When a waxy crude oil is cooled, i.e. in a submarine pipeline, the crude oil temperature reaches the ambient temperature. At temperatures below die cloud point/wax appearance point (WAP), paraffins start to crystallize.

The wax precipitated from oil mixtures primarily consists of C18 to C36 (paraffin waxes) or C20 to C60 (microcrystalline waxes), both made up of aligned paraffinic and naphtenic molecules(1) ). Paraffin waxes are also called macrocrystalline(2) .

The wax may be deposited in pipelines at higher temperatures than those measured in the laboratory where the pipeline wall roughness and/or presence of nucleation sites, such as solids, corrosion products etc., play great role for depositing wax from undersaturated fluids.

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