Preparation and Performance Evaluation of a Variable Viscosity Friction Reducer Suspension with High Salt Tolerance and Low Damage

In view of challenges such as the long dissolution time of powder friction reducers in high-salinity water, poor environmental friendliness of water-in-oil (W/O) emulsion friction reducers, and the poor proppant-carrying capacity of conventional slickwater, a novel variable viscosity friction reducer suspension (EACM) with high salt tolerance, low damage, and strong proppant-carrying capacity was prepared by dispersing salt-tolerant polymer powder in alcohol solvents. The solubility, drag reduction ability, viscoelasticity, proppant-carrying capacity, temperature and shear resistance, and gel breaking ability of EACM were investigated. The results showed that the best solvent for the friction reducer suspension was polyethylene glycol 400, in which EACM exhibited a rapid dissolution rate with a thickening rate of 89.5% within 2 min. Due to the synergic effect between fumed silica and polyamide wax as antisedimentation agents, both at a concentration of 2.0 wt %, the EACM could remain stable for 60 days. EACM showed an excellent drag reduction performance at both low and high viscosities in 100 000 mg/L salt brine. Specifically, a drag reduction of up to 72.4% was obtained using 0.21 wt % EACM (4.65 mPa s), and a 60.8% drag reduction was achieved using 1.0 wt % EACM (35.5 mPa s). When the concentration increased from 0.13 to 1.0 wt %, the EACM solution changed from viscous to elastic; the spatial network structure of the solution became more compact, and the proppant-carrying capacity was enhanced. The viscosity of 1.6 wt % EACM solution could be maintained at 55.9 mPa s after shearing at 90 °C for 120 min at a shear rate of 100 s–1. EACM solution also exhibited the advantages of easy breaking and low residue. This paper provides guidance for the design and selection of a novel friction reducer suspension in the oil and gas industry.