- Home
- Conferences
- Conference Proceedings
- Conferences
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
21 - 40 of 484 results
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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).
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-
-
-
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.
-