Abstract: Improved methods of fracture-acidizing producing zones in subterranean formations are provided. The methods basically comprise creating one or more fractures in the zone, causing the fractures to close and injecting acid into and through the closed fractures so that flow channels are formed therein. The fractures are then extended in the zone, caused to close and acid is injected through the previously formed flow channels and through the extended portions of the fractures so that flow channels are formed in the extended portions. The steps of extending the fractures, causing the fractures to close and injecting acid are repeated until fractures having flow channels formed therein are extended desired distances in the zone.

Abstract: A method for placing a foamed treating fluid in the upper portion of a fracture comprising the steps of: (i) introducing a foamed preflush fluid into the fracture; (ii) introducing an inert gas into the fracture to form a flow channel over the foamed preflush fluid located therein and (iii) introducing a foamed treatment fluid into the fracture whereby said treatment fluid is caused to flow through the flow channel over the foamed preflush fluid and enter the upper portion of the fracture.

Abstract: Methods are provided for treating an underground well formation whereby the treatment is confined to a desired zone within the formation. The methods comprise introducing one or more preflush fluids into one or more fractures in the formation followed by the introduction of a treating fluid having a density differing sufficiently from the density of the preflush fluids whereby the treating fluid is segregated and caused to flow into a desired zone within the formation.

Abstract: Methods are provided for treating an underground well formation whereby the treatment is confined to a desired zone within the formation. The methods comprise introducing one or more preflush fluids into one or more fractures in the formation followed by the introduction of a treating fluid having a density differing sufficiently from the density of the preflush fluids whereby the treating fluid is segregated and caused to flow into a desired zone within the formation.