| 摘要 |
<p>A method of cementing a conduit in a borehole penetrating an earthen formation, by introducing a salt-tolerant cementing composition into the space between said conduit and said formation, wherein the cementing composition comprises cement and:… (a) water containing in excess of about 10% salt by weight of the water, and… (b) a fluid loss additive comprising an admixture of:… (i) at least one member selected from carboxymethylhydroxyethylcellulose and copolymers or copolymer salts of N,N-dimethylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid or acid salts thereof, having a mole ratio from about 1:4 to about 4:1 and a molecular weight such that a 0.1% aqueous solution of said copolymer has a Brookfield viscosity reading at 5 rpm of the U.L. Adapter Spindle in the range of about 30 to about 250 centipoise (.03 to .25 Pa s), present in an amount of from about 0.1% to about 1.0% by weight of dry cement: and… (ii) a copolymer or copolymer salt of acrylic acid and 2-acrylamido-2-methylpropane sulfonic acid or acid salt thereof, having a mole ratio of from about 1:5 to about 5:1 and a molecular weight such that a 10% aqueous solution of said copolymer has a Brookfield viscosity reading at 20 rpm of the U.L. Adapter Spindle in the range of about 5 to about 50 centipoise (.005 to .05 Pa s), present in an amount of from about 0.1% to about 3.0% by weight of dry cement.</p> |
