The drilling of troublesome shale formations leads to severe wellbore instability problems due to swelling and dispersion of the shale cuttings in the welllbore. Hence, the formulation of inhibitive water-based drilling fluid system with enhanced rheological properties and filtration characteristics is a critical issue for these complex shale formations. This research article consists of a favourable drilling fluid system developed using potassium chloride (KCL), partially hydrolyzed polyacrylamide (PHPA), ethylene glycol and xanthan gum polymer. The rheological properties and filtration characteristics were measured as per API recommended standard procedures for field testing of drilling fluids. The developed system has low plastic viscosity, good gel strength, high consistency index, and moderate apparent viscosity for the optimum performance of the drilling fluid system while dealing with shale formations. The developed drilling fluid formulations exhibited low fluid loss volume during the filtration studies. This system has high inhibition property which controls the hydration and dispersion of the shale cuttings inside the wellbore. Hence, developed inhibitive water-based drilling fluid system may be suitable for the drilling of sensitive shale formations. Keywords: drilling fluid, rheological properties, filtration characteristics, inhibition
