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A comparative study of the molecular and isotopic composition of biomarkers in immature oil shale (Aleksinac deposit, Serbia) and its liquid pyrolysis products (open and closed systems)
The molecular and isotopic composition of biomarkers in initial bitumen isolated from immature (0.41% Rr) oil shale samples (Aleksinac deposit) and liquid products obtained by pyrolysis in open (OS) and closed (CS) systems are studied. The influence of pyrolysis type and variations of kerogen type on biomarkers composition and their isotopic signatures in liquid products is determined. The applicability of pyrolysis type, numerous biomarkers and carbon isotopic compositions (δ13C) of n-alkanes in liquid pyrolysates is established. Pyrolysis experiments were performed on two selected samples that showed high content of total organic carbon and hydrocarbon generation potential, but also certain variations in sources/depositional environment of organic matter (type I and mixed type I/II kerogen) within previous research of the oil shales sample set. The biomarker signatures were evaluated using gas chromatography-mass spectrometry (GC-MS) and δ13C of individual n-alkanes in bitumen and li...quid pyrolysates. The molecular composition of liquid pyrolysates from the OS is very similar to those in initial bitumen, independently on kerogen type, confirming algal origin of organic matter (OM) deposited in lacustrine environment, even more apparently than results of initial bitumen. Therefore, OS can be useful for assessment of source and depositional environment of OM. Pyrolysis in the CS caused more intense thermal alterations, therefore the source fingerprints sometimes notably disappear. The liquid pyrolysates from the CS have the distributions of biomarkers similar to those in crude oils. The biomarker maturity parameters showed slightly higher values in the CS pyrolysate of mixed type I/II kerogen in relation to type I kerogen. δ13C of n-alkanes in liquid pyrolysates from the OS are isotopically lighter in comparison to bitumen, independently on kerogen type. Oppositely, in liquid pyrolysates from the CS, they become heavier than in bitumen, indicating the thermal influence on δ13C signatures, with more pronounced difference for type I kerogen.
Keywords:
Outcrop oil shale / Aleksinac deposit / Organic matter / Open and closed system pyrolysis / Biomarkers / Stable carbon isotope composition
This is the peer-reviewed version of the following article: Gajica, G.; Šajnović, A.; Stojanović, K.; Schwarzbauer, J.; Kostić, A.; Jovančićević, B. A Comparative Study of the Molecular and Isotopic Composition of Biomarkers in Immature Oil Shale (Aleksinac Deposit, Serbia) and Its Liquid Pyrolysis Products (Open and Closed Systems). Marine and Petroleum Geology 2022, 136, 105383. https://doi.org/10.1016/j.marpetgeo.2021.105383.
TY - JOUR
AU - Gajica, Gordana
AU - Šajnović, Aleksandra
AU - Stojanović, Ksenija A.
AU - Schwarzbauer, Jan
AU - Kostić, Aleksandar
AU - Jovančićević, Branimir
PY - 2022
UR - http://cherry.chem.bg.ac.rs/handle/123456789/4847
AB - The molecular and isotopic composition of biomarkers in initial bitumen isolated from immature (0.41% Rr) oil shale samples (Aleksinac deposit) and liquid products obtained by pyrolysis in open (OS) and closed (CS) systems are studied. The influence of pyrolysis type and variations of kerogen type on biomarkers composition and their isotopic signatures in liquid products is determined. The applicability of pyrolysis type, numerous biomarkers and carbon isotopic compositions (δ13C) of n-alkanes in liquid pyrolysates is established. Pyrolysis experiments were performed on two selected samples that showed high content of total organic carbon and hydrocarbon generation potential, but also certain variations in sources/depositional environment of organic matter (type I and mixed type I/II kerogen) within previous research of the oil shales sample set. The biomarker signatures were evaluated using gas chromatography-mass spectrometry (GC-MS) and δ13C of individual n-alkanes in bitumen and liquid pyrolysates. The molecular composition of liquid pyrolysates from the OS is very similar to those in initial bitumen, independently on kerogen type, confirming algal origin of organic matter (OM) deposited in lacustrine environment, even more apparently than results of initial bitumen. Therefore, OS can be useful for assessment of source and depositional environment of OM. Pyrolysis in the CS caused more intense thermal alterations, therefore the source fingerprints sometimes notably disappear. The liquid pyrolysates from the CS have the distributions of biomarkers similar to those in crude oils. The biomarker maturity parameters showed slightly higher values in the CS pyrolysate of mixed type I/II kerogen in relation to type I kerogen. δ13C of n-alkanes in liquid pyrolysates from the OS are isotopically lighter in comparison to bitumen, independently on kerogen type. Oppositely, in liquid pyrolysates from the CS, they become heavier than in bitumen, indicating the thermal influence on δ13C signatures, with more pronounced difference for type I kerogen.
