Factors Affecting the Viscosity of Polysaccharide Solution

Welan gum is a high molecular weight water soluble exopolysaccharide produced through fermentation of carbohydrates by alcaligenes. Studies show that welan gum is soluble readily in water to form solution whose viscosity increases as the concentration of welan gum increases. The apparent viscosity of the welan solutiondecreases shear rate increases, and the shear stress, in the meantime, increases, showing a typical pseudo-plastic behavior. At low shear rate, the welan solution has high apparent viscosity. Guar gum solution retains its viscosity at neutral condition, and loses its viscosity in acidic or basic environment. Contrary to the guar gum, welan gum solution maintains most of its viscosity at pH range of 2-12. Moreover, welan gum has better temperature stability than guar gum. Unlike other polysaccharides, welan gum forms a network structure that is free from the effect of high valence ions. Welan gum will be a new ideal viscosifier for use in well fracturing.