Oil-based fluids were first used in the late 1940's to fracture stimulate a variety of wells, the first of which was in Hugoton Field. Subsequently, fluids evolved with soap and aluminum phosphate esters being employed as gellants. Because gelling, gel stability, and ease of mixing have been historically problematic, a new phosphate ester system has been developed for use in formations which may be damaged by water contact.

The Morrow Formation in the Mid-Continent region is known for its sensitivity to fresh water. Due to this fact, treatment designs have been implemented to reduce the amount of water placed into the formation. Foams and gelled oil treatments have been the options available. Foams, while reducing the amount of water placed in the formation, still have a water phase to deal with. Gelled oils eliminate the water phase, but do not have the benefit of the load recovery assistance provided by the gaseous phase of the foam. This paper details the treatment of the Morrow Formation in Southern Oklahoma in which carbon dioxide is introduced into the gelled oil phase. This practice, while common in Canada, has not been utilized in the United States to a great extent. This paper deals with the development and laboratory testing of the fluid system, the treatment design, and the results of such treatments in Grady County in Oklahoma.

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