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GEOLOGICAL SYNTHESIS OF THE ORINOCO OIL BELT, EASTERN VENEZUELA
Author(s) -
Isea Andreina
Publication year - 1987
Publication title -
journal of petroleum geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 42
eISSN - 1747-5457
pISSN - 0141-6421
DOI - 10.1111/j.1747-5457.1987.tb00205.x
Subject(s) - geology , cretaceous , transgressive , structural basin , paleontology , basement , paleozoic , tectonics , fault (geology) , delta , source rock , geochemistry , sedimentary depositional environment , archaeology , geography , aerospace engineering , engineering
The Orinoco Oil Belt, considered to be the largest hydrocarbon accumulation in the world, is located on the southern border of the Eastern Venezuela basin. The stratigraphic column of the area includes rocks of Pre‐Cambrian to Recent ages, but more than 90% of the crude oils are found in Miocene sediments. Three transgressive‐regressive cycles with wide regional distributions are recognised in the Tertiary system: Cycle 1 includes the La Pascua, Roblecito and Chaguaramas formations of Oligocene age; and Cycles 2 and 3 include the Officina, Upper Chaguaramas and Freites formations of Miocene age. Within the cycles, five lithostratigraphic units are defined, and a sedimento logical model for Units I and III is consequently established, recognizing north‐orientated, wave and tide‐influenced, prograding deltas. Tensional tectonics characterize the area as having two structural provinces, separated by the Hato Viejo fault system: the Eastern Province, characterized by a transgressive sequence overlying the Pre‐Cambrian basement; and the Western Province, where the Tertiary unconformably overlies Cretaceous and Paleozoic sediments. Hydrocarbon accumulations in the Orinoco Oil Belt predominantly occur in stratigraphic traps, but are controlled by regional structures. Four types of crude oils are identified, with density values between 8.5 and 13° API. The volume of oil in‐place in the Orinoco Oil Belt totals 187,897 MM † cu. m(1,181 B brl). The largest accumulations are found in the sands of Unit I .