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Abstract: Petroleum Systems of the Burgua Depression, Tachira and Apure States, Venezuelan Andes

M. Ostos, A. Callejon, S. Talukdar, F. Yoris, R. Lander, A. Gonzalez, H. Ave Lallemant, J. Oldow

The Burgua Depression (southeast extension of the Tachira Depression) underwent a severe subsidence during the Andean orogeny. lts tectonosedimentary evolution was controlled by Paleozoic discontinuities. The sedimentary sequence contains Jurassic/Lower Cretaceous syn-rifting transgressive rocks, syn-deformational Paleocene/Eocene and Neogene rocks. Deformation is diachronic from SE (Oligocene) to NW (Pleistocene). From oil-rock correlation data, Navay and Los Cuervos samples render excellent potential source rocks. The analyses indicate a marine algal-bacterial organic matter source for Navay and higher plants for Los Cuervos, which plot as moderate yield type II kerogen and low yield type II-III, respectively. Although, the samples are immature (0.50-0.55% Ro), ID model ing (BasinMod) suggests that they reached maturation during the Andean orogeny. Oil seeps correlate with Navay and Los Cuervos and were expelled at the peak of oil generation (0.85-0.90% R0). These source rocks define the Navay-K/T(!) and Los Cuervos-K/T(!) petroleum systems. Potential clastic and carbonatic reservoirs were identified in surface and wells. The Guafita Formation is the regional seal, never extending northward of the Brujas High. Modelling indicates that migration started during late Pliocene and took place northward and south/southeastward of the Andean foredeep.

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