2
A. G. RYDER
2. PETROLEUM COMPOSITION
The chemical composition of crude petroleum oils varies enormously, and their
characterization requires the application of considerable instrumentation and time
resources. Both Hunt
2 and North
3 provide good foundations in the basics of petroleum
composition, and the geological factors that influence changes in oil composition.
Comprehensive, laboratory based chemical analysis of crude oils is done using a variety
of gravimetric, solvent extraction, and chromatographic techniques.
6, 7 Details of these
methods, their advantages, and disadvantages are outside the scope of this review.
However, it should be noted that the different methodologies employed, could provide
subtly different values for oil composition parameters. The primary compositional
parameters reported in fluorescence studies (if at all, see table 1) tend to be obtained from
column chromatography and in chemical terms are: an alkane (or paraffin, or aliphatic)
fraction, an aromatic fraction, a polar (or resin) fraction, and an asphaltene fraction.
8 The
asphaltene fraction is that portion of the oil, which is insoluble in pentane or heptane and
comprises of high molecular weight species.
9 Often the methods used, and the results
obtained for chemical composition will differ from laboratory to laboratory (depending
on the chromatographic conditions used, and whether the light, volatile fraction has been
removed prior to chromatographic analysis). Therefore much care should be taken in
comparing fluorescence data and results from different crude oil studies. In general, for
accurate characterisation of crude oil fluorescence one should have information on the
source rock, its density (API gravity), and the gross chemical composition (alkane,
aromatic, polar, and asphaltene concentration).
10
Table 1. Survey of crude oil data provided for fluorescence studies from a selection of
literature sources.
Reference
Location API gravity Source rock Chemical data
Abu-Zeid, et al.
11
Partial
No
No
No
Alpern et al.
12
No
Yes
a
No
Partial
Blanchet et al.
13
Yes
Yes
No
No
Camagni et al.
14
Partial
No
No
No
Hagemann & Hollerbach,
15
Yes
Partial
Partial
Partial
Measures et al.
16
Yes
Yes
No
No
Mullins, Mitra-Kirtley, & Zhu.
17
No
No
No
No
Mullins and Downare.
18
Partial
No
No
No
Quinn et al.
19
No
Yes
No
No
Rayner & Szabo.
20
Partial
Partial
No
No
Ryder, & Ryder et al.
21, 22
Partial
Yes
No
Partial
Ryder et al.
23
Yes
Yes
Yes
Yes
Ryder (2004),
10
Yes
Yes
Yes
Yes
Stasiuk et al.
24
Yes
No
No
Yes
Wang & Mullins.
25
Partial
Yes
No
No
Zhu & Mullins.
26
Partial
No
No
No
a Provided as oil density.
A. G. RYDER
2. PETROLEUM COMPOSITION
The chemical composition of crude petroleum oils varies enormously, and their
characterization requires the application of considerable instrumentation and time
resources. Both Hunt
2 and North
3 provide good foundations in the basics of petroleum
composition, and the geological factors that influence changes in oil composition.
Comprehensive, laboratory based chemical analysis of crude oils is done using a variety
of gravimetric, solvent extraction, and chromatographic techniques.
6, 7 Details of these
methods, their advantages, and disadvantages are outside the scope of this review.
However, it should be noted that the different methodologies employed, could provide
subtly different values for oil composition parameters. The primary compositional
parameters reported in fluorescence studies (if at all, see table 1) tend to be obtained from
column chromatography and in chemical terms are: an alkane (or paraffin, or aliphatic)
fraction, an aromatic fraction, a polar (or resin) fraction, and an asphaltene fraction.
8 The
asphaltene fraction is that portion of the oil, which is insoluble in pentane or heptane and
comprises of high molecular weight species.
9 Often the methods used, and the results
obtained for chemical composition will differ from laboratory to laboratory (depending
on the chromatographic conditions used, and whether the light, volatile fraction has been
removed prior to chromatographic analysis). Therefore much care should be taken in
comparing fluorescence data and results from different crude oil studies. In general, for
accurate characterisation of crude oil fluorescence one should have information on the
source rock, its density (API gravity), and the gross chemical composition (alkane,
aromatic, polar, and asphaltene concentration).
10
Table 1. Survey of crude oil data provided for fluorescence studies from a selection of
literature sources.
Reference
Location API gravity Source rock Chemical data
Abu-Zeid, et al.
11
Partial
No
No
No
Alpern et al.
12
No
Yes
a
No
Partial
Blanchet et al.
13
Yes
Yes
No
No
Camagni et al.
14
Partial
No
No
No
Hagemann & Hollerbach,
15
Yes
Partial
Partial
Partial
Measures et al.
16
Yes
Yes
No
No
Mullins, Mitra-Kirtley, & Zhu.
17
No
No
No
No
Mullins and Downare.
18
Partial
No
No
No
Quinn et al.
19
No
Yes
No
No
Rayner & Szabo.
20
Partial
Partial
No
No
Ryder, & Ryder et al.
21, 22
Partial
Yes
No
Partial
Ryder et al.
23
Yes
Yes
Yes
Yes
Ryder (2004),
10
Yes
Yes
Yes
Yes
Stasiuk et al.
24
Yes
No
No
Yes
Wang & Mullins.
25
Partial
Yes
No
No
Zhu & Mullins.
26
Partial
No
No
No
a Provided as oil density.