Evaluation of Bentonite Colloids for Potential Use as an In-Depth Fluid Diversion Agent

Abstract

In this study, API-grade bentonite sample was characterized using XRD and FTIR techniques. The effect of gravity and centrifugal sedimentation on bentonite colloid size and size distribution was examined. Also, rheological properties of 1000-, 2000-, and 3000-ppm dispersions were measured using Anton Paar rheometer. Finally, stability and critical salt concentration (CSC) were determined by using Turbiscan Classic. The objective is to evaluate the potential application of these dispersed particles as an in-depth fluid diversion. XRD data indicate the presence of a smectite with minor amounts of impurities such as quartz and dolomite. Sedimentation was found effective for preparing a controlled size dispersion which can be adjusted to target high water production zones. Different colloidal dispersions of different mean hydrodynamic sizes are obtained ranging from 340 nm down to 260 nm in average with less than 8 µm as the maximum diameter. These sizes fall in the range of existing IFD that often used for improving sweep efficiency in heterogeneous rock matrix. Bentonite dispersions exhibited a water-like viscosity at low concentrations studied, which is in favor of IFD. However, increasing salt concentration and temperature sharply increased viscosity. The stability of bentonite colloids is reduced with increasing solution salinity above CSC. In addition, the CSC was found dependent on the colloidal concentrations. At 3000 ppm, bentonite dispersion showed a higher critical salt concentration. For low salinity formation water and low salinity dispersion make-up water, controlled bentonite colloids could be effectively stabilized and transported in porous media and serve as IFD for improving sweep efficiency. However, at higher salinity conditions, bentonite aggregation and stability will become an issue.