Effects of additive concentrations on cement rheology at differenttemperature conditions

Previous studies suggest that the rheology of cement slurries used during oil well cementing operations is an explicit function of temperature, additive type & concentration and cement grade. This study analyzes the effect of these factors on a water based mud (WBM). 27 experiments were conducted by varying three additive concentrations; retarders, fluid loss additives and dispersants. Shear rate and stress were then experimentally determined at varying temperature and concentration, while the plastic viscosity (PV) and yield point (YP) were determined analytically. The slurries were conditioned as set out in API RP 10B-2.Linear regression was used to build models describing the effect of temperature and additive concentration on PV and YP of the cement slurry. Results from the analysis reveal that for a temperature increase of125% and Retarder concentration increase of 200%, there were significant decline in PV (-41%) and YP(-44%). Whereas increasing the Fluid loss additive by 100% caused a significant increase in YP (+51%) and relatively insignificant increase in PV (+4.4%). This study concludes that the coupled effect of increasing temperature and retarder concentrations of cement slurries has a significant negative impact on both the YP and PV.