Methods of delivering calcium carbonate producing microbes or enzymes downhole

1. A method of delivering a microbe or enzyme to a selected location, the method comprising:

conveying a coated aggregate to a selected location; the coated aggregate comprising an aggregate and a coating disposed on the aggregate; the coating comprising a polymer matrix and a calcium carbonate producing agent comprising a microbe, an enzyme, or a combination comprising at least one of the foregoing;

releasing the calcium carbonate producing agent from the coating; and

contacting the released calcium carbonate producing agent with urea, a calcium ion source, and water.

2. The method of claim 1 , wherein conveying the coated aggregate comprises pumping the coated aggregate into a wellbore penetrating a subterranean formation.

3. The method of claim 2 , wherein conveying the coated aggregate comprises pumping a settable composition comprising the coated aggregate into the wellbore.

4. The method of claim 3 , wherein the settable composition further comprises an uncoated aggregate.

5. The method of claim 4 , wherein the weight ratio of the coated aggregate relative to the uncoated aggregate is about 1:99 to about 99:1.

6. The method of claim 4 , wherein the weight ratio of the coated aggregate relative to the uncoated aggregate is about 1:9 to about 9:1.

7. The method of claim 4 , wherein the sum of the weights of the coated aggregate and uncoated aggregate is about 10 wt. % to about 95 wt. % based on the total weight of the settable composition.

8. The method of claim 4 , wherein the sum of the weights of the coated aggregate and uncoated aggregate is about 20 wt. % to about 70 wt. % based on the total weight of the settable composition.

9. The method of claim 3 , further comprising allowing the settable composition to set.

10. The method of claim 9 , wherein the calcium carbonate producing agent is present in an amount effective to set the settable composition in about 10 minutes to about 48 hours in the wellbore.

11. The method of claim 1 ,

the released calcium carbonate producing agent is contacted with urea, the calcium ion source, water, and a nutrient provided that the calcium carbonate producing agent comprises a microbe.

12. The method of claim 11 , wherein the nutrient comprises yeast extract, peptone from soy, lactose mother liquor, corn steep liquor, or a combination comprising at least one of the foregoing.

13. The method of claim 1 , wherein releasing the calcium carbonate producing agent from the coating comprises abrading the coated aggregate with an uncoated aggregate.

14. The method of claim 1 , further comprising coating the aggregate to form the coated aggregate.

15. The method of claim 14 , wherein coating the aggregate comprises spray coating, drum coating, pan coating, fluid bed coating, continuous pour coating, or a combination comprising at least one of the foregoing.

16. The method of claim 1 , wherein the polymer matrix comprises an epoxy, a phenolic resin, a melamine-formaldehyde, a polyurethane, a carbamate, a polycarbodiimide, a polyamide, a polyamide imide, a furan resin, a polyolefin, or a combination comprising at least one of the foregoing.

17. 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.

18. 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; and the enzyme comprises urease, amidase, carbonic anhydrase, glutamade dehydrogenase, glutamate synthase, or a combination comprising at least one of the foregoing.

19. The method of claim 1 , wherein the coating further comprises urea, a calcium ion source, a nutrient for the microbe, a stabilizer for the enzyme, or a combination comprising at least one of the foregoing.

20. The method of claim 19 , wherein the nutrient comprises yeast extract, peptone from soy, lactose mother liquor, corn steep liquor, or a combination comprising at least one of the foregoing.

21. The method of claim 19 , wherein the stabilizer comprises casein, albumin, powdered milk, whey protein, or bovine serum albumin, or a combination comprising at least one of the foregoing.

22. The method of claim 1 , wherein the coating has a thickness of about 0.1 to about 50 micrometers.

23. 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.