Methods and compositions for sealing subterranean earth formations

Claim 2

A CEMENTING COMPOSITION FOR SEALING A HIGHLY PERMEABLE FORMATION COMPRISING A PUMPABLE SLURRY WHICH WILL NOT SET WHILE BEING AGITATED AND WHICH RAPIDLY SETS WHEN IN A STATIC CONDITION, SAID SLURRY COMPRISING SUFFICIENT WATER TO FORM A PUMPABLE SLURRY MIXED WITH THE COMPONENTS WHICH FORM A THIXOTROPIC COMPOSITION CONSISTING ESSENTIALLY OF HYDRAULIC CEMENT, A SILICATE COMPOUND PRESENT IN AN AMOUNT OF UP TO ABOUT 18% BY WEIGHT OF DRY CEMENT, A HYDROXIDE PRESENT IN AN AMOUNT OF AT LEAST 0.5% BY WEIGHT OF DRY CEMENT AND A SALT PRESENT IN AN AMOUNT OF ABOUT 0.5%-30% BY WEIGHT OF DRY CEMENT.

Claim 3

A cementing composition of claim 1 foR sealing a highly permeable formation comprising a pumpable slurry which will not set while being agitated and which rapidly sets when in a static condition, said slurry comprising sufficient water to form a pumpable slurry mixed with the components which form a thixotropic composition consisting essentially of a hydraulic cement, an aqueous silicate compound present in an amount of up to about 18% by weight of dry cement, an alkali metal hydroxide which retards premature gellation of the silicate compound present in an amount of at least 0.5% by weight of dry cement and a salt which reduces viscosity of the slurry without appreciably affecting the set time present in an amount of about 0.5%-30% by weight of dry cement.

Claim 4

A cementing composition of claim 1 for sealing a highly permeable formation comprising a pumpable slurry which will not set while being agitated and which rapidly sets when in a static condition, said slurry comprising sufficient water to form a pumpable slurry mixed with the components which form a thixotropic composition consisting essentially of a hydraulic cement, an alkali metal silicate present in an amount of up to about 18% by weight of dry cement, hydroxide selected from ammonium hydroxide and an alkali metal hydroxide which retards premature gellation of the silicate compound, said hydroxide being present in an amount of at least 0.5% by weight of dry cement and a salt of an alkali metal which reduces viscosity of the slurry without appreciably affecting the cementing composition set time, said salt being present in an amount of about 0.5-30% by weight of dry cement.

Claim 5

A cementing composition of claim 1 for sealing a highly permeable formation comprising a pumpable slurry which will not set while being agitated and which rapidly sets when in a static condition, said slurry comprising sufficient water to form a pumpable slurry mixed with the components which form a thixotropic composition consisting essentially of a hydraulic cement; an alkali metal silicate, said silicate being present in an amount of up to about 18% by weight of dry cement and said silicate forming an aqueous solution with said water; a hydroxide selected from ammonium hydroxide and an alkali metal hydroxide which retards premature gellation of the silicate, said hydroxide being present in an amount of at least 0.5% by weight of dry cement and a salt of an alkali metal which reduces viscosity of the slurry without appreciably affecting the cementing composition set time, said salt being present in an amount of about 0.5-30% by weight of dry cement.

Claim 6

A cementing composition of claim 1 for sealing a highly permeable formation comprising a pumpable slurry which will not set while being agitated and which rapidly forms a shearable gel and sets when in a static condition, said slurry comprising sufficient water to form a pumpable slurry mixed with the components which form a thixotropic composition which rapidly forms a shearable gel of said slurry under static conditions, said thixotropic composition consisting essentially of a hydraulic cement; an alkali metal silicate present in an amount of up to about 18% by weight of dry cement and said silicate forming an aqueous solution with said water; a hydroxide selected from ammonium hydroxide and an alkali metal hydroxide which retards premature gellation of the silicate, said hydroxide being present in an amount of at least 0.5% by weight of dry cement and a salt of an alkali metal which reduces viscosity of the slurry without appreciably affecting the cementing composition set time, said salt being present in an amount of about 0.5%-30% by weight of dry cement.

