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SERRANO, I., J. L. PERDOMO, T. CATLIN, J. ESTEVES, E. GONZALES, J. PERALTA, and L. SAGE, Maraven, S.A., Caracas, Venezuela

ABSTRACT: A New Look at the Petroleum System of the Foothills of the Sierra de Perija, Western Maracaibo Basin

Since 1991, Maraven S.A., affiliate of Petroleos de Venezuela, has conducted a multidisciplinary study over the Perija foothills in order to establish their hydrocarbon potential. An extensive seismic survey was recorded and thirty oil seepages and six key surface sections were sampled for geochemical and biostratigraphic analyses. Chronostratigraphic correlation was the starting point for sequence analysis used to integrate the new data with that of eleven oil fields present in the adjacent plains. As a result of this study, the existence of two oil-prone Cretaceous marine source rocks was confirmed. Both are presently within the oil window and generation started during the lower Miocene. The oils from seeps and wells are of marine origin. However, terrestrial sourced oils exist in t e northern part of the range. Multiple reservoirs are present, ranging from fractured lower Cretaceous limestones with low matrix porosity (av. 4%) to widespread thick, highly porous (15 to 25 %) middle to upper Eocene sandstones. The best targets are structures of Eocene age. However, most structures are Mio-Pliocene faulted anticlines and blocks thrusted to the east. Timing and lateral seals are critical aspects and constitute the main risks. In the light of the new studies, the petroleum potential of the area looks promising. As much as 800 million bbl of medium to very light oil could have accumulated, not only in structural, but also in stratigraphic and combination traps.

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