An Experimental Approach To Assess the Dispersion of Shale in Fracturing Fluids

Abstract

We propose an experimental approach to evaluate how typical fluids influence shale dispersion. In this approach, finely ground shale is left to settle in the fracturing fluid, generating particle-size and concentration profiles within the settling column. Samples are taken at various settling times and depths and then analyzed with regard to turbidity and capillary-suction-time (CST) behavior. Particle-size-distribution (PSD) measurements are used to further substantiate analysis. Turbidity data indicate the volume of particles present, and PSD data indicate the sizes of these particles (or flocs). This approach was tested using ground shale, Eagle Ford brine (EFB), and three typical fluid additives. Without additives present, shale flocculation resulted in rapid particle settling, and samples taken from suspension gave low turbidity and CST values. With additives present, suspensions were better dispersed and hence tended to give higher CST values. Some additives hindered flocculation more effectively than others. The results suggest that low CST numbers might not always be desirable; additives that are good inhibitors might hinder flocculation of shale particulates and hence promote higher CST numbers. In this paper we discuss how our proposed experimental approach can give insights into the influence of additives on the degree and nature of shale dispersion.