Sealant compositions for use in subterranean formation operations

1. A method comprising:

providing a sealant composition comprising an aqueous base fluid, a crosslinkable polymer composition, and a density segregation prevention agent,

wherein the crosslinkable polymer composition comprises a crosslinkable organic polymer and a crosslinker, wherein the crosslinker is an organic polymer, an organic copolymer, or any combination thereof;

introducing a particulate density reducing agent into the sealant composition,

wherein the particulate density reducing agent causes the sealant composition to adopt a reduced density as compared to the sealant composition without the particulate density reducing agent, thereby creating a reduced density sealant composition;

introducing the reduced density sealant composition into a subterranean formation; and

crosslinking the reduced density sealant composition into a gel to form a seal in the subterranean formation;

wherein the density segregation prevention agent is selected from a welan gum and a diutan, and the density segregation agent provides stability to the sealant composition against settling, density segregation, and/or phase separation, wherein upon injection of a gas, bubbles form within the gel and a size of the bubbles is uniform for at least a period of about 18 hours.

2. The method of claim 1 , wherein the crosslinkable organic polymer is an acrylamide-based polymer; any copolymer thereof; and any combination thereof.

3. The method of claim 1 , wherein the crosslinkable organic polymer is selected from the group consisting of a polyacrylamide; an acrylamide copolymer; an acrylamide-co-t-butylacrylate copolymer; a 2-acrylamido-2-methylpropane sulfonic acid/acrylamide copolymer; a sulfonated styrene/maleic anhydride copolymer; a vinylpyrrolidone/2-acrylamido-2-methylpropane sulfonic acid/acrylamide terpolymer; a 2-acrylamido-2-methylpropane sulfonic acid/N—N-dimethylacrylamide/acrylamide terpolymer; a polyketone; any derivative thereof; and any combination thereof.

4. The method of claim 1 , wherein the crosslinker is an amine-containing polymer; any copolymer thereof; and any combination thereof.

5. The method of claim 1 , wherein the crosslinker is selected from the group consisting of a polyalkyleneimine; a polyalkylenepolyamine; a polyfunctional aliphatic amine; a chitosan; a polylysine; a vinyl alcohol/vinylamine copolymer; any derivative thereof; and any combination thereof.

6. The method of claim 1 , wherein the crosslinkable organic polymer and the crosslinker are water-soluble.

7. The method of claim 1 , wherein the particulate density reducing agent is selected from the group consisting of a deformable low-density particulate; a non-deformable low-density particulate; and any combination thereof.

8. The method of claim 7 , wherein the deformable low-density particulate is selected from the group consisting of a hollow elastomer; a solid elastomer; an elastomer encapsulating a droplet of a volatile organic fluid; and any combination thereof.

9. The method of claim 8 , wherein the elastomer forming the deformable low-density particulate is selected from the group consisting of an ethylene-propylene rubber; an ethylene-propylene-diene rubber; a styrene-butadiene copolymer; an acrylonitrile-butadiene-styrene rubber; a vinylidenefluoride homopolymer; a vinylidenedichloride polymer; a vinylidenedichloride copolymer; and any combination thereof.

10. The method of claim 7 , wherein the non-deformable low-density particulate is selected from the group consisting of a hollow glass particulate; a hollow fly ash particulate; a solid fly ash particulate; a hollow polypropylene particulate; a solid polypropylene particulate; a hollow polyethylene particulate; a solid polyethylene particulate; a hollow polystyrene particulate; a solid polystyrene particulate; a hollow polyacrylate particulate; a solid polyacrylate particulate; and any combination thereof.

11. The method of claim 1 , wherein the density segregation prevention agent is a welan gum.

12. A method comprising:

providing a sealant composition comprising an aqueous base fluid, a crosslinkable polymer composition, a density segregation prevention agent, and a gas,

wherein the crosslinkable polymer composition comprises a crosslinkable organic polymer selected from an acrylamide-based polymer any copolymer thereof or any combination thereof and a cross-linker selected from an amine-containing polymer, any copolymer thereof, or any combination thereof;

introducing a particulate density reducing agent into the sealant composition,

wherein the particulate density reducing agent is selected from the group consisting of a deformable low-density particulate; a non-deformable low-density particulate; and any combination thereof,

wherein the particulate density reducing agent causes the sealant composition to adopt a reduced density as compared to the sealant composition without the particulate density reducing agent, thereby creating a reduced density sealant composition;

introducing the reduced density sealant composition into a subterranean formation; and

crosslinking the reduced density sealant composition into a gel, to form a seal in the subterranean formation, wherein the gas in the sealant composition forms bubbles in the gel;

wherein the density segregation prevention agent is selected from a welan gum and a diutan, and the density segregation agent provides stability to the sealant composition against settling, density segregation, and/or phase separation whereby a size of the bubbles is uniform for at least a period of about 18 hours;

wherein the reduced density sealant composition comprising the gas has a foam quality in the range of from about 30% to about 80%.

13. The method of claim 12 , wherein the crosslinkable organic polymer is selected from the group consisting of a polyacrylamide; an acrylamide copolymer; an acrylamide-co-t-butylacrylate copolymer; a 2-acrylamido-2-methylpropane sulfonic acid/acrylamide copolymer; a sulfonated styrene/maleic anhydride copolymer; a vinylpyrrolidone/2-acrylamido-2-methylpropane sulfonic acid/acrylamide terpolymer; a 2-acrylamido-2-methylpropane sulfonic acid/N—N-dimethylacrylamide/acrylamide terpolymer; a polyketone; any derivative thereof; and any combination thereof.

14. The method of claim 12 , wherein the crosslinker is selected from the group consisting of a polyalkyleneimine; a polyalkylenepolyamine; a polyfunctional aliphatic amine; a chitosan; a polylysine; a vinyl alcohol/vinylamine copolymer; any derivative thereof; and any combination thereof.

15. The method of claim 12 , wherein the sealant composition further comprises a stabilizer selected from the group consisting of a foaming surfactant; a hydrophobically modified water-soluble polymer; and any combination thereof;

wherein the combination of the density segregation agent and the stabilizer provides an enhanced stability in a composition to the sealant composition against settling, density segregation, and/or phase separation whereby a size of the bubbles is uniform for at least a period of about 18 hours at a temperature in the range of about 25° C. to about 176.7° C.;

wherein the enhanced stability is not observed in a sealant composition having only a stabilizer or only a density segregation prevention agent.

16. The method of claim 15 , wherein the hydrophobically modified water-soluble polymer is formed by hydrophobic modification of a hydrophilic polymer.

17. The method of claim 15 , wherein the hydrophobically modified water-soluble polymer is formed by a polymerization reaction of a hydrophilic monomer and a hydrophobically modified hydrophilic monomer.

18. The method of claim 15 , wherein the foaming surfactant is selected from the group consisting of a nonionic surfactant; an anionic surfactant; a cationic surfactant; an amphoteric surfactant; a zwitterionic surfactant; and any combination thereof.