The permeability of a siliceous formation is increased by injecting in sequence, a fluoboric acid solution followed by a mud acid (HCl/HF) solution. The method is particularly advantageous in formations which have a tendency to plug initially upon contact with mud acid, or with HCl commonly used as a preflush ahead of mud acid. When contacted initially with fluoboric acid, such formations show little or no plugging effects when subsequently treated with mud acid.
A gelled aqueous fluoboric acid fluid useful as a carrying fluid for particulate solids (i.e. "gravel") to position such gravel in a wellbore against a permeable incompetent formation to minimize the migration of sand and other granular material from the formation into the wellbore when fluids are subsequently produced from the formation. For example, an 80 lb. per 1000 gallon aqueous gel of hydroxyethylcellulose containing about 8 wt percent fluoboric acid in the aqueous solution is loaded with from 10 to 20 lbs. of 20/40 mesh (0.42-0.84 mm) gravel and placed between a screen or slotted liner in the perforated casing and the face of an incompetent formation in a wellbore.
Aqueous liquid compositions for increasing the permeability of a subterranean formation are disclosed, the compositions being characterized by provision of fluoborate anion (fluoboric acid) and a specified compound or compounds, or mixture thereof, which chelate aluminum ions and aluminum fluoride species. Methods of treating a subterranean formation by injection of the composition(s) into the formation are also described.
Aqueous liquid compositions for increasing the permeability of a subterranean formation are disclosed, the compositions being characterized by provision of fluoborate anion (fluoboric acid) and a specified compound or compounds, or mixture thereof, which chelate aluminum ions and aluminum fluoride species. Methods of treating a subterranean formation by injection of the composition(s) into the formation are also described.
Silicon carbide is used as a proppant during a hydraulic fracturing process. The proppant is particularly useful when steam-flooding or acidizing a formation. This proppant is crush resistant and impervious to HCl and HCl/HF acids. High formation and reservoir stimulation temperatures do not affect said proppant. Induced fractures are therefore more effectively propped.
A method for improving the permeability in a subterranean formation by acid treatment is disclosed. In this method, an aqueous acidizing solution containing hydrofluoric acid and excess fluoride is injected into the formation. The acidizing solution dissolves siliceous materials and reduces precipitation of dissolved species from the spent acidizing solution. Further, the acidizing solution has lower acidity than presently employed acidizing solutions and thus a reduced tendency to corrode wellbore tubing and equipment.
