Methods and compositions for treating subterranean zones
Methods and compositions for breaking treatment fluids utilized in the stimulation of a subterranean formation.
1. A treating fluid composition comprising:
water, a viscosity increasing polymer and a water-soluble strongly delayed polymer breaker composition, comprising a hydrogen peroxide source, a ferrous ion source and a chelating agent, wherein the water soluble, strongly delayed polymer breaker composition comprises a molar ratio of the chelating agent to the ferrous ion source of from 3:1 to 6:1.
2. The treating fluid composition according to claim 1 wherein the hydrogen peroxide source is selected from the group consisting of sodium perborate tetrahydrate and hydrogen peroxide.
3. The treating fluid composition according to claim 1 wherein the ferrous ion source is selected from the group consisting of iron (II) sulfate heptahydrate, iron (II) chloride and iron (II) gluconate.
4. The treating fluid composition according to claim 1 wherein the chelating agent is selected from the group consisting of citric acid, sodium citrate and iminodiacetic acid.
5. The treating fluid composition according to claim 1 wherein the water soluble, strongly delayed polymer breaker composition comprises a molar excess of the chelating agent relative to the ferrous ion source.
6. The treating fluid composition according to claim 1 wherein the water soluble, strongly delayed polymer breaker composition further comprises sodium chloride.
7. The treating fluid composition according to claim 1 wherein the water soluble, strongly delayed polymer breaker composition has a pH in the range of from about 3 to about 7.
8. The treating fluid composition according to claim 1 wherein the viscosity increasing polymer comprises a polysaccharide.
9. The treating fluid composition according to claim 8 wherein the viscosity increasing polymer comprises a polysaccharide selected from the group consisting of biopolymers and modified gums or celluloses and derivatives thereof.
10. The treating fluid composition according to claim 9 wherein the viscosity increasing polymer comprises xanthan gum.
11. The treating fluid composition according to claim 1 wherein the temperature of the subterranean zone ranges from about 80° F. to about 150° F.
12. A treating fluid composition comprising:
water and a water-soluble strongly delayed polymer breaker composition, comprising a hydrogen peroxide source, a ferrous ion source and a chelating agent, wherein the water soluble, strongly delayed polymer breaker composition comprises a molar ratio of the chelating agent to the ferrous ion source of from 3:1 to 6:1.
13. The treating fluid composition according to claim 12 wherein the hydrogen peroxide source is selected from the group consisting of sodium perborate tetrahydrate and hydrogen peroxide.
14. The treating fluid composition according to claim 12 wherein the ferrous ion source is selected from the group consisting of iron (II) sulfate heptahydrate, iron (II) chloride and iron (II) gluconate.
15. The treating fluid composition according to claim 12 wherein the chelating agent is selected from the group consisting of citric acid, sodium citrate and iminodiacetic acid.
16. The treating fluid composition according to claim 12 wherein the water-soluble, strongly delayed polymer breaker composition comprises a molar excess of the chelating agent relative to the ferrous ion source.
17. The treating fluid composition according to claim 12 wherein the water-soluble, strongly delayed polymer breaker composition further comprises sodium chloride.
18. The treating fluid composition according to claim 12 wherein the water soluble, strongly delayed polymer breaker composition has a pH in the range of from about 3 to about 7.
19. The treating fluid composition according to claim 12 wherein the temperature of the subterranean zone ranges from about 80° F. to about 150° F.