Parameters Affecting CBS Slurry Design

American Petroleum Institute (API) has developed standards for testing downhole cements that are described in API recommended practice 10 [3]. In API specifications (API Spec. 10), if one assumes an ambient temperature of 80 °F (25°C), then the depth dependence of the downhole temperature is approximately given by 

The temperature (F) is measured in Fahrenheit, and depth d) in feet. This static temperature is that temperature, where the CBS will be placed and will set. The actual circulating temperature is considered to be the average of the downhole temperature and the surface temperature  

Chapter 15 Chemically Bonded Phosphate Ceramic Borehole Sealant 

As discussed in Chapters 4 and 5, CBPC formation is governed by the oxide solubility. The solubility, in turn, is related to the Gibbs free energy, which is a function of temperature and pressure. As a result, the CBS formulation depends on the downhole temperature and pressure. The effect of the temperature on the solubility has already been discussed in Section 6.4. The pressure effect can be assessed in a similar manner, but as we shall see, it is negligibly small and can be ignored for all practical purposes. 

Consider a typical solubility equation of an oxide such as MgO or AI2O3 in the neutral region. For these metal oxides, where the metal valency is x, the solubility equation 5.3 is reproduced here  

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