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10th International Congress of the Brazilian Geophysical Society
- Conference date: 19 Nov 2007 - 23 Nov 2007
- Location: Rio de Janeiro, Brazil
- Published: 19 November 2007
1 - 50 of 484 results
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An AVO Indicator Based on the Impedance Concept
Authors V. Grosfeld and L. Tunes SantosIn the last two decades, many approximations for the PP reflection coefficient have been proposed in the literature. Basically, all of them are derived from the classical approximation of Aki & Richards, using additional assumptions on the medium parameters. The aim of constructing such approximations is to establish reliable attributes that can be capable to indicate the presence of oil or gas. In this work we review some well known approximations and their respective attributes. We also introduce a new indicator
based on a impedance-type of approximation for the reflection coefficient. Numerical examples are also provided.
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Reservoir characterization using lithology cube on a Cretaceous field offshore Brazil
Combining AVO inversion results with rock physics on lithology and fluid information from well data in a Cretaceous field in Campos basin enables the use of statistical techniques to discriminate two types of igneous rocks in the area: low impedance and high impedance basalts, and the evaluation of the probability of the fluid content on a regional scale.
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A FORTRAN Facility to Compute Physical Parameters for Multigroup Gamma Ray-based Logs
More LessEfficient numerical solutions of gamma ray transport equations in geological media normally require an additional process that includes a scheme of diffusion for multiple coupled energy groups. To predict adequately the values of the experimental and theoretical parameters in a such scheme it is necessary a new look that takes into account the wide variation of nuclear parameters with gamma ray energies. Unfortunately, many of these parameters cannot be determined directly from the tabulated data. To overcome this problem it is introduced FORTRAN algorithms to include these groups coupling and can at the same time be applied to a wide variety of lithologies with 1 ≤ Zeff ≤ 20. To perform this approach, many FORTRAN subroutines and functions are developed to compute diffusion coefficient and total and scattering cross-sections for a large number of discrete energy groups. It is found that any intervals of energy below 5 MeV can be simply implemented and have successful applications on the computation of these parameters in addition to the elements of a transition matrix that couples energy groups. As a help an useful and simple scheme for group selection is also proposed, which has improved the accuracy of the FORTRAN algorithms.
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Comparison of VSP and sonic-log data in non-vertical wells in a hetereogeneous structure
Authors Petr Bulant and Ludĕk KlimešIn order to compare the results of sonic-log measurements and of vertical seismic profiling (VSP), the sonic-log velocities are used to estimate the corresponding travel time in the geological structure, which is then compared with the VSP travel time. In this paper we show how to calculate the sonic-log travel time in the geological structure from the sonic-log velocities while taking into account the effects of the non-vertical propagation of seismic waves due to the source offset and due to the heterogeneous velocity in the structure, together with the effects of well trajectory differing from strictly vertical. We also estimate the errors due to the commonly used assumption of vertical propagation.
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Calibração do perfil sônico a partir do perfil VSP
Authors Roseane M. Misságia and Marcos V. Barbosa MachadoIn this work, it was carried out a synthetic sonic log analysis made from a model simulating a reservoir between two low permeability beds. This analysis related on the log correction with check shot data and the application of the new data to VSP modeling. The procedure showed efficient to calibration of the different scales involves in the log and in the wellbore seismic.
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Coplanar coil array in laminated formations with linear transition zones
More LessThe one-dimensional profiles obtained by one coplanar coil array show polarization horns in front of horizontal bed interfaces, caused by accumulation of electric charges on those boundaries. This polarization effect allows a good positioning of thinly laminated reservoirs. Such horns are smoothed out when there is a gradational transition between the beds. In this work, we study the response of a coplanar coil array in a thinly laminated reservoir. We also study the behavior of the polarization horns in linear transition zones between beds. We build the transition zone with a sequence of thin homogeneous layers whose resistivities varies linearly.
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Investigações geofísicas em áreas submersas rasas: qual o melhor método?
The objective of this article is to discuss and assess the applicability of geophysical methods by focusing on seismic methods in studies conducted in shallow waters. Criteria to help to select the most appropriate geophysical method to solve geological or eotechnical issues must be established to minimize problems, particularly environmental ones. The focus on shallow waters was driven by the lack of systematic data and the demand for geological and geotechnical knowledge in these areas, due to the concentration, in these sectors, of the main economic activities of our current society like projects of ports, moles, ducts, marinas, bridges, tunnels, fishing activities, beach regeneration, mineral prospecting, waterways, dredging and reservoirs. In any of these
topics, basic geological knowledge of the bottom and sub bottom of water-covered areas is essential to ensure the success of the project. Considering this, geophysical methods, particularly seismic ones, are investigation tools that effectively contribute to generate new information, and are the only set of tools available to quickly and objectively provide enough data to improve the geological understanding of the area under investigation.
