Method for dissolving clay
AssigneeHalliburton Company
InventorBobby E. Hall
Life of this patent
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Abstract
A method for dissolving clay is disclosed which comprises contacting the clay, in alteration, with separate slugs of a hydrogen ion-containing chemical and a fluoride ion-containing chemical. The hydrogen ions and fluoride ions react on the surface of the clay to produce hydrofluoric acid to dissolve the clay. The method is particularly valuable in dissolving the clay in a mixture of sand and clay without dissolving the sand. This finds immediate value in the practice of acid treating subterranean sandstone formations to increase permeability or to restore permeability damaged by clay.
Claims15
A method of dissolving clay comprising treating said clay with at least a one-stage treatment of at least two different chemicals, in alternate slugs, said one stage being comprised of
- contacting said clay with a slug of a first chemical and thereafter
- contacting said clay with a slug of a second chemical different from said first chemical to thereby form hydrofluoric acid on the surface of said clay,
- wherein said first chemical supplies one of hydrogen ions or fluoride ions and said second chemical supplies fluoride ions, if hydrogen ions are supplied by said first chemical, or hydrogen ions if fluoride ions are supplied by said first chemical wherein said chemical supplying said fluoride ions is an aqueous solution of a fluoride-containing chemical selected from the group consisting of ammonium bifluoride, ammonium fluoride, and mixtures thereof.
A method of acid treating a subterranean sandstone formation comprising contacting said formation with an aqueous hydrochloric acid solution containing about 5 percent hydrochloric acid by weight of solution, contacting said formation with an aqueous solution containing about 3 percent hydrofluoric acid and about 12 percent hydrochloric acid by weight of solution, contacting said formation with at least one stage of a clay dissolving system wherein said stage consists of an aqueous solution containing about 3 percent ammonium fluoride by weight of solution, followed by an aqueous solution containing about 5 percent hydrochloric acid by weight of solution and thereafter contacting said formation with a 5 percent by weight solution of hydrochloric acid or a 3 percent by weight solution of ammonium chloride.
A method of acid treating a subterranean sandstone formation comprising
- contacting said formation with an aqueous hydrochloric acid solution containing about 5 percent hydrochloric acid by weight of solution;
- contacting said formation with at least one stage of a clay dissolving system wherein said stage consists of an aqueous solution containing about 3 percent ammonium fluoride by weight of solution, followed by an aqueous solution containing about 5 percent hydrochloric acid by weight of solution;
- contacting said formation with an aqueous solution containing about 3 percent hydrofluoric acid and about 12 percent hydrochloric acid by weight of solution;
- and
- thereafter contacting said formation with a 5 percent by weight solution of hydrochloric acid or a 3 percent by weight solution of ammonium chloride.
Dependencies are inferred from the claim text.