Fluoro-inorganics for well cleaning and rejuvenation
The present invention generally relates to methods for increasing recovery of crude oil from a subterranean hydrocarbon-containing formation and for removing or inhibiting deposits in a well, the methods comprising contacting an acid composition that comprises a salt of a nitrogen base having a fluoro inorganic anion with the well or the formation.
1. A method for increasing recovery of crude oil from a subterranean hydrocarbon-containing formation, the method comprising:
injecting an acid composition comprising a salt of a nitrogen base having a fluoro inorganic anion into a well which is in contact with the subterranean hydrocarbon-containing formation.
2. The method of claim 1 , wherein the acid composition is diverted toward a zone of the subterranean hydrocarbon-containing formation that has a lower permeability to fluid than an adjacent zone.
3. The method of claim 2 , wherein the subterranean hydrocarbon-containing formation comprises a sandstone reservoir or a carbonate reservoir.
4. The method of claim 3 , wherein the subterranean hydrocarbon-containing formation comprises a carbonate reservoir.
5. The method of claim 1 , wherein the acid composition further comprises a surfactant.
6. The method of claim 5 , wherein the surfactant is a nonionic surfactant.
7. The method of claim 1 , wherein the fluoro inorganic anion comprises a borate ion, a phosphate ion, or a combination thereof.
8. The method of claim 7 , wherein the fluoro inorganic anion is tetrafluoroborate, hexafluorophosphate, or a combination thereof.
9. The method of claim 8 , wherein the fluoro inorganic anion comprises tetrafluoroborate.
10. The method of claim 1 , wherein the nitrogen base is urea, biuret, an alkyl urea, an alkanolamine, an alkylamine, a dialkylamine, a trialkylamine, an alkyldiamine, an alkyltriamine, an alkyltetramine, a polyamine, an acrylamide, a polyacrylamide, a vinyl pyrollidone, a polyvinyl pyrollidone, or a combination thereof.
11. The method of claim 10 , wherein the nitrogen base comprises urea.
12. The method of claim 1 , wherein the fluoro inorganic anion comprises tetrafluoroborate and the nitrogen base comprises urea and the molar ratio of urea to tetrafluroboric acid used to prepare the salt is 1:3 to 3:1.
13. The method of claim 12 , wherein the concentration of the acid composition is from about 5 wt. % to about 30 wt. % based on the total weight of the aqueous mixture injected.
14. A method for increasing recovery of a geothermal fluid from a subterranean geothermal fluid-containing formation, the method comprising:
injecting an acid composition comprising a salt of a nitrogen base having a fluoro inorganic anion into a well which is in contact with the subterranean geothermal fluid-containing formation.
15. The method of claim 14 , wherein the acid composition is diverted toward a zone of the subterranean geothermal fluid-containing formation that has a lower permeability to fluid than an adjacent zone.
16. The method of claim 15 , wherein the subterranean geothermal fluid-containing formation comprises a sandstone reservoir or a carbonate reservoir.
17. The method of claim 16 , wherein the subterranean geothermal fluid-containing formation comprises a carbonate reservoir.
18. A method for removing an inorganic or organic deposit by contacting an acid composition with an internal surface of a well, the surface being in contact with a liquid containing deposit-forming species,
wherein the acid solution comprises a salt of a nitrogen base having a fluoro inorganic anion.
19. The method of claim 18 , wherein the well is an oil well, a geothermal well, a disposal well, or a reinjection well.
20. The method of claim 18 , wherein the deposit is a metal oxalate, a metal carbonate, a silicate, a metal sulfate, or a combination thereof.