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Estimativas de teores de umidade de solos empregando o método GPR em área de escorregamentos em Ubatuba/SP
Authors Renato Luiz Prado, Rodolfo Moreda Mendes and Fernando A. M. MarinhoGround penetrating radar (GPR) reflection and direct travel time data were used to estimate soil water content in two unstable hillside areas in the city of Ubatuba, state of São Paulo, Brazil. Data were collected during five different campaigns over a period of one year using multioffset geometry with 100 MHz and 200 MHz antennas. The moisture content data obtained by the reflection travel time data allowed to construct 1D profile up to 10 meters depth, but did not show a significant seasonal variations. However, it was observed for the surface horizon by the exam of the direct travel time.
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Influência do dossel da floresta de Caxiuanã nos fluxos de calor entre o solo e a atmosfera
Air temperatures at 8, 30 and 52 m above ground and vertical fluxes of latent heat and sensible heat at 54 m height, were measured during one month of the dry season (August, 2005) and another month (April, 2005) of the rainy season at Caxiuanã’s forest micrometeorological tower. The average temperature profiles for daylight and night periods, as well as, the sensible and latent heat fluxes estimated and measured, showed significantly different and frequently opposite behavior of these quantities, within two layers defined between 8 and 30 m, below the forest canopy, and 30 to 52 m, above the canopy. The canopy seems to act as a heat source during the daylight hours and a sink of heat at night. Overall, the sum of the sensible and latent heat fluxes may reach 90% of the short wave net radiation, over this site. The results suggest that more attention should be given to the air layer below the canopy, if one seeks to understand the heat and water vapor exchanges between the soils surface and the atmosphere, above the canopy of such type of forest.
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“Risk, Reward & Regulatory Compliance – New Challenges for Geophysical Information Systems?”
More LessGeophysics was traditionally a specialist’s province, a tool to help locate, quantify and produce hydrocarbons. But with public interest in the energy sector growing exponentially and topics such as climate change, corporate accountability and energy politics appearing in seemingly every news bulletin, many other groups are starting to demand geophysical information. Additionally, geophysicists are demanding access to a wider range of data types and data sources than ever before. This is revolutionizing the way we manage seismic and other types of E&P data. With the assistance of recent case studies, this paper will examine the new tools at our disposal and make suggestions for a real-time, integrated and above all holistic approach.
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Localização de Tubulações Metálicas Instaladas no Sitio Controlado de Geofísica Rasa do IAG-USP através dos Métodos Eletromagnético Indutivo e GPR
Authors Vinícius Rafael Neris dos Santos and Jorge Luís PorsaniThis research shows some results obtained with Inductive Electromagnetic (EM38 equipment), and GPR-Ground Penetrating Radar methods applied for detect steel pipes buried at test site of the IAG/USP. Steel pipes until 1.5 meters deep were detected by Inductive Electromagnetic method. 200MHz GPR profiles permit to detect the steel pipes and the depth slices were important for characterize the pipes extension. The results obtained by two different geophysical methods present good agreement, and can be used to mapping interferences buried in subsoil.
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Long Offset Transient Electromagnetic (LOTEM) for monitoring fluid injection in petroleum reservoirs – Preliminar results of Fazenda Alvorada Field (Brazil)
More LessThis work presents the preliminary results obtained using LOTEM (“Long Offset Transient Electromagnetic”) method in a producing petroleum field in Northeast Region of Brazil (Bahia State). The main goal of the study is to produce subsurface images for monitoring fluid injection after EOR (Enhanced Oil Recovery) operations. Five stations were selected, and, a careful processing was applied in all of them to remove noisy data. A preliminary one-dimensional (1D) interpretation was done using forward models, where it was possible to observe oil/injected water contacts.
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Resistividade elétrica utilizada no imageamento da contaminação proveniente da disposição de resíduos de óleos lubrificantes
Geophysics has been showing to be effective in identifying areas contaminated by waste disposal, contributing to the soundings programs aiming direct sampling and monitoring well installation to become more efficient. In this context, the purpose of this work was to evaluate the potential of the resistivity method in characterizing the contamination of the lubricant oil residues disposal area in Ribeirão Preto - SP. The geophysical methods used enabled the geophysical anomalies identification, which characterized the contamination produced by the leachate migration originated in the cells filled with the lubricant oil waste.
