| 摘要 |
<p>Set retarders of copolymers of at least one polymerizable ethylenically unsaturated monomer and at least one alkoxylated sulfate, phosphate or ketonic salt are capable of delaying the hardening of a cementitious slurry when introduced into a subterranean formation until a downhole temperature greater than or equal to 500° F. is obtained, even in the absence of an intensifier. The ethylenically unsaturated monomer is preferably a carboxylic acid, amido carboxylic acid, carboxylic acid ester, amido carboxylic acid ester, hydroxylated alkyl ester of a carboxylic acid or a hydroxylated amido carboxylic acid ester, sulfonic acid, phosphonic acid or amide as well as mixtures thereof and the alkoxylated sulfate, phosphate or ketonic salt is of the formula: wherein unit R1 is H or a C1-C4 alkyl; R2 is —(CH2CH2—O—)n or (—CH2CHCH3—O—)n or a mixture thereof; n ranges from about 1 to about 100; X is an anionic radical selected from —SO3, —PO3 or —COO or a water soluble cationic moiety which counterbalances the valence of the anionic radical X.</p> |
