Light weight high temperature well cement compositions and methods

An improved cement composition useful in cementing high temperature wells containing carbon dioxide consisting essentially of:

• calcium aluminate present in an amount in the range of from about 15% to about 45% by weight of said composition;
• ASTM Class F fly ash present in an amount in the range of from about 25% to about 45% by weight of said composition;
• ground rubber particles present in an amount in the range of from about 10% to about 40% by weight of said composition;
• sufficient water to form a pumpable slurry;
• a foaming agent present in an amount effective to facilitate foaming;
• a foam stabilizer present in an amount effective to stabilize a foam;
• and
• a gas present in an amount sufficient to form a foam having a density in the range of from about 9.5 to about 14 pounds per gallon.

A light weight well cement composition useful in cementing high temperature wells containing carbon dioxide comprising:

• calcium aluminate present in an amount of about 28% by weight of said composition;
• sodium polyphosphate present in an amount of about 19% by weight of said composition;
• ASTM class F fly ash present in an amount of about 49% by weight of said composition;
• sufficient water to form a pumpable slurry;
• a foaming agent present in an amount effective to facilitate foaming;
• a foam stabilizer present in an amount effective to stabilize a foam;
• and
• a gas present in an amount sufficient to form a foam having a density in the range of from about 9.5 to about 14 pounds per gallon.

A method of cementing a subterranean zone containing carbon dioxide penetrated by a well bore comprising the steps of:

• (a) forming a well cement composition consisting essentially of calcium aluminate, ASTM Class F fly ash, sufficient water to form a pumpable slurry, a foaming agent comprising an alpha-olefinic sulfonate having the formula
• H(CH.sub.2).sub.n --CH.dbd.CH--(CH.sub.2).sub.m SO.sub.3 Na
• wherein n and m are integers in the range of from about 6 to about 16, said foaming agent being present in an amount in the range of from about 1.0% to about 2.0% by weight of the water in said composition, a foam stabilizer comprising a betaine having the formula
• R--CONHCH.sub.2 CH.sub.2 N.sup.+ (CH.sub.3).sub.2 CH.sub.2 CO.sub.2.sup.-
• wherein R is a radical selected from the group of decyl, cetyl, oleyl, lauryl and cocoyl, said foam stabilizer being present in an amount in the range of from about 0.5% to about 1.0% by weight of the water in said composition and a gas present in an sufficient to form said foam having a density in the range of from about 9.5 to about 14 pounds per gallon;
• (b) pumping said cement composition into said subterranean zone by way of said well bore;
• and
• (c) allowing said cement composition to set into a hard impermeable mass therein.

A method of cementing a high temperature subterranean zone containing carbon dioxide penetrated by a well bore comprising the steps of:

• (a) forming a light weight well cement composition comprised of calcium aluminate, sodium polyphosphate, fly ash, sufficient water to form a pumpable slurry, a foaming agent, a foam stabilizer and a gas present in an amount sufficient to form a foam having a density in the range from about 9.5 to about 14.0 pounds per gallon;
• (b) pumping said cement composition into said subterranean zone by way of said well bore;
• and
• (c) allowing said cement composition to set into a hard impermeable mass therein.