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Aplicação da técnica CDI de imageamento para o sistema GEOTEM
More LessThe objective of subsurface imaging is to transform responses measured by ATDEM methods in an image of the electrical conductivity versus depth (CDI) and with this, to get information on target geometry and conductivity (geoele ctrical model). This work presents a methodology to get CDIs over the measurement profile (2-D) used subsequently to visualize the geoelectrical model in 3-D, which would help to integrate and to understand the local geology. To accomplish this, a layered geoelectrical model is used (1-D) together with the depth attained by the maximum electrical induced current concept. The conductivity and the layer characterization are based on a simplified modeling algorithm (late asymptote approximations). Resultant software was adapted processes GEOTEM data.
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Processamento de dado AEM: CDI e inversão para o sistema GEOTEM
More LessThe aim of this paper is to carry out a comparison between two types of 2D electromagnetic modeled sections. They are normally used on AEM (Airborne EletroMagnetic) quantitative interpretation, especially on those obtained from ATDEM measurements (ATDEM). One is derived from fast modeling of the asymptotic secondary magnetic flux decay and is one of the most common quantitative interpretation tool. The other is based on the wave equation and is of more restrict usage as 1D inversion techniques, both parametric and structural. The two approaches were applied to airborne GEOTEMTM system real data, collected on a survey at San Pedro Valley (Southeast Arizona) in 1997. The available data from this survey was made available by the USGS and was used in this quantitative analysis. As such, 2D sections from 1D model inversion were obtained. The geoelectrical model from these sections were further 3D (volumetric) interpolated (voxels), allowing a 3D representation form off the region spatial conductivity distribution.
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Constrained inversion of 3-D electromagnetic HMD and VMD data
Authors Frayzer L. Almeida and Luiz RijoThis work presents an algorithm for 3-D inversion of electromagnetic data associated with inductive sources: HMD (horizontal magnetic dipole) and VMD (vertical magnetic dipole). The proposed inversion algorithm is based on the method of Marquardt subsidized by a scheme of normalization of the objective function using the amplitude and phase of the vertical component of the observed magnetic field combined with the absolute constrain of the body’s depth and the conductivity of a region around the body. The forward problem was solved by the finite element method using the three components of the magnetic vector potential plus the electric scalar potential and the Coulomb gauge. The results of the experiments with the three models show that the proposed inversion algorithm, with the imposed constrains, is able to delineate clearly 3-D conductive simple bodies hosted in resistive media.
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Estudo comparativo das técnicas de Elementos Finitos e Equação Integral na modelagem eletromagnética bidimensional
More LessThe Finite Element Method and the Integral Equation Method are used extensively in the electromagnetic modeling in Geophysics. In this work we compare the processing times in both methods to calculate the fields generated by an infinite line of current over a 2D earth, in several different models. We find that the Finite Element Method is generally faster in our modeling.
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Ausência de Reflexão Interna Total em Meios Condutores
Authors Luiz G. Guimarães and Edson SampaioBaseados nas equações de Maxwell e Lei de Ohm, mostaremos neste trabalho que em meios condutores a propagação de ondas planas depende de vários fatores tais como, estado de polarização, freqüência temporal bem como das relações constitutivas do meio. Como conseqüência direta destes fatos, mostraremos que a lei de Snell em meios condutores é bem distinta daquela usual em meios dielétricos. Uma das grandes diferenças é ausência de reflexão interna total na propagação de ondas entre meios condutores. Além disso, também mostraremos que tais meios se comportam como “filtros de polarização”. Analisaremos este problema para o caso em que uma onda eletromagnética gerada no mar penetra em uma rocha sobreposta a um reservatório contendo hidrocarbonetos.
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Forward modeling of self-potential fields in mineral exploration
More LessNatural self-potential (SP) fields observed in the vicinity of conductive ore bodies can be explained in terms of electrochemical reactions the conductor participates. Battery-like models assume that a buried conductor creates an anode-cathode pair by conveying to oxidizing areas in the near surface a flow of electrons from reducing areas at depth. For conductors with invariant composition (inert electrode model) a quantitative formulation is already available. This paper employs numerical Green’s functions to optimize the evaluation of SP fields from inert electrode models and simulates their response from common conditions found in mineral exploration.
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Estrutura geoelétrica da Bacia do Iguatu, Ceará, Brasil
Authors Jean M. Flexor, Giovanni C. Stael, Carlos R. Germano and Sergio L. FontesA set of forty five broadband (001-1000sec) magnetotelluric (MT) soundings have been made along two profiles (SW-NE) and (NW-SE ) crossing the Iguatu Basin, Ceará, Brazil, a Brazilian intra cratonic basin. The shape of the basin is almost elliptic and these two profiles correspond to the two semi axes. The static shift galvanic effects which distorts the TE mode of MT data were removed using time domain transient electromagnetic measurements (TDEM) at each sounding station. 2-D inversions of MT profiles gives an estimate of the geoelectric structure in subsurface. In the SW-NE profile, the depth of basement reaches a maximum of about 1800 m with a depocenter displaced in the NE direction. In the NW-SE profile, almost perpendicular to the regional geological trend, the maximum depth is about 1200 m. These depths and shapes are compared with 3-D inversion gravity models.
