Relative Effectiveness of Scale Control Chemicals

Nucleating agents can perform very well at unbelievably low dosages. This has been established by the fact that polyphosphates (which are also sequestering agents) perform at dosages that are only a very small fraction of those theoretically required to sequester the salts known to be present. This remarkable increase in effectiveness is attributed to nucleation. 

Scale control chemicals that act as nucleating agents frequently are the only chemicals that can be economically justified for use in oil wells producing large volumes of water and heavy scale deposits. 

Their dosage requirements are virtually independent of the total amormt of scale-depositing salts present Presumably this is because a large amormt of the film-forming agent can be consumed in coating the very surface areas presented by a relatively small amormt of minute scale crystals. 

Film-forming thus can be economically attractive for use in high-water-volume oil wells, but dosage requirements may become excessive in such wells if the scale problems are severe that is, if very large amounts of scale-forming constituents are present. 

Generally the commonly used, less-expensive sequestering agents for oil wells are water-soluble. This is necessary because the ions they must tie up are in the water phase. However, this situation means that an extremely large amount of sequestrate must be added to an oil well producing large 

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