Abstract: A fracturing fluid composition for use in fracturing underground formations, such as oil or gas wells is described. It includes at least one anhydrous aliphatic alcohol, a modified guar gum polymer, and as a complexor, a sodium borate salt. A gel breaker which acts over a time period to degrade the guar gum cross linked polymer and thereby reduce the viscosity of the gel is provided as well to aid in the removal thereof from an oil or gas well that has been fractured by application of the fluid under pressure.

Abstract: A method is described for fracturing a subterranean formation penetrated by a wellbore. A fracturing fluid in the form of a mixture of liquid carbon dioxide and a liquid hydrocarbon component of specific characteristics is injected down the wellbore under pressure to cause fracturing. The hydrocarbon component contains at least 70 wt. % of C.sub.5 -C.sub.14 constituents and at least 8 wt. % aromatics and has an average molecular mass of less than 200, a pour point of less than -40.degree. C. and a density of from 0.77 to 0.85 g/ml at 15.degree. C. This hydrocarbon component provides a higher viscosity than the liquid carbon dioxide at lower temperatures and is also an excellent solvent, simplifying clean-up. The novel fracturing fluid may also contain the usual proppants.

Abstract: A viscosity-increased liquid carbon dioxide fracturing fluid is provided for the treatment of subterranean gas-bearing formations. The composition comprises liquid carbon dioxide which has been thickened by the addition of a small amount of a copolymer which is the reaction product of liquid carbon dioxide and an alkene oxide, preferably propylene oxide. The use of the copolymer thickener provides a CO.sub.2 fracturing fluid which may be pumped at a high rate, will not readily boil or foam, will carry a propping agent and will completely degrade within the formation.

Abstract: Underground formation fracturing compositions comprise a fracturing fluid composition for use in fracturing underground formations, such as oil or gas wells, comprising at least one substantially anhydrous aliphatic alcohol, a non-ionic homopolymer to form a gel with the alcohol and having a molecular weight from about 4 million to about 5 million, and as gel activating agent an alkali metal halide or an alkaline earth metal halide. A gel breaker comprising a salt containing iron or chromium, can be present.