GENESIS OF HYDROCARBONS OF JURASSIC AND PRE-JURASSIC COMPLEXES OF CHISTINNOE FIELD (KOLTOGORSK URENGOY PALEORIFT AREA)

• Main Authors: Yuriy V. Korzhov, Galina A. Lobova, Valeriy I. Isaev, Andrey I. Starikov, Marina Ya. Kuzina, Sergey A. Orlov
• Format: Article
• Language: Russian
• Published: Tomsk Polytechnic University 2019-10-01
• Series: Известия Томского политехнического университета: Инжиниринг георесурсов
• Subjects: jurassic and pre-jurassic complexes; lithology; «main source» of hydrocarbons; optical microscopy and methods of organic geochemistry; geochemical model of migration and accumulation of hydrocarbons in riftogenic zones of the west siberian plate
• Online Access: http://izvestiya.tpu.ru/archive/article/view/2303/2082
• ISSN: 2500-1019; 2413-1830

The genesis of hydrocarbons in the Jurassic and pre-Jurassic complexes of the Chistinnoe group of oil fields located in the Koltogorsk-Urengoy paleorift zone is determined. The research is relevant to substantiate the strategy of searching for oil and gas deposits, taking into account the tectonics of the basement of the West Siberian plate. The aim of the research is to determine the «main source» of hydrocarbons of Jurassic and pre-Jurassic horizons in the rift zones of the basement. Objects and methods. The core of Jurassic and pre-Jurassic complexes of productive and non-productive wells of the Chistinnoe group of fields of the Vartovsky oil and gas area is studied. Lithological and petrographic characteristics were determined using optical microscopy. The content of mobile hydrocarbons in the rock, including the series of n-alkanes, n-alkylbenzenes, components of the series of naphthalene and phenanthrene was determined by methods of organic geochemistry, chromatography and mass spectrometry. Results and conclusions. The authors have constructed the geochemical model of inter- and intra-layer migration of hydrocarbons. Hydrocarbon composition of the upper part of the Jurassic section indicates that the oil deposits in the Vasyugan formation (stratum Yu11) were formed as a result of emigration of hydrocarbons from the shales of the Bazhenov and Georgiev formations. The organic substance of the basement and bottom rocks of the Jurassic section differs from the overlying sediments in molecular and group composition of hydrocarbons and probably did not participate in filling the upper Jurassic traps. Triassic volcanics are not favorable for formation of hydrocarbon reservoirs, voids are filled with secondary minerals due to developed hydrothermal processes and the lack of significant disjunctive tectonics, the forecast of filling the weathering crust traps from the overlying «Jurassic source» is unlikely. The organic substance of Paleozoic genesis may form small deposits in the pre-Jurassic base. In the area of the continental paleorift depression the classic mode of petroleum formation is implemented.