The Effect of Mixing Energy and Shear Rate on the Thickening Time of Cement Slurry

Achieving optimum cement slurry design involves being able to simulate actual field experience in the laboratory. This work is on how mixing energy and shear rate affect the thickening time of cement slurry.Using conventional pressurized consistometer, fitted with a variable speed motor, a comparative thickening time test was obtained. This device allows for simulation of shear rate, temperature and pressure found in the well bore during pumping. The API procedure was used to evaluate the mixing energy applied to the slurry.Results obtained show that for mixing energy, the principal thing is deflocculation. Once the slurry is deflocculated, then no other effect of mixing energy is felt on the thickening time and it is not a function of the geometry of wellbore. Results also show that the temperature profile and geometry of the well from surface to bottom is an important consideration in modeling the influence of shear on how long the cement slurry will remain pumpable. Modeling along this line will lead to optimum slurry quality and design.