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Influence of sea water resistivity on MCSEM data
Authors Edelson da Cruz Luz and Cícero Roberto Teixeira RégisThe Marine Controlled Source ElectroMagnetic (MCSEM) is a new geophysical method that is very promising in the detection of resistive layers in the rocks under the oceanic floor, a useful information for the oil industry. In this work is model MCSEM data including variations in the resistivity of the ocean water. Such variations can arise from the influence of marine currents, temperature gradients or any other source of influence on the water salinity. We observe that the data from this method are significantly affected by those variations. As much the variation in resistivity how much in the thickness of the water layer it can affect the results of the MCSEM in similar form.
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Comparações de dados sintéticos mCSEM 2.5-D e 3-D
Authors Marcos Welby Correa Silva, Marco Polo P. Buonora and Luiz RijoThe marine Controlled Source Electromagnetic is new geophysical method for detection of oil-filled reservoirs in deep-water areas. The method maps the contrast of electrical resistivity between the reservoir and the host sedimentary layers. In this paper, using the integral equation method (INTEM3D software) we modelled the mCSEM method in the presence of a 3-D structure with fixed length and variable width. The responses achieved were shown as anomalies of normalized electric field amplitudes. According with the results, the amplitudes do not change if the width of the heterogeneity is equal or higher than its length. In this case, we compared the results of the 3-D modelling with 2.5-D ones, were we used the finite element method (eGs software) to compute the mCSEM response, and we conclude the computationally less expensive 2.5-D modelling can be used perfectly, without loss of information.
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Crystalline basement characterization using magnetotellurics in the Chacoparanaense basin (31.5ºS), Argentina
Authors Alicia Favetto, Cristina Pomposiello and John BookerNew magnetotelluric data were collected in the Llanura Chacopampeana through the western part of Córdoba province up to the Rio Uruguay. These data allowed us to complete the characterization of the eastern end of the Chacoparanense sedimentary basin. The crystalline basement depth and electrical features of sediments permitted to describe the boundaries between the different formations. Dimensionality analysis showed that electrical structure is one dimensional (1D) for periods less than 30 s while for longer periods they are mainly two-dimensional (2D). In the last case a strike direction oriented parallel to the surface geological strike (around NS) was found. From previous results at profiles measured to the west, the resistivity model permitted to delimitate the western part of the basin. The model obtained in this paper shows the description of the basin where the bottom of the sedimentary basin extends to a depth of about 5 - 6 km in the central part and being in agreement with data from deep wells existing in the area.
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Joint Evaluation of Electromagnetic and Electric Methods for Groundwater Exploration
Authors Emin Ulugergerli, José Pedro Rebes Lima and Nelson RaulinoElectrical and electromagnetic methods jointly used and evaluated for hydro-geological investigation. Geoelectrical sections and porosity approximation helps to identify possible well locations. A survey conducted in Itapiúna (Ceará) using direct current
resistivity method and two-loop electromagnetic method. Jointly evaluation of result from two dimensional modelling of direct current resistivity data and the result of empirical one-dimensional modelling of two-loop electromagnetic data maps lateral variations and provides valuable depth information to locate drillings. Results also indicate that fracture zones with and without water can be traced. As a result of experimental works, a number of drilling locations were proposed. Some of the locations already had wells in use.
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Comparação entre respostas magnetotelúricas e sísmicas obtidas por meio da modelagem de soleiras de diabásio bifurcadas e saltadas da província de São Mateus na Bacia do Solimões/AM
The magnetotelluric and seismic modelling of São Mateus, an important gas province of Solimões Basin (Amazonian), it was accomplished to help to discuss as the magnetotelluric method can contribute with seismic method in the search below diabase sills.
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Medidas magnéticas, eletromagnéticas e elétricas no ambiente natural do campo de testes da UFPA
Magnetic, electromagnetic, and resistivity imaging measurements were taken in an area where a field laboratory for controlled geophysical experiments is being constructed. The field laboratory is going to be used mainly for teaching and for training students in
collecting geophysical field data. The work was performed to know the geophysical answer of the natural environment (background) before artifacts to simulate geophysical anomalies are buried in the area. The measurements showed several anomalies probably related to materials previously dumped in the area which was been used to discard useless materials, and indicated the best places to bury the artificial sources of anomalies.
