The abnormal phenomenon of class G oil well cement endangering the cementing security in the presence of retarder

Aiming at the abnormal phenomenon of the setting time of the cement slurry with retarder at around 85 °C surpassing the low temperature, the effect of retarder dosage, the dosage of extra lime (CaO), the mixing mode of the extra lime (CaO), and the precuring of the cement slurry at high temperature on the setting time of cement slurry were studied. The setting time of the cement slurry without the retarder changed a little as the increase of the dosage of the extra lime while the setting time of cement slurry with the retarder shortened obviously. The free lime contained in the cement itself had a great influence on the setting time of the cement slurry with the retarder. The content drop of the Ca(OH)2 in the cement slurry induced by the reaction acceleration between C4AF and Ca(OH)2 was responsible for the abnormal phenomenon.