Research and Application of Ultra-high Salinity Variable Viscosity Fracturing Fluid System

Abstract Aiming at the problems of the shortage of fresh water resources for fracturing in the Qaidam Basin and the inability to achieve low-cost reuse of oilfield produced water due to its extremely high mineralization degree, a suspended weakly associated polymer fracturing fluid system with ultra-high mineralization resistance integrating functions such as salt resistance, resistance reduction, viscosity increase, anti-swelling and demulsification was synthesized indoors using AM, AA, AMPS and C16DMAAB. The results of the indoor comprehensive performance evaluation show that all the indicators of this system meet the relevant index requirements in SY/T 7627-2021 “Technical Requirements for Water-based Fracturing Fluids”. In addition, it has an extremely strong ability to withstand high mineralization, with a salt resistance capacity as high as 30×104mg/L and a calcium and magnesium ion resistance capacity as high as 2×104mg/L. The on-site application results show that the variable viscosity fracturing fluid system resistant to ultra-high mineralization has the advantages of “no on-site mixing, low cost, low damage and high efficiency”. Its performance is stable during the construction process and the effect after the measures is good. This system not only meets the technical requirements of high efficiency and low cost for the transformation of fracturing measures in the Qaidam Basin, but also achieves the goal of preparing fracturing fluid with ultra-high mineralization formation water. It has laid a foundation for achieving breakthrough progress in the reuse of highly mineralized formation water in the Qaidam Basin.