Molecular Characterisation of Petroleum M. Ahmed,1 S. Gong,1 D. Fuentes,1 S. Sestak,1 F. Theobald,2 and K. D’Silva3;1CSIRO Earth Science and Resource Engineering, North Ryde, Australia2Environmental Consulting, Cologne, Germany3Thermo Fisher Scientific, Bremen, Germany

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Key WordsAnalysis of aliphatic, aromatic and branched/cyclic hydrocarbon fractions, Thermo Scientific DFS High Resolution Mass Spectrometer

IntroductionComprehensive molecular characterisation of petroleum is used to solve issues related to exploration and production of oil and gas. It can help identify processes that occurred in reservoirs and along migration pathways. It provides the ability to understand the key geological information encoded in the geochemistry of gas and liquid hydrocarbons and can help oil companies deduce the origin and maturity of petroleum hydrocarbons (natural gas, coal seam gas or oils). Geochemical fossils or biological markers, popularly called biomarkers, frequently convey genetic information about the types of organisms contributing to the organic matter of sediments. They are used for correlations (oil-oil and oil-source rock), for reconstitution of depositional environments, and also as indicators for diagenesis and catagenesis.1

CSIRO Organic Geochemistry Team is a world leading provider of research services to the petroleum industries and state and federal agencies.

Located in Sydney Australia, CSIRO Organic Geochemistry Team have conducted genetic characterisation of oils, fluid inclusion oils, natural gases and potential source rock extracts for various research projects on behalf of international energy companies including Chevron, PETRONAS, Woodside, Oil Search, Exxon-Mobil, Petrobras, Interoil, Origin Energy, Roc Oil, and BP Exploration & Production Inc.

CSIRO Organic Geochemistry Team currently use a Thermo Scientific™ DFS™ high resolution GC-MS for the molecular analyses of sedimentary organic matter, e.g., crude oils, fluid inclusion oils, condensates, potential source rock extracts, solid bitumen, pyrolyzates of ashpaltene/kerogen, etc. The DFS instrument provides a range of capabilities required for this application, including; high resolution, full scan, selected ion monitoring (also known as multiple ion detection, MID) and multiple reaction monitoring (MRM) with stable and predictable metastable product ion formation. All of these capabilities are combined by CSIRO for comprehensive analyses of petroleum hydrocarbons.

2 This application note presents a brief description of the methods and chromatographic conditions, using the DFS high resolution GC-MS for the analyses of:

• Aliphatic and aromatic hydrocarbon fractions of the North Sea Oil-1, a geochemical standard sample from the Norwegian Petroleum Directorate

• Branched /cyclic hydrocarbon fraction of a standard mixture of oils called AGSO STD obtained from Geoscience Australia (formerly, the Australian Geological Survey Organization)

Results of these analyses for the identification/quantification of some selected hydrocarbon biomarkers are presented in the following section.

Methods

Gas Chromatographic Methods

GC Thermo Scientific Trace Ultra™ GC

Sampler Thermo Scientific TriPlus XT™

Carrier gas Helium

Carrier gas flow rate Constant (1.5 mL/min)

Injector Split/Splitless

Injection temperature 260°C

Injection volume 1 µL

Sample concentration 100 - 500 µg/mL in dichloromethane

GC column equivalent TraceGOLD™ TG-1MS 60 m × 0.25 mm, 0.25 µm film P/N 26099-1540 and

TraceGOLD TG-5MS 60 m × 0.25 mm, 0.25 µm film P/N 26098-1540

Temperature programs A) 40 °C ( 2 min) @ 4 °C min-1 to 310 °C (40 min)

B) 40 °C (2 min) @ 20 °C min-1 to 200 °C (0 min) 2 °C min-1 to 310 °C (40 min)

Mass Spectrometer Parameters

MS Thermo Scientific DFS

Electron energy 70 eV

Resolution 1000 at 5% peak height

Injection temperature 260 °C

Transfer line temperature 280 °C

Source temperature 280 °C

Mass Spectrometer Data Acquisition Methods

Full scan of analysis of aliphatic and m/z 50-550, scan rate 0.5 sdec-1. aromatic hydrocarbons GC program A.

