Physicochemical Characterization of Asphaltenes (original) (raw)
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Spectroscopic Analysis of Crude Oil Asphaltenes at Molecular Level
Petroleum Chemistry, 2020
In the present study, a scientific challenge of determination of various structural parameters of asphaltenes of medium heavy, heavy, and light crude oils is overcome by different spectroscopy techniques. Fourier Transform Infrared spectroscopy methods revealed indexing information besides clarification of different functional groups of asphaltenes. Analysis of Raman spectra of asphaltenes exhibited a higher average molecular size and more complicated chemical structures for the light crude oil asphaltenes compared to the ones from the heavy and medium heavy oils. Clarification of such chemical structures reveals why asphaltene molecules form aggregates leading to precipitation in particular when the percentage of asphaltenes is closer to and less than 1 wt % as in the case of light crude oils.
The Stabilization of Asphaltenes in Different Crude Fractions: A Molecular Approach
Journal of the Brazilian Chemical Society, 2021
The conditions of petroleum extraction may allow asphaltenes to precipitate, causing deposition that clogs wells, pipes and equipment, consequently reducing productivity. In this work, the solubility parameters and precipitation onset of polar fractions of heavy crudes from Brazilian fields were estimated using a simplified system of n-heptane/toluene mixtures. Asphaltenes were extracted by two different methods with regard to pressure and temperature. The samples were physically and chemically characterized, and both density (1053-1159 kg m-3) and molecular weight (1176-5316 g mol-1) were estimated based on the density of diluted asphaltenes in toluene solutions. The solubility of those fractions was studied as well as their solubility parameter (ca. 19-23 MPa0.5) based on regular solution theory, Flory-Hüggins theory and empirical correlation. The influence of asphaltene concentration (between 0.5 and 5.0 g L-1) on the solubility parameter and precipitation onset was studied, and ...
Critical review of asphaltene properties and factors impacting its stability in crude oil
2019
Asphaltene is a component of crude oil that has been reported to cause severe problems during production and transportation of the oil from the reservoir. It is a solid component of the oil that has different structures and molecular makeup which makes it one of the most complex components of the oil. This research provides a detailed review of asphaltene properties, characteristics, and previous studies to construct a guideline to asphaltene and its impact on oil recovery. The research begins with an explanation of the main components of crude oil and their relation to asphaltene. The method by which asphaltene is quantified in the crude oil is then explained. Due to its different structures, asphaltene has been modeled using different models all of which are then discussed. All chemical analysis methods that have been used to characterize and study asphaltene are then mentioned and the most commonly used method is shown. Asphaltene will pass through several phases in the reservoir beginning from its stability phase up to its deposition in the pores, wellbore, and facilities. All these phases are explained, and the reason they may occur is mentioned. Following this, the methods by which asphaltene can damage oil recovery are presented. Asphaltene rheology and flow mechanism in the reservoir are then explained in detail including asphaltene onset pressure determination and significance and the use of micro-and nanofluidics to model asphaltene. Finally, the mathematical models, previous laboratory, and oilfield studies conducted to evaluate asphaltene are discussed. This research will help increase the understanding of asphaltene and provide a guideline to properly study and model asphaltene in future studies.
