Análise quimioestratigráfica de uma porção do grupo Guaritas

Abstract

Stratigraphic analysis of sedimentary sequences can be made by surface outcrop information and/or by core descriptions or indirect geophysical methods in the subsurface environments. One of the main tools used to define variations in the lateral and vertical physical and chemical proprieties is geophysical and geochemical logs. Fluvial and eolian deposits are good water and hydrocarbon reservoirs and display varying scales of heterogeneity, from microscopic to reservoir scales. In the present work, it is presented a stratigraphic analysis of fluvial and eolian deposits using chemostratigraphy to unravel the stratigraphic heterogeneities in a vertical facies log. The study area corresponds to the Pedra Pintada and Varzinha Formations of Guaritas Group, Camaquã Supergroup. This unit is exposed in the western region of Santana da Boa Vista town, in the Serra do Apertado region. To reach the goals it was used facies analysis and chemostratigraphic methods, with the acquisition of vertical sections and geochemical analysis. The geochemical analysis were acquired using a X-ray Fluorescence equipment, which measures the characteristic wave length that is emitted from the formation when it is bombarded by X-rays. After data acquisition, information were integrated in facies and facies associations and subsequently correlated and establishment of composed vertical logs. Chemostratigraphy associated with facies analysis, integrated in a 1D model allowed the definition of the chemostratigraphic units of the fluvial and eolian deposits, helping in delimiting stratigraphic units and in the modeling of analog reservoirs.