Claims
- 1. A process for acidizing a subterranean formation penetrated by at least one well comprising injecting into said formation, without a crosslinking agent, a water soluble thickened acid composition comprising: (1) water: (2) acid; and (3) a linear copolymer prepared from the monomers consisting of a N-vinyl lactam monomer and an alpha, beta-unsaturated amide monomer of the formula ##STR10## where R' is methyl, ethyl or hydrogen, said copolymer being made in the absence of a crosslinking agent during polymerization of the monomers.
- 2. A method according to claim 1 wherein said acidizing is carried out under matrix conditions.
- 3. A method according to claim 1 wherein said composition is injected under sufficient pressure to fracture said formation.
- 4. A method according to claim 1 wherein said subterranean formation exhibits hostile conditions as defined by a temperature of 170.degree. to 400.degree. F.
- 5. A method according to claim 4 wherein said hostile conditions further comprise a multivalent electrolyte content of at least 500 ppm.
- 6. A method according to claim 4 wherein said acid has a concentration of at least 15 weight percent.
- 7. A process according to claim 1 comprising in addition back producing at least a substantial part of said thus injected composition after said acidizing is effected.
- 8. A method according to claim 1 wherein said composition is injected to acid etch subsequent to injection of a hydraulic fracturing fluid.
- 9. A method according to claim 1 wherein said acidizing is carried out under mud acidizing conditions.
- 10. A method according to claim 1 wherein said copolymer is produced by inverse emulsion polymerization.
- 11. A method according to claim 1 wherein said copolymer comprises 30-70 weight per cent of said N-vinyl lactam and 30 to 70 weight percent of said unsaturated amide.
- 12. A method according to claim 11 wherein said N-vinyl lactam is N-vinyl-2-pyrrolidone, said unsaturated amide is acrylamide or N,N-dimethyl acrylamide and said acid is hydrochloric acid.
- 13. A method according to claim 12 wherein said copolymer is produced by inverse emulsion polymerization.
- 14. A method according to claim 1 wherein copolymer is produced by irradiation initiation.
- 15. A method according to claim 1 wherein said copolymer is prepared using a chemical initiator at a temperature wherein the range of 5.degree. to 25.degree. C.
- 16. A method according to claim 1 wherein said acid is a combination of (1) in situ generated HF and HCl or (2) an organic acid and HCl.
- 17. A method according to claim 16 wherein said copolymer is present in an amount within the range of 0.1 to 2 weight percent based on the total weight of said composition and said acid has a concentration within the range of 15 to 28 weight percent based on the total weight of said acid and said water.
- 18. A method according to claim 1 wherein said acid has a concentration within the range of 15 to 28 weight percent based on the weight of said acid and said water.
- 19. A method according to claim 1 wherein said acid is hydrochloric acid.
- 20. A method according to claim 1 wherein a foaming agent selected from nitrogen or carbon dioxide and a surfactant are also present.
- 21. A method according to claim 20 wherein said copolymer is made at a pH within the range of 8.5 to 10.5.
- 22. A method according to claim 1 wherein said copolymer is made at a pH within the range of 8.5 to 10.5.
- 23. A method according to claim 1 wherein said copolymer is made at a temperature within the range of 5.degree. to 25.degree. C.
- 24. A method according to claim 1 wherein said copolymer is produced in an aqueous solution of electrolytes.
- 25. A process for acidizing a subterranean formation penetrated by at least one well comprising injecting into said formation without a crosslinking agent a composition comprising:
- (1) water;
- (2) an acid; and
- (3) a water thickening amount of a copolymer, made from a monomer composition consisting of a N-vinyl lactam and an alpha, beta-unsaturated amide of the formula sodium ##STR11## where R' is methyl, ethyl or hydrogen, said copolymer being made in the absence of a crosslinking agent during polymerization of the monomers,
- said copolymer being produced in a mixed electrolyte aqueous solvent comprising at least one electrolyte selected from a first group consisting of alkali metal salts and at least one electrolyte selected from a second group consisting of alkaline earth metal salts.
- 26. A method according to claim 25 wherein said acidizing is carried out under matrix acidizing conditions.
- 27. A method according to claim 25 wherein said composition is injected under sufficient pressure to fracture said formation.
- 28. A method according to claim 25 wherein said subterranean formation is a hostile environment.
- 29. A method according to claim 25 wherein said copolymer is a linear copolymer.
BACKGROUND OF THE INVENTION
This application is a division of application Ser. No. 586,504, filed Mar. 5, 1984, now U.S. Pat. No. 4,578,201.
US Referenced Citations (25)
Divisions (1)
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Number |
Date |
Country |
Parent |
586504 |
Mar 1984 |
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