Paraffin-base crude

The composition of crude oil may vary with the location and age of an oil field, and may even be depth dependent within an individual well or reservoir. Crudes are commonly classified according to their respective distillation residue, which reflects the relative contents of three basic hydrocarbon structural types paraffins, naphthenes, and aromatics. About 85% of all crude oils can be classified as either asphalt based, paraffin based, or mixed based. Asphalt-based crudes contain little paraffin wax and an asphaltic residue (predominantly condensed aromatics). Sulfur, oxygen, and nitrogen contents are often relatively higher in asphalt-based crude in comparison with paraffin-based crudes, which contain little to no asphaltic materials. Mixed-based crude contains considerable amounts of both wax and asphalt. Representative crude oils and their respective composition in respect to paraffins, naphthenes, and aromatics are shown in Figure 4.1. 

The presence of paraffin wax is usually reflected in the paraffinic nature of the constituent fractions, and a high asphaltic content corresponds with the naphthenic properties of the fractions. As a result, the misconception has arisen that paraffin-base crude oils consist mainly of paraffins and asphalt-base crude oils mainly of cyclic (or naphthenic) hydrocarbons. In addition to paraffin- and asphalt-base oils, a mixed base had to be introduced for those oils that leave a mixture of bitumen and paraffin wax as a residue by nondestructive distillation. 

Petroleum crude oils, which are divided for the purposes of conventional classification into three main types—asphalt (or naphthenic)-base, paraffin-base, and mixed-base—contain varying amounts of hydrocarbons which readily solidify and are identified as wax. The asphalt-base crudes may contain only a trace of wax, while the wax content of the paraffin-base crudes and the mixed-base crudes may be as high as 15% or higher (73). Crude oils with a wax content as high as 35% are known. 

Paraffin-Base Crude Oil Crude oil containing little or no asphalt, yielding at the refinery a high percentage of paraffin, lubricating oil and kerosene. 

Paraffinic-based crude oil. About 95% of the crude oil available is paraffinic-based, compared to about 5 % that is naphthenic-based. 

It is a mixture of oils and waxes stabilised by a third component and is obtained from still residues of paraffin base crudes after fractionation. It does not leave an oily stain on paper as wax is the external phase and oil tile internal phase. It can be used as a grease. 

Fig. 4-5. Tnie-boiling-point evaluation curves of a 42.2 API paraffin-base crude oil.

The evaluation of a paraffin-base crude oil is particularly simple because the oil contains no asphalt. Only a true-boiling-point distillation, con-... 

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