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LICHERI J., M. MORALES, and H. CERQUONE, Exploration Department, Corpoven, S.A., Venezuela

ABSTRACT: 3D Seismic in an Overthrust Area. Northern, Eastern Venezuelan Basin

The Eastern Venezuelan Basin is divided into a northern fold-thrust belt and a southern stable platform. The northern flank has several large oil fields associated with Miocene compressive structures (thrust-related folds). Among those fields are the El Tejero and West Carito fields, considered to be two of the most prolific in the Western Hemisphere. They are located below the Pirital thrust, where low velocity (3000 m/s) Tertiary strata underlie, in tectonic contact, high velocity (4000 m/s) Cretaceous rocks which comprise a complex overburden. In order to obtain an optimal reservoir model of these two fields, a 3-D seismic survey was acquired over an area of 150 sq km.

We herein describe the criteria used for designing acquisition and processing parameters of the survey, as well as benefits obtained from its interpretation.

A cross-shooting patch was selected 96 shots on a single line and 480 receiver stations distributed on four east-west oriented lines (120 each), parallel to the strike of the structures. This direction was also chosen to have the highest fold and preferential azimuthal distribution, in order to obtain a higher signal to noise ratio and to avoid strong non-hyperbolic moveouts caused by the complex overburden.

A comparison between the 2D and 3D data sets shows an improvement in structural definition of reservoirs that allows for better location of future development wells.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.