The Cerro Negro accumulation of Venezuela's Orinoco Belt - the favorable convergence of several geological processes

Conference · Mon Feb 01 00:00:00 EST 1993 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5939155

Swanson, D C ^[1]; Tarache, C ^[2]

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1. Swanson Consulting Services, Houston, TX (United States)
2. Lagoven S.A., Caracas (Venezuela)

The Cerro Negro Area is a major part of eastern Venezuela's Orinoco Belt. Here upper Eocene fluvial-deltaic deposits of the Oficina Fm. reservoir billions of barrels of heavy oil, much of which is in valley-fill deposits. Maturation, migration and accumulation of these hydrocarbons in thick, porous and permeable sandstones were the logical conclusion to several major geological events in eastern Venezuela during the Tertiary. In the Cerro Negro Area, Cretaceous clastics were deposited on an igneous and metamorphic basement after which the sea withdrew northward toward the axial part of the Eastern Venezuelan Basin. The basement and Cretaceous deposits were weathered and eroded during the Eocene, Oligocene, and early Miocene, forming the unconformity on which the Oficina Fm. is deposited. Historic reconstruction begins with this unconformity, a paleotopographic surface strongly influencing the character and distribution of the overlying Oficina Fm. As relative sea level fell and gradients increased, streams incised into the shelf while transporting great amounts of coarse clastic load northward. At Cerro Negro, a mature topography of low ridges and hills were developed with differential elevations of several hundred feet. During the Miocene, a sea transgressed across the stream-etched unconformity. Streams carrying large amounts of clastic load encountered an elevating sea level. They consequently dropped their coarse load, forming long, linear, transgressive, valley-fill deposits. By Late Miocene, hydrocarbons generated in the deeper basin began to migrate southward through the long linear fluvial-deltaic clastic conduits that were separated laterally and vertically into complex [open quotes]plumbing systems.[close quotes] As the hydrocarbons moved shelfward, normal faults cut the conduits into numerous reservoir segments. The timing between migration and faulting is critical to present-day hydrocarbon distribution in these segments.

• OSTI ID: 5939155
• Report Number(s): CONF-930306-; CODEN: AABUD2
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 77:2; Conference: International congress of the American Association of Petroleum Geologists (AAPG), Caracas (Venezuela), 14-17 Mar 1993; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
58 GEOSCIENCES
HYDROCARBONS
MATURATION
MIGRATION
PETROLEUM DEPOSITS
ORIGIN
SANDSTONES
SOURCE ROCKS
VENEZUELA
RESERVES
BASEMENT ROCK
CONVERGENCE
CRETACEOUS PERIOD
DEPOSITS
EOCENE EPOCH
GEOLOGIC HISTORY
PETROLEUM GEOLOGY
RESERVOIR ROCK
TERTIARY PERIOD
TOPOGRAPHY
CENOZOIC ERA
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
LATIN AMERICA
MESOZOIC ERA
MINERAL RESOURCES
ORGANIC COMPOUNDS
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SOUTH AMERICA
020200* - Petroleum- Reserves
Geology
& Exploration
580000 - Geosciences