Proppant Transport using High Viscosity Friction Reducer Fluids: Part I- Rheology and Static Settling Velocity Characterization

Measuring proppant static settling velocity in high viscosity friction reducers (HVFRs) plays a critical key for evaluating proppant transport in hydraulic fracture treatment. Settling of particles is governed by several factors such as fluid rheology (viscosity and elasticity), proppant size, retardation confining walls effect, and fracture orientation. The objective of this experimental study was to determine how these factors would influence particle settling velocity in hydraulic fracturing applications. The experiments were conducted in unconfined and confined fluid conditions. Fracture cell was designed in certain ways to capture the impact of fracture orientation on settling velocity. Results showed HVFR provided better proppant transport capability than regular frictional reducers concentrations used in slickwater. In most of the settling measurements, proppant settling velocity using HVFR decreased significantly compare to the settling velocity measured using slickwater. HVFR with low loading of 2 gpt caused drag enhancement or proppant settling velocity reduction across wide ranges of particle sizes due to the elasticity properties of fluid. Changing fracture orientation from vertical position to 45° led to a high reduction in proppant settling velocity due to contact force or friction force from the inclined fracture sidewall. The importance of measuring proppant static settling velocity and fracture fluid rheology is crucial to mimic the low shear rate conditions of fracture treatment after stop pumping the proppant