Drilling fluid is a complex fluid, including base fluid and other materials, carrying out the vital functions during drilling operation such as cutting transport and controlling formation pressure. In order to optimize performance of a drilling process, a reliable rheological model is required in the computation of fluid flow dynamics. Timeindependent Generalized Newtonian formulation are the most common models for describing the rheological behavior of drilling fluids due to its simplicity and ease of use, in spite the fact that they are not able to predict the normal stresses and could not consider effects of active components on the rheological behavior of the drilling fluid and also could not describe the internal microstructures changes in the fluid during its flow. In this paper, a rather simple model in the mesoscopic level of study through the Generalized Bracket formalism have been developed to consider the influence of salts and electrolytes on the rheology of drilling fluid which has received less attention in the previous models. The advantage of this model is that it provides a description for the structural and orientation changes during transient and steady state fluid flows beside prediction of the transient and steady rheological behavior of salt containing suspensions of bentonite in polymeric solutions. Comparison of the model predictions with the published data from literature shows that the model predictions for the effects of the drilling fluid components including clay and salts are in well agreement with those of the rheological experimental data.

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