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The present invention relates to methods of generating gas in and forming cement compositions that may be introduced into a subterranean zone. A method of the present invention provides a method of generating gas in a cement composition that comprises providing the cement composition comprising a hy

The present invention relates to methods of generating gas in and forming cement compositions that may be introduced into a subterranean zone. A method of the present invention provides a method of generating gas in a cement composition that comprises providing the cement composition comprising a hydraulic cement and water; providing an oxidizing agent; providing at least one gas generating chemical; and contacting the cement composition with the oxidizing agent and/or the gas generating chemical downstream of at least one cement pump so that a gas is generated in the cement composition downstream of at least one cement pump. Methods of foaming cement compositions are also provided.

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1. A method of generating gas in a cement composition comprising the steps of:providing the cement composition comprising a hydraulic cement, water, and an oxidizing agent; providing an aqueous solution or dispersion that comprises at least one gas generating chemical; and contacting the cement comp

1. A method of generating gas in a cement composition comprising the steps of:providing the cement composition comprising a hydraulic cement, water, and an oxidizing agent; providing an aqueous solution or dispersion that comprises at least one gas generating chemical; and contacting the cement composition downstream of at least one cement pump with the aqueous solution or dispersion so that a gas is generated in the cement composition. 2. The method of claim 1 wherein the weight ratio of the oxidizing agent to the gas generating chemical is in the range of from about 15:1 to about 1:1.3. The method of claim 1 wherein the hydraulic cement comprises a Portland cement, a pozzalana cement, a gypsum cement, an aluminous cement, a silica cement, and/or a slag cement.4. The method of claim 1 wherein the hydraulic cement is a Portland cement.5. The method of claim 1 wherein the water in the cement composition comprises fresh water or salt water.6. The method of claim 1 wherein the water is present in the cement composition in an amount in the range of from about 30% to about 70% by weight of the hydraulic cement in the cement composition.7. The method of claim 1 wherein the oxidizing agent in the cement composition comprises ammonium persulfate, sodium persulfate, potassium persulfate, sodium chlorite, sodium chlorate, hydrogen peroxide, sodium perborate, sodium peroxy carbonate, calcium hypochlorite, sodium hypochlorite, sodium hypobromite, sodium bromite, sodium bromate, sodium chlorate, and/or a mixture thereof.8. The method of claim 1 wherein the oxidizing agent in the cement composition comprises sodium chlorite.9. The method of claim 1 wherein the oxidizing agent is present in the cement composition in an amount in the range of from about 5% to about 25% by weight of the hydraulic cement in the cement composition.10. The method of claim 1 wherein the aqueous solution or dispersion comprises a water component that comprises fresh water or salt water.11. The method of claim 1 wherein the gas generating chemical in the aqueous solution or dispersion comprises a hydrazine group, a hydrazine salt, azodicarbonamide, azobis(isobutyronitrile), p-toluene sulfonyl hydrazide, p-toluene sulfonyl semicarbazide, carbohydrazide, p-p′-oxybis(benzenesulfonylhydrazide), and/or a mixture thereof.12. The method of claim 1 wherein the gas generating chemical in the aqueous solution or dispersion comprises carbohydrazide.13. The method of claim 1 wherein the gas generating chemical is present in the aqueous solution or dispersion in an amount in the range of from about 10% to about 50% by weight of a water component in the aqueous solution or dispersion.14. The method of claim 1 wherein the aqueous solution or dispersion further comprises a surfactant.15. The method of claim 14 wherein the surfactant is present in the aqueous solution or dispersion in an amount in the range of from about 2% to about 15% by weight of a water component in the aqueous solution or dispersion.16. A method of generating a gas in a cement composition comprising the steps of:providing the cement composition comprising a hydraulic cement and water; providing an oxidizing agent; contacting the cement composition with the oxidizing agent; contacting the cement composition downstream of at least one cement pump with at least one gas generating chemical; allowing the gas generating chemical to react so as to generate gas in the cement composition; and placing