Biomarkers of Georgian petroleum
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2022-06-27 13:22
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KHETSURIANI, Natela, TOPURIA, Elza, TSITSISHVILI, Vladimer, CHKHAIDZE, Madlena. Biomarkers of Georgian petroleum. In: Achievements and perspectives of modern chemistry, 9-11 octombrie 2019, Chişinău. Chisinau, Republic of Moldova: Tipografia Academiei de Ştiinţe a Moldovei, 2019, p. 224. ISBN 978-9975-62-428-2.
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Achievements and perspectives of modern chemistry 2019
Conferința "International Conference "Achievements and perspectives of modern chemistry""
Chişinău, Moldova, 9-11 octombrie 2019

Biomarkers of Georgian petroleum


Pag. 224-224

Khetsuriani Natela1, Topuria Elza1, Tsitsishvili Vladimer2, Chkhaidze Madlena1
 
1 Petre Melikishvili Institute of Physical and Organic Chemistry at Ivane Javakhishvili Tbilisi State University,
2 Ivane Javakhishvili Tbilisi State University
 
Disponibil în IBN: 11 noiembrie 2019


Rezumat

 Relict hydrocarbons after deposition in rocks, retained the identity or underwent insignificant change in composition and structure of carbon skeleton of the original biomolecules that participated in the processes of crude oil formation. These relicts are considered to be the most important biomarkers or geochemical labels. Any regularity of their concentration distribution in the samples are geochemical criteria and allow us to judge the nature and origin of the source of raw materials in this region of sedimentation, its age, degree of decomposition and catagenetic maturity. This information is used to carry out various geochemical correlations, genetic and chemical typifications of oils and solving various problems of crude oil geochemistry. The most important biomarkers are normal and isoprenoid alkanes, C19-C35 sterane and terpenehydrocarbons of sesqui-, di- and triterpene series, terpenoids, steroids, porphyrins and little-studied aromatic hydrocarbons of the relict type structure. Currently, more than 1000 different representatives of them are identified in crude oils and organic matter of rocks. Biomarkers along with carbon isotope composition are the main carriers of information about the life of the ancient periods of the Earth. The relict hydrocarbons of some Georgian oils, the genetic and geochemical aspects of their chemical composition, and the main geochemical criteria allowing for various genetic correlations to be considered have been studied. The saturated portions of the 50–200°C, 200–350°C, 200–420°C and > 420°C fractions of oils from the main oil and gas region of Eastern Georgia were studied using GLC on highly efficient capillary columns, MS and GC/MS methods. As a result of the study, Georgian crude oil was identified as belonging to various chemical types: B1, B2, A1 and A2. It has been established that, despite the difference in chemical composition, the studied crude oils belong to a single genetic type. A characteristic feature of Georgian oils was revealed – high concentrations of isoprenoid alkanes, such as pristane (iC19) and phytane (iC20) with a large predominance of pristan, therefore the ratio iC19/iC20>1. In the middle boiling fractions of Taribani, Satskhenisi, Norio and Teleti crude oils were identified polymethylsubstituted decalines, relict type hydrocarbons having C14-C16 composition that most likely are related to significant triterpene relicts – hopanes. In high-boiling fractions > 420°C, large tetra- and pentacycloalkane (C27-C33) molecules were identified – steranes and triterpenes with predominance of hopans belonging to the 17a(H)-hopan (C30H52) series, which was present at maximum concentration. The main mass of steranes is made by thermodynamically more stable isosteranes. The degree of catagenetic transformation of crude oils was determined by the ratios ZnC13-nC15/ZnC25-nC27, ZiC19-iC20/ZnC17-nC18, a-isosteranes, etc. The highest degree of conversion was determined for Samgori crude oil, and the least degree – for Shromis-Ubani crude oil. Studies of Georgian crude oils revealed the presence of well-known relic structures, peculiarities in composition, quantitative and relative distribution of certain biomarkers, various geochemical indicators, which give reason for carrying out a more thorough study of the genetic code of Georgian Petroleum.