Molecular Structure and Aggregation of Asphaltenes and Petroleomics

After successful isolation of the most interfacially active subfraction of asphaltenes (IAA) reported in part one of this series of publications, comprehensive chemical analyses including ES-MS, elemental analysis, FTIR and NMR were used to determine how the molecular fingerprint features of IAA are different from those of the remaining asphaltenes (RA).Compared with RA, the IAA molecules were shown to have higher molecular weight and higher contents of heteroatoms (e.g., three times higher oxygen content). The analysis on the elemental content and FTIR spectroscopy suggested that IAA contained a higher content of high polarity sulfoxide groups which were not present in the RA. The results of ES-MS, NMR, FTIR and elemental analysis were used to construct average molecular representations of IAA and RA molecules. These structures were used in molecular dynamic (MD) simulation to study interfacial and aggregation behaviors of the proposed representative molecules. MD simulation study showed little affinity of representative RA molecules to the oil/water interface while the representative IAA molecules had a much higher interfacial activity, which corresponds to the extraction method. The aggregation of IAA molecules in the bulk oil phase and their adsorption at oil/water interface were not directly related to the ring system but rather to the associations between or including sulfoxide groups. The IAA molecules self-assembled in solvent, forming supramolecular structures and a porous network at the oil/water interface as suggested in our previous work. The results obtained in this study provide a better understanding of the role of asphaltenes in stabilizing petroleum emulsions.

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“…About 75% of the sulfur atoms in RA and IAA were assigned as thiophenes, which is in agreement with literature. [43] Page 17 of 41…”

Section: Molecular Representations For Iaa and Ra (Chemdraw)mentioning

confidence: 99%

Asphaltene Subfractions Responsible for Stabilizing Water-in-Crude Oil Emulsions. Part 2: Molecular Representations and Molecular Dynamics Simulations

et al. 2015

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“…As a definition, petroleum asphaltenes is the fraction of the crude oil that precipitates upon addition of n -alkanes at a solvent to oil ratio of 40:1 . Furthermore, asphaltenes are monomeric polycyclic aromatic hydrocarbons containing heteroatoms such as N, O, and S and metal compounds such as V, Ni, and Fe. , The petroleum asphaltenes constitute a potential risk for precipitation during oil recovery, leading to problems with organic deposition and water-in-crude oil formation. − Asphaltenes that are obtained from dead crude oils in the laboratory may not be the same as asphaltenes precipitated under oil recovery conditions. This has in fact been shown recently by Klein et al, who compared asphaltenes obtained down hole by pressure drop with heptane-precipitated asphaltenes.…”

Section: Introductionmentioning

confidence: 99%

Asphaltenes Precipitated by a Two-Step Precipitation Procedure. 1. Interfacial Tension and Solvent Properties

et al. 2007

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Asphaltenes were precipitated into two fractions using a two-step precipitation procedure. The first fraction was obtained by mixing 3:1volumes of n-pentane/crude oil followed by filtration. In the following step the second fraction was precipitated out from the filtrate using 18:1 volumes of n-pentane/crude oil. Whole asphaltenes were precipitated using 40:1 pentane-to-crude oil ratio. Three crude oils were used and the asphaltene fractions obtained were characterized with regard to onset of precipitation, interfacial tension and radius of gyration. The second fraction was more soluble at increasing heptane-to-toluene ratios, more interfacially active and showed different organization properties at the interface between oil and water. Small angle neutron scattering showed that the second fraction formed aggregates with lower radius of gyration. The results show that asphaltenes consist of fractions with different solvent properties and indicates that asphaltenes should be looked at as more than one solubility class.

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New, Highly Effective Asphaltene Removal System With Favorable HSE Characteristics

Frost

Daussin

Domelen

2008

SPE International Symposium and Exhibition on Formation Damage Control

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Paraffin and asphaltene problems can significantly reduce well profitability, causing troublesome operational issues, damaging formations, and decreasing production. Although often mentioned together, paraffin and asphaltene are distinctly different in their composition and behavior and different remediation solutions are required. In comparison, asphaltene deposition and removal is much more problematic than paraffin deposition and removal. The most common asphaltene removal techniques use xylene or xylene mixtures, which typically have limited effectiveness in addition to undesirable health, safety, and environmental characteristics. This paper describes laboratory investigation of alternative solvent systems for removal of asphaltene deposits. Theoretical solvency parameter comparison based upon methods developed by Hildebrand and Hansen allowed solvents and cosolvents to be screened. The problem of formation wettability was addressed through the use of water-wetting surfactants. Finally, it was discovered that the primary solvent and cosolvent(s) could be dispersed in water yielding a water/aromatic solvent mixture that would not only effectively dissolve and disperse asphaltene, but also leave the formation in a water-wet state to delay production decline. The new water-based asphaltene removal system was first applied in southern Europe in 2005. Since then, the system has been optimized for broader global operations whilst maintaining the favorable HS&E characteristics of the initial development. The system is unique as it provides a high-flashpoint water/solvent mixture with solvency power often greater than xylene and the additional benefit of leaving the formation strongly water-wet. Introduction Problems associated with asphaltene and paraffin deposition have been identified in petroleum literature for over 70 years. Although often mentioned together, paraffin and asphaltene are distinctly different in composition and behavior. As a result, different remediation solutions are required. Paraffins are composed of straight-chain hydrocarbons generally accepted to be C18–20 up to C70 or higher. Paraffins may also contain a variety of branched alkyl or saturated cyclic groups. Asphaltenes are heterocyclic unsaturated macromolecules consisting primarily of carbon, hydrogen, and minor components such as sulfur, oxygen, nitrogen, and various heavy metals. These higher-molecular-weight components of crude oil are in equilibrium under normal reservoir conditions. As crude oil is produced, this equilibrium may be upset by a number of factors leading to asphaltene deposition. Asphaltene Deposition and Remediation Asphaltene deposition can occur anywhere in the production life cycle: in the formation, in the near-wellbore region including perforations, in the tubing, downhole and surface chokes, surface flow lines, and separation equipment. Predicting where asphaltene deposition might occur requires an understanding of the mechanisms for asphaltene deposition. The key causes are pressure decrease and the introduction of incompatible fluids (Newberry and Barker 2000).

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Molecular Structure and Aggregation of Asphaltenes and Petroleomics

Cited by 4 publications

References 41 publications

Asphaltene Subfractions Responsible for Stabilizing Water-in-Crude Oil Emulsions. Part 2: Molecular Representations and Molecular Dynamics Simulations

Asphaltene Subfractions Responsible for Stabilizing Water-in-Crude Oil Emulsions. Part 2: Molecular Representations and Molecular Dynamics Simulations

Asphaltenes Precipitated by a Two-Step Precipitation Procedure. 1. Interfacial Tension and Solvent Properties

New, Highly Effective Asphaltene Removal System With Favorable HSE Characteristics

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