Multiple ion detection (MID) analysis m/z 128, 134, 142, 154, 156, 166, of aromatic hydrocarbon fraction, 168, 170, 178, 183. GC program A. Method-A

Multiple ion detection (MID) analysis m/z 178, 180, 182, 183, 184.03, of aromatic hydrocarbon fraction, 184.12, 192, 197, 198.05, 198.14, Method-B 202, 206, 212, 216, 220, 234. GC program A.

Multiple ion detection (MID) analysis m/z 177, 183, 191, 205, 217,218, of aliphatic hydrocarbon or its 231.11, 231.21,253, 259. GC program B. branched chain and cyclic fraction

Multiple Reaction Monitoring (MRM) m/z 370>191, 384>191, 398>191, analysis for hopanes 412>191, 426>191, 440>191, 454>191, 468>191, 482>191. GC program B.

Multiple Reaction Monitoring m/z 358>217, 372>217, 386>217, (MRM) analysis for steranes 400>217, 414>217, 414>231. GC program B.

ResultsCrude oils and source rock extracts are complex mixtures of many classes of compounds including source and maturity related biomarkers such as n-alkanes, isoprenoids, terpanes, steranes and diasteranes. Some biomarkers are often present in very low concentrations requiring different modes of GC-MS analyses for their identification and/or quantification; full scan, multiple ion detection and multiple reaction monitoring (MRM).

Full scan analyses provide mass spectra for structural elucidation and chromatograms of all ions. Multiple ion detection (MID) methods acquire only selected ions, e.g., m/z 123, 191, 217, etc. and provide results of better sensitivity than full scan, providing information about trace components. This method can be used to determine the fingerprints for the selected compound types (e.g., bicyclic sesquiterpanes, hopanes, steranes and diasteranes). Multiple reaction monitoring analyses monitor a selected daughter ion (e.g., m/z 217) formed from molecular ions that decompose in the first field-free region of a double-focussing mass spectrometer. This method provides the necessary selectivity required to analyze these specific compounds in such a complex matrix; resulting in better sensitivity and signal-to-noise ratios.

3Full Scan Analyses

Figure 1. Full scan (a) Total ion chromatogram and (b) m/z 85 extracted ion chromatogram of the aliphatic hydrocarbon fraction showing the distributions of n-alkanes and isoprenoids. Pr = Pristane, Ph = Phytane.

n ‐C 14

Squalane

Contaminant NL:2.25E9TIC MS NSO1_ALI_01A_M

RT: 0.00 - 99.01

24

26 32.8736.0629.49 39 08

[a]Squalane (IS)

14

16

18

20

22

24

Abu

ndan

ce

29.49 39.0825.91

47.2522.11 63.4749.72

52.0818.14

n ‐C 8 n ‐C

Pr

Ph

2

4

6

8

10

12

Rela

tive

67.9069.56

14.1073.26

75.5081.22 84.898.08 89.29

7.980 14

RT: 0.00 - 99.01

10032.87

36.06

NL:7.92E7

m/z= 84.60-85.60 MS

NSO1_ALI _01A_M

n ‐C 14

0 10 20 30 40 50 60 70 80 90Time (min)

00.14

[b]

50

60

70

80

90

bund

ance

29.4939.08 41.95

25.91

47.25

22.1149.72

Squalane (IS)

[b]

10

20

30

40

50

Rela

tive A

b

52.0863.47

58.5918.14

14.1064.38

67.8910.3469.56

73 269 44

n ‐C 8

n ‐C 37

PrPh

0 10 20 30 40 50 60 70 80 90Time (min)

0

10 73 .269.44 75.51 81.21 89.287.99

37

4

C30 αβ

C29 αβ

C30*

RT: 20.00 - 82.00 SM: 5G

20 25 30 35 40 45 50 55 60 65 70 75 80 Time (min)

0

10

20

30

40

50

60

70

80

90

100

Rela

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Abun

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C31 αβ S

R S R

R R R

S

S S

Ts Tm

C29Ts

C30 βα

Gammacerane

C31 βα

C32 αβ C33 αβ

C34 αβ C35 αβ 19/3

20/3

21/3 23/3 24/3 25/3 24/4

26/3

C29*

MID Analyses

44.00 - 64.00 SM: 5G100

70

80

90

NL: 5.92E4m/z = 216.95 - 217.45 MSNSO1_110923_ALI_D

30

40

50

60

10

20

30

44 46 48 50 52 54 56 58 60 62 64Time (min)

RT:

Rela

tive

Abun

danc

e

20SC27βα

20RC27βα

20RC27αβ

20SC27αβ

20SC27ααα

20SC28αβ

20S*C28βα

20R*C28βα

20R + C βα 20S C27αββ

29

20S + C αβ 20R* C27αββ

28

20RC27ααα

20RC29βα

αβC29

20S

20RC28αββ

20SC28αββ

αααC28

20R

20SC29ααα

20RC29αββ

20SC29αββ

20RC29ααα

20SC30ααα

20SC30αββ

20RC30αββ

20RC30ααα

20S*C28ααα

Figure 3. MID mass chromatogram m/z 217 of the aliphatic hydrocarbon fraction showing C27

–C29

steranes and diasteranes. Peak assignments define stereochemistry at C-20 (S and R ); βα, αβ, ααα and αββ denote 13β(H),17α(H)-diasteranes, 13α(H),17β(H)-diasteranes, 5α(H),14α(H),17α(H)-steranes and 5α(H),14β(H),17β(H)-steranes, respectively. * = isomeric peaks (24S and 24R ).

Figure 2. MID mass chromatogram m/z 191 of the aliphatic hydrocarbon fraction showing the distribution of terpanes. Peak assignments define stereochemistry at C-22 (S and R ); αβ and βα denote 17α(H), 21β(H) -hopane and 17β(H), 21α(H)-moretane, respectively. 19/3 – 26/3 = C

19 – C

26 tricyclic terpanes, 24/4 = C

24

tetracyclic terpane, Ts = C27

18α(H), 22,29,30-trisnorneohopane, Tm = C27

17α(H), 22,29,30-trisnorhopane.

5

Figure 4. (a) m/z 170.11, (b) m/z 192.09, (c) m/z 206.11 and (d) m/z 234.14 mass chromatograms of the aromatic hydrocarbon fraction showing the distributions of C

3-alkylnaphthalenes, methylphenanthrenes, C

2-alkylphenanthrenes and retene, respectively. TMN = Trimethylnaphthalene, MP= Methylphenanthrene,

EP = Ethylphenanthrene, DMP = Dimethylphenanthrene.

RT: 36.8 - 39.8 SM:5G

70

80

90

100 NL: 1.41E6m/z = 169.61- 170.61 MSNSO1_ARO _24JUL_B

70

80

90

100[a]

1,3,7‐TMN

1,3,6‐TMN

1,3,5‐+ 1,4,6‐TMN2,3,6‐TMN

1,2,7‐TMN3 MP

2‐MP

9‐MP

1‐MP

20

30

40

50

60

20

30

40

50

601,6,7‐TMN

1,2,5‐TMN

1,2,4‐

1,2,6‐TMN

3‐MP

37.0 37.5 38.0 38.5 39.0 39.5Time (min)

0

10

20

47.0 47.5 48.0 48.5 49.0Time (min)

0

10

20

100 100

1,2,3‐TMNTMN

Retene1,3‐+ 3,9‐+ 3,10‐+ 2,10‐DMP

50

60

70

80

90

50

60

70

80

90

3,5‐+ 2,6‐DMP

2,7‐DMP

1,6‐+ 2,9‐+ 2,5‐DMP

1,7‐DMP

0

10

20

30

40

0

10

20

30

40

3‐EP

9‐+ 2‐+ 1‐EP +3,6‐DMP

, ,

2,3‐+ 1,9‐+ 4,9‐+ 4,10-DMP

1,8‐DMP1,2‐DMP

49.5 50.0 50.5 51.0 51.5 52.0 52.5Time (min)

52 53 54 55 56 57 58 59 60Time (min)

0

Rela

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Abun

danc

eRe

lativ

e Ab

unda

nce

[c] NL: 9.86E5m/z = 205.61- 206.61 MSNSO1_aro _24jul_c

RT: 49.50 - 52.50 SM:5G

[b] NL: 1.54E6m/z = 191.59 - 192.59 MSnso1_aro _24jul_C

RT: 47.00 - 49.00 SM:5G

Rela

tive

Abun

danc

e

NL: 9.86E5m/z = 205.61- 206.61 MSNSO1_aro _24jul_c

[d]

Rela

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Abun

danc

e

RT: 52.00 - 60.00 SM:5G

6

42.00 - 58.00 SM: 5GRT:

40

60

80

NL: 1.15E4

m/z= 215.70-232.70 F: + c

EI SRM ms2

372.40@cid0.00

[215.70-218.70] MS

AGSO 06AUG12 STER

XT

60

80

1000

20_ _

NL: 4.02E3

m/z= 215.70-232.70 F: + c

EI SRM ms2

386.40@cid0.00

[215 70 218 70] MSXT

XT

m/z 386 →217

80

1000

20

40.