the cement composition into a subterranean zone. 17. The method of claim 16 wherein the oxidizing agent is provided as a component of the cement composition or in an aqueous solution or dispersion comprising the gas generating chemical.18. The method of claim 17 wherein the aqueous solution or dispersion further comprises a surfactant.19. The method of claim 18 wherein the surfactant comprises a mixture of a foaming and a foam stabilizing surfactant.20. The method of claim 19 wherein the mixture comprises an ethoxylated alcohol ether sulfate surfactant, an alkyl amidopropyl betaine surfactant, an alkene amidopropyl betaine surfactant, an alkyl amidopropyl dimethylamine oxide surfactant, or an alkene amidopropyl dimethylamine oxide surfactant.21. The method of claim 17 wherein the aqueous solution or dispersion further comprises a hydraulic cement.22. The method of claim 16 wherein the weight ratio of the oxidizing agent to the gas generating chemical is in the range of from about 15:1 to about 1:1.23. The method of claim 16 wherein the hydraulic cement comprises a Portland cement, a pozzalana cement, a gypsum cement, an aluminous cement, a silica cement, and/or a slag cement.24. The method of claim 16 wherein the water in the cement composition comprises fresh water or salt water.25. The method of claim 16 wherein the water is present in the cement composition in an amount in the range of from about 30% to about 70% by weight of the hydraulic cement in the cement composition.26. The method of claim 16 wherein the oxidizing agent in the cement composition comprises ammonium persulfate, sodium persulfate, potassium persulfate, sodium chlorite, sodium chlorate, hydrogen peroxide, sodium perborate, sodium peroxy carbonate, calcium hypochlorite, sodium hypochlorite, sodium hypobromite, sodium bromite, sodium bromate, sodium chlorate, and/or a mixture thereof.27. The method of claim 16 wherein the gas generating chemical comprises a hydrazine group, a hydrazine salt, azodicarbonamide, azobis(isobutyronitrile), p-toluene sulfonyl hydrazide, p-toluene sulfonyl semicarbazide, carbohydrazide, p-p′-oxybis(benzenesulfonylhydrazide), and/or a mixture thereof.28. A method of cementing a subterranean zone comprising the steps of:providing the cement composition that comprises a hydraulic cement and water; contacting the cement composition downstream of at least one cement pump with an oxidizing agent and at least one gas generating chemical; allowing gas to generate in the cement composition; placing the cement composition in the subterranean zone; and allowing the cement to set in the subterranean zone. 29. The method of claim 28 wherein the oxidizing agent or the gas generating chemical is provided as a component of the cement composition or in an aqueous solution or dispersion.30. The method of claim 29 wherein the aqueous solution or dispersion further comprises a surfactant.31. The method of claim 30 wherein the surfactant comprises a mixture of a foaming and a foam stabilizing surfactant.32. The method of claim 31 wherein the mixture comprises an ethoxylated alcohol ether sulfate surfactant, an alkyl amidopropyl betaine surfactant, an alkene amidopropyl betaine surfactant, an alkyl amidopropyl dimethylamine oxide surfactant, or an alkene amidopropyl dimethylamine oxide surfactant.33. The method of claim 29 wherein the aqueous solution or dispersion further comprises a hydraulic cement.34. The method of claim 28 wherein the weight ratio of the oxidizing agent to the gas generating chemical is in the range of from about 15:1 to about 1:1.35. The method of claim 28 wherein the subterranean zone is located in an annulus in a well bore.36. The method of claim 28 wherein the cement composition comprises a second oxidizing agent.37. The method of claim 28 wherein the cement composition comprises a Portland cement.38. The method of claim 28 wherein the water is present in the cement composition in an amount in the range of from about 30% to about 70% by weight of the hydraulic cement in the cement composition.39. The method of claim 28 wherein the gas generating chemical comprises toluene sulfonyl hydrazide, carbohydrazide, hydrazine, a hydrazine salt, azodicarbonamide, azobis(isobutyronitrile), azodicarboxylic acid, an azodicarboxylic salt of an alkali earth metal, an azodicarboxylic salt of an alkaline earth metal, or a mixture thereof.40. The method of claim 28 wherein the gas generating chemical is present in an amount in the range of from about 2% to about 15% by weight of the hydraulic cement in the cement composition.41. The method of claim 28 wherein the oxidizing agent is present in an amount in the range of from about 5% to about 25% by weight of the hydraulic cement in the cement composition.42. A method of cementing a subterranean zone comprising the steps of:providing a cement