Formation Damage Caused by Modified Guar Gum at Different pH

A modified guar gum developed at low pH is used to formulate a fracturing fluid,which is used in place of guar gum modified at high pH values. The formulated fracturing fluid has a viscosity of 256 mPa·s shearing at 170 s-1 for 90 min,and the fracturing fluid has a viscosity of less than 5 mPa·s after gel breaking. Permeability impairment is about 20%. Laboratory studies show that guar gum fracturing fluid formulated at alkaline solution generates a weak polymer network,leading to invasion of liquid phase into formation through filtration and plugging of pore throat by the network film. Guar gum modified at weak acidic solution(pH 4.5) ,however,give birth to a strongfrozen gel-like network,which hinders the invasion of solid particles and residue gel into pore throat,much lesser harmful to formation permeability than guar gum modified at high pH.