Claim 7

A cementing composition of claim 1 wherein said silicate compound is an alkali metal silicate which dissolves in water and has a weight ratio of alkali metal oxide to silicon dioxide in the range of about 1:2 to 1:4 and said silicate compound being present in an Amount of about 6-18% by weight of dry cement, wherein said hydroxide is selected from ammonium hydroxide and an alkali metal hydroxide and said hydroxide is present in an amount of about 0.5-6% by weight of dry cement and wherein said salt is a salt of an alkali metal which dissolves in said water and which is present in an amount of about 0.5-30% by weight of dry cement.

Claim 8

A cementing composition of claim 1 comprising a pumpable slurry which rapidly forms a shearable gel when in a static condition wherein said silicate compound is an alkali metal silicate which dissolves in water and which has a weight ratio of alkali metal oxide to silicon dioxide in the range of about 1:2 to 1:4 and said silicate being present in an amount of about 6-10% by weight of dry cement, wherein said hydroxide is selected from ammonium hydroxide and an alkali metal hydroxide and said hydroxide being present in an amount of about 0.5-6% by weight of dry cement and wherein said salt is a salt of an alkali metal which dissolves in water and which is present in an amount of about 0.5-6% by weight of dry cement.

Claim 9

A cementing composition of claim 7 wherein the hydraulic cement is an API cement selected from Class C and H, the silicate is sodium silicate, the alkali is sodium hydroxide and the salt is sodium chloride.

Claim 10

A cementing composition of claim 7 wherein the hydraulic cement is a Portland cement; the silicate is selected from sodium silicate and potassium silicate; the hydroxide is selected from ammonium hydroxide, sodium hydroxide and potassium hydroxide and wherein said salt is selected from sodium chloride and potassium chloride.

Claim 11

A cementing composition of claim 9 wherein the silicate is sodium silicate, wherein the hydroxide is sodium hydroxide and wherein the salt is sodium chloride.

Claim 12

In a cementing composition for sealing a highly permeable formation comprising a cement mixed with sufficient water to form a pumpable slurry, the improvement of using a thixotropic cement composition in said slurry which rapidly forms a shearable gel in said slurry under static conditions, said thixotropic cement composition consisting essentially of a hydraulic cement; an alkali metal silicate present in an amount of up to about 18% by weight of dry cement, said silicate having a weight ratio of alkali metal oxide to silicon dioxide in the range of about 1:2 to 1:4 and said silicate dissolving in said water; a hydroxide selected from ammonium hydroxide and an alkali metal hydroxide which retards premature gellation of said silicate, said hydroxide being present in an amount of at least 0.5% by weight of dry cement and a salt of an alkali metal which reduces viscosity of the slurry without appreciably affecting the cementing composition set time, said salt being present in an amount of about 0.5-30% by weight of dry cement.

Claim 13

In a cementing composition for sealing a highly permeable formation comprising a cement mixed with sufficient water to form a pumpable slurry, the improvement of using a thixotropic cement composition in said slurry which rapidly forms a shearable gel in said slurry under static conditions, said thixotropic cement composition consisting essentially of a hydraulic cement; an alkali metal silicate present in an amount of up to about 18% by weight of dry cement, said silicate having a weight ratio of alkali metal oxide to silicon dioxide in the range of about 1:2 to 1:4 and said silicate dissolving in said water; a hydroxide selected from ammonium hydroxide and an alkali metal hydroxide which retards premature gellation of said silicate, said hydroxide being present in an amount of at least 0.5% by weight of dry cement and a salt of an alkali metal which reduces viscosity of the slurry without appreciably affecting the cementing composition set time, said salt being present in an amount of about 0.5-30% by weight of dry cement.

Claim 14

A cementing composition of claim 11 wherein the hydraulic cement is a Portland cement, the silicate is selected from sodium silicate and potassium silicate, the hydroxide is selected from ammonium hydroxide, sodium hydroxide and potassium hydroxide and wherein said salt is selected from sodium chloride and potassium chloride.