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Modelagem de dados mCSEM 3D usando computação paralela
Authors Victor Cezar Tocantins de Souza and Luiz RijoWe develop the numerical modeling of marine controlled-source electromagnetic (mCSEM) data in three-dimensional models of hydrocarbon exploration using parallel computation. The models have as reference three stratified layers, formed by the air, the sea and the sediment host with a thin threedimensional reservoir buried. We show the parallelism of the mCSEM 3D data in a multitransmitting survey, where for each transmitter position we have a different forward model. For this, we use MPI library and the client server approach. We observe that when the width and the length of this reservoir are in the same magnitude order, the in-line responses are very similar and the three-dimensional effect is not detected. In turn, when the difference in the sizes of the width and
the length of the reservoir is great, the effect 3D is detected in in-line measures of the biggest dimension of the reservoir.
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2-D MT smooth model for the central portion of Paraná Basin
The Paraná Basin is formed mostly by an intracratonic structure, with one of the most voluminous flood basalt complex up to 2 km thick, covering an area of some 800,000 km2. The basalt overlies a series of Paleozoic sediments including hydrocarbon source rocks. Broadband magnetotelluric data were collected at 6 sites with a frequency range spanning from 0.001 Hz to 250Hz, along a regional NW-SE profile with 341 km in the central portion of Paraná Basin. This paper presents a 2-D model of the crustal structure of Paraná Basin. The model has revealed some new information on the structure of the basin.
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Multi-Transient ElectroMagnetic the CSEM for Onshore and Shallow-water - An Onshore Case Study from Trinidad
Authors Jason Robinson and Bruce WalkerWe present the application of the Multi-Transient Electromagnetic (MTEM) method applied to a field development project in Trinidad. The Multi-Transient Electromagnetic (MTEM) technique produces resistivity profiles which can enable the identification of hydrocarbons in the subsurface.
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Delimitação geofísica eletromagnética de detalhe da intrusão salina em aqüíferos da zona costeira de Caucaia e Pecém-Ce
The present study analyses the free aquifer of the Dunes / Barreiras Formation system, at the shoreline of Caucaia and Pecém-Ce, near to the estuaries of Ceará, Juá and Cauípe rivers to the northwest of Fortaleza. This is coastal district characterized by intense tourist influx besides a considerable real state expansion. At this place there are uncontrolled focuses of salt-water intrusions, and incidences of salinizacion in saturated zone. Excessive water pumping from wells that go into salt-water wedge,
associated with other residual contaminations, resulted in number of abandoned wells. The coastal geomorphology has also been analyzed in order to help in the location of the saline front. Four aquifer systems were recognized: (i) dunes / paleodunes; (ii) alluvia, and (iii) sediments of the Barreiras Formation; and (iiii) Barreiras / Crystalline. Based on topography, distance, and vulnerability, these systems are contaminated at different intensities by salt-water intrusion and marine spray. The geophysical surveys (EM34-3XL and SEV) provided information about the apparent conductivity, which has been translated into water quality data, through the STD hydro chemical factor, obtained from electrical conductivities measured in wells. In addition, the isoconductivity redictive map reveals the behavior of the salt-water intrusion in respect of the distance from the salt-water front and of the preferential flow paths. All the presently achieved data, including (i) analyses of geophysical data grids of vertical and horizontal dipoles measurements (1800 records), and (ii) reinterpretation of published geophysical data, have been integrated on a Georeferential Information System (GIS). The obtained results have also contributed to the development of a methodology, which permits a precise
aquifer modeling. The final model allows us a permanent monitoring, even do physical or sequential changes will be occurred, either provoked by the salt-water intrusion or by leakages and waste of not determined sources.
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Uncertainty analysis in regularized multidimensional electromagnetic imaging: A nonlinear most-squares approach
By Max A. MejuFormally, model uncertainty and non-uniqueness can be reduced by combining measurements of fundamentally different physical attributes of a subsurface target under investigation or by using available a priori information about the target. Geophysical measurements are typically band-limited in nature and contain noise. The nonlinear most-squares formalism allows for combining observations and their associated errors in an objective manner to determine the model bounds. A regularized most-squares appraisal method is described in detail and illustrated with a field example.
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Utilização de mapas de Resistividade e Cargabilidade para posicionamento de Sistema de Monitoramento Geoambiental
Geophysical methods, particularly the electrical methods, can be used to study different environmental characteristics and they are very important during the site characterization for waste disposal and monitoring of migration of contamination plumes. This paper shows the results obtained of a geoenvironmental investigation program from a municipal solid waste disposal site, that includes the use of resistivity and induced polarization methods. 2D resistivity and chargeability data obtained during geoelectrical profiling could be used to generate resistivity maps at different depths and they were used to assess the horizontal direction of contaminant flow. These results were important to determine the location of specific tests to complement the geoenvironmental site
characterization as well as to define the best position for monitoring system.
