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GALLANGO, OSWALDO, Intevep, S.A., Caracas, Venezuela, and FRANCOIS PARNAUD, Beicip-Franlab, Rueil Malmaison, France

ABSTRACT: 2-D Computer Modeling of Oil Generation and Migration in a Transect of the Eastern Venezuela Basin

The aim of the study was a two-dimensional computer simulation of the basin evolution based on available geological, geophysical, geochemical, geothermal and hydrodynamic data with the main purpose of determining the hydrocarbon generation and migration history. The modeling was done in two geological sections (platform and pre-thrusting) located along the Chacopata-Uverito Transect in the Eastern Venezuelan Basin.

In the platform section an hypothetic source rock equivalent to the Guayuta Group was considered in order to simulate the migration of hydrocarbons. The thermal history reconstruction of hypothethic source rock confirms that this source rock does not reach the oil window before the middle Miocene and that the maturity in this sector is due to the sedimentation of the Freites, La Pica and Mesa-Las Piedras formations. The oil expulsion and migration from this hypothetic source rock began after middle Miocene time. The expulsion of the hydrocarbons took place mainly along the Oligocene-Miocene reservoir and do not reach at the present time zones located beyond of the Oritupano field, which imply that the oil accumulated in south part of the basin was generated by a source rock located to the north, in the actual deformation zone. Since 17 m.y. ago water migration pattern from north to south was observed in this section.

In the pre-thrusting section the hydrocarbon expulsion started during the early Tertiary and took place mainly toward the lower Cretaceous (El Cantil and Barranquim formations). At the end of the passive margin the main migration occur across the Merecure reservoir, through which the hydrocarbon migrated forward to the Onado sector before the thrusting.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.