Liquid carbon dioxide has long been employed in aqueous acidizing solutions to retard the acid reaction rate and aid in recovering the spent acid. However, its effectiveness is limited due to its relatively low solubility in aqueous acid solutions. For example, at 75.degree.C and under 1000 psi pressure carbon dioxide is soluble in water only to the extent of about 0.033 gram per gram of water. It has also been long recognized that an alcohol may be added to an aqueous acidizing solution which is employed to stimulate the production of fluids from subterranean formations. For example, see the teachings of U.S. Pat. Nos. 2,024,718 and 2,059,459.
It has now been discovered that greatly superior acidizing stimulation treatments can be performed by employing a mixture of an acid, an alcohol and carbon dioxide as the acidizing solution.
USPTO Backgrounds
USPTO Backgrounds