Paraffin Problems in Crude Oil Production And Transportation: A Review

Summary Problems related to crystallization and deposition of paraffin waxes during production and transportation of crude oil cause losses of billions of dollars yearly to petroleum industry. The goal of this paper is to present the knowledge on such problems in a systematic and comprehensive form. The fundamental aspects of these problems are defined, and characterizatin of paraffins and their solubility tendencies have been discussed. It has been established conclusively that n -paraffins are predominantly responsible for this problem. Comprehensive discussion on the mechanism of crystallization of paraffins has been included. Compounds other than n-paraffins, especially asphaltenes and resins, have profound effects on solubility of n-paraffins. In evaluations of the wax potential of a crude, the climate of the area concerned should be considered. Under the most favorable conditions, n-paraffins form clearly defined orthorhombic crystals, but unfavorable conditions and the presence of impurities lead to hexagonal and/or amorphous crystallization. The gelation characteristics are also affected the same way. An attempt was made to classify the paraffin problems into those resulting from high pipeline pressure, high restarting pressure, and deposition on pipe surfaces. Fundamental aspects and mechanism of these dimensions are described. Wax deposition depends on flow rate, the temperature differential between crude and pipe surface, the cooling rate, and surface properties. Finally, methods available in the literature for predicting these problems and evaluating their mitigatory techniques are reviewed. The available methods present a very diversified picture; hence, using them to evaluate these problems becomes taxing. A top priority is standardizing these methods for the benefit of the industry.