2D TEM Modeling for a Hydrogeological Study in the Paraná Sedimentary Basin, Brazil

Abstract

This work uses 2D TEM (Transient Electromagnetic) modeling for a hydrogeological study in the Paraná sedimentary basin. The study area is located at the northern region of the state of São Paulo, Brazil, where groundwater is exploited from two aquifer systems: one sedimentary, shallow, and the other crystalline, deep. The interest in applying the TEM method in this area owes to the high exploitation rates of groundwater from the crystalline aquifer system for irrigation, which is triggering considerable seismic activity locally. This aquifer system is composed of fractured basalt within the Serra Geral Formation and is about 120 m deep. Eighty-six TEM soundings were acquired at this location, but in nine cases the data did not fit the modelled curve for 1D geoelectrical models due to the geological complexity of the area. This paper shows 2D geoelectrical modeling results based on the FDTD (Finite Differences in Time Domain) method to explain the lateral resistivity variation within the geological setting. A 2D model was generated for each sounding and compared with 1D inversion models as well as with direct information from wells. The results show some vertical variations of about 10 to 30 meters on the upper interface of the basalt layer from Serra Geral Formation. They are located at approximately 60 meters from the center of the soundings. The existence of these 2D structures in the subsurface can be related to the drainage system in the study area. The presence of these structures may indicate a connection between the shallow and deep aquifer systems, acting like a conduit that may contribute to the seismic activity reported.

Curupira V1.0: Joint Inversion of VES and TEM for Environmental and Mass Movements Studies

“…The local stratigraphy consists of a Cretaceous sedimentary cover made up of the sandstones of the Bauru Group [34] and [35]. This is overlaid by Late Cretaceous basalt layers and Jurassic sandstones of the Botucatu Formation, which houses the Guarani Aquifer [36]. VES and TEM soundings were conducted in two distinct areas of the city: the Andes and Botafogo districts.…”

Investigação de Depósitos Auríferos no Quadrilátero Ferrífero, MG, Por Meio da Análise de Dados HTEM

“…The TEM method or Time Domain Electromagnetic (TDEM) method is an inductive electromagnetic (EM) method used to map the electrical conductivity (or resistivity) contrast in subsurface. The method is quite versatile and finds applications in the mineral exploration (Oliveira, 2014;Couto et al, 2016;Viezzoli et al, 2016;Couto et al, 2017b;Oliveira, 2020), hydrogeology investigation (Danielsen, et al, 2002;Porsani et al, 2012aPorsani et al, , 2012bBortolozo et al, 2014;Bortolozo et al, 2015;Almeida, et al, 2017;Campaña, et al, 2017;Hamada, et al, 2018;Leite, et al, 2018;Rangel, et al, 2018).The TEM methodology was developed in face of the difficulties in the applications of the Frequency Domain Electromagnetic (FDEM) method, which the induction of the EM field in subsurface (secondary field) is generated through an alternate current (AC) within a transmitter loop (Tx) on surface and the secondary field is measured through a receiver coil (Rx) still in the presence of the primary field generated by the current in Tx (Figure 3. 1-a).…”

Modelagem de anomalias de dados HTEM para exploração mineral no Quadrilátero Ferrífero, MG

“…Desde então, o método TDEM tem sido aplicado também com grande sucesso na exploração de água subterrânea (Fitterman & Stewart, 1986;Porsani et al, 2012a;Porsani et al, 2012b;Bortolozo et al, 2014;Couto Jr., 2015;Almeida et al, 2017;Campaña et al, 2017;Leite et al, 2018;Hamada et al, 2018;, exploração mineral (McNeill, 1994;Couto Jr. et al, 2019), mapeamentos estratigráficos de bacias sedimentares, prospecção de hidrocarbonetos (Cardador et al, 2003), entre outros. A Figura 10 apresenta um esquema de difusão em subsuperfície das "Eddy currents" em uma geometria definida por "anéis de fumaça" ou "smoke rings", conforme demonstrado por Nabighian (1979).…”