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Abstract: Geochemical Modelling of the Principal Source Rocks of the Barinas and Maracaibo Basins, Western Venezuela

Rafael Tocco, Oswaldo Gallango, Francois Parnaud

This study presents a geochemical modelling of the principal source rocks in the western Venezuelan Basins. The area covers more than 100,000 km2, and includes Lake Maracaibo and Barinas Basins. The geochemical modelling recognizes three source rocks: 1) A principal, K3- K4-K5 Cretaceous sequences, represented by La Luna, Capacho and Navay formations, 2) a secondary, corresponding to the T4 Oligocene sequence, represent by the Carbonera Formation, and 3) an accessory source rock, K7-K8 Paleocene sequences, represented by the carbonaceous shales and coals of the Orocue Group and Marcelina Formation.

Three periods of hydrocarbon expulsion were defined for La Luna Formation (Early Eocene-Late Eocene, Middle Miocene-Early Miocene and Early Miocene-Holocene) and a principal period of hydrocarbon expulsion for Orocue Group and Carbonera Formation (Plio-Pleistocene and Middle Miocene Plio-Pleistocene). The 90% of hydrocarbons generated correspond to the principal source rock La Luna Formation, and the 10% to Tertiary source rocks (Carbonera Formation and Orocue Group).

Five petroleum systems were identified: Lake Maracaibo, southwest of the Lake Maracaibo Basin, the Lara nappes, the extensive basins of eastern Zulia and the Barinas subbasin.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela