Methods of fracturing subterranean zones penetrated by well bores and fracturing fluids therefor

• US 6,986,391 B2
• Filed: 11/26/2002
• Issued: 01/17/2006
• Est. Priority Date: 11/26/2002
• Status: Active Grant

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Funkhouser, Gary P., Norman, Lewis R.
• Primary Examiner(s): SUCHFIELD, GEORGE A
• Application Number:
  US10/304,430
• Publication Number:
  US 20040211568A1
• Time in Patent Office: 1,148 Days
• Field of Search: 166/278, 166/280.1, 166/300, 166/308.5, 507/119, 507/120, 507/121, 507/224, 507/225, 507/226, 507/267, 507/271, 507/277, 507/903, 507/922
• US Class Current: 166/300
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 220/56 Acrylamide; Methacrylamide
• CPC Class Codes: C08F 220/585 and containing other heteroatoms, e.g. 2-acrylamido-2-methylpropane sulfonic acid [AMPS]
• CPC Class Codes: C09K 8/68 containing organic compounds
• CPC Class Codes: C09K 8/685 containing cross-linking agents
• CPC Class Codes: Y10S 507/903 Crosslinked resin or polymer
• CPC Class Codes: Y10S 507/922 Fracture fluid

Abstract

The present invention provides improved methods of fracturing subterranean zones penetrated by well bores and improved fracturing fluids. The fracturing fluids are basically comprised of water, a terpolymer of 2-acrylamido-2-methylpropane sulfonic acid, acrylamide and acrylic acid, or its salts, a cross-linking agent for the terpolymer and a delayed viscosity breaker for effecting a controlled reduction in the viscosity of the fracturing fluid.

Claims

1. A method of fracturing a subterranean zone comprising:

pumping a viscous aqueous fracturing fluid into said subterranean zone by way of a well bore at a rate and pressure sufficient to fracture said zone, said aqueous fracturing fluid comprising water, a terpolymer of 2-acrylamido-2-methylpropane sulfonic acid present in an amount of about 55 to about 65 weight %, acrylamide present in an amount of about 34.5 to about 44.5 weight % and acrylic acid, or its salts present in an amount of about 0.1 to about 1 weight %, a cross-linking agent for said terpolymer and a delayed viscosity breaker for effecting a controlled reduction in the viscosity of said fracturing fluid; and

creating a fracture in said formation.

2. The method of claim 1 defined further to include admixing a proppant with at least a portion of said fracturing fluid introduced into said subterranean zone and depositing said proppant in at least a portion of said created fracture.

3. The method of claim 1 wherein said cross-linking agent is selected from the group consisting of titanium(IV)(triethanolaminato)isopropoxide, tetrakis(triethanolaminato)zirconium(IV) and hafnium(IV)acetylacetonate.

4. The method of claim 3 wherein said cross-linking agent is tetrakis(triethanolaminato)zirconium(IV).

5. The method of claim 1 wherein said cross-linking agent is present in said fracturing fluid in an amount in the range of from about 0.02% to about 0.7% by weight of water therein.

6. The method of claim 1 wherein said delayed viscosity breaker is sodium bromate.

7. The method of claim 1 wherein said cross-linking agent is a source of titanium (IV), zirconium (IV) or hafnium (IV) ions.

8. The method of claim 1 wherein said delayed viscosity breaker is present in said fracturing fluid in an amount in the range of from about 0.01% to about 1.0% by weight of water therein.

9. The method of claim 1 wherein said fracturing fluid further comprises a buffer for maintaining the pH of said fracturing fluid in the range of from about 5 to about 6.

10. The method of claim 9 wherein said buffer is an acetic acid-acetate buffer.

11. The method of claim 9 wherein said buffer is present in said fracturing fluid in an amount in the range of from about 0.1% to about 1.0% by weight therein.

12. The method of claim 1 wherein said water is selected from the group consisting of fresh water and salt water.

13. The method of claim 1 wherein said terpolymer of 2-acrylamido-2-methylpropane sulfonic acid, acrylamide and acrylic acid is present in said fracturing fluid in an amount in the range of from about 0.24% to about 2% by weight of water therein.

