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Paraffin inhibitors are used in petroleum production operations to reduce wax deposition and/or reduce viscosity or complete gelling of high-wax-content petroleum fluids. When the treatment is for viscosity reduction or gel prevention, the paraffin inhibitor is commonly called a pour-point depressant. The active chemistries of paraffin inhibitor/pour-point depressant products are specialty polymers that alter the wax crystallization process, which, in turn, changes the characteristics of wax deposits and wax gel networks. The polymers are typically formulated in a carrier fluid for easy delivery (with a simple injection pump) to the petroleum stream that is to be treated. Most commonly, the polymer is dissolved in a solvent. This formulation must, of course, be stable and suitable for use in its particular application environment. The environment (principally ambient temperature) can vary widely depending on the geographical region and the season of the year. Similarly, constraints placed on paraffin inhibitor formulations vary accordingly. For example, paraffin inhibitors have been applied in conditions ranging from stringent extreme cold arctic locations (with temperatures to -40 degrees C and below) to tropical locations where warm year-round ambient temperatures are very amenable to the formulation of stable, high-activity products in carrier solvents. Paraffin inhibitors are also used in deep-water umbilical applications in which the formulation not only must be stable at the cold ambient seafloor temperatures (similar to 4 degrees C) but also must handle the combined effect of elevated pressure present in the umbilical line. In contrast, paraffin inhibitors are also applied, in applications in which thermal conditions are controlled with heated storage and injection. Although not widely used, heated injection allows the most active concentrated formulations to be applied and the widest range of chemistries to be selected. This paper discusses different paraffin inhibitor formulations and continuous injection applications in a variety of different environments. The applications discussed range from heated injection, to surface injection, to deep-water dry-tree applications, to deep-water umbilical applications, and to applications in subfreezing environments (from moderate freezing to extreme cold arctic conditions).