organic geochemistry characterization in oil and gas generating potential source rock and exploration.

1. Organic Geochemistry Characterization in Oil & Gas
Generating Potential of Source Rock and exploration
AamirAli
MasterCandidate
7/3/2021
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2. Contents
• overview of petroleum organic geochemistry characterization
• Source rock evaluation
• Methodology
• Result & Discussion
i. TOC & Rock Eval analysis
ii. Biomarker characterization
iii. Isotopic analysis
• Conclusion
• References
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3. overview of petroleum organic geochemistry
characterization
• Petroleum originates from a small fraction of
the organic matter deposited in sedimentary
environments
• Terrestrially-derived organic (plant) &
marine (zooplankton)
• Lagoons, estuaries, deep basins within the
continental margins have both organic
contributions, sedimentation and a
reasonable anaerobic environment.
• petroleum generation: 1)Diagenesis, 2)
Catagenesis 3) Metagenesis
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Conversion of organic matter into hydrocarbon
Oil Window is the depth range over which
oil generation occurs.
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5. SOURCE ROCK EVALUATION
• Quantity of organic matter(TOC%):
• Determining the quantity of OM in Source rock
• Toc indicator the richness of OM, kerogen & bitumen
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Source
rock
Potential
Effective
Possible
Thermal maturity & immature Source
potential/May
have hydrocarbon
expelled
Already generated &
expelled hydrocarbon

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Quality of
organic
matter
Rock Eval pyrolysis:
Decomposition of
organic matter by
temperature and
anoxic condition
Quality of kerogen are usually
interpreted on graph derived
from traditional Van Krevelen
Diagram; H/C, O/C ratios with
HI and OI.

7. • Kerogen types and hydrocarbon potential
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Kerogen type based on HI

8. • Vitrinite Reflectance(Ro%)
• Dominant organic constituent humic coals; Measure the maturity of
organic matters in rocks
• Measure the fraction of incident beam that is reflected from an individual
vitrinite particle.
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9. • Thermal maturation
• Maturity increases temperature at which the maximum rate of
pyrolysis occur increases.
• Tranformation ratio: S1(S1+S2)
• Increasing maturity, kerogen is converted to
bitumen(S2 de while S1 inc).
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10. Methodology
• Rock Eval II instrument
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Rock Eval prolyser LECO carbon analyzer

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Leica microscope: vitrinite
reflectance

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Gas chromatography-Mass spectrometry: Biomarkers
Gas Chromatograph: Stable Isotope

13. Result & Discussion
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TOC and Rock
pyrolysis
Biomarker
characteristics
Stable Isotopic
analysis

14. 1. TOC and Rock pyrolysis
• Source rocks evaluated by bulk geochemical data such as TOC
content and pyrolysis S1 and S2 yields.
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Pyrolysis and TOC content analyses with calculated parameters
with measured vitrinite reflectance of the source rocks
Pyrolysis S2 versus total organic carbon (TOC) plot showing
generative source rock potential for the rock units

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Plot of vitrinite reflectance data (Ro) versus depths showing
thermal maturity stages of the Source rocks
Plots of Hydrogen index (HI) versus Oxygen index (OI),
showing kerogen quality

16. 2. Biomarker characterization
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• Biomarker are organic compound that act as chemical tracer of
certain ancient organism.
• Molecular fossil, geochemical fossil & biological marker.

17. • Alkanes & Isoprenoids
• Alkanes:
• Carbon preference Index(CPI):applied to n-alkanes to help determine
the biological origin, the maturity of sediments, oils and source rock
extracts and/or the paleoenvironmental conditions.
• CPI > 1 (Marine Source Rock)
• CPI < 1 (Terrestrial to Lacustrine source rock)
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18. • Isoprenoids
• Pristane /Phytane ratio
• Isoprenoids are lipids constructed
from isoprane or isoprene(5-
carbon)subunits.
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Fig: Chromatograms biomarker maturity level and analyzed under
similar conditions. A) deep water. B) Shallow water. (Samuel et al.
2009)

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Fig. Cross plot of pristane/phytane ratios (pr/ph) an indicator of anoxia against
gammacerane separates oils into families consistent with their depositional
environment and organic matter, (Samuel et al. 2009)
A. Terrestrial organic matter
B. Peat/coal environment
C. Mixed organic sources
D. Marine organic matter

20. • Steranes and triterpanes
• Biomarker distribution of
deeper oil : major marine
phytoplankton & terrigenous
land plant.
• Abundant C27 Steranes in
Marine & low C29 Steranes
shallow water oil
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Fig. Ternary diagram showing the plot ofC27,C28 and C29 sterane
peaks from appropriate GC–MS–MS transitions) interpreted in terms
of likely kerogen precursors.

21. • Distribution & abundance of
peaks C28 and C29 tricyclic
terpane in oil samples reveals
an interesting relationship of
oils with different depositional
environment.
• Tricyclic/hopanes parameter is
useful fro maturity and source
dependent parameters
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Fig. Cross plot showing Tricyclic terpane index (TrTI), tricyclic terpanes/C30 -
hopane; Tetracyclic terpane index (TeTI): C24 Tetracyclic terpane/C30
17a(H),21b(H)-hopane.

22. Stable Isotopic Analysis
• Carbon isotopic
composition of an oil is
typically dependent upon
the δ13C value of the
kerogen in the source
rock.
• Depositional environment
condition
• stable carbon isotope
analyses are performed
on n-alkanes in saturated
hydrocarbon fractions
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Fig. Stable carbon and hydrogen isotope compositions of whole oils
do not distinguish between marine and non- marine source rock
organic matter.

23. Plot showing a nearly flat to positive n-alkane stable carbon isotope
profile typical of oils of the marine super family.
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Fig. δ13C values of saturated and aromatic hydrocarbon fractions
of oils

24. Conclusion
• Geochemical results of Rock- Eval pyrolysis, isotopic analysis
coupled with biomarker are used to provide information on the
existence of organic matter and petroleum resources.
• TOC, HI and S1+S2 values determine organic matter type, thermal
maturity, the shale samples are generally fair to good source rock.
• The traditional analysis to determine the classic biomarkers(n-
alkane, isoprenoid, Steranes, triterpanes, Tricyclic, Hopanes)are
fossil organic molecules that contain information about either the
precursor organisms or the environmental conditions that
generated petroleum
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25. • The δ13C value of kerogen depends, in turn, on the types of
organisms pre- served and on depositional environmental
conditions. Carbon isotope signatures and molecular compositions
indicate that the shallower gas accumulations are severely
biodegraded, unlike the deeper environment.
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26. References
• Al-Areeq, Nabil Mohammed. 2018. “Petroleum Source Rocks Characterization and
Hydrocarbon Generation.” In Recent Insights in Petroleum Science and Engineering,
https://app.dimensions.ai/details/publication/pub.1100897042.
• Cesar, Jaime, Veith Becker, and Bernhard Mayer. 2020. “Organic and Isotope
Geochemistry Analysis of Petroleum Condensates from the Unconventional Portion of the
Montney Formation, Western Canada.” Fuel 282(July): 118879.
https://doi.org/10.1016/j.fuel.2020.118879.
• Zhang, Shuichang, and Haiping Huang. 2005. “Geochemistry of Palaeozoic
Marine Petroleum from the Tarim Basin, NW China: Part 1. Oil Family
Classification.” Organic Geochemistry 36(8): 1204–14.
• Other reference mention in the organic geochemistry report.
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