14. A method of fracturing a subterranean zone comprising:

pumping a viscous aqueous fracturing fluid into said subterranean zone by way of a well bore at a rate and pressure sufficient to fracture said zone, said aqueous fracturing fluid being comprised of water, a terpolymer formed of from about 15 to about 80 weight % of 2-acrylamido-2-methylpropane sulfonic acid, from about 20 to about 85 weight % of acrylamide and up to about 10 weight % of acrylic acid or its salts present in said fracturing fluid in an amount of from about 0.24 to about 2% by weight of water therein;

a tetrakis(triethanolaminato)zirconium(IV) cross-linking agent present in said fracturing fluid in an amount of about 0.02 to about 0.7% by weight of water therein and a delayed viscosity breaker comprising sodium bromate present in an amount of from about 0.01 to about 1% by weight of water therein wherein said delayed viscosity breaker is encapsulated in a material which slowly releases said delayed viscosity breaker in said aqueous fracturing fluid; and

creating a fracture in said formation.

15. The method of claim 14 wherein said fracturing fluid further comprises an acetic acid-acetate buffer present in an amount sufficient to maintain the pH of said fracturing fluid in the range of from about 5 to about 6 during pumping.

16. The method of claim 14 defined further to include admixing a proppant with at least a portion of said fracturing fluid introduced into said subterranean zone and depositing said proppant in at least a portion of said created fracture.

17. A fluid composition comprising:

water;

a terpolymer of 2-acrylamido-2-methylpropane sulfonic acid, acrylamide and acrylic acid or its salts for viscosifying said fluid;

a cross-linking agent for said terpolymer; and

a delayed viscosity breaker for effecting a controlled reduction in the viscosity of said fluid.

18. The composition of claim 17 wherein said 2-acrylamido-2-methylpropane sulfonic acid or its salts is present in said terpolymer in an amount in the range of from about 15 weight % to about 80 weight %, said acrylamide is present in an amount in the range of from about 20 weight % to about 85 weight % and said acrylic acid or its salts is present in an amount in the range of from about 0 weight % to about 10 weight %.

19. The composition of claim 17 wherein said 2-acrylamido-2-methylpropane sulfonic acid or its salts is present in said terpolymer in an amount of about 55 to about 65 weight %, said acrylamide is present in an amount of about 34.5 to about 44.5 weight % and said acrylic acid or its salts is present in an amount of about 0.1 to about 1 weight %.

20. The composition of claim 17 wherein said terpolymer is present in said fluid composition in an amount in the range of from about 0.24% to about 2% by weight of water therein.

21. The composition of claim 17 wherein said cross-linking agent is selected from the group consisting of titanium(IV)(triethanolaminato)isopropoxide, tetrakis(triethanolaminato)zirconium(IV) and hafnium(IV)acetylacetonate.

22. The composition of claim 17 wherein said cross-linking agent is tetrakis(triethanolaminato)zirconium(IV).

23. The composition of claim 17 wherein said cross-linking agent is present in said fluid composition in an amount in the range of from about 0.02% to about 0.7% by weight of water therein.

24. The composition of claim 17 wherein said delayed viscosity breaker is sodium bromate.

25. The composition of claim 17 wherein said delayed viscosity breaker is present in said fluid composition in an amount in the range of from about 0.1% to about 1.0% by weight of water therein.

26. The composition of claim 17 wherein said fluid composition further comprises a buffer for maintaining the pH of said fluid composition in the range of from about 5 to about 6.

27. The composition of claim 26 wherein said buffer is an acetic acid-acetate buffer.

28. The composition of claim 27 wherein said buffer is present in said fluid composition in an amount in the range of from about 0.1% to about 1.0% by eight of water therein.

29. The composition of claim 17 wherein said water is selected from the group consisting of fresh water and salt water.

30. The composition of claim 17 wherein the delayed viscosity breaker is encapsulated in a material which slowly releases the delayed viscosity breaker in the fracturing fluid.

31. The composition of claim 30 wherein the material encapsulating the delayed viscosity breaker is precipitated silica, alumina, a zeolite, a clay, or a hydrotalcite.