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Analise comparativa da taxa de dose eritematosa e dados meteorológicos
Authors Lívia L. P. Gabrich, Fernanda L. Mayrink and Abel A. SilvaThe ultraviolet (UV) component of the solar electromagnetic spectrum plays an important role in the terrestrial nature. Many biological effects on human beings are ascribed to the UV, and the incidence of such radiation depends on many geophysical and meteorological parameters. In this work we assess the relationship between the erythemal dose rate and the meteorological parameters of surface air temperature and cloud cover in Belo Horizonte (19.92° S, 43.94° W, 858 m asl, Brazil).
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Modeling the solar ultraviolet erythemal dose
Authors Abel A. Silva, Lívia L. P. Gabrich and Fernanda L. MayrinkThe ultraviolet radiation (UVR) from the Sun plays an important role in the biosphere ruling some natural events that can be beneficial or harmful to humans. Despite that, UVR measurements are not as common in Brazil as meteorological and geophysical
parameters measured by ground weather stations and satellites. In this work the relationship between UVR erythemal dose measurements in Belo Horizonte (19.92° S, 43.94° W, 858 m asl, Brazil) and both the air temperature from a local weather station and the column ozone and reflectivity from the Ozone Monitoring Instrument on board the Aura satellite is assessed.
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Levantamento de resistividade 3-D em uma área contaminada em Bauru – Brasil – resultados preliminares
A contaminated site downstream a landfill in Bauru – Brasil was investigated using a 3-D resistivity imaging technique. The purpose of this investigation was to detect and delineate the contamination plume produced by the wastes and to acquire detailed information about the affected area. The data set was inverted as a complete 3-D survey. The 3-D data set consisted of a series of parallel electrical profile data, acquired with the dipole-dipole array. The profile lines were spaced in 5 meters, the same spacing as the dipoles. This acquisition technique is less troublesome than a complete 3-D survey, and despite of yielding a poorer resistivity model, the resulting model still provide the major resistivity contrasts and enables a tridimensional picture of the main features. In this work we present two depth slices, from the 3-D model obtained using a 3-D least-squares smoothness constrained inversion technique. The results suggest the presence of a contamination plume, which is in good agreement with chemical analysis of waters in the local wells. They also point to a preferential path for the contamination plume that follows the underground flow. The 3-D technique reveals to be efficient in waste disposal sites investigation, and should be taken into account when choosing the investigation technique for complex contaminated sites.
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Monitoramento das Doses de Inativação Esporular, radiação UV-B e temperatura no Observatório Espacial do Sul, São Martinho da Serra, RS, no período 1999 - 2006
In this work an overview of UV-B, spore dosimetry and temperature monitoring at the Southern Space Observatory, in São Martinho da Serra, south of Brazil from 2000 to 2006 is reported. Using Bacillus subtillis TKJ 6312 (uvr,spl) as biosensor of solar radiation in form of spore inactivation doses, Brewer measurements of UV-B and temperature, profiles of seasonal variations were observed. In this context, the impact of the solar radiation and temperature on biological systems has been studied. The temperature, UV-B and SID varied about 40%, 80% and 92% along of the analyzed period. The principal perturbations of the temperature on the spore inactivation doses are observed in the end of Spring and in Summer, indicating an influence of about 11% on the absolute values.
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Investigação da subsuperfície rasa na área do Parque Ambiental de Belém-PA
Inductive electromagnetic and resistivity measurements were carried out in the Parque Ambiental de Belém, where the municipal surface water supply reservoir is located. The measurements were performed to verify if the water reservoir can be reached by contamination via shallow subsurface. Correlation of the geophysical data to the lithology of monitoring wells showed that: (a) shallow clays have high resistivity and can be mistaken to sandy material in the geophysical interpretation; (b) the electromagnetic
data give excellent answer in mapping clayed and sandy units; (c) there is a low probability for underground contamination of the water reservoir.
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Estudo da contaminação por hidrocarbonetos em postos de serviços de Abaetetuba-PA utilizando georadar
More LessThe results of GPR profiling executed to investigate the subsurface under two gas stations are presented. The correlation of the GPR data to the local groundwater flux and to the gathered information about the gas stations history aloud to classify the
subsurface of one of the stations as suspect of contamination and the other as probably contaminated. The GPR signature for the contamination was intense low reflection zones overlying zones of normal reflections.
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Integrated electrical tomography and remote sensing survey for location of shallow subsurface gas
More LessThe main goal of this paper is to summarize the results of the geological and geophysical surveys performed at the future location of the Caraguatatuba Gas Treatment Unit (UTG-CA) for the evaluation of shallow subsurface gas. The unit will be responsible for receiving, separating and distributing the gas produced at the Mexilhão field, located approximately 130 km SE of the São Sebastião island, at the Santos Basin. Shallow gas was identified during the initial stages of the project when preliminary geotechnical drilling was conducted. From a total of 159 cores, 17 showed the presence of gas. These cores are preferentially located in the west side of the area, but showed no homogeneous distribution. In order to delineate the limits of the gas body integrated geo-electric and remote sensing surveys were conducted. The results showed that the gas has its occurrence limited to the west side of the area, is trapped by a relatively thick marine clay layer and does not escape to the surface.