AGSO_06AUG12_STER

NL: 9.22E3

m/z= 215.70-232.70 F: + c

EI SRM ms2

XTXT C28 Steranes and

diasteranes

100

0

20

40

60 400.40@cid0.00

[215.70-218.70] MS

AGSO_06AUG12_STER

NL: 8.80E2

20

40

60

80 m/z= 215.70-232.70 F: + c

EI SRM ms2

414.40@cid0.00

[215.70-218.70] MS

AGSO_06AUG12_STER

20Sm/z 414 → 217

C30 Steranes and diasteranes 

42 44 46 48 50 52 54 56 58Time (min)

0

C30βα

20RC30βα

20SC30ααα

20RC30αββ

20SC30αββ

αααC30

20R

m/z 400 → 217

20SC29βα

C29 Steranes and diasteranes 

R20C29αβ

20RC29βα

C29αβ20S

20RC29αββ

20SC29ααα 20RC29

ααα

20SC29αββ

20S*C28βα

20R*βαC28

S20C28αβ

20R*C28αβ

20S*C 28ααα 20R C28

αββ20SC28

αββ

m/z 372 → 217C27 Steranes and diasteranes 

20RC27ααα

20SC27αββ

20RC27αββ20SC27

ααα

R20C27αβ

S20C27αβ20RC27

βα20SC27

βα

Rela

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100

20RC28ααα

MRM Analyses

Figure 6. MRM chromatograms showing m/z M+>217 metastable transitions of C27

, C28

, C29

and C30

steranes and diasternaes. Peak assignments define stereochemistry at C-20 (S and R ); βα, αβ, ααα and αββ denote 13β(H),17α(H)-diasteranes, 13α(H),17β(H)-diasteranes, 5α(H),14α(H),17α(H)-steranes and 5α(H),14β(H),17β(H)-steranes, respectively. XT = cross talks, * = isomeric peaks (24S and 24R ).

RT: 50.00 - 80.00 SM: 5G

40

60

80

100 NL: 1.90E4

m/z= 189.70-192.70 F: + c EI SRM ms2 370.40@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

 m/z 370 →191C27 Hopanes

TsTm

Bicadinane T

Bicadinane T1

80

1000

20

40

NL: 1.08E4m/z = 189.70-192.70 F: + c EI SRM ms2 384.40@cid0.00 [189.70-192.70] MS AGSO 25JUL HOPS

Bicadinane RC 27

XT

80

1000

20

40

_

NL: 4.32E4

m/z = 189.70-192.70 F: + c EI SRM ms2 398 40@cid0 00

28,3

0-BN

H

TNH

C 29 αβ

1000

20

40

60

.

[189.70-192.70] MS AGSO_25JUL_HOPS

NL: 3.97E4

C 29 Ts

C 29* C 29 25 ‐nor

C 30 αβ

XT

20

40

60

80m/z = 189.70-192.70 F: + c EI SRM ms2 412.40@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

C

Oleanane±Lupane

C 30* C 30 30 ‐norGammacerane

50 55 60 65 70 75 80Time (min)

0

20

40

60

80

100 NL: 8.87E3TIC F: + c EI SRM ms2 440.40@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

C 32SR

RT: 58.59 - 88.59 SM: 5G

40

60

80

100

ative

Abu

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NL: 1.53E4m/z= 189.70-192.70 F: + c EI SRM ms2 426.40@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

C 31S

R

020

Rel C 31

20

40

60

80

1000

20

NL: 4.49E3m/z= 189.70-192.70 F: + c EI SRM ms2 454.50@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

C 33S

R

20

40

60

80

1000

0

NL: 2.08E3m/z= 189.70-192.70 F: + c EI SRM ms2 468.50@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

C 34S

R

20

40

60

80

1000

NL: 1.69E3m/z= 189.70-192.70 F: + c EI SRM ms2 482.50@cid0.00 [189.70-192.70] MS AGSO_25JUL_HOPS

