuitable for continuous mixing at the wellsite. Thus, an instantly dissolving fracturing fluid technology using hydrophobic associating polymer has been developed by comprehensively combining mechanical and chemical methods. The solubility parameter for fluid preparing was reduced through the development of a cosolvent, and the swelling time of polymer was accelerated by utilizing the negative entropy factor. The coaxial bi-directional stirring device was designed to improve the turbulent flow of solid-liquid mixture and to shorten the curing time of the polymer. Experiments showed that the solubility parameter and the swelling micelle diameter were the key factors affecting the swelling and curing of polymer. The swelling ratio of hydrophobic associating polymer reached 92% in 4 min by adding 4% cosolvent. We found that the stirring rate has little effect on the curing time of such polymer, and further, the stirring method is the main factor affecting the curing speed of polymer. The swelling ratio of the coaxial bi-directional stirring method reached 86% in 6 min, and the developed instant dissolving hydrophobic associating polymer fracturing fluid system have the shear resistance of greater than 180 mPa·s at 90 °C, which satisfies the field requirements. The new fracturing fluid technology could achieve the continuous mixing of polymer fracturing fluid, and reduce the influence of residual fluids on the environment, which provided technical support for the implementation of large-scale volumetric fracturing in factory mode.