Caracterização Hidrogeológica do Aqüífero São Sebastião na Área de Captação do CIA-Bahia, usando Perfilagens Elétricas de Poços

Abstract

The upper section of the intermediate member of the São Sebastião Formation, near the area of the Centro industrial de Aratu (CIA)-Bahia, comprises a multi-storey aquifer system. Part of the water supply for the industrial activities in this region is extracted from this aquifer by a group of 42 wells drilled up to an average depth of 200 m. The electrical logs interpretation of 21 wells gave useful information as to the geo-hydrological characterization of the aquifer layers tapped by the wells. Stratigraphical correlation allowed the definition of the three-dimensional configuration of four permeable sandstone layers that represent fluvial point bar sand deposits. These layers extend throughout the area and are separated from each other by shales whose thickness(es) varies from 10 to 30 m. Petrophysical properties of the sandstones were determined from the logs and data on the quality of the water in each layer were obtained both from the logs and from chemical analysis. Average aquifer coefficients in the area were estimated from pumping text data. These overall results constitute essential toll for optimizing groundwater exploration programs.