Research and Application of Salt-Resistant Thickener for High Salinity Flowback Fluid Preparation

N the development process of unconventional oil and gas resources, large-scale volume fracturing is the main means of increasing production, but the resulting large amount of backflow fluid needs to be treated harmlessly to avoid environmental pollution. The high treatment cost and the reality of water scarcity in northern oil regions of China make it urgent to study the reuse technology of fracturing backflow fluid. This article focuses on the high concentration of salt ions (Na+, K+, Mg2+, Ca2+) in fracturing flowback fluids, and synthesizes a salt tolerant polymer thickener NY-1. Based on four different mineralization contents of fracturing flowback fluids (FP-1 ~ FP-2), relevant research is conducted. The indoor experimental results show that the thickening agent NY-1 has excellent performance under different mixing water conditions: at a salinity of 65436.54mg/L, the apparent viscosity is 85mPa·s, the viscosity retention rate can reach 68.3%, and the dissolution time is less than 180s; Shear at 80 ℃ and 100s-1 for 110 min, and the apparent viscosity can stabilize to 50mPa · s; The maximum elastic modulus and viscous modulus of fracturing fluid can reach 1.39Pa and 1.02Pa, respectively, exhibiting as elastic fluid; Static suspension of 30–50 mesh quartz sand with fracturing fluid for 5 min without significant settling; At 80 ℃ and 0.04% APS dosage, the fracturing fluid can break the gel within 2 h, and the surface tension of the gel breaking fluid is higher than the technical indicators required in the industry standard SY/T 7626–2021 Water based Fracturing Fluid Technical Requirements. The gas production from the field test well after fracturing is not significantly different from that of the adjacent well using water-based fracturing fluid, demonstrating the excellent water reduction effect of this system and indicating a broad application prospect.