Structural Study of Asphaltenes from Iranian Heavy Crude Oil
Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles, 2013
-Étude structurale d'asphaltènes de pétrole brut lourd iranien-Dans la présente étude, la précipitation d'asphaltènes du pétrole brut lourd iranien (au large du golfe Persique) a été effectuée au moyen de n-pentane (n-C 5) et de n-heptane (n-C 7) comme alcanes légers précipitants. Plusieurs techniques analytiques, chacune utilisant différents principes, ont ensuite été utilisées pour caractériser la structure des asphaltènes précipités. Le rendement en asphaltènes obtenu par l'utilisation du précipitant n-pentane était plus élevé que pour les asphaltènes précipités à l'aide du n-heptane. L'extraction des asphaltènes a affecté les fractions de maltènes n-C 5 et n-C 7 à des températures inférieures à 204 °C, comme l'indiquent les données obtenues par la technique de distillation simulée. La viscosité du pétrole lourd est influencée par la teneur et le comportement des asphaltènes. La dépendance de la viscosité du pétrole lourd testé avec le taux de cisaillement appliqué a été déterminée et l'écoulement était faible à γ. supérieur à 25 s-1. Les échantillons de pétrole lourd reconstitués ont été préparés en ajoutant différentes quantités d'asphaltènes aux maltènes (pétrole lourd désasphalté) et les effets des asphaltènes ont été plus prononcés à la basse température de 25 °C, comparés à ceux obtenus à des températures plus élevées. Selon le modèle de loi de puissance utilisé dans cette étude, la fluidité du pétrole lourd testé a révélé un caractère pseudoplastique. Les résultats structuraux obtenus à partir de la spectroscopie InfraRouge à Transformée de Fourier (IRTF) ont montré la présence de différents groupes fonctionnels dans les asphaltènes précipités. Par exemple, la présence de différents hydrocarbures (aliphatique, aromatique et alicyclique), basée sur leurs caractéristiques dans le spectre IRTF, a été confirmée. Les résines sont des dispersants efficaces et le retrait de cette fraction du pétrole brut perturbe la nature colloïdale du pétrole lourd, la floculation et la précipitation des asphaltènes finissant par se produire. L'apparition de pores sur les images SEM (Scanning Electron Microscopy) a été utilisée comme indicateur du détachement de la résine. A l'aide de la spectroscopie de Résonance Magnétique Nucléaire (RMN) 1 H et 13 C, deux paramètres structuraux importants des asphaltènes ont été déterminés. A savoir, l'aromaticité (f a) et le nombre moyen d'atomes de carbone par chaîne alkyle latérale (n carbone), où f a pour les asphaltènes n-C 5 était plus faible (0,39) que celui obtenu avec le solvant n-C 7 (0,49). En outre, les valeurs du paramètre n carbone étaient respectivement de 7,7 et 5,7 pour les asphaltènes n-C 5 et n-C 7. L'identification structurale des composés du pétrole représente un prérequis pour les différentes techniques utilisables pour la transformation du pétrole lourd.
Adsorption Science & Technology, 2014
Five crude oil samples with different physical properties have been studied with respect to asphaltene stability. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging approach of n-heptane-induced precipitation has been used to monitor crude oil behaviour under dilution with a flocculation agent. For each sample, the dynamics of asphaltene precipitation has been observed by applying this chemical imaging method. Based on these data, the stability of crude oil samples has been compared and the correlation between asphaltene stability and crude oil properties has been proposed.
Asphaltenes in heavy crude oil: Designation, precipitation, solutions, and effects on viscosity
Journal of Petroleum Science and Engineering, 2016
The results of the evaluation of asphaltene content in heavy crude oil depend on the solvent chosen; and the products obtained at this evaluation have varying effects on oil viscosity. In the experiments performed to separate compounds that might be assigned conditionally to the group of asphaltenes, not only standard solvents such as pentane and hexane but also diethyl and diisopropyl ethers as well as hexamethyldisiloxane were employed. The chemical composition of asphaltenes (as estimated using the IR method) depends on the precipitant used. The quantity of precipitated asphaltenes is directly correlated with the energy of the intermolecular interaction of the solvent. In this study, the effects of different "asphaltenes" on oil properties were evaluated by measuring the rheology of the solutions in tetralin at a wide range of temperatures. These solutions demonstrate very different properties (from Newtonian fluid to gel) depending on the concentration. Viscosity depends on the nature of the solvent used to precipitate asphaltenes. Using diethyl ether yields the smallest quantity of asphaltenes but they creates the most viscous solutions. The removal of asphaltenes leads to a significant decrease in heavy oil viscosity. Heavy oil viscosity can be decreased by 2-3 orders. The intensity of the effect is determined by the solvent's solubility parameter.
Asphaltene Stability of Some Iraqi Dead Crude oils
Journal of Engineering
Asphaltene is one of the fractions of the crude oil which is soluble in aromatics such as benzene or toluene and insoluble in alkane such as n-heptane, n-pentane or petroleum ether (mixture of alkane compounds). Asphaltene precipitation is one of the most common problems that sometimes occurs in both oil recovery and refinery processes as a result of changing in pressure, oil composition, or temperature. Therefore the stability of asphaltene in the crude oil must be studied to show the tendency of it for precipitating asphaltene to prevent it (Asphaltene precipitation and deposition problem) and eliminate the burden of high treatment costs. In the present study, saturate, aromatic, resin and asphaltene (SARA) analysis of the six dead crude oil samples from different Iraqi oil fields was conducted by using open column liquid chromatography after separating the asphaltene from them through filtration process. The asphaltene stability of dead crude oil samples was studied depending on...