Correlating viscoelastic measurements of fracturing fluid to particles suspension and solids transport

An experimental study was performed to understand the relationship between fluid characteristics and its solids transport and sand suspension capabilities. In this study, borate crosslinked guar gels were prepared at three different pHs. The linear guar was crosslinked with borate crosslinker at concentrations from zero to the values where the gel exhibited phase separation at each pH. These gels were then characterized for viscoelastic properties and suspension settling velocities. At each pH, a crosslinker concentration was selected to evaluate the gels for their solids transport behavior in two large size slot models. The gels that satisfactorily transported solids through the slots had similar elastic moduli. The results show that the fluid elasticity, not viscosity, correlates with the solids transport capability of the crosslinked guar gels. Furthermore, the drag coefficients for the suspensions settling in the crosslinked gels prepared at three pHs were dissimilar, even at similar Weissenberg numbers. The drag on the suspensions settling in the viscoelastic guar gels was observed to be both more and less than the drag on the suspensions settling in the Newtonian fluids. Further work is needed to better understand these drag behaviors on the suspensions settling in viscoelastic guar gels.