composition comprising a hydraulic cement, water, and an oxidizing agent; contacting the cement composition downstream of at least one cement pump with an aqueous solution or dispersion that comprises water and at least one gas generating chemical; allowing gas to be generated in the cement composition to form a foamed cement composition; placing the foamed cement composition in the subterranean zone; and allowing the foamed cement composition to set in the subterranean zone. 43. The method of claim 42 further comprising the step of contacting the foamed cement composition with a surfactant before allowing the foamed cement composition to set in the subterranean zone to at least partially stabilize the foamed cement composition to produce an at least partially stabilized foamed cement composition.44. The method of claim 43 wherein the ratio of the gas generating chemical to the oxidizing agent to the surfactant in the at least partially stabilized foamed cement composition is in the range of from about 1:1:0.1 to about 1:15:0.6.45. The method of claim 43 wherein the surfactant comprises an ethoxylated alcohol ether sulfate surfactant, an alkyl amidopropyl betaine surfactant, an alkene amidopropyl betaine surfactant, an alkyl amidopropyl dimethylamine oxide, or an alkene amidopropyl dimethylamine oxide.46. The method of claim 42 wherein the hydraulic cement in the cement composition comprises a Portland cement, a pozzalana cement, a gypsum cement, an aluminous cement, a silica cement, or a slag cement.47. The method of claim 42 wherein the water in the cement composition comprises fresh water or sea water.48. The method of claim 42 wherein the gas generating chemical comprises toluene sulfonyl hydrazide, carbohydrazide, hydrazine, a hydrazine salt, an azodicarbonamide, azodicarboxylic acid, an azodicarboxylic salt of an alkali earth metal, an azodicarboxylic salt of an alkaline earth metal, or a mixture thereof.49. The method of claim 42 wherein the gas generating chemical is present in an amount in the range of from about 2% to about 15% by weight of the hydraulic cement in the cement composition.50. A method of foaming a cement compositionproviding the cement composition comprising a hydraulic cement and water; contacting the cement composition with an aqueous solution or dispersion that comprises at least one gas generating chemical; contacting the cement composition with an oxidizing agent downstream of at least one cement pump; placing the cement composition in the subterranean zone; and allowing the gas generating chemical to react so as to generate a gas in the cement composition to foam the cement composition in a subterranean zone to form a foamed cement composition. 51. The method of claim 50 further comprising the step of introducing a surfactant mixture to the cement composition to stabilize the foamed cement composition.52. The method of claim 50 wherein the hydraulic cement comprises calcium, aluminum, silicon, oxygen, or sulfur.53. The method of claim 50 wherein the hydraulic cement comprises a Portland cement.54. The method of claim 50 wherein the water in the cement composition comprises fresh water or salt water.55. The method of claim 50 wherein the water is present in the cement composition in an amount in the range of from about 30% to about 100% by weight of the hydraulic cement in the cement composition.56. The method of claim 50 wherein the gas generating chemical comprises a compound capable of generating a gas in the cement composition that comprises nitrogen, carbon dioxide, or carbon monoxide.57. The method of claim 50 wherein the oxidizing agent comprises ammonium persulfate, sodium persulfate, potassium persulfate, sodium chlorite, sodium perborate, sodium peroxy carbonate, calcium hypochlorite, sodium hypochlorite, sodium hypobromite, sodium bromite, sodium bromate, or sodium chlorate.58. The method of claim 50 wherein the oxidizing agent is present in an amount in the range of from about 2% to about 20% by weight of the hydraulic cement in the cement composition.59. The method of claim 50 wherein the aqueous solution or dispersion further comprises a surfactant mixture.60. The method of claim 59 wherein the surfactant mixture comprises an ethoxylated alcohol ether sulfate surfactant, an alkyl amidopropylbetaine surfactant, an alkene amidopropylbetaine surfactant, an alkyl amidopropyldimethylamine oxide surfactant, or an alkene amidopropyl dimethylamine oxide surfactant.61. The method of claim 59 wherein the surfactant mixture is present in the aqueous solution or dispersion in an amount in the range of from about 2% to about 15% by weight of a water component in the aqueous solution or dispersion.62. The method of claim 50 wherein the aqueous solution or dispersion comprises fresh water or salt water.63. The method of claim 50 wherein the weight ratio of the oxidizing agent to the gas generating chemical is in the range of from about 15:1 to about 1:1.64. The method of claim 50 wherein the aqueous solution or dispersion further comprises a hydraulic cement.65. The method of claim 64 wherein the hydraulic cement is present in an amount in the range of from about 150% to about 300% by weight of a water component in the aqueous solution or dispersion.66. The method of claim 50 wherein the gas generating chemical comprises hydrazine, a hydrazine salt, azodicarbonamide, azobis(isobutyronitrile), p-toluene sulfonyl hydrazide, p-toluene sulfonyl semicarbazide, carbohydrazide, p-p′-oxybis(benzenesulfonylhydrazide), or a mixture thereof.67. The method of claim 50 wherein the gas generating chemical is present in the aqueous solution or dispersion in an amount in the range of from about 0% to about 50% by weight of a water component in the aqueous solution or dispersion.68. The method of claim 50 further comprising the step of introducing a surfactant mixture to the cement composition or the foamed cement composition.69. A method of reducing gas-locking problems when cementing a subterranean zone comprising the steps of:providing a cement composition that comprises a hydraulic cement, water, and an oxidizing agent; contacting the cement composition downstream of at least one cement pump with an aqueous solution or dispersion that comprises water and a gas generating chemical; allowing the gas generating chemical to react so as to produce gas in the cement composition to produce a foamed cement composition; placing the cement composition in a chosen subterranean zone; and allowing the foamed cement composition to set in the subterranean zone. 70. The method of claim 69 further comprising contacting the cement composition with a surfactant.71. A method of generating gas in a cement composition comprising the steps of:providing the cement composition comprising a hydraulic cement, water, and at least one gas generating chemical; providing an aqueous solution or dispersion that comprises an oxidizing agent; and contacting the cement composition downstream of at least one cement pump with the aqueous solution or dispersion so that a gas is generated in the cement composition downstream of at least one cement pump. 72. The method of claim 71 wherein the weight ratio of the oxidizing agent to the gas generating chemical is in the range of from about 15:1 to about 1:1.73. The method of claim 71 wherein the hydraulic cement comprises a Portland cement, a pozzalana cement, a gypsum cement, an aluminous cement, a silica cement, or a slag cement.74. The method of claim 71 wherein the hydraulic cement is a Portland cement.75. The method of claim 71 wherein the water in the cement composition comprises fresh water or salt water.76. The method of claim 71 wherein the water is present in the cement composition in an amount in the range of from about 30% to about 70% by weight of the hydraulic cement in the cement composition.77. The method of claim 71 wherein the oxidizing agent in the cement composition comprises ammonium persulfate, sodium persulfate, potassium persulfate, sodium chlorite, sodium chlorate, hydrogen peroxide, sodium perborate, sodium peroxy carbonate, calcium hypochlorite, sodium hypochlorite, sodium hypobromite, sodium bromite, sodium bromate, sodium chlorate, and/or a mixture thereof.78. The method of claim 71 wherein the oxidizing agent in the cement composition comprises sodium chlorite.79. The method of claim 71 wherein the oxidizing agent is present in the cement composition in an amount in the range of from about 5% to about 25% by weight of the hydraulic cement in the cement composition.80. The method of claim 71 wherein the aqueous solution or dispersion comprises a water component that comprises fresh water or salt water.81. The method of claim 71 wherein the gas generating chemical in the aqueous solution or dispersion comprises a hydrazine group, a hydrazine salt, azodicarbonamide, azobis(isobutyronitrile), p-toluene sulfonyl hydrazide, p-toluene sulfonyl semicarbazide, carbohydrazide, p-p′-oxybis(benzenesulfonylhydrazide), and/or a mixture thereof.82. The method of claim 71 wherein the gas generating chemical in the aqueous solution or dispersion comprises carbohydrazide.83. The method of claim 71 wherein the gas generating chemical is present in the aqueous solution or dispersion in an amount in the range of from about 10% to about 50% by weight of a water component in the aqueous solution or dispersion.84. The method of claim 71 wherein the aqueous solution or dispersion further comprises a surfactant.85. The method of claim 84 wherein the surfactant is present in the aqueous solution or dispersion in an amount in the range of from about 2% to about 15% by weight of a water component in the aqueous solution or dispersion.