The invention provides a method of treating a sandstone-containing subterranean formation penetrated by a wellbore. The method is carried out by forming a slurry of a carrier fluid containing a viscosifying agent and encapsulated particles of a hydrogen fluoride source without settling of the particles. The carrier fluid may be an acid-based carrier fluid. The encapsulated hydrogen fluoride source may be encapsulated with a solid polymer acid precursor. The hydrogen fluoride source is present within the slurry in an amount of about 10% or more by weight of the slurry. The slurry is introduced into the wellbore at a pressure above the fracture pressure of the formation under conditions wherein the hydrogen fluoride source is released.