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MUNOZ, PEDRO, and XIOMARA VERENZUELA, Maraven S.A., Caracas, Venezuela, RAYMOND FRANSSEN and VOLKER VAHRENRAMP, Shell Research B.V., Rijswijk, The Netherlands

ABSTRACT: Sedimentological and Petrophysical Characterization of the Cogollo Group, Cretaceous, Block IX, Maracaibo Lake

The present study contains the most important results from the sedimentological and petrophysical analysis of two Cretaceous cores (SVS-225/229) located in the Block IX of Lake Maracaibo, northwestern Venezuela. The purpose of the study is to provide practical solutions to better define and locate prospective intervals, their extrapolation and effective application to the exploitation of the Cretaceous reservoirs. The study is based on the calcareous facies description and their relationship to matrix porosity, open fractures, sedimentary and flow units. The sedimentary units have been grouped in packages bearing similar characteristics and having vertical and horizontal extrapolation potential. Moreover, they serve as indicators to determine the major sedimentary environments and hel define the sedimentological model for the section under study.

The most prospective calcareous facies are composed of dolomites, wackestones, packstones and grainstones. They are all related to the open fractures, their orientation and density. The flow units were determined using these characteristics together with the oil impregnation observed in the cores. Also they were found to be mainly related to the coarsening upwards sedimentary sequences.

The identification of these units and their correlation to neighboring areas becomes a very useful and applicable tool in the effective managing processes for the Cretaceous oil reservoirs.

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