Abstract Integrated studies of the hydrocarbon system in frontier areas are important to assess exploration risk. The Rubio block located in the Táchira Depression has been the focus of various geological studies, yet very few studies of its petroleum system have been published. Based on seismic, surface geologic, and geochemical data, a study of the petroleum system has been developed. We have identified, based on quality limited seismic and surface data, at least three major periods of deformation in the study area, ranging from the Upper Cretaceous to the present. The first event is of Late Cretaceous age and is characterized by compression. The second period is characterized by extension and took place at least during the Paleocene. Both events may be related to the development of the Colombian Central Cordillera and the flexure caused by its tectonic load, which affected western Venezuela from the Upper Cretaceous to the Paleocene. The third event is characterized by compression that has occurred quite recently, and it may be associated with the development of the Mérida Andes. This last event is responsible for the development of the major structures in the Rubio block. It is worth noting that western Venezuela also was affected by a Jurassic extensional event that is not illuminated by the seismic data of the study area but has been amply shown in both surface and seismic data in the surrounding areas. According to the 1-D and 2-D geochemical modeling results, we propose that maturity of the source rock (the La Luna Formation) is greater to the west than to the east. Hydrocarbon expulsion from the source rock started in the western portion of the area 25 m.y. This local kitchen stopped expelling because of its uplift, which was caused by the latest compression. On the other hand, the La Luna Formation in the eastern portion started to expel hydrocarbon very recently, which is still ongoing. This active oil kitchen may be feeding the oil seeps in the eastern part of the study area.

Abstract The purpose of this two-dimensional computer simulation of basin evolution, based on geologic, geophysical, geochemical, geothermal, and hydrodynamic data, was to determine the hydrocarbon generation and migration history of the basin. The modeling covered two geologic sections (platform and prethrusting) located along the Chacopata-Uverito transect in the Eastern Venezuela basin. In the platform section, a hypothetical source rock equivalent to the Guayuta Group was used to simulate the migration of hydrocarbons. The thermal history reconstruction of the hypothetical source rock confirms that it would not have reached 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 expulsion of the hydrocarbons took place mainly into the Oligocene-Miocene reservoir and has not yet reached zones located beyond the Oritupano field. This implies that the oil in the southern part of the basin was generated by a source rock located to the north, in the actual deformation zone. For the past 17 m.y., water has migrated from north to south in this section. In the prethrusting section, the hydrocarbon expulsion started during the early Tertiary and migrated mainly into Lower Cretaceous reservoirs (El Cantil and Barranqum formations). At the end of the passive margin stage, hydrocarbons migrated across the Merecure reservoir zone and into the Onado area before thrusting began.

Abstract Two main petroleum provinces are described for the central part of the Eastern Venezuelan basin. These include the southern foreland platform near the Orinoco, with its heavy oil fields of the Faja Petrolifera, and in the north, the giant El Furrial and related traps in the frontal thrusts of the Serrania. To identify the petroleum systems and define attractive petroleum plays in this complex foreland fold and thrust belt system, an integrated geologic model of the area has been built using Stratigraphic, structural, reservoir, and geochemical data. The major results of the study are as follows: (1) a reliable Stratigraphic synthesis including updated ages; (2) a coherent structural interpretation in the thrusted zones validated by a balanced north-south cross section, with relevant new interpretations being the discovery of out-of-sequence thrusts (Pirital thrust) and the involvement of upper crust in the deformation; (3) the description of reservoir and hydrodynamic models that emphasize the importance of the major Las Piedras, Oficina, and Merecure reservoirs; and (4) characterization of three different source rocks of marine and continental origin in the Guayuta Group (two marine sources) and Carapita Formation (one continental source). To better understand the petroleum generation in this area—the maturation of potential source rocks, expulsion, and migration of the hydrocarbons—one- and two-dimensional numerical modeling has also been attempted in the platform area for times before and after thrusting. This method has given an estimate of 420-1350 billion bbl of generated oil, of which 6-15% have been recognized within the study area.