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Application of acoustic profiling to study sedimentation processes in a tailings disposal dam
The production process of some minerals, such as iron and zinc, requires grinding and washing stage to be performed to separate the valuable material from the not useful fraction. The solution encountered to treat the resulting fluidized waste is to dispose it in an artificial basin, often located along a stream valley closed by a retention dam. Such waste is composed by a mixture of residual minerals of grain size and composition depending on the origin of the mineral and the separation process.
The present paper describes the application of highresolution acoustic profiling to the study of sedimentation process in a zinc metallurgy disposal site. A 10kHz subbottom profiler was used to detect the original topography of the basin and observe the structure of the depositional process. As ancillary result, an estimate of the volume of waste fluid was given.
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Métodos elétricos e eletromagnético na avaliação de contaminação no aqüífero cristalino do alto Rio Curaçá por rejeitos de mineração
More LessThis work presents the results obtained with electrical and inductive electromagnetic-EM34 methods applied to outline the aquifer structure and its eventual contamination related to wastes from the copper sulfide mining in the Pilar district, Curaçá valley, Bahia. The interpreted results shows the presence of conductive, elongated bodies, that may be related to acid drainage contamination leaking from the disposal lagoon of the liquid effluents from the mineral treatment process.
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Estudo de Caso- Avaliação de Áreas Impactadas por Hidrocarbonetos em Solo, Utilizando a Integração de Métodos Geofísicos e Geoquímicos
A elaboração do presente trabalho tem como finalidade apresentar a metodologia utilizada pela Brain tecnologia para diagnóstico geoambiental em área impactada por hidrocarboneto decorrente da deposição incorreta de resíduos oleosos. Para tal foram utilizadas as técnicas GPR (Ground Penetrating Radar) e Eletroresistividade (Eletrical Resistivity Imaging Survey-ERIS) juntamente com um plano de sondagem detalhado para a definição do arcabouço geológico da região e execução de análises geoquímicas para a avaliação da área impactada por hidrocarbonetos.
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Caracterização da Eletroresistividade sob Influência da Biodegradação em Áreas Impactadas – Aplicação de SEVME
Authors Rodrigo R. Oliveira, Maria C. Pessoa and Cleide RomãoAnálise da eletroresistividade através da sondagem Elétrica Vertical Multieletrodo (SEVME), tem sido utilizada frequentemente em estudos de áreas impactadas. Arranjos distintos e complementares são utilizados para atingir objetivos específicos. Neste trabalho serão apresentados resultados de aquisições geofísicas realizadas em áreas de depósito de resíduos oleosos, sob efeito da biodegradação e confinamento de gases.
Para cumprir os objetivos propostos os arranjos utilizados foram: Dipolo-dipolo, Wenner e Gradientes Múltiplos que constituíram a campanha de geofísica. Dados diretos foram utilizados para balizar a interpretação, tais como sondagem e geoquímica de solo.
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Interpretação Integrada de dados de GPR 2-D e SEVME 2-D em Áreas Impactadas
Authors Maria C. Pessoa and Rodrigo R. OliveiraO presente trabalho apresenta resultados geofísicos oriundos de um levantamento de GPR 2-D e SEVME 2-D realizado em áreas com risco de 100% de explosividade e confinamento de gases. Os dados foram adquiridos em área de depósito de resíduos oleosos com duração de mais de 30 anos. As aquisições geofísicas foram específicas para atingir profundidades superiores a 20,0m com resolução vertical e horizontal suficientes para interpretação detalhada e consistente.
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Aplicação de Ferramentas Geofísicas no Diagnóstico Geoambiental
More LessThe present work makes reference to the methodology used by Brain Tecnologia (2007) for diagnosis in areas impacted for hidrocarbonets. For the execution geophysical techniques were used (GPR - Ground Penetrating Radar and VESM - Vertical Electric Survey Multielectrod) associated to a consistent survey plan and, consequently the lease of wells. The correct integration of the geophysical tools comes as an efficient for the evaluation of environmental impacts caused by accidents involving hidrocarbonets e/ou chemical products.
