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A cementitious composition for cementing an oil or gas well and which exhibits, when cured, increased flexural strength and a flexural strength to compressive strength ratio between from about 0.29 to about 0.80, contains a hydraulically-active cementitious material, such as Portland cement, and sub

A cementitious composition for cementing an oil or gas well and which exhibits, when cured, increased flexural strength and a flexural strength to compressive strength ratio between from about 0.29 to about 0.80, contains a hydraulically-active cementitious material, such as Portland cement, and substantially spherical zeolite. Representative zeolites include natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite. The weight percent of zeolite in the cement composition is generally less than or equal to 15 percent. In practice, a well bore may be cemented by pumping the activated slurry and pumping it within the well bore to a pre-selected location and allowing it to solidify.

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What is claimed is: 1. A method of cementng an oil or gas well, comprising a. introducing into the well a cementitious composition comprising a hydraulically-active cementitious material, substantially spherical zeolite and water wherein the compressive strength of the cementitious composition, whe

What is claimed is: 1. A method of cementng an oil or gas well, comprising a. introducing into the well a cementitious composition comprising a hydraulically-active cementitious material, substantially spherical zeolite and water wherein the compressive strength of the cementitious composition, when cured, is equal to or less than the compressive strength of a neat cementitious composition not containing the zeolite; and b. allowing the slurry to setup in the well. 2. The method of claim 1, wherein the zeolite is selected from the group consisting of natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite. 3. The method of claim 2, wherein the zeolite is clinoptilolite. 4. The method of claim 1, wherein the weight percent of zeolite in the cementitious composition is less than or equal to 15 percent. 5. The method of claim 4, wherein the weight percent of zeolite in the cementitious composition is less than or equal to 10 percent. 6. The method of claim 1, wherein the compressive strength of the cementitious composition, when cured, is at least 15% lower than the compressive strength of the neat cementitious composition. 7. The method of claim 6, wherein the compressive strength of the cementitious slurry, when cured, is at least 25% lower than the compressive strength of the neat cementitious slurry. 8. A method of cementitious an oil or gas well comprising a. introducing into the well a cementitious composition comprising a hydraulically-active cementitious material; substantially spherical zeolite; and water wherein the zeolite is present in the cementitious composition in an amount sufficient to increase the flexural strength of the cementitious composition, when cured, as compared to the flexural strength of a cementitious composition, when cured, which does not contain zeolite; and b. allowing the slurry to set up in the well. 9. The method of claim 8, wherein the compressive strength of the cementitious composition, when cured, is equal to or less than the compressive strength of a neat cementitious composition. 10. The method of claim 8, wherein the amount of zeolite in the cementitious composition is less than about 15 weight percent. 11. The method of claim 10, wherein the amount of zeolite in the cementitious composition is less than or equal to about 10 weight percent. 12. The method of claim 8, wherein the flexural strength to compressive strength ratio (FS/CS) of the cementitious composition, when cured, is between from about 0.29 to about 0.80. 13. The method of claim 8, wherein the zeolite is selected from the group consisting of natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite. 14. The method of claim 13, wherein the zeolite is clinoptilolite. 15. A method of cementing a section of a well penetrating subterranean formation comprising the steps of: a. introducing into the well a cementitious slurry comprising: a hydraulically-active cementitious material; substantially spherical zeolite; and water wherein the flexural strength to compressive strength ratio (FS/CS) of the slurry, when cured, is from about 0.29 to about 0.80; and b. allowing the slurry to set up in the well to provide zonal isolation in the well bore. 16. The method of claim 15, wherein the zeolite is porous. 17. The method of claim 15, wherein the compressive strength of the cementitious slurry, when cured is equal to or less than the compressive strength of a neat cementitious slurry containing no zeolite, when cured. 18. The method of claim 17, wherein the compressive strength of the cementitious slurry, when cured is at least 15% lower than the compressive strength of the neat cementitious slurry containing no zeolite, when cured. 19. The method of claim 15, wherein the zeolite is selected from the group consisting of natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite. 20. The method of claim 15, wherein the FS/CS of the cement slurry, when cured, is at least 15% higher than a neat cementitious slurry containing no zeolite, when cured. 21. In a method of cementing downhole in a well bore in which a drilling fluid has been used to drill the well, the improvement comprising: a. introducing into the well a cementitious slurry comprising hydraulically-active cementitious material, substantially spherical zeolite and water, wherein the flexural strength to compressive strength ratio (FS/CS) of the slurry, when cured, is between from about 0.29 to about 0.80, the cement being less dense than the drilling fluid; b. activating the slurry; c. pumping the activated slurry into a pre-selected location within the well bore; and d. allowing the slurry to set up in the well to provide zonal isolation in the well bore. 22. A method of cementing an oil, gas, steam injection or geothermal well which comprises: a. introducing into the well a cementitious composition comprising a hydraulically-active cementitious material, substantially spherical zeolite and water wherein, when cured, the flexural strength and tensile strength of the cementitious composition are greater than the flexural strength mid tensile strength of a neat cementitious composition containing no zeolite when cured and further wherein the zeolite is selected from the group consisting of natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite; and b. allowing the slurry to set up in the well. 23. In a method of cementing downhole in a well in which a drilling fluid has been used to drill the well the improvement comprising: a. introducing into the well a cementitious slurry comprising hydraulically-active cementitious material, substantially spherical zeolite and water, wherein the compressive strength of the cementitious slurry, when cured, is less than the compressive strength of a neat cementitious slurry not containing zeolite; b. activating the slurry; c. pumping the activated slurry into a pre-selected location within the well; and d. allowing the slurry to set up in the well. 24. The method of claim 23, wherein the zeolite is selected from the group consisting of natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite. 25. A method of cementing an oil, gas, steam injection or geothermal well comprising the steps of: a. introducing into the well a cementitious composition comprising a hydraulically-active cementitious material, substantially spherical zeolite and water, wherein the flexural strength to compressive strength ratio (FS/CS) of the cementitious composition, when cured for sufficient time to be near its final compressive strength, is equal to or higher than the FS/CS ratio of a similar neat cementitious composition not containing zeolite, when cured under identical conditions: and b. allowing the cementitious composition to set up in the well to provide zonal isolation. 26. The method of claim 25, wherein the zeolite is selected from the group consisting of natrolite, heulandite, analcime, chabazite, stilbite, and clinoptilolite. 27. The method of claim 26, wherein die zeolite is clinoptilolite. 28. The method of claim 25, wherein the weight percent of zeolite in the cementitious composition is less than or equal to 15 percent. 29. The method of claim 28, wherein the weight percent of zeolite in the cementitious composition is less than or equal to 10 percent. 30. The method of claim 25, wherein the cementitious composition further comprises sand, silica powder and/or silica flour. 31. The method of claim 25, wherein the compressive strength of the cementitious composition, when cured, is lower than the compressive strength of a neat cementitious composition not containing zeolite, when cured, under identical conditions. 32. The method or claim 25, wherein the flexural strength of the cementitious slurry, when cured is higher than the flexural strength of a neat cementitious composition not containing zeolite, when cured, under identical conditions. 33. The method of claim 25, wherein the flexural strength to compressive strength ratio (FS/CS) of the cementitious composition, when cured, is between from about 0.29 to about 0.80. 34. The method of claim 25, wherein the zeolite is porous.