Meisam Mirarab Razi - School of Chemical Engineering, Iran University of Science and Technology (IUST), Tehran, Iran
Fatemeh Mirarab Razi - Mathematics and Computer Science Department, Amirkabir University of Technology, Tehran, Iran
Hamid Saadati - School of Chemical Engineering, Iran University of Science and Technology (IUST),Tehran, Iran

This paper presents the results of the measurements of apparent viscosity of waterbased drilling fluids over a wide range of temperature (27-54 ) and concentrationof guar gum added (17.5-46.4 kg/m3), using a coaxial cylinder viscometer. Bingham plastic, power law, Herschel-Bulkley and Casson models have been selected todescribe rheological properties of drilling fluids. The results showed that power law and the Herschel-Bulkley models have higher accuracy to describe the non-Newtonian behavior compared to the other two models, specially, when the concentration of the guar gum increases. The effect of temperature on the apparentviscosity was very well correlated with the Arrhenius equation (0.977

Drilling Fluid; Apparent viscosity; Guar gum; Rheological models;Arrhenius model