--> Abstract: Petroleum Geochemistry and Exploration Potential of the Pripyat Basin, (USSR), by J. L. Clayton, G. Ulmishek, P. G. Lillis, M. Ball, G. Dolton, T. Daws, R. Mast, A. Warden, M. Keller, V. Bogino, Z. Poznaikovitch, and J. Yang; #90987 (1993).

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CLAYTON, JERRY L., G. ULMISHEK, P. G. LILLIS, M. BALL, G. DOLTON, T. DAWS, R. MAST, and A. WARDEN, U.S. Geological Survey, Denver, CO; M. KELLER, Scientific Research Geologic Petroleum Institute, Moscow; V. BOGINO, and Z. POZNAIKOVITCH, Geologic Prospecting Research Institute, Minsk; and YANG JIANQIANG, Research Institute of Exploration and Development, Karamay, China

ABSTRACT: Petroleum Geochemistry and Exploration Potential of the Pripyat Basin, (USSR)

The Pripyat basin is in the extreme northwestern end of the middle Paleozoic, Donets-Pripyat aulacogen that separates the Ukrainian shield from the rest of the Russian craton. Geophysical data suggest that the basement structure is typical of intracontinental rifts and consists of east-west-trending tilted blocks bounded by listric normal faults. The sedimentary section is as much as 6 km thick. The lowest, pre-rift rocks consist of basal terrigenous clastics overlain by thin Middle Devonian quartz sandstones, shales, carbonates, and anhydrites. This lowermost unit grades upward into a lower salt of Frasnian age that contains some interbedded carbonate. The lower salt is overlain by the "intersalt carbonate," which contains black shale source rocks. A deformed upper salt of Famennian ge caps the intersalt carbonate and is overlain by terrigenous clastics of Devonian to Quaternary age. Most of the hydrocarbon reserves are in the synrift "intersalt carbonate" sequence. Additional reserves are in pre-rift carbonate and clastic reservoir rocks below the lower salt. Marginally mature to mature source rocks present in the "intersalt carbonate" contain as much as 3 weight percent organic carbon (type II and III kerogen). Both thermally mature and very immature oils are produced from the northern part of the basin. Carbon isotope ratios of saturated and aromatic hydrocarbons contained in the oils vary by about 4 o/oo, and some are extremely depleted in {13}C (-29 to -33 o/oo). The oils contain some features typical for oils derived from source rocks in carbonate-evaporite se uences (e.g., abundant phytane, gammacerane). The isotope data and biomarker (steranes, terpanes) analyses indicate that two genetic oil-types may be present in the basin. Thetwo oil-types may be from two different source beds or may indicate a change in organic-matter type laterally within the same source-rock unit. These geochemical data indicate promising directions for future exploration in the basin.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.