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Juan Di Croce1, Bruno De Toni2, Alonso Navarro2, Raúl Ysaccis2, Eduardo Alvarez2, Santosh Ghosh2, Leonardo Duerto2, Luis Porras2, Renzo Violino2
(1) PDVSA E&P, Caracas, Venezuela
(2) PDVSA E&P, Venezuela

Abstract: Key Petroleum System Elements of the Venezuelan Basins in an Improved Chronostratigraphic Framework

A regional-scale integrated study of the Venezuelan Basins allows to highlight the key elements of the petroleum system. Based on information from seismic transects and wells, both from onshore foreland basins and offshore transpressional depocenters, the tested reservoirs, proven source rock and seals are illustrated on a composite chronostratigraphic chart. The structural as well as the biostratigraphic interpretation are the products of new seismic information and recent update of available well and surface geological data. The updated chronostratigraphic chart reveals the presence of three unconformities related to major events which control the key petroleum system elements and the occurrence of the hydrocarbon accumulation. Two of these unconformities characterize the onshore basins. The first type is related to the encroachment of the passive margin, whereas the second type is related to the evolution of the foredeeps. In these basins the hydrocarbon is mostly trapped in sequences inmediately above and below these regional discontinuities. A third set of unconformities, related to the growth of syntectonic structures, as observed in the offshore area, is the key to understanding the hydrocarbon distribution in these basins. In the western onshore basins, reservoirs are mainly in the Paleogene and also in the Cretaceous sequences, whereas on the east the most important reservoirs are within the Neogene sequences. The offshore basins, on the other hand, are characterized by oil and gas reservoirs within the progressively younger (NW to SE) Early Neogene sequences. The understanding of existing reservoirs within the framework of this improved tectonochronostratigraphic chart provides a predictive tool for the development of new plays in these basins.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana