Structural, lithological and petrophysical characterization of the recôncavo aquifer system in the Capivara River Basin, Bahia State, Brazil

Abstract

The hydrogeophysical features of the Recôncavo aquifer system in the area of the Capivara Grande and Capivara Pequena rivers, in Camaçari and Dias D'Ávila counties were studied through the analysis of 64 Schlumberger vertical electrical soundings expanded to AB/2 spacing of 1.000 m. This characterization was also supported by the analysis of lithologic logs of 29 water exploration wells, 14 of which have available geophysical logs. The results were useful to outline the structural configuration of the regional aquifer system in the area, from the surface up to 450 m in depth. The multi-confined component is the dominant portion of the system with the main storage being within São Sebastião sandstone bodies. The aquifer substratum is mostly represented by a thick shale sequence inter-layered with siltstones and fine shaly sandstones, referred by Lima (1999) as the Upper Shaly Sequence (SAS). The geometry of the aquifer system is basically controlled by normal faults oriented NNE and WSW, that transect the São Sebastião Formation in the area. A large undulated synclinal was recognized between Salvador Fault and the western water divide of Capivara Grande and Capivara Pequena river basins. The central zone of this structure, where the aquifer substratum is deeper, corresponds to the Capivara Grande river valley. © 2013 Sociedade Brasileira de Geofísica.