--> Pros and Cons of Five Hypotheses of Migration of Oil to the Eastern Part of the Orinoco Oil Belt, Eastern Venezuela Foreland Basin, by R. P. George, Jr. and M. B. Socas; #90986 (1994).

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Abstract: Pros and Cons of Five Hypotheses of Migration of Oil to the Eastern Part of the Orinoco Oil Belt, Eastern Venezuela Foreland Basin

Richard P. George Jr., Mercedes B. Socas

1.2 × 1012 bbls of oil in the Orinoco Oil Belt (OOB) in the eastern Venezuela basin's (EVB) south flank charged their middle Middle Miocene sandstone reservoirs during middle Middle Miocene to present by long-distance migration from the northern flank of an Upper Cretaceous source. Which parts of this vast area of source, ranging from Guarico to offshore eastern Trinidad, contributed strongly to eastern OOB oils? We consider five hypotheses: Trinidad source, Maturin autochthon source, very slow Serrania source, remigration from downdip megatraps, and Guarico source. We favor the first and remain open to the second, because both involve straightforward updip migration along carrier beds that were south of the zone heavily deformed by early middle Miocene thrusting. The irst requires migration from NE to SW; perhaps NE-plunging regional folds skewed the migration to a direction oblique to the south flank's regional north dip. The second hypothesis suffers, because the Upper Cretaceous in the autochthon may not be organic rich. The third and fourth are attractive in relying on source directly north of the eastern OOB. However, the third's migration timing is problematic: early middle Miocene thrusting cut the migration conduits from the Serrania to the autochthon before deposition of many of the OOB reservoirs. The fourth lacks plausible autochthonous sites for early middle Miocene storage of eastern OOB oils. The fifth explains accumulations in the western but not eastern OOB; there oil compositions are different, NE-trending barriers northwest of the G eater Oficina area blocked SE-migration of Guarico oils to the eastern OOB.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994