Compositions and methods for cementing a wellbore using microbes or enzymes

1. A method of cementing a wellbore penetrating a subterranean formation, the method comprising:

injecting into the wellbore a settable slurry comprising: an aqueous carrier; an aggregate; urea; a calcium ion source; and a calcium carbonate producing agent comprising a microbe, an enzyme, or a combination comprising at least one of the foregoing;

wherein the settable slurry further comprises an enzyme stabilizer, the enzyme stabilizer comprising casein, albumin, powdered milk, whey protein, or bovine serum albumin, or a combination comprising at least one of the foregoing;

and allowing the settable slurry to set.

2. The method of claim 1 further comprising forming the settable slurry by mixing the aqueous carrier; the aggregate; urea; the calcium ion source; and the calcium carbonate producing agent.

3. The method of claim 1 , wherein injecting the settable slurry comprises pumping the settable slurry via a tubular in the wellbore.

4. The method of claim 1 , wherein injecting the settable slurry comprises pumping the settable slurry into an annulus between a tubular and a wall of the wellbore via the tubular.

5. The method of claim 1 , wherein microbe is from a genus selected from Bacillus sp., Sporosarcina sp., Spoloactobacilus sp., Clostridium sp., Desulfotomaculum sp., or a combination thereof.

6. The method of claim 1 , wherein the microbe comprises Sporosarcina pasteurii; Bacillus megaterium, Sporosarcina ureae; Pseudomonas aeruginosa; Proteus Vulgaris; Bacillus sphaericus; Myxococcus xanthus; Leuconostoc mesenteroides; Bacillus subtilis; Deleya halophila; Halomonas eurihalina, Proteus mirabilis ; or Helicobacter pylori , or a combination comprising at least one of the foregoing.

7. The method of claim 6 , wherein the settable slurry further comprises a nutrient for the microbe.

8. The method of claim 1 , wherein the microbe comprises Sporosarcina pasteurii.

9. The method of claim 1 , wherein the enzyme comprises urease, amidase, carbonic anhydrase, glutamade dehydrogenase, glutamate synthase, or a combination comprising at least one of the foregoing.

10. The method of claim 1 , wherein the calcium ion source comprises calcium chloride, calcium bromide, calcium nitrate, or a combination comprising at least one of the foregoing.

11. The method of claim 1 , wherein the aggregate comprises sand, gravel, crushed stone, slag, recycled concrete, silica, grass spheres, limestone, feldspar, or a combination comprising at least one of the foregoing.

12. The method of claim 1 , wherein the settable composition comprises solids in an amount of about 50 wt. % to about 95 wt. % based on the total weight of the settable slurry.

13. The method of claim 1 , wherein the settable composition further comprises an additive which comprises a reinforcing agent, a self-healing additive, a fluid loss control agent, a weighting agent, an extender, a foaming agent, a dispersant, a thixotropic agent, a bridging agent or lost circulation material, a clay stabilizer, or a combination comprising at least one of the foregoing.

14. The method of claim 1 , wherein the wellbore is a horizontal, lateral or deviated wellbore.

15. The method of claim 1 , wherein the settable slurry remains pumpable at wellbore conditions until setting.

16. The method of claim 1 , wherein the calcium ion source is present in an amount effective to provide about 2 mM to about 2.5 M of calcium ions in the settable slurry.

17. The method of claim 1 , wherein the calcium ion source is present in an amount effective to provide about 250 mM to about 1.8 M of calcium ions in the settable slurry.

18. A settable slurry for cementing a wellbore penetrating a subterranean formation, the settable slurry comprising:

an aqueous carrier;

an aggregate which comprises sand, gravel, crushed stone, slag, recycled concrete, silica, grass spheres, limestone, feldspar, or a combination comprising at least one of the foregoing aggregate;

urea;

a calcium ion source;

a calcium carbonate producing agent comprising a microbe, an enzyme, or a combination comprising at least one of the foregoing;

an enzyme stabilizer, the enzyme stabilizer comprising casein, albumin, powdered milk, whey protein, or bovine serum albumin, or a combination comprising at least one of the foregoing; and

solids in an amount of about 50 wt. % to about 95 wt. % based on the total weight of the settable slurry.

19. The settable slurry of claim 18 , wherein the microbe is from a genus selected from Bacillus sp., Sporosarcina sp., Spoloactobacilus sp., Clostridium sp., Desulfotomaculum sp., or a combination thereof.

20. The settable slurry of claim 18 , wherein the microbe comprises Sporosarcina pasteurii; Sporosarcina ureae, Bacillus megaterium, Pseudomonas aeruginosa; Proteus Vulgaris; Bacillus sphaericus; Myxococcus xanthus; Leuconostoc mesenteroides; Bacillus subtilis; Deleya halophila; Halomonas eurihalina, Proteus mirabilis ; or Helicobacter pylori , or a combination comprising at least one of the foregoing microbe; and the enzyme comprises urease.

21. The settable slurry of claim 18 , wherein the settable slurry has a pH of about 7 to about 10.

22. The settable slurry of claim 18 , wherein the urea is present in an amount of about 5 mM to about 2 M based on the total volume of the settable slurry.

23. The settable slurry of claim 18 , wherein the aggregate is present in an amount of about 10 wt. % to about 95 wt. % based on the total weight of the settable slurry.