Abstract

The ability to effectively transport sand without the use of guar-based fluids has led to the development of friction reducers that build viscosity. These new products, also known as high viscosity friction reducers (HVFR) generate viscosities comparable to or greater than linear gel fluids. The selection criteria have focused primarily on achieving greater than 10 cP at 300 RPM (511s-1). As the salinity of the base fluid changes, the HVFR dosages must be increased up to 4X to meet this target. However, there is limited data available on how this viscosity correlates to the fluid’s ability to transport sand. This study presents methodology used to screen HVFR’s in various fluids and results on product performance, which identifies need for alternative specifications to viscosity.

The sand transport capacity under dynamic conditions was evaluated for two commercially available HVFR’s in up to 120,000 TDS synthetic water. A slot flow apparatus was used to mimic fluid flow through a fracture under different shear and flow conditions. The viscosity and elasticity were also measured using an advanced rotational rheometer. For comparison, a linear gel fluid was also evaluated.

While viscosity targets can be achieved by many commercially available HVFR products in freshwater, when salinity is increased, these products fail to meet the same targets. A comparison of the viscosity versus the sand transport capacity of these fluids, suggests viscosity does not indicate sand carrying capacity. The author did not find a correlation between higher viscosity and better sand transport. The results provided insight into the effect of flow rate on sand transport. The effect of salinity on s and transport suggests good performance can be achieved even at low viscosity. Elasticity testing of those same products suggested that HVFR’s have a critical elasticity range at which they will provide optimal performance.

This paper provides insight into the HVFR properties which correlate to sand transport and highlights the need for development of standardized test criteria other than viscosity. Further testing and screening of HVFR’s will increase the understanding of key factors influencing sand transport.

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