C 35S

R

60 65 70 75 80 85Time (min)

0

29,3

0-BN

H

25,3

0-BN

H

β

60

Rela

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Rela

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lativ

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Rela

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e

αβ

αβ

_

αβ

αβ

Rela

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danc

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*

αβ

m/z 384 →191C28 Hopanes

m/z 398 →191C29 Hopanes

C29βα

m/z 412 →191C30 Hopanes

m/z 426 →191C31 Hopanes

m/z 440 →191C32 Hopanes

m/z 454 →191C33 Hopanes

C 32*

C 33*

m/z 468 →191C34 Hopanes

m/z 482 →191C35 Hopanes

Figure 5. MRM chromatograms showing m/z M+>191 metastable transitions of C27

, C28

, C29

, C30

, C31

, C32

, C33

, C34

and C35

hopanes. XT = cross talk, BNH = Bisnorhopane, TNH = 17 α(H), 18 α(H), 21 β(H)-trisnorhopane.

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ConclusionsThe capabilities of the Thermo Scientific DFS high resolution mass spectrometer have enabled the continuation and development of oil biomarker research at CSIRO Organic Geochemistry Laboratories.

The results generated using the DFS instruments allow CSIRO to elucidate and quantify the molecular distribu-tions of the aliphatic and aromatic hydrocarbon biomarkers, such as, n-alkanes, regular isoprenoids, steranes and diasteranes, tri- and tetracyclic terpanes, hopanes, alkylnapthalenes, alkylphenanthrenes, retene, etc. (Figs 1 – 6). These results provide useful tools for the assessment of:

• Secondary alteration processes - biodegradation, evaporative fractionation, water washing

• Source or origin of organic matter - higher plants, algae, prokayriotic, eukaryotic

• Thermal maturity - immature, mature, over mature

• Palaeo-environmental condition - marine, deltaic, lacustrine, terrigeneous

• Lithology - clay rich, carbonates

• Geological age

• Oil-oil and/or oil-source correlations

Applications of such results in petroleum exploration geochemistry are described in numerous papers2–5 and also in CSIRO publications.6–9

AcknowledgementsWe would like to thank the team at CSIRO Sydney for the analysis of all samples and preparation of this application note.

References1. Tissot, B.P., Welte, D.H., 1984. Petroleum formation

and occurrence, pp. 699. Springer, Berlin.

2. Seifert, W.K., Moldowan, J.M., Jones, R.W., 1979. Applications of biological marker chemistry to petroleum exploration, 2, pp. 425-438. Heyden, London.

3. Mackenzie, A.S., 1984. Applications of biological markers in petroleum geochemistry. In: J.M. Brooks, D.H. Welte (Eds.), Advances in Petroleum Geochemistry 1 (Ed. by J.M. Brooks, D.H. Welte), pp. 115-212. Academic Press, London.

4. Peters, K.E., Walters, C., Moldowan, J.M., 2005. The Biomarker Guide, pp. 1155 pp. Cambridge University Press, Cambridge.

5. Alexander, R., Larcher, A.V., Kagi, R.I., Price, P.L., 1988. The use of plant derived biomarkers for correlation of oils with source rocks in the Cooper/Eromanga Basin System, Australia. APEA Journal, 28(1), 310-324.

6. George, S.C., Volk, H., Dutkiewicz, A., Ridley, J., Buick, R., 2008. Preservation of hydrocarbons and biomarkers in oil trapped inside fluid inclusions for >2 billion years. Geochimica et Cosmochimica Acta, 72, 844-870.

7. Gong, S., George, S.C., Volk, H., Liu, K., Peng, P., 2007. Petroleum charge history in the Lunnan Low Uplift, Tarim Basin, China - Evidence from oil-bearing fluid inclusions. Organic Geochemistry, 38, 1341-1355.

8. Volk, H., Kempton, R.H., Ahmed, M., Gong, S., George, S.C., Boreham, C.J., 2009. Tracking petroleum systems in the Perth Basin by integrating microscopic, molecular and isotopic information on petroleum fluid inclusions. Journal of Geochemical Exploration, 101, 109.

9. Ahmed, M., Volk, H., Allan, T., Holland, D., 2012. Origin of oils in the Eastern Papuan Basin, Papua New Guinea. Organic Geochemistry, 53, 137-152.