Effects of Additive Concentrations on Cement Rheology at Different Temperature Conditions

Cement slurries are designed to achieve zonal isolation; improve rheological properties and displacement efficiency of cementing system. Oil well cement slurries depend on temperature, additive concentrations; quality and quantity, to contribute to the placement and success of cementing operation. This study aims at analysing the effects of cement slurry additive concentration on rheology at different temperature conditions. Three additive concentrations were varied; Retarder, Fluid Loss Additive and Dispersant. Using full factorial design, 27 experiments were carried out to analyse the effect of these additives at different temperatures. Rheological properties like plastic viscosity, yield stress, shear rate and shear stress were experimentally determined at different temperatures and concentrations of additives. A simple cement slurry design which consists of:  Dyckerhoff Class G, Fluid Loss Additive, Retarder, Dispersant, Defoamer and Drill Water, was used for the laboratory experiments. The slurry was conditioned in accordance with the procedure set out in API RP 10B-2. Linear regression was then used to build models describing the effect of temperature and additive concentration on plastic viscosity and yield point of the cement slurry. Ms-Excel plots were used as a tool in presenting the relationships between Shear Stress and shear rates at varying temperature conditions. Results from the analysis reveal that for a Temperature increase of 125% and Retarder concentration increase of 200%, there were significant decline in Plastic viscosity (-41%) and Yield point (-44%). Whereas increasing the Fluid loss additive by 100% caused a significant increase in Yield point (+51%) and relatively insignificant increase in Plastic Viscosity (+4.4%).