Geochemical evidence for Paleozoic oil in Lower Cretaceous O sandstone, northern Denver basin

Journal Article · Tue Aug 01 04:00:00 EDT 1989 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:5535670

Clayton, J L ^[1]

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1. Geological Survey, Denver, CO (USA)

Organic geochemical properties of the oil produced from the Lower Cretaceous O sandstone on the eastern flank of the Denver basin indicate that this oil has been derived from a different source rock than other Cretaceous oils in the basin. O sandstone oil is characterized by low pristane/phytane ratio, high isoprenoid/n-alkane ratios, high asphaltene content, high sulfur content, and slight predominance of even-carbon numbered n-alkanes in the C{sub 25+} fraction. These features are evidence of a Paleozoic source and indicate a carbonate rock is the likely source. Preliminary source rock evaluation and correlation data suggest that calcareous black shales and marls of Middle Pennsylvanian (Desmoinesian) age are the source of the O sandstone oil. This is the first reported occurrence of oil from paleozoic source rocks in a Cretaceous reservoir in the Denver basin. Two important implications for further exploration are evident if vertical migration from Paleozoic source rocks has occurred. First, Paleozoic rocks of Middle Pennsylvanian age or younger are potential exploration objectives where reservoirs and suitable trapping mechanisms are present. Second, future exploration for oil in the O sandstone and upper Paleozoic rocks should consider stratigraphic relationships between possible source and reservoir rocks and possible migration conduits. 9 figs., 2 tabs.

• OSTI ID: 5535670
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Vol. 73:8; ISSN 0149-1423; ISSN AABUD
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
CHEMISTRY
COLORADO
CRETACEOUS PERIOD
FEDERAL REGION VIII
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
MESOZOIC ERA
MIGRATION
MINERAL RESOURCES
NORTH AMERICA
ORIGIN
PENNSYLVANIAN PERIOD
PETROLEUM DEPOSITS
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SOURCE ROCKS
USA