Upper Cretaceous source rocks of Northern South America

Conference · Sun Jan 31 23:00:00 EST 1993 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5941206

Talukdar, S C ^[1]; DeToni, B ^[2]; Marcano, F ^[3]; Sweeney, J ^[4]; Rangel, A ^[5]

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1. DGSI, The Woodland, TX (United States)
2. Intevep, Los Teques (Venezuela)
3. Maraven, Caracas (Venezuela)
4. Lawrence Livermore National Lab., CA (United States)
5. ICP, Bucaramanga (Colombia)

Upper Cretaceous source rocks sourced most of the oil accumulations in Trinidad, Venezuela and Colombia. Extensive areas of mature to overmature organic-rich, calcareous shales and limestones are present in basins throughout the area. Paleogeographic reconstruction shows deposition of the source rocks in open marine, outer shelf-inner slope environments on the passive margin of the Cretaceous South American continent. Deposition is primarily related to marine transgressions caused by eustatic sea level changes and to Upper Cretaceous oceanic anoxic events. Sedimentological and geochemical data show regional variations in organic facies across the huge Upper Cretaceous shelf margin. Source rocks deposited in the pelagic domain in outer shelf-slope towards north and northwest are commonly organic-rich and contain oil prone, type II kerogen with essentially marine amorphous organic matter. In this organic facies, variations in organic content were primary controlled by changes in marine organic productivity and sedimentation rate, while the kerogen quality was influenced by short-term fluctuations in the thickness of oxygen-minimum layer. Source rocks deposited in outer neritic environment, towards south and southeast are usually less organic-rich and include oil and gas prone kerogen between types II and III with both marine amorphous and terrestrial organic matter. Temporal changes in the influx of terrestrial organic matter and fluctuations in relative anoxicity controlled the kerogen quality. Hydrocarbon generation from these source rocks occurred during the Tertiary. Basin modelling quantifies oil and gas generation and expulsion from the various organic facies. Oil characteristics can be predicted by the organic facies in the effective source area.

• OSTI ID: 5941206
• Report Number(s): CONF-930306--
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 77:2; ISSN 0149-1423; ISSN AABUD2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CENOZOIC ERA
CHEMISTRY
COLOMBIA
CONTINENTAL MARGIN
CONTINENTAL SHELF
CRETACEOUS PERIOD
DEPOSITION
DEVELOPING COUNTRIES
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
ISLANDS
KEROGEN
LATIN AMERICA
LESSER ANTILLES
LEVELS
MATERIALS
MATTER
MESOZOIC ERA
MINERAL RESOURCES
ORGANIC MATTER
PETROLEUM DEPOSITS
PRODUCTIVITY
RESOURCES
ROCKS
SEA LEVEL
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SEDIMENTATION
SHALES
SOURCE ROCKS
SOUTH AMERICA
TERTIARY PERIOD
TRINIDAD AND TOBAGO
VENEZUELA
WEST INDIES