The function of cement retarder is to effectively prolong or maintain the time of cement slurry in liquid state and pumpability. The best retarder should have retarding effect in any temperature range, and the length of thickening time is directly proportional to its dosage. It has good adaptability with various oil well cements and good compatibility with different types of other admixtures. In other words, it does not affect other properties of cement slurry, such as thickening, increasing static shear force, hindering strength development, etc. The thickening time of cement slurry with specified formula has good predictability and repeatability. It should also be anti pollution, non-toxic, tasteless, non explosive, non combustible and non polluting to the environment.

 

There are several types of oil well cement retarders:

 

(1) Lignosulfonate and its isomers or derivatives;

 

(2) Tannins, sulfonated tannins and their derivatives;

 

(3) Carboxylic acids, hydroxycarboxylic acids, isomers or derivatives and salts thereof;

 

(4) Sodium or calcium salts of gluconic acid and its derivatives

 

(5) Cellulose and its derivatives with low relative molecular weight;

 

(6) Organic or inorganic phosphate,

 

(7) Boric acid and its salts, etc.