Programa de Pós-Graduação em Geodinâmica e Geofísica
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Doctoral Thesis O papel de falhas como condutos hidráulicos a partir da análise de modelos numéricos e geoelétricos - o exemplo do Aquífero Barreiras-RN(Universidade Federal do Rio Grande do Norte, 2020-10-23) Alves, Rafaela da Silva; Lucena, Leandson Roberto Fernandes de; ; http://lattes.cnpq.br/4673404543485023; ; http://lattes.cnpq.br/0150143538288213; Nascimento, Aderson Farias do; ; http://lattes.cnpq.br/8600906973888297; Castro, Vera Lucia Lopes de; ; http://lattes.cnpq.br/5179660919760767; Righetto, Antônio Marozzi; ; http://lattes.cnpq.br/0476984348484601; Cabral, Natalina Maria Tinoco; ; http://lattes.cnpq.br/6787133958525104The occurrence of faults in aquifers of a clastic nature conditions, in terms of structural compartmentalization, their geometry and offers an increase in anisotropy which is reflected in variations in hydraulic conductivity, variation in saturated thicknesses, changes in the underground flow pattern and variations in hydraulic gradient. The Barreiras Aquifer System, the target of the present study in a sector of the southern coast of the state of Rio Grande do Norte, has a predominantly unconfined hydraulic characteristic and shows itself structurally compartmentalized by Neogenous faults. The area in question involves a battery of 12 producing tubular wells, 39 piezometers, in addition to another 6 for research and monitoring, installed in 2011, which capture about 750 m³ / h destined to supply water for inland municipalities with water deficit. The local structure, evidenced by the main faults Boa Cica and Tabatinga, NW and NE respectively, offers complexity to the Barreiras Aquifer System, either in quantitative or qualitative terms, the latter case particularly regarding to possible anomalies in the freshwater-saltwater on the coast line. This thesis, through different methodological approaches, presents an analysis of the behavior of the aquifer with emphasis on the role of the Boa Cica and Tabatinga faults in the form of their permeable or semiimpermeable limits, also aiming to simulate the possibility of saline intrusion in the area. In addition, we sought to identify the most promising sectors for the location of new pumping wells, with a view to increasing the water supply and subsidizing sustainable aquifer management. The methodology initially involved the characterization of the structural compartmentalization of the aquifer through correlation in well profiles, 1D inverse geoelectric models and field investigations. The behavior of the aquifer in a structurally controlled environment was simulated using the software Visual MODFLOW. In this context, the numerical models were elaborated considering two different scenarios for the role of failures, such as hydraulic ducts or barriers, respectively, zones of increase and reduction of hydraulic conductivity in relation to the surrounding environment. The results of the simulations were compared with 2D reverse geoelectric sections and aquifer tests carried out in local wells. The 2D geoelectric models, specifically, were used in order to characterize the fault locally near the coastline and whether it would be in the form of a resistive anomaly (compatible with the barrier model) or conductive (compatible with the conduit model). Reinterpretations of aquifer tests were carried out in order to identify possible recoveries of dynamic levels in the vicinity of the faults. The numerical models of density dependent flow, used to simulate saline intrusion in the aquifer, were generated on the SEAWAT platform. Simulations were carried out using as a parameter the current exploitation of 750 m³/h for a period of time equivalent to 20 years. To check the most promising sectors for drilling new wells, in addition to all the methods applied, a saturated thickness map was generated to guide the numerical simulations performed in Visual MODFLOW. The numerical flow model was calibrated with a residual error of 8.9%, considering anisotropies in the aquifer in the form of lateral contacts between different hydraulic conductivities and variations in the saturated thickness resulting from the failures. The simulations carried out showed that the main local faults are compatible with duct models, that is, they correspond to areas of high hydraulic conductivity. Such results were corroborated with the characterization of conductive anomalies in 2D geoelectric imaging, associated with one of the simulated faults, Boa Cica Fault (NW). The aquifer tests, in turn, showed a trend of recovery of dynamic levels as the respective depression cones reach the main fault zones. The calibrated transient model, in accordance with the calibrated flow model, considered the faults as zones of relatively greater hydraulic conductivity and representing preferential paths to the evolution of saline intrusion. This result is also corroborated by the conductive geoelectric anomaly in the Boa Cica Fault (NW), where its kinematic aspect of a transtensional nature favors a greater reach of this saline contamination. Similar results were obtained in simulations involving recharge variations between the dry and rainy periods, with the faults representing preferential conduits to the increase in intrusion. In terms of additional well locations, guided by numerical flow models and a saturated thickness map, they indicate the northeast portion of the study area as the most promising, mainly because it has greater saturated thicknesses (70 to 90 meters). The numerical simulations, in particular, showed that the areas of relative grains are the most propitious for future drilling, in the face of greater available drawdowns and, consequently, greater exploitation flows.Master Thesis O sistema aquífero Barreiras na região de Parnamirim, RN: uso das águas e potencialidades(Universidade Federal do Rio Grande do Norte, 2015-08-21) Alves, Rafaela da Silva; Melo, José Geraldo de; ; ; Diniz Filho, José Braz; ; Vasconcelos, Mickaelon Belchior;The study area is within the Pirangi River Basin, eastern sector of Rio Grande do Norte state, where is located of the Parnamirim city. It has an area of approximately 370 km². Urbanization has developed much fast without an appropriate infrastructure, mainly by the lack of sewage systems, with risks of contamination of groundwater that may cause serious damage to the health of the population. The Barreiras Aquifer System groundwater in the area represents the main source of water supply for urban and rural populations. The use of groundwater occurs without adequate planning and therefore, important recharge areas are being occupied. This study was conducted to quantify the use and evaluation of the potential of groundwater, in order to increase good water quality supply and lower risks of being affected by polluting activities. With these objectives, the following activities were carried out: 268 points of water have been registered; characterization of the lithological, thickness and hydrogeological structure of the Barreiras aquifer, based on the correlation of well logs; and evaluation of hydrodynamic parameters of the aquifer, from the interpretation of results well pumping tests. It was found that the saturated thickness increases from west to east towards the sea, with values ranging from 15,47-56,5 m with an average of 32,45 m. The hydrodynamic parameters using Cooper-Jacob method were: average transmissivity of 5,9x10-3 m²/s and average hydraulic conductivity 2,82x10-4 m/s. The effective porosity is of 15%, obtained by applying Biecinski equation. The potentiometric map shows the main direction of groundwater flow, from west to east, and identifies the recharge areas corresponding to the region of the tablelands of the "Barreiras". The river valleys refer to the discharge areas of the aquifer system. The Recharge was estimated at 253 mm/year, which corresponds to the 16.4% rate of infiltration.