Petroleum geochemistry of Atrau region, Pre-Caspian Basin, Kazakhstan
- TPAO dis Projeler Grup Baskanligi, Ankara (Turkey)
Pre-Caspian Basin covers an area of approx. 500,000 sq. km. and is characterized mainly by thick (0-5000 m) Kungurian salts. Atrau region occupies 100,000 sq.km. and is located at the southern part of the basin. Oils of this basin are found in the sub-salt (Carboniferous reefs) and supra-salts (Triassic red beds and Jurassic-Cretaceous clastics) reservoirs. Seventeen crude oil samples analyzed from different wells appear to be paraffinic and paraffinic-naphthenic type. Some of the oils hardly contained any n-alkanes, probably owing to biodegradation. Biomarker signatures of saturate and aromatic fractions and stable carbon isotopes of whole oils revealed two genetically different oil families; family I and family II. Family I was generated from clastic supra-salt sediments having immature (%Rc=0.55) terrestrial organic matter. Family II was generated from carbonate rich sub-salt sediments, containing mature (%Rc=0.65-0.80) marine organic matter. Majority of Triassic, Kungurian and Upper Cretaceous successions contained enough organic matter with considerably low total petroleum potential (S1+S2). Upper Carboniferous sediments, on the other hand, contain enough and oil prone organic matter that reached peak oil generation stage (233.1 Ma) and hydrocarbon saturation level for expulsion as a result of high sedimentation rates in the Lower to Middle Triassic succession in Kobyekovskaya-2 well. Maximum paleotemperature reached in the area was not enough for H{sub 2}S formation and cracking of already generated hydrocarbons to natural gas.
- OSTI ID:
- 127433
- Report Number(s):
- CONF-950995-; ISSN 0149-1423; TRN: 95:005942-0128
- Journal Information:
- AAPG Bulletin, Vol. 79, Issue 8; Conference: International conference and exhibition of the American Association of Petroleum Geologists, Inc.: managing change at the turn of the century, Nice (France), 10-13 Sep 1995; Other Information: PBD: Aug 1995
- Country of Publication:
- United States
- Language:
- English
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