Critical review on wax deposition in single-phase flow

• Published in: Fuel (Guildford) Vol. 293; p. 120358
• Main Authors: van der Geest, Charlie, Melchuna, Aline, Bizarre, Letícia, Bannwart, Antonio C., Guersoni, Vanessa C.B.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.06.2021; Elsevier BV
• Subjects: Crystals; Deposition; Empirical analysis; Flow assurance; Heat transfer; Mass transfer; Molecular diffusion; Molecular modelling; Phase transitions; Single-phase flow; Wax deposition; Waxes; Waxy crude oil; Flow assurance; Wax deposition; Waxy crude oil
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.120358

•Molecular Diffusion may not be the dominant mechanism in wax deposition.•Phase transition (partial freezing), often disregarded, might be the dominant phenomena.•All evidence shows a constant temperature of the interface (Phase Transition!).•There are several assumptions regarding the morphology of crystals in the deposit that have never been experimentally verified. Wax deposition is a costly problem for the O&G industry, especially for pipelines in cold environments. For at least three decades, the scientific community has overwhelmingly agreed that molecular diffusion is the main mechanism for wax deposition. There are, however, severe problems with models based on molecular diffusion. They rely on untested hypotheses and several empirical correlations; hence, they can hardly predict the experimental data from laboratory. For real fields, the prediction is no better than an educated guess – heuristic solutions. Several research areas in wax deposition need to be better understood, and these are discussed in detail here, with a highlight to the most important concern: the controlling mechanism. Is wax deposition indeed a mass transfer controlled phenomenon? What is the evidence supporting this “general knowledge”? Is it possible that, for some conditions, mass transfer is dominant, and for others, the phase transition mechanism is dominant? Apart from this, we also discuss other issues: the accuracy of empirical correlations for diffusivity, the behavior of crystals in the deposit and how that influences the general deposit behavior, non-Newtonian influence on heat transfer and mass transfer, among others. Wax deposition is a complex topic that has been reviewed over and over. In this review, however, we focus on both presenting what has been discussed in the literature and make a critical analysis. The goal is to increase the general knowledge by highlighting a number of gaps and challenges related to this complex and financially exorbitant issue.