Review of studies on asphaltene - wax interaction and the effect thereof on crystalilization

Abstract

T his paper reviews the impact of asphaltenes on wax crystallization and on the properties of crude oils, and the consequences thereof on the flow assurance of waxy crude oil. It initially includes studies of the crystallization of both pure n-alkanes as well as the mixtures thereof, because they have led to an understanding of how their precipitation occurs along with their transitions of crystalline phases, particularly, by studies of X-ray diffraction (XRD). This is followed by the studies and results of crystallization in crude oils and/or the fractions thereof and how their properties are affected in the presence of asphaltenes.The results on the influence of asphaltenes are inconclusive and sometimes contradictory: some confirm that their presence decreases pour point, others affirm that it increases it and yet others say there is no effect. Similar results have been reported for properties such as crystallization point, phase transition and rheological properties. The influence of the chemical structure of asphaltenes on the change in crude oil properties has not been generalized either. It has been inferred that is possibly due to the interaction between aliphatic chains of asphaltenes and waxes, and it has been established that there is synergy in coprecipitation due to evidence in the analysis of organic deposits. ABSTRACT REVISIÓN DE LOS ESTUDIOS SOBRE INTERACCIÓN ASFALTENOS Y PARAFÍNAS E INCIDENCIA EN SU CRISTALIZACIÓN 40É apresentada uma revisão do efeito que os asfaltenos têm na cristalização de parafinas, nas propriedades de crus parafínicos e nas consequências na garantia de escoamento. Inicialmente são incluídos os estudos de cristalização de n-alcanos puros e de suas misturas onde foi possível entender como ocorre sua precipitação e transições de fases cristalinas, especialmente, por estudos de difração de raios-X (DRX). São analisados os resultados de estudos de cristalização em crus e/ou suas frações e como a presença dos asfaltenos afeta suas propriedades.Sobre a influência dos asfaltenos, os resultados não são conclusivos e em ocasiões são contraditórios: alguns confirmam sua contribuição para diminuir o ponto de fluidez, outros que o aumenta e em alguns casos que não o afeta. Resultados semelhantes são relatados para o ponto de cristalização, a transição de fases e as propriedades reológicas. Também não é possível generalizar qual é a influência da estrutura química dos asfaltenos sobre as propriedades dos crus. Infere-se que possivelmente é devida à interação entre suas cadeias alifáticas com as parafinas e estabelece-se que existe sinergia na coprecipitação pela evidência nas análises dos depósitos orgânicos. Se presenta una revisión del efecto que tienen los asfaltenos en la cristalización de parafinas, en las propiedades de crudos parafínicos y las consecuencias en el aseguramiento de flujo. Inicialmente se incluyen los estudios de cristalización de n-alcanos puros y de sus mezclas donde se ha podido entender como ocurre su precipitación y transiciones de fases cristalinas, especialm...

Adsorption-desorption of n–C7 asphaltenes over micro- and nanoparticles of silica and its impact on wettability alteration

“…A current description establishes that the chemical structure of asphaltenes is generally composed of polyaromatic cores attached to aliphatic chains, and they contain metals, such as vanadium, iron, and nickel, and heteroatoms, such as nitrogen, oxygen, and sulfur (Mullins, 2010). These heteroatoms polar functional groups are primarily responsible for the high dipole moment of asphaltenes promoting asphaltene self-association (Ariza-León, Molina-Velasco, Chaves-Guerrero, 2014;Goual and Firoozabadi, 2002). Asphaltene content in the oil depends on their classification, which is based on the American Petroleum Institute (API) gravity.…”

Wax-Inhibitor Interactions Studied by Isothermal Titration Calorimetry and Effect of Wax Inhibitor on Wax Crystallization

“…Heteroatoms, such as oxygen, nitrogen, sulfur or certain metals, are found in asphaltenes as well. The effect of asphaltenes on wax precipitation is discussed contradictorily in literature [16]. It has been reported that the presence of asphaltenes decreases pour point and strength of the formed wax-oil gel [26][27][28][29].…”

On the Optimum Aging Time: Magnetic Resonance Study of Asphaltene Adsorption Dynamics in Sandstone Rock

“…In addition to asphaltene adsorption, there is at least one another highly competitive mechanism responsible for severe formation damage and to pipeline transportation problems, that is, paraffin wax deposition. Though the primary cause of wax deposition is a loss in solubility in the crude oil, some reports suggest that asphaltenes play an important role providing crystal nucleation sites or simply restricting the diffusion of paraffins (the opposite effect on diffusion was also regularly reported). , A good review on the topic of asphaltene effects on wax crystallization is provided by Ariza-Léon et al So far, there is no consensus regarding the direction and magnitude of the effect of asphaltenes on wax precipitation, point of crystallization, pour point, and rheology of a host fluid.…”