Comportamento hidrodinâmico e hidroquímico dos aquíferos Barreiras-Jandaíra e Açu na região de Fazenda Belém, setor oeste da Bacia Potiguar, Estado do Ceará

Abstract

The evaluation of the hydrodynamic and hydrochemistry behavior of the aquifers in areas under the influence of the oil exploration activity is essential to the protection and management of the groundwater resource. In this sense, were analyzed in this work the relationship between hydraulic loads of aquifers Barreiras-Jandaíra and Açu, in the oil production concession area of Fazenda Belém, West sector of the Potiguar Basin, State of Ceará, and its implications on the quality of groundwater. The Açu Aquifer is composed by Units 2 and 3 of Açu Formation, composed predominantly of thick sandstones at the base, with decreasing grain size to the top, with metrics and decimetrics beds of mudstone and silt. On top of the Açu Aquifer occurs a 70 meters thick package of mudstone and silt of Unit 4 of Açu Formation, which covers and seals the Units 2 and 3 of Açu Aquifer, giving a confined character to it. The Aquifer system Barreiras-Jandaíra is represented by sandstones and conglomerates of the Barreiras Formation and Quaternary Sediments, which cover the carbonates of Jandaíra Formation (packstones and wackstones) and expose the groundwater of this Aquifer at atmospheric pressure. The potentiometric surfaces of the two aquifers systems for different periods, since its original state, before the influence of the oil exploration activity, until the present day were set, as well the variations in hydrochemistry of these units, throughout this period and the saturated thickness of the two Aquifer units. With this amount of information is possible to presume that the Açu and Barreiras–Jandaíra aquifers correspond to individual aquifers systems without hydraulic communication with each other. The distinct water chemical classes of the two aquifers confirm the isolation between them indicating the absence of water mix between the two systems, since its original state until the present. The study has identified a local fall in the potentiometric surface of the Açu aquifer, which points to the need to propose measures of control, through the continuous monitoring of water levels of the aquifer and the quality of its waters.