Identificación y caracterización de facies de la Formación Hollín en un afloramiento ubicado en el Proyecto Hidroeléctrico Coca-Codo Sinclair, provincia de Napo

Abstract

This project was performed in order to identify the environments and facies of the Hollín Formation, which is an important in the Oriente Basin of Ecuador. The study was carried out on an outcrop in the Sub-Andean of the Basin. Facies characterization included a macroscopic description of hand samples, thin sections analysis, X-ray diffraction, petrophysical analysis, and interpretation of structures at the outcrop. In this project a total of 17 lithofacies are identified. These lithofacies are distributed along a ~100 meters thick outcrop section and they were defined based on its lithological characteristics and associated sedimentological structures with a formation environment. The interval corresponding to Lower Hollín Member was formed in a fluvial environment dominated by braided rivers. Lithofacies associated with this environment are those that presented the best reservoir characteristics including clean sands coarse grained, and little cemented. The Hollín Superior interval is associated with a coastal environment, with tidal influence, including supratidal, intertidal and subtidal sub-environments. The lithofacies associated with this environment have lower ranges of permeability by the presence of mud layers that diminish the quality of reservoir rock. The best reservoir within this tide dominated environment correspond to the tidal bars and tidal channels, although these sands have a limited extension.