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Asphaltene 1

Asphaltene

Possible asphaltene molecule

Asphaltenes are molecular substances that are found in crude oil,

along with resins, aromatic hydrocarbons, and saturates (i.e. saturated

hydrocarbons such as alkanes).[1][2]

The word "asphaltene" was coined

by Boussingault in 1837 when he noticed that the distillation residue of 

some bitumens had asphalt-like properties. Asphaltenes in the form of 

asphalt or bitumen products from oil refineries are used as paving

materials on roads, shingles for roofs, and waterproof coatings on

building foundations.

Composition

Asphaltenes consist primarily of carbon, hydrogen, nitrogen, oxygen,

and sulfur, as well as trace amounts of vanadium and nickel. The C:H

ratio is approximately 1:1.2, depending on the asphaltene source.

Asphaltenes are defined operationally as the n-heptane (C

7H

16)-insoluble, toluene (C

6H

5CH

3)-soluble component of a carbonaceous material such as crude oil, bitumen, or coal. Asphaltenes have been shown

to have a distribution of molecular masses in the range of 400 u to 1500 u, but the average and maximum values are

difficult to determine due to aggregation of the molecules in solution.[3]

Analysis

The molecular structure of asphaltenes is difficult to determine because the molecules tend to stick together in

solution.[4]

These materials are extremely complex mixtures containing hundreds or even thousands of individual

chemical species. Asphaltenes do not have a specific chemical formula: individual molecules can vary in the number

of atoms contained in the structure, and the average chemical formula can depend on the source. Although they have

been subjected to modern analytical methods, including the well known SARA analysis, mass spectrometry, and

nuclear magnetic resonance, the exact molecular structures are difficult to determine. Given this limitation,

asphaltenes are composed mainly of polyaromatic carbon ring units with oxygen, nitrogen, and sulfur heteroatoms,

combined with trace amounts of heavy metals, particularly chelated vanadium and nickel, and aliphatic side chains

of various lengths.[5] Many asphaltenes from crude oils around the world contain similar ring units, which are linked

together to make highly diverse large molecules.[6]

Geochemistry

Asphaltenes are today widely recognised as dispersed, chemically altered fragments of kerogen, which migrated out

of the source rock for the oil, during oil catagenesis. Asphaltenes had been thought to be held in solution in oil by

resins (similar structure and chemistry, but smaller), but recent data shows that this is incorrect. Indeed, it has

recently been suggested that asphaltenes are nanocolloidally suspended in crude oil and in toluene solutions of 

sufficient concentrations. In any event, for low surface tension liquids, such as alkanes and toluene, surfactants are

not necessary to maintain nanocolloidal suspensions of asphaltenes.

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Asphaltene 2

The nickel to vanadium contents of asphaltenes reflect the pH and Eh conditions of the paleo-depositional

environment of the source rock for oil (Lewan, 1980;1984), and this ratio is, therefore, in use in the petroleum

industry for oil-oil correlation and for identification of potential source rocks for oil (oil exploration).

Occurrence

Heavy oils, oil sands, bitumen and biodegraded oils (as bacteria can not assimilate asphalten[e]s, but readily

consume saturated hydrocarbons and certain aromatic hydrocarbon isomers - enzymatically controlled) contain much

higher proportions of asphaltenes than do medium-API oils or light oils. Condensates are virtually devoid of 

asphaltenes.

Measurement

Asphaltene aggregation, precipitation or deposition can be predicted by modeling or artificial intelligent methods. It

also can be measured using imaging methods or filtration.

Production problemsAsphaltenes impart high viscosity to crude oils, negatively impacting production, also the variable asphaltene

concentration in crude oils within individual reservoirs creates a myriad of production problems.

Heat exchanger fouling

Asphaltenes are known to be one of the largest causes of fouling in the heat exchangers of the crude oil distillation

preheat train. They are present within micelles in crude oil, which can be broken down by reaction with paraffins

under high temperature. Once the protective micelle has been removed polar asphaltenes agglomerate and are

transported to the tube walls, where they can stick and form a foulant layer.

