Concentration Effects on the Settling Velocities of Proppant Slurries

Abstract

ABSTRACT In this paper, we study the sedimentation of single particles and of suspensions in quiescent fracturing fluids. In the first part of the paper, measurements of the terminal fall velocities of single spheres in hydroxypropyl guar solutions are reported. Classical viscometric measurements show that the viscosity function of these fluids is well represented by the Ellis model. After correction for boundary effects, the experimentally measured velocities compare well with theoretical predictions based on the Ellis model. In the second part of the paper, we investigate the settling behaviour of concentrated proppant suspensions (5 to 41 % by volume of solids). The solid volume fraction is determined, as a function of vertical distance and time, using gammaray attenuation measurements. Settling velocities are compared with single sphere data. Finally, the effects of the proppant concentration are discussed in relation with several existing models for hindered settling.