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

Abstract

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. In order to better define and locate sites for exploratory drilling, a study was undertaken to describe calcareous facies and their relationship to matrix porosity, open fractures, sedimentary and flow units. The sedimentary units were grouped on the basis similar characteristics and vertical and horizontal extrapolation potential. They also serve as indicators to determine the major sedimentary environments and help define the sedimentological model for the section under study. The most promising 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 upper sedimentary sequences. The identification of these units and their correlation to neighboring areas is useful for in the effectively managing processes for the Cretaceous oil reservoirs.