Settable compositions and methods of use

1. A method for introducing a settable composition into a wellbore, the method comprising:

providing a settable composition comprising pumice, hydrated lime, a set retarder, and water, wherein the pumice, hydrated lime, and set retarder form a suspension in the water;

introducing the settable composition into a wellbore; and

allowing the settable composition to remain static in the wellbore, wherein the settable composition remains in a pumpable fluid state for a period of about 1 day or longer while static in the wellbore;

wherein the settable composition is activated by inclusion of a set activator prior to the step of introducing the settable composition into the wellbore.

2. The method of claim 1 wherein the introducing the settable composition into the wellbore displaces at least a portion of a drilling fluid from a subterranean formation.

3. The method of claim 2 further comprising:

introducing a cement composition into the wellbore so as to at least partially displace the settable composition from the subterranean formation, wherein a portion of the settable composition remains in the wellbore;

allowing the cement composition to set in the wellbore; and

allowing the portion of the settable composition remaining in the wellbore to set.

4. The method of claim 1 , wherein the settable composition is introduced into the wellbore such that the settable composition forms a puddle in the bottom of the wellbore, and wherein the method further comprises:

placing a conduit into the puddle formed by the settable composition in the bottom of the wellbore; and

allowing the settable composition to set in an annulus surrounding the conduit.

5. The method of claim 1 wherein the set retarder comprises at least one retarder selected from the group consisting of a phosphonic acid, a phosphonic acid derivative, a lignosulfonate, a salt, an organic acid, a carboxymethylated hydroxyethylated cellulose, a synthetic co- or ter-polymer comprising sulfonate and carboxylic acid groups, and a borate compound.

6. The method of claim 5 wherein the settable composition comprises an additional set retarder that is distinct from the set retarder.

7. The method of claim 1 wherein the settable composition further comprises a dispersant.

8. The method of claim 7 wherein the dispersant comprises at least one dispersant selected from the group consisting of a sulfonated-formaldehyde-based dispersant, a polycarboxylated ether dispersant, and any combination thereof.

9. A method for introducing a settable composition into a wellbore, the method comprising:

providing a settable composition comprising pumice, hydrated lime, a set retarder, and water wherein the set retarder comprises a phosphonic acid derivative, and wherein the settable composition further comprises a polycarboxylated ether dispersant;

introducing the settable composition into a wellbore; and

allowing the settable composition to remain static in the wellbore, wherein the settable composition remains in a pumpable fluid state for a period of about 1 day or longer while static in the wellbore.

10. The method of claim 1 where the settable composition further comprises at least one set activator selected from the group consisting of zeolites, amines, silicates, Groups IA and IIA hydroxides, monovalent salts, divalent salts, nanosilica, and polyphosphates.

11. The method of claim 1 wherein the settable composition remains in a fluid state of less than 70 Bc for a time period of about 5 days or longer while static in the wellbore.

12. The method of claim 1 wherein the settable composition has a compressive strength of less than about 50 psi and a yield point of less than about 20 lbs./ft. 2 after remaining static in the wellbore for a period of about 1 day or longer.

13. A method for introducing a settable composition into a wellbore, the method comprising:

providing a settable composition comprising pumice, hydrated lime, a set retarder, and water, wherein the pumice, hydrated lime, and set retarder form a suspension in the water;

introducing the settable composition into the wellbore such that the settable composition forms a puddle in the bottom of the wellbore; and

allowing the settable composition to remain static in the wellbore, wherein the settable composition remains in a pumpable fluid state for a period of about 1 day or longer while static in the wellbore;

wherein the settable composition is activated by inclusion of a set activator prior to the step of introducing the settable composition into the wellbore.

14. The method of claim 13 further comprising placing a conduit into the puddle formed by the settable composition in the bottom of the wellbore; and allowing at least a portion of the settable composition to set in an annulus surrounding the conduit.

15. The method of claim 13 wherein the set retarder comprises at least one retarder selected from the group consisting of a phosphonic acid, a phosphonic acid derivative, a lignosulfonate, a salt, an organic acid, a carboxymethylated hydroxyethylated cellulose, a synthetic co- or ter-polymer comprising sulfonate and carboxylic acid groups, and a borate compound.

16. The method of claim 13 wherein the settable composition further comprises at least one set activator selected from the group consisting of zeolites, amines, silicates, Groups IA and IIA hydroxides, monovalent salts, divalent salts, nanosilica, and polyphosphates.

17. The method of claim 13 wherein the settable composition remains in a fluid state of less than 70 Bc for a time period of about 5 days or longer while static in the wellbore.

18. The method of claim 13 wherein the settable composition has a compressive strength of less than about 50 psi and a yield point of less than about 20 lbs./ft. 2 after remaining static in the wellbore for a period of about 1 day or longer.

19. A settable composition system for setting a casing comprising:

wellbore casing disposed within a wellbore;

a settable composition for placing into the wellbore and capable of remaining in a fluid state of less than 70 Bc for a time period of about 1 day or longer while static in the wellbore, wherein the settable composition comprises:

water,

pumice,

hydrated lime,

a set retarder, and

a set activator;

wherein the pumice, hydrated lime, and set retarder form a suspension in the water;

wherein settable components present in the settable composition consist essentially of the pumice and hydrated lime;

mixing equipment capable of mixing the settable composition; and

pumping equipment capable of pumping the settable composition into the wellbore.

20. The system of claim 19 wherein the settable composition is capable of remaining in a fluid state of less than 70 Bc for a time period of about 5 days or longer while static in the wellbore.