Research and Application of Slick Water and Gel-Liquid Integrated Fracturing Fluids

Due to its low viscosity, slick water has limited efficacy in inducing fractures, low carrying capacity for large particles, and a low sand concentration that fails to meet the needs for operation, which limits the efficiency of large-scale fracturing in unconventional reservoirs. Therefore, SFFRE-1, a heat resistant friction reducer dissolves instantly with acrylic acid(AA), acrylamide(AM), 2-acrylamide-2-methylpropyl sulfonic acid(AMPS) and Monomer A as raw materials, was developed by inverse emulsion polymerization. A slick water and gel-liquid integrated fracturing fluid was produced by researching and developing an optimal clay stabilizer and an efficient cleanup agent highly compatible with SFFRE-1. The resulting fracturing fluid can resist temperature as high as 160 °C, and its viscosity can be adjusted from 1 to 120 mPa·s by adjusting added amount of SFFRE-1. In this way, on site mixing and real-time transition between the slick water and gel-liquid in fracturing treatments can be achieved. The fracturing fluid has been applied in shale gas wells in Sichuan Basin and tight oil wells in Shengli Oilfield. It has shown excellent performance in friction reduction and sand carrying: the friction reduction rate reached 86% and the sand concentration was boosted to 43%. The research and field application show that the slick water and gel-liquid integrated fracturing fluid can meet the requirements of large-scale fracturing in unconventional reservoirs.