Variations in organic facies and sedimentary environments of the La Luna Formation and Machiques Member in the Perija Mountain Range, Venezuela

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

OSTI ID:6108501

Escandon, M; Vallejos, C ^[1]; Pratt, L ^[2]; Gambino, F Y ^[3]

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1. Intevep S.A., Los Teques (Venezuela)
2. Indiana Univ., Bloomington (United States)
3. Intevep, Los Teques (Venezuela)

In a detailed geochemical study of core samples from four oil wells and outcrop samples from four sections, the vertical and areal variations of organic facies within the main source rocks in the western part of the Maracaibo Basin have been performed. In addition, oils and oil seeps of the basin have been geochemically correlated to each one of these facies. Based on geochemical and micropaleontological data, two organic facies related to variations in sedimentary environment are recognized in the La Luna Formation (Cenomanian-Santonian). The sulphur richer organic facies includes the Cenomanian intermiddle shales and the shales from the Cenomanian-Turonian boundary, both characterized by higher values of total organic carbon, bitumen, hydrogen index and benzotiophenes content. This facies probably is an earlier generation source rock than the rest of the La Luna Formation and its correlation with crude-oils indicates that most of the crudes display a distribution of hopane and sulphur aromatic compounds typical of these more anoxic facies. Within the Machiques Member of the Apon Formation (Aptian), two organic/lithological facies have been identified. These are transgressive basal shales and the overlying regressive mudstones with an upward decrease in hydrocarbon potential, anoxia and paleobathymetry. This member presents no benzotiophenes and differences in the relationships between terpanes and aromatic hydrocarbons which allow us distinguish it from La Luna Formation extracts. This is a powerful technique to recognize the genesis of crude oils derived from a particular marine source rock interval in the Maracaibo Basin.

• OSTI ID: 6108501
• 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
CHEMISTRY
DEVELOPING COUNTRIES
DISTRIBUTION
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOCHEMISTRY
HYDROCARBONS
LATIN AMERICA
NONMETALS
OIL WELLS
ORGANIC COMPOUNDS
ORIGIN
PALYNOLOGY
PETROLEUM
RESOURCE POTENTIAL
ROCKS
SEDIMENTARY ROCKS
SEEPS
SHALES
SOURCE ROCKS
SOUTH AMERICA
SULFUR
VENEZUELA
WELLS