PB - Elsevier
T2 - Marine and Petroleum Geology
T1 - A comparative study of the molecular and isotopic composition of biomarkers in immature oil shale (Aleksinac deposit, Serbia) and its liquid pyrolysis products (open and closed systems)
VL - 136
SP - 105383
DO - 10.1016/j.marpetgeo.2021.105383
ER -
@article{
author = "Gajica, Gordana and Šajnović, Aleksandra and Stojanović, Ksenija A. and Schwarzbauer, Jan and Kostić, Aleksandar and Jovančićević, Branimir",
year = "2022",
abstract = "The molecular and isotopic composition of biomarkers in initial bitumen isolated from immature (0.41% Rr) oil shale samples (Aleksinac deposit) and liquid products obtained by pyrolysis in open (OS) and closed (CS) systems are studied. The influence of pyrolysis type and variations of kerogen type on biomarkers composition and their isotopic signatures in liquid products is determined. The applicability of pyrolysis type, numerous biomarkers and carbon isotopic compositions (δ13C) of n-alkanes in liquid pyrolysates is established. Pyrolysis experiments were performed on two selected samples that showed high content of total organic carbon and hydrocarbon generation potential, but also certain variations in sources/depositional environment of organic matter (type I and mixed type I/II kerogen) within previous research of the oil shales sample set. The biomarker signatures were evaluated using gas chromatography-mass spectrometry (GC-MS) and δ13C of individual n-alkanes in bitumen and liquid pyrolysates. The molecular composition of liquid pyrolysates from the OS is very similar to those in initial bitumen, independently on kerogen type, confirming algal origin of organic matter (OM) deposited in lacustrine environment, even more apparently than results of initial bitumen. Therefore, OS can be useful for assessment of source and depositional environment of OM. Pyrolysis in the CS caused more intense thermal alterations, therefore the source fingerprints sometimes notably disappear. The liquid pyrolysates from the CS have the distributions of biomarkers similar to those in crude oils. The biomarker maturity parameters showed slightly higher values in the CS pyrolysate of mixed type I/II kerogen in relation to type I kerogen. δ13C of n-alkanes in liquid pyrolysates from the OS are isotopically lighter in comparison to bitumen, independently on kerogen type. Oppositely, in liquid pyrolysates from the CS, they become heavier than in bitumen, indicating the thermal influence on δ13C signatures, with more pronounced difference for type I kerogen.",
publisher = "Elsevier",
journal = "Marine and Petroleum Geology",
title = "A comparative study of the molecular and isotopic composition of biomarkers in immature oil shale (Aleksinac deposit, Serbia) and its liquid pyrolysis products (open and closed systems)",
volume = "136",
pages = "105383",
doi = "10.1016/j.marpetgeo.2021.105383"
}
Gajica, G., Šajnović, A., Stojanović, K. A., Schwarzbauer, J., Kostić, A.,& Jovančićević, B.. (2022). A comparative study of the molecular and isotopic composition of biomarkers in immature oil shale (Aleksinac deposit, Serbia) and its liquid pyrolysis products (open and closed systems). in Marine and Petroleum Geology
Elsevier., 136, 105383.
https://doi.org/10.1016/j.marpetgeo.2021.105383
Gajica G, Šajnović A, Stojanović KA, Schwarzbauer J, Kostić A, Jovančićević B. A comparative study of the molecular and isotopic composition of biomarkers in immature oil shale (Aleksinac deposit, Serbia) and its liquid pyrolysis products (open and closed systems). in Marine and Petroleum Geology. 2022;136:105383.
doi:10.1016/j.marpetgeo.2021.105383 .
Gajica, Gordana, Šajnović, Aleksandra, Stojanović, Ksenija A., Schwarzbauer, Jan, Kostić, Aleksandar, Jovančićević, Branimir, "A comparative study of the molecular and isotopic composition of biomarkers in immature oil shale (Aleksinac deposit, Serbia) and its liquid pyrolysis products (open and closed systems)" in Marine and Petroleum Geology, 136 (2022):105383,
https://doi.org/10.1016/j.marpetgeo.2021.105383 . .
