Methods for controlling the rheological properties of viscoelastic surfactants based fluids

• US 20030134751A1
• Filed: 12/19/2002
• Published: 07/17/2003
• Est. Priority Date: 04/04/2001
• Status: Active Grant

• Current Assignee: Schlumberger Technologies Incorporated (Schlumberger NV), Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Nelson, Erik, Sullivan, Philip, Lee, Jesse, England, Kevin
• Granted Patent: US 7,084,095 B2
• Time in Patent Office: Days
• US Class Current: 507/200
• CPC Class Codes: C09K 2208/30 Viscoelastic surfactants [VES]
• CPC Class Codes: C09K 8/536 characterised by their form or by the form of their components, e.g. encapsulated material
• CPC Class Codes: C09K 8/5753 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: C09K 8/62 Compositions for forming crevices or fractures
• CPC Class Codes: C09K 8/68 containing organic compounds
• CPC Class Codes: C09K 8/74 combined with additives added for specific purposes
• CPC Class Codes: C09K 8/92 characterised by their form or by the form of their components, e.g. encapsulated material C09K8/70 takes precedence
• CPC Class Codes: Y10S 507/921 Specified breaker component for emulsion or gel

Abstract

It was found that the addition of polymers to viscoelastic surfactant base system allows to adjust the rheological properties of the base fluid. Depending in particular on one side of the ratio of the concentration of added polymer and the concentration of viscoelastic surfactant and on the other side of the molecular weight of the added polymer, the same polymer—or the same type of polymer—may perform different functions such as viscosity enhancer, viscosity breaker or viscosity-recovery enhancer

Claims

1. A method of treating a subterranean formation comprising the steps of:

(a) injecting down a well an aqueous fluid comprising a thickening amount of a viscoelastic surfactant;

(b) providing a polymer additive that causes a change in theology of the fluid under downhole conditions.

2. The method of claim 1, wherein said polymer additive causes a reduction in viscosity of the fluid.

3. The method of claim 2, wherein said polymer has a molecular weight of less than about 25,000.

4. The method of claim 2, wherein said viscoelastic surfactant is an anionic surfactant.

5. The method of claim 2, wherein said viscoelastic surfactant is a cationic surfactant.

6. The method of claim 2, wherein said viscoelastic surfactant is a zwitterionic surfactant.

7. The method of claim 1, wherein said polymer additive causes an increase in viscosity of the fluid.

8. The method of claim 7, wherein said polymer has a molecular weight greater than about 25,000 and the weight ratio of polymer to the weight of viscoelastic surfactant is above 7%.

9. The method of claim 1, wherein said polymer additive causes an increase in viscosity of the fluid.

10. The method of claim 7, wherein said viscoelastic surfactant is EMHAC.

11. The method of claim 3, wherein said viscoelastic surfactant comprises an oleic acid.

12. The method of claim 5, wherein said viscoelastic surfactant is a betaine.

13. The method of claim 1, wherein said polyelectrolyte is encapsulated.

14. The method of claim 1, wherein said polyelectrolyte comprises a non-ionic polymer.

15. The method of claim 1, wherein said polymer is a non-ionic polymer.

16. The method of claim 6, wherein said non-ionic polymer is polypropylene glycol.

17. The method of claim 1, wherein said polyelectrolyte comprises an anionic polymer.

18. The method of claim 1, wherein said polyelectrolyte is a cationic polymer.

19. The method of claim 14, wherein said anionic polymer is sodium polynapthalene sulfonate.

20. The method of claim 1, wherein said polyelectrolyte is polystyrene sulfonate.

21. The method of claim 1, wherein said polyelectrolyte is a styrene/maleic anhydride sulfonate.