Geochemical characteristics of terrestrial organic matter in the upper paleozoic complex of the vilyui syneclise and some features of its transformation under thermobaric conditions at great depths. / Dolzhenko, Kirill V.; Fomin, Alexander N.; Melenevsky, Vasily N.
In: Georesursy, Vol. 21, No. 4, 10, 14.11.2019, p. 77-84.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Geochemical characteristics of terrestrial organic matter in the upper paleozoic complex of the vilyui syneclise and some features of its transformation under thermobaric conditions at great depths
AU - Dolzhenko, Kirill V.
AU - Fomin, Alexander N.
AU - Melenevsky, Vasily N.
N1 - Funding Information: The study was supported by the Russian Foundation for Basic Research (project no. 18-35-00337) and as part of the Federal Research Project no. 0331-2019-0022 “Organic Geochemistry and the History of the Geological Development of Dominant Petroleum Systems of the Upper Proterozoic and Phanerozoic of Siberia”. Funding Information: The authors are grateful to the staff of the Laboratory of Petroleum Geochemistry, Trofimuk Institute of Petroleum Geology and Geophysics of the Siberian Branch of the Russian Academy of Sciences for analytical work. The authors thank the reviewer whose valuable comments and suggestions helped to improve the manuscript. The study was supported by the Russian Foundation for Basic Research (project no. 18-35-00337) and as part of the Federal Research Project no. 0331-2019-0022 "Organic Geochemistry and the History of the Geological Development of Dominant Petroleum Systems of the Upper Proterozoic and Phanerozoic of Siberia". Publisher Copyright: © 2019, Georesursy LLC. All rights reserved.
PY - 2019/11/14
Y1 - 2019/11/14
N2 - A combination of geochemical methods were used to study organic matter from Permian rocks in the central part of the Vilyui syneclise (East Siberia) penetrated by the Srednevilyuiskaya-27 ultra-deep well in the depth range of 3370-6458 m. This study discusses variations in the pyrolysis indices (HI, Tmax), hydrocarbon type content (hydrocarbons-resins-asphaltenes), vitrinite reflectance (R0, %), organic vt carbon content (Corg), as well as some trends in the saturated and aromatic hydrocarbon compositions of bitumen extracts from the Upper Paleozoic rocks. Below a depth of about 4.5 km (late mesocatagenesis), the hydrocarbon type composition is characterized by a sharp decrease in the content of asphaltenes from < 30 % (at 4.5-5.0 km) to < 15 % (at 5.0-5.5 km), which are not detected at greater depth. In turn, the resins became the dominant constituent (~ 50-70 %), whereas hydrocarbons account for < 20 % at depths down to 5 km and < 40 % at greater depth. These depths are also characterized by a predominance of saturated hydrocarbons over aromatic compounds with a decrease in the relative contents of high molecular weight compounds in both fractions, as indicated by mass chromatograms. The hydrocarbon index (HI) of organic matter decreases to the first tens from the depth of 4.9 km and to the bottomhole (6519 m); the temperature of the maximum hydrocarbon yield (Tmax) varies between 570-580 °C, showing a slightly increasing trend. Our results show that the generative potential of organic matter from the rocks within the studied depth range (4.9-6.5 km) has been exhausted and that the terrestrial organic matter undergoes significant changes under severe temperature and pressure conditions at great depths.
AB - A combination of geochemical methods were used to study organic matter from Permian rocks in the central part of the Vilyui syneclise (East Siberia) penetrated by the Srednevilyuiskaya-27 ultra-deep well in the depth range of 3370-6458 m. This study discusses variations in the pyrolysis indices (HI, Tmax), hydrocarbon type content (hydrocarbons-resins-asphaltenes), vitrinite reflectance (R0, %), organic vt carbon content (Corg), as well as some trends in the saturated and aromatic hydrocarbon compositions of bitumen extracts from the Upper Paleozoic rocks. Below a depth of about 4.5 km (late mesocatagenesis), the hydrocarbon type composition is characterized by a sharp decrease in the content of asphaltenes from < 30 % (at 4.5-5.0 km) to < 15 % (at 5.0-5.5 km), which are not detected at greater depth. In turn, the resins became the dominant constituent (~ 50-70 %), whereas hydrocarbons account for < 20 % at depths down to 5 km and < 40 % at greater depth. These depths are also characterized by a predominance of saturated hydrocarbons over aromatic compounds with a decrease in the relative contents of high molecular weight compounds in both fractions, as indicated by mass chromatograms. The hydrocarbon index (HI) of organic matter decreases to the first tens from the depth of 4.9 km and to the bottomhole (6519 m); the temperature of the maximum hydrocarbon yield (Tmax) varies between 570-580 °C, showing a slightly increasing trend. Our results show that the generative potential of organic matter from the rocks within the studied depth range (4.9-6.5 km) has been exhausted and that the terrestrial organic matter undergoes significant changes under severe temperature and pressure conditions at great depths.
KW - Catagenesis
KW - Chromatography-mass spectrometry
KW - Hydrocarbon type composition
KW - Pyrolysis
KW - Terrestrial organic matter
KW - Ultra-deep well
KW - Vilyui syneclise
KW - ultra-deep well
KW - hydrocarbon type composition
KW - terrestrial organic matter
KW - catagenesis
KW - pyrolysis
KW - chromatography-mass spectrometry
UR - http://www.scopus.com/inward/record.url?scp=85075921630&partnerID=8YFLogxK
UR - https://www.elibrary.ru/item.asp?id=41879786
U2 - 10.18599/grs.2019.4.77-84
DO - 10.18599/grs.2019.4.77-84
M3 - Article
AN - SCOPUS:85075921630
VL - 21
SP - 77
EP - 84
JO - Георесурсы
JF - Георесурсы
SN - 1608-5043
IS - 4
M1 - 10
ER -
ID: 25765445