Asphaltene removal

Chemical treatments for removing asphaltene include:

1.1. solvents

2.2. dispersants/solvents

3.3. oil/dispersants/solvents

The dispersant/solvent approach is used for removing asphaltenes from formation minerals. Continuous treating may

be required to inhibit asphaltene deposition in the tubing. Batch treatments are common for dehydration equipment

and tank bottoms. There are also asphaltene precipitation inhibitors that can be used by continuous treatment or

squeeze treatments.[7]

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Asphaltene 3

References

[1][1] Mullins, OC et al. Editors, Asphaltenes, Heavy Oils and Petroleomics, Springer, New York (2007) 700 pages, 23 Chapters, 46 contributing

scientists.

[2] Asphaltene (http:/   /  tigger.  uic. edu/  ~mansoori/  Asphaltene. Molecule_html)

[3] Podgorski, D. C., et al. (2013). "Heavy Petroleum Composition. 5. Compositional and Structural Continuum of Petroleum Revealed." Energy

& Fuels 27(3): 1268-1276.

[4] McKenna, A. M., et al. (2013). "Heavy Petroleum Composition. 3. Asphaltene Aggregation." Energy & Fuels 27(3): 1246-1256[5][5] Asomaning, S., 1997. Heat exchanger fouling by petroleum asphaltenes. Ph.D. Thesis, University of British Columbia

[6] Rueda-Velasquez, R. I., et al. (2013). "Characterization of Asphaltene Building Blocks by Cracking under Favorable Hydrogenation

Conditions." Energy & Fuels 27(4): 1817-1829

[7] UNDERSTANDING PARAFFIN AND ASPHALTENE PROBLEMS IN OIL AND GAS WELLS, Petroleum Technology Transfer Council,

South Midcontinent Region, July 16, 2003 Workshop in Smackover, Arkansas at the Arkansas Natural Resources Museum (http:/   /  www. pttc.

org/  workshop_summaries/  sol_2003/  523.  htm)

External links

€ An in-depth article on asphaltenes from OilfieldWiki.com, the oilfield encyclopedia (http:/   /  www. oilfieldwiki.

com/  wiki/  Asphaltenes)

€ Article regarding asphaltene fouling by Irwin A. Wiehe (http:/   /  www. aiche-chicago. org/  symposium06/  wiehe.

pdf)

€ Asphaltene Aggregation from Crude Oils and Model Systems Studied by High-Pressure NIR Spectroscopy (http:/ 

 /  www. camo. com/  downloads/ 

Asphaltene_Aggregation_from_Crude_Oils_and_Model_Systems_Studied_by_High-Pressure_NIR_Spectroscopy.

pdf) (Source : American Chemical Society)

€ A comprehensive website about asphaltene and its role in petroleum fouling by Prof. GA Mansoori at the Univ. of 

Illinois at Chicago (http:/   /  www. uic. edu/  ~mansoori/  HOD_html)

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Article Sources and Contributors 4

Article Sources and ContributorsAsphaltene  Source: http://en.wikipedia.org/w/index.php?oldid=616521862 Contributors: A876, Akburnham, Albmont, AsmundErvik, BD2412, Beagel, BigrTex, Biscuittin, Brawny84,

Callanecc, ChemNerd, Craig Pemberton, Crowsnest, Daniel MerinoGarcia, Dpoduval, Duncan.france, Ebsirota, Edgar181, GGenov, Jacopo Werther, Jeffq, Knuto, Lamro, Michael Devore,

Mikenorton, Mr Accountable, Murrayrgray, Niceguyedc, Nick Y., Oftesb nise, Ohnoitsjamie, Oliver mullins, Petroleumengineer88, Petronerd, Rich Farmbrough, Saehrimnir, Saehry, Scifi.ss,

Still, Theanphibian, Tiddly Tom, Wavelength, Ynhockey, 58 anonymous edits

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