Abstract

The understanding of the plate tectonic interactions between the Caribbean, South America, and Atlantic plates and their integration with the timing of the basin configurations, its source rock deposition, and thermal maturation provides important insights to interpret the Venezuelan petroleum systems. The different tectonic settings in northern Venezuela offered the right environmental conditions for the deposition of world-class–Cretaceous organic-rich source rocks all through its northern margin, allowing the generation, expulsion, migration, entrapment, and geographical distribution for most of the 1.8 trillion bls of original oil in place and 200 TCFG in discovered-proven resources in the 14 main basins of Venezuela.

The integrated and comprehensive approach of this study allowed the proposal of an orogenic float partitioning tectonic model that couples the development of the southern Caribbean plate along oblique terrane accretions and subduction below northern South America concurrently with the Atlantic oceanic-crust subduction below the Caribbean plateau. The orogenic float glides on the underlying Caribbean–South American lithosphere coupling, along a basal decollement surface with two deformation fronts that forced a foreland basin to the south in the arc–continent collision (“A” subduction) and coeval forearc basins on Caribbean oceanic-crust subductions under Caribbean terranes or “B” subduction. Right-lateral–strike-slip fault activity along the Oca, San Sebastian, El Pilar, and Arima systems occurs synchronously with the eastward rejuvenation of Caribbean accretion and thrusting. These offsets are the consequence of the oblique convergence between the plates to balance the eastward displacement with the southward thrusting and foredeep subsidence. We report evidence for 100 km (60 mi) of right-lateral displacement along the Oca fault. In our model, the orogenic float used the weakness of the crust along old transform system that formed during the Mesozoic rifting event, to create internal strain-partitioning and displace the arc–continent deformation front along northwest–southeast right-lateral transfer-fault systems of Barquisimeto, Burro Negro, Guárico, Margarita, Urica, and Tobago to name the most important.

This succession of tectonic events had implications for basin development north and south of the suture, on the autochthonous side and on the transported terranes. The understanding of the Andean orogenesis as well as the rest of the northern ranges, and the timing and subsidence of adjacent basins, along with the related petroleum systems allowed us to identify and locate from Eocene to present the main oil and gas kitchens for the Cretaceous and Cenozoic source rocks in northern onshore and offshore Venezuela. This facilitated the identification of remaining exploration potential even on mature and explored basins, such as the Cretaceous and Eocene-subcrop plays in Golfo de Venezuela, the foreland subthrust belt play in Ensenada de Barcelona with autochthonous Cretaceous to Paleogene reservoirs, a possible pre-Cretaceous source rock within Espino graben, and several transtensional and transpressional plays in the offshore basins of Blanquilla, Cariaco, Bonaire, and northeastern Falcón basins.