Abstract The sedimentary basins of western Venezuela contain large volumes of oil. However, most of the large structures have already been produced. Exploration for new reserves of light and medium oil now depends on integrated studies that lead to a more comprehensive basin evaluation. This paper presents an integrated account of the Lake Maracaibo and Barinas-Apure basins of western Venezuela. It is a fully integrated study but focuses on the genetic and seismic stratigraphy of more than 600 wells, reference outcrops, and 4000 km of reflection seismic data. Six unconformity-bounded supersequences record the dynamics of Mesozoic-Cenozoic basin evolution from extension to collision. Supersequence A was deposited during an episode of Jurassic rifting, and supersequence B corresponds to the subsequent Early-Late Cretaceous passive margin. Supersequence C marks the transition to a compressive regime in the Late Cretaceous and early Paleocene. Compression resulted from collision and obduction of the Pacific volcanic arc with the South American plate. Supersequence D records the development of the late Paleocene-middle Eocene foreland basin in front of the volcanic arc and emplacement of the Lara nappes. Supersequences E and F are attributed to modification of the foreland basin by late Eocene-Pleistocene collision of the Panama arc. The uplifted Serranla de Perija, Macizo de Santander, and Mérida Andes partitioned the foreland basin, creating the present Lake Maracaibo and Barinas-Apure basins. Supersequence B contains the Cretaceous La Luna source rock (sequences K3, K4, K5). The Colon and Burgúita formations form the principal supersequence C seals (sequence K6). The principal reservoir units occur in supersequence D, including the prolific Eocene Misoa and Gobemador formations (sequences TI, T2). Reservoirs of the La Rosa and Lagunillas formations occur in supersequence F and in the Betijoque Molasse.

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.