Xanthan and guar polymer solutions for water shut off in high salinity reservoirs

In this research the influence of salt concentration on the rheology of xanthan and guar solutions and their combined mixtures was investigated. Shear viscosity at wide shear rate range was measured for all solutions at various conditions of temperature, polymer concentration, mixing ratio, and salt content. It was found that while xanthan solutions were more susceptible to salt presence in the solutions which has led to reduction in shear viscosity, the viscosity of guar solutions tended to increase upon increasing salt concentration and this was equally pronounced at low and high polymer concentration, i.e. 500 ppm and 3000 ppm. Synergism was not significantly observed for the xanthan/guar mixtures at all ratios used, i.e. 1:1, 1:2, and 2:1. Salt greatly affected the rheology of xanthan/guar mixtures except for mixtures where the guar content was high. We believe that this method, i.e. combining xanthan and guar solutions, is an effective strategy to control rheology and morphology of solutions to be used in enhanced oil recovery field.