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Padrão de salinização de águas subterrâneas na bacia do rio Curaçá: Avaliação química e isotópica
Authors Vicente Amorim Junior and Antonio Expedito G. de AzevedoGroundwater from crystalline aquifers in the Curaçá basin, northern part of Bahia state, display generally very high salinity. To investigate the origin of this salinization the chemical and stable isotope (±D and ±18O) composition of samples from 16 well boreholes and 2 surface reservoirs was measured. The deuterium and oxygen-18 concentration are much higher in surface samples than in groundwaters, while the major ions concentrations are much higher in groundwater than in surface samples. This indicates that the infiltrating waters that reach the aquifers does not suffer high evaporation and the origin of salinity is from dissolution of salts in the water interaction with the soils and the rocks of the reservoir.
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Análise do fluxo subsuperficial por eletrorresistividade
More LessThis paper proposes a comparative analysis of data obtained through electrical imaging. The methodology applied to observe the underground water flow paths and infiltration distribution is here presented. The base flow was traced by saline water applied in a rectangular area and measured in different times by surface measurements of apparent resistivity with a pseudo-depth section perpendicularly to a slope. The obtained data were compared and the results represent the differences along time.
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Avaliação de áreas impactadas através de Eletroresistividade associada à geoquímica
More LessA elaboração do presente trabalho tem como principal finalidade apresentar a metodologia utilizada para diagnóstico ambiental em área impactada por hidrocarboneto decorrente da disposição de resíduos oleosos em um corpo de água superficial. Para cumprir
os objetivos propostos foram utilizados métodos diretos (geoquímica) e indiretos de investigação da qual destaca - se a eletroresistividade (Eletrical Resistivity Imaging Survey-ERIS). Esta resistividade é obtida injetando-se corrente elétrica no solo e medindo-se simultaneamente a diferença de potencial gerada em diferentes pontos da superfície. A aquisição dos dados é formada ao se repetir esse procedimento diversas vezes em vários pontos da superfície. Agregado a um plano de sondagem bem detalhado, orientado pelo ERIS, com análises químicas de amostras de solo e sedimento de fundo a eletroresistividade é uma importante ferramenta de imageamento subterrâneo principalmente para o caso específico desse trabalho, uma vez que distingue materiais, que possuam resistividade elétrica contrastante, como é o caso de hidrocarbonetos no solo. A integração das ferramentas geofísicas e geoquímicas apresenta-se como uma metodologia precisa para a avaliação de impacto ambiental causado por acidentes envolvendo hidrocarbonetos e/ou produtos químicos. A profundidade atingida pelo imageamento está intrinsecamente ligada ao comprimento da seção. A resolução é diretamente proporcional ao espaçamento mínimo entre eletrodos, e diminui gradativamente com a profundidade. A parte mais rasa do terreno é a que mais influencia na medida, portanto uma boa modelagem superficial é importante mesmo quando o que se deseja visualizar está bem profundo.
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Aplicação de Métodos Geoelétricos na Caracterização de Áreas Contaminadas
As contaminações por hidrocarbonetos em solo e água subterrânea têm sido alvo de inúmeras pesquisas, principalmente devido à complexidade dos fenômenos químicos e bioquímicos que ocorrem a partir do momento que o contaminante é absorvido pelo solo. Técnicas diretas tradicionais como sondagens mecânicas e coleta de amostras para análise são comumente utilizadas no mapeamento de plumas de contaminação, mas limitadas devido ao seu custo e morosidade. Levando em consideração este fato, as investigações geofísicas estão sendo comumente aplicadas na caracterização geológica de subsuperfície e na identificação de áreas contaminadas por hidrocarbonetos do tipo LNAPLs (light non-aqueous phase liquids). Buscando diagnóstico de menor custo e maior agilidade, utilizou-se os métodos de eletrorresistividade e potencial espontâneo, aplicando as técnicas de sondagem elétrica vertical (SEV) e imageamento elétrico 3D na identificação de possíveis plumas de contaminação, em área onde ocorreram vazamentos de hidrocarbonetos.
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Composição isotópica do carbono combinado com os íons (Ca+2, Mg+2, SO4 =) para avaliar a interação água-rocha no sistema aqüífero Salitre-Ba
Analysis of stable isotope composition (δC13) of carbon dissolved inorganic of carbonates and major ion concentration in groundwater from the Salitre basin in Bahia was carried out to investigate the water-rock interaction in the aquifers of that region. The important aquifers of the Salitre basin are the fractured metasedimentary rocks of Chapada Diamantina Group and the Karsts of the carbonates rocks of the Una Group and Caatinga Formation. The chemical data show a dear distinction between the two groups with a much lower concentration of dissolved salts in waters from the metasedimetary aquifers. The δC13 of carbon dissolved inorganic ranged from -4,3 to -13,2‰ with the water samples from the karst aquifers enriched in C13 indicating a higher interaction with the carbonate rocks. One sample very rich in sulfates from one well in metasedimentary rock rich in C13 shows that in some points the pyrite oxidation can be an important source for dissolution.
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