TY - JOUR

T1 - Lithologic, geochemical and geophysical characteristics of the boundary strata of the Bazhenov and Kulomza Horizons (lower cretaceous base) in the central regions of the West Siberia

AU - Eder, V. G.

AU - Ryzhkova, S. V.

AU - Kostyreva, E. A.

AU - Pavlova, M. A.

AU - Sotnich, I. S.

AU - Zamirailova, A. G.

AU - Ponomareva, E. V.

N1 - Funding Information: The research was supported by grants of the FSR (Fundamental Scientific Research) projects: № 0331-2019-0021 – Basic Sedimentation and Post-sedimentation Processes and Their Evolution in the Proterozoic and Phanerozoic Sedimentary Basins of Siberia; № 0331-2019-0022 – Organic Geochemistry and the History of Evolution of Dominating Petroleum Systems of the Upper Proterozoic and Phanerozoic in Siberia; № 0331-2019-0019 – Geology, Formation Conditions and Characteristics of Difficult Hydrocarbon Accumulation in the West-Siberian Megabasin. Publisher Copyright: © 2020, V.S. Sobolev IGM, Siberian Branch of the RAS. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

PY - 2020/7

Y1 - 2020/7

N2 - The gradual transition of the Bazhenov Formation top into the overlying deposits makes it difficult to establish its upper boundary. The problem is aggravated by the lack of core material when the formation is recognized according to the results of geophysical well studies. A comprehensive analysis of geochemical and lithological data and the results of geophysical well surveys enabled us not only to determine the specific structure of the transitional zone from the Bazhenov Formation top to the rocks of the sub-Achimov member, but also to propose the criteria for delineating the upper boundary in the central regions of the West Siberian sedimentary basin within the Khentei hemianteclise, the South Nadym megamonoclise and the Mansi syneclise. Four members are distinguished in the transitional zone of the studied well sections (from bottom to top), which differ in lithological, geochemical and geophysical characteristics: (I) the "coccolithic"upper part of the Bazhenov Formation; (II) transitional member from the upper part of the Bazhenov Formation to the bottom of the sub-Achimov member; (III) transitional member from the bottom of the sub-Achimov member to its lower part; and (IV) the lower part of the sub-Achimov member. Member II is virtually not distinguished within the Khentei hemianteclise and the South Nadym megamonoclise. Member III contains the boundary between zones with different redox conditions. In case member II is distinguished, the upper boundary of the Bazhenov Formation corresponds to its top. To recognize the Bazhenov Formation top, it is necessary to use the integrated analysis results of the lithological and geochemical studies of the well core, and logging data (gamma-ray logging, neutron gamma-ray logging and its variations, lateral logging, and induction logging) when focusing attention mainly on radioactivity.

AB - The gradual transition of the Bazhenov Formation top into the overlying deposits makes it difficult to establish its upper boundary. The problem is aggravated by the lack of core material when the formation is recognized according to the results of geophysical well studies. A comprehensive analysis of geochemical and lithological data and the results of geophysical well surveys enabled us not only to determine the specific structure of the transitional zone from the Bazhenov Formation top to the rocks of the sub-Achimov member, but also to propose the criteria for delineating the upper boundary in the central regions of the West Siberian sedimentary basin within the Khentei hemianteclise, the South Nadym megamonoclise and the Mansi syneclise. Four members are distinguished in the transitional zone of the studied well sections (from bottom to top), which differ in lithological, geochemical and geophysical characteristics: (I) the "coccolithic"upper part of the Bazhenov Formation; (II) transitional member from the upper part of the Bazhenov Formation to the bottom of the sub-Achimov member; (III) transitional member from the bottom of the sub-Achimov member to its lower part; and (IV) the lower part of the sub-Achimov member. Member II is virtually not distinguished within the Khentei hemianteclise and the South Nadym megamonoclise. Member III contains the boundary between zones with different redox conditions. In case member II is distinguished, the upper boundary of the Bazhenov Formation corresponds to its top. To recognize the Bazhenov Formation top, it is necessary to use the integrated analysis results of the lithological and geochemical studies of the well core, and logging data (gamma-ray logging, neutron gamma-ray logging and its variations, lateral logging, and induction logging) when focusing attention mainly on radioactivity.

KW - Geochemistry

KW - Geographical parameters

KW - Lithology

KW - Organic matter

KW - Upper boundary of the Bazhenov formation

KW - Upper jurassic-lower cretaceous

KW - West Siberia

KW - geographical parameters

KW - geochemistry

KW - ROCKS

KW - lithology

KW - ORGANIC-MATTER

KW - SECTIONS

KW - upper boundary of the Bazhenov Formation

KW - Upper Jurassic-Lower Cretaceous

KW - PALEOGEOGRAPHY

KW - organic matter

UR - http://www.scopus.com/inward/record.url?scp=85093824286&partnerID=8YFLogxK

U2 - 10.15372/RGG2019124

DO - 10.15372/RGG2019124

M3 - Article

AN - SCOPUS:85093824286

VL - 61

SP - 767

EP - 782

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 7

ER -