A method of treating a subterranean formation penetrated by a wellbore is carried out by introducing an emulsion composition into the formation through the wellbore wherein the formation has a formation temperature surrounding the wellbore of at least 120° C. The emulsion composition is formed from an aqueous acid component that forms an internal phase of the emulsion, non-aqueous component that forms an external phase of the emulsion, and a surfactant. The emulsion composition also includes an amount of fibers formed from high temperature polymer material. The high temperature polymer material is characterized by the property of not substantially degrading in water at pH