Estimativa De Parâmetros Hidráulicos Do Aquífero Barreiras-Rn a Partir De Análise Computacional De Imagens De Lâminas Delgadas

Abstract

The attainment of hydraulic parameters derive primarily from the interpretation of aquifer tests, practice that usually involves a fairly complex logistics in terms of equipment and staff required. Thus, the digital processing and analysis of two-dimensional micrographs of aquifer rocks samples is presented as an alternative tool for the characterization of hydraulic parameters, and constitutes a promising procedure accordingly. The methodology is based on a flowchart involving (1) sampling and preparation of thin sections and their respective images, (2) segmentation and geometric characterization, (3) three-dimensional reconstruction and flow simulation. Taking as a target for the present study The Barreiras Aquifer System, in the eastern coast of Rio Grande of Norte state (northeastern Brazil).The computational image analysis of thin sections of its rocks showed reservoir storage coefficients, associated in this context with effective porosities (free hydraulic character), ranging from 0.035 to 0.12, with averages of 0.076; its hydrogeological carbonate substrate showed effective porosities on the order of 2 %. Relative to the transport of fluids, it was found that the method presented results smaller than those found in bibliographic data (related to hydraulic conductivity), probably due to the size of the scale under study and the heterogeneity of the investigated medium.

Reserve evaluation of a fault-conditioned aquifer: the Barreiras Aquifer in the coastal region of NE Brazil

“…The Barreiras Aquifer (RN State borders) is underlain by the hydrogeological basement, represented by the top of the buried Mesozoic carbonate sequence. The sequence contains sandy clay to clayey sedimentary rocks with calciferous cementation and reduced hydraulic conductivities (Lucena et al 2006, Silva et al 2014. Like the formation, the Barreiras Aquifer is dominated by clayey sandstones, with a predominantly unconfined hydraulic character (Lucena et al 2006, Silva et al 2014.…”

“…The sequence contains sandy clay to clayey sedimentary rocks with calciferous cementation and reduced hydraulic conductivities (Lucena et al 2006, Silva et al 2014. Like the formation, the Barreiras Aquifer is dominated by clayey sandstones, with a predominantly unconfined hydraulic character (Lucena et al 2006, Silva et al 2014. The quaternary stratigraphic units outcropping in the region and associated with abundant sand cover and dune fields are important areas for recharge by direct infiltration of rainwater owing to high porosity, high hydraulic conductivity, and low runoff.…”

“…Melo et al (2013) performed pumping tests in the area to evaluate parameters such as hydraulic conductivity and transmissivity, reporting average values of 1.0 × 10 -4 and 3.0 × 10 -3 m 2 /s, respectively, for the unconfined aquifer. Silva et al (2014) obtained an average effective porosity of 7.6% from petrophysical studies and image processing of thin sections of the Barreiras Formation. These samples were collected throughout the east coast of the state of RN.…”

Uso de dados hidrogeofísicos e modelos numéricos como alternativa na otimização de locações de poços em um aquífero não confinado

“…Autores como Lucena et al, (2013) e Alves et al, (2016) estimaram porosidades eficazes de 10%. Estudos petrográficos e processamento de imagens de lâminas delgadas dessa formação aquífera realizados por Silva et al, (2014), por outro lado, definiram porosidades eficazes de 7,6%. Já Lucena et al, (2016) obteve porosidades eficazes superiores a 11% em arenitos similares nas proximidades, embora de idade Mesozoica, igualmente a partir de análise computacional de imagens provenientes de lâminas delgadas.…”

Busca pelo mínimo resíduo para escolha do parâmetro de forma utilizado em RBF’s aplicadas no método assimétrico livre de malhas (MESHLESS) para simulação de fluxo subterrâneo

“…Por suas próprias características, um aquífero apresenta vantagens para sua utilização como manancial destinado ao abastecimento. Nesse sentido, é importante conhecer a dinâmica que envolve a exploração das águas subterrâneas, uma vez que, conforme Silva et al (2014), os excessos na exploração e falhas de gerenciamento podem interferir gravemente nas reservas existentes, contribuindo, assim, para uma possível crise no abastecimento.…”