AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
New Exploration Traps in the Espino Graben. Eastern Venezuela Basin
(1) Exploration, PDVSA, Puerto La Cruz, Venezuela.
The Espino Graben has an area of 50.000 Km2, Its axis has a N60°E direction. The Pre-Cretaceous sedimentary thickness exceeds 20,000 feet, practically all of which remains unexplored. Eight sequences were defined between basement and Cretaceous-Jurassic unconformity. The sequences included lacustrine deposits, that generate good seals and source rocks (Solorzano et al ., 2001). This graben was formed during the Jurassic rifting, produced by the separation of the North and South American plates. The work focused on the Pre-Cretaceous also allowed the delineation of Cretaceous-Neogene structures along the main faults that formed the shoulders and other related faults. In these prospective alignments already are important oilfields that need to be extended.
Most interpretations made in the area were concentrated in the producing Cretaceous and Tertiary formations; however, in Venezuela the Pre-Cretaceous sedimentary rocks have been poorly studied. New 2D3C and 3D seismic surveys have very good resolution. Stratigraphic seismic sequence analysis was used to define the Pre- Cretaceous sequences. Paleozoic sediments have not been drilled in the graben, but probably they are present considering that the Cambrian rocks are found outside the graben, deposited under tidal influence (Solorzano et al ., 2001). The Jurassic deposits has mostly a fluvial origin with some indications of marine influence indicates that the Espino Graben was frequently connected to the open sea.
The study accurately determined structure of the graben interpreted as intense block faulting and inversion structures.The bounding faults of the graben have great extension and slip however, they are not continuous; this discontinuity is associated with important transfer zones that generate positive structures and depocenters with lacustrine deposits favor the prospectivity of the area. The graben has been reactivated in several occasions, producing the three types of structures: rotated blocks, transfer zone ande roll over, evidenced by the propagation of its faults at different levels during the Cretaceous-Oligocene and Miocene.
The Espino Graben represents one of the most important exploration opportunities in the country and according to the economic evaluation, the expectations associated with the six structural tramps are significant.