HEC provides high performance in increasing viscosity,and is excellent in control filtration loss in oilfield drilling and completion fluids.HEC is stable to various salts,even at Calcium salt solution.Oilfield fluids containing HEC exhibit high apparent viscosity,high yield point and low fragile gel strength.Its shear-thinning behavior known as pseudoplasticity help both increase penetration rates under high shear and provide excellent suspending action for optimum hole cleaning under low shear while viscosity is regained.