Low density cement slurry and its use

A hydraulic cement slurry which comprises:

• hydraulic cement, from about 8 to about 50 weight percent hollow glass microspheres by weight of the cement and sufficient water to form a pumpable slurry with an API free water content of no more than about 2 volume percent, wherein said slurry is free from effective amounts of sodium metasilicate and said microspheres have ANSI/ASTM D 2840-69 average true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, ANSI/ASTM D 3102-72 hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.

A cement slurry which comprises:

• hydraulic cement, about 8 to about 50 weight percent hollow glass microspheres based on the weight of the cement and, as substantially all of the water in the slurry, an amount of water required to produce a pumpable slurry with the hydraulic cement and microspheres having an API free water content of no more than about 2 volume percent, wherein said microspheres have ANSI/ASTM D 2840-69 true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, ANSI/ASTM D 3102-72 hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.

A cement slurry which comprises:

• hydraulic cement, about 8 to about 50 weight percent hollow glass microspheres based on the weight of the cement and, as substantially all of the water in the slurry, an amount of water required to produce a pumpable slurry with the hydraulic cement having an API free water content of no more than about 2 volume percent and an additional amount of water equal to about the amount shown in FIG. 4 for each weight percent of said microspheres, wherein said microspheres have ANSI/ASTM D 2840-69 true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, ANSI/ASTM D 3102-72 hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.

A cement slurry which comprises:

• hydraulic cement, about 8 to about 50 weight percent hollow glass microspheres based on the weight of the cement and an amount of water required to produce a pumpable slurry with an API free water content of less than about 2 volume percent, wherein said microspheres have ANSI/ASTM D 2840-69 average true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, average particle diameters of less than about 500 microns and ANSI/ASTM D 3102-72 hydrostatic collapse strength after collapse of about 10 volume percent of said microspheres substantially as shown in FIG. 2.

A cement slurry which comprises:

• hydraulic cement, about 8 to about 50 weight percent hollow glass microspheres based on the weight of the cement and an amount of water required to produce the pumpable slurry with an API free water content of less than about 2 volume percent, wherein said microspheres are manufactured by the procedure described in Beck, et al, U.S. Pat. No. 3,365,315, have ANSI/ASTM D 2840-69 average true particle densities of about 0.2 to about 0.5 gm/cm.sup.3, ANSI/ASTM D 3102-72 hydrostatic collapse strengths of at least 500 psi (3447 kPa) and average particle diameters of less than about 500 microns.

A pumpable, lightweight hydraulic cement slurry useful for oilfield cementing and the like comprising a mixture of a finely-ground hydraulic cement;

• between about 8 and 50 weight percent (by weight of cement) of finely-divided hollow glass microspheres having a density not substantially exceeding an ANSI/ASTM average true particle density of 0.5 gm/cm.sup.3, an ANSI/ASTM hydrostatic collapse strength of at least 500 psi (3447 kPa), and a softening temperature not less than about 480.degree. C., said microspheres having an average particle diameter in the range of about 10 to about 300 microns;
• and water in an amount to produce a maximum slurry consistency not substantially exceeding 30 B.sub.c (API) and less than that producing 2 volume percent free water content (API).

A set hydraulic cement slurry of relatively high strength and low thermal conductivity at elevated temperatures (that is, at temperatures of the order of at least 230.degree. F. or 110.degree. C.)

• comprising an essentially homogeneous mixture of commercially available portland cement and a density reducer comprising between 8 and 50 weight percent (by weight of cement) of finely-divided hollow glass microspheres having an ANSI/ASTM true particle density in the range of about 0.2 to about 0.5 gm/cm.sup.3, an ANSI/ASTM hydrostatic collapse strength of at least about 500 psi (3447 kPa), average particle diameters in the range of about 10 to about 300 microns, and a thermal conductivity of the order of 8 to 11 (Kcal)(cm)(hr)(sq m)(.degree.C.), to which was added during slurrying an amount of water, (in excess of the conventional amount of water based on the cement for producing a slurry with said cement having an API normal water content), amounting to between about 1.2 and about 2.2 weight percent times the weight percent of said spheres.