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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
51 - 100 of 484 results
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Composição Isotópica do carbono em n-alcanos de sedimentos da Baía de Todos os Santos e suas possíveis aplicações na diferenciação da matéria orgânica e como traçador de fluxo de material orgânico de origem terrestre
More LessSix sediment cores from Todos os Santos Bay collected in the area between Landulpho Alves Refinery and São Francisco do Conde city have been analyzed in order to evaluate the sources of organic matter in that region. In this work, the stable isotope composition of carbon (δ13C) of the n-alkanes with carbon number between C22 and C30 along the sediment cores, measured by gas chromatography coupled with mass spectrometer, are utilized to differentiate organic matter of terrestrial sources from marine and petrogenic sources. The values of δ13C of the n-alkanes have shown, in average, an impoverishment in 13C of the sediment cores closer to the Subaé estuary. This difference is more evident in the values of δ13C of the n-alkanes between C27 and C30,
mainly in the C29, evidencing one more time the contribution of terrestrial organic matter in these sediment cores. In the three cores collected closer to Subaé estuary was observed that the averaged δ13C values from C29 are less negatives with increasing distance from Subaé estuary indicating that this parameter can be utilized as a runoff tracer.
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Levantamento, processamento e interpretação de dados de gamaespectrometria terrestre realizado em área utilizada para cultivo agrícola
The present work shows the use of gamma-ray spectrometry applied to precision agriculture in the sub-tropical area. Our dataset comprises measurements both in rock and residual soil. The soil data shows a reduction of 20% on U and Th and 10% on K, when compared to rock samples. This difference could be related to K supplementation associated to chemical fertilization.
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Application of the electrical resistivity method in studies of contamination in cemetery - case of Vila Rezende - Piracicaba/SP – Brazil
This paper shows the results obtained in the application of the electrical resistivity method, using the technique of the vertical electric survey (VES) and electric profiling (EP) (Schlumberger and dipole – dipole arrays), in the investigation underground contamination for - necrochorume in Vila Rezende’s cemetery, Piracicaba - São Paulo, Brazil. The results indicated a depth of the water table between 2 and 6m, with two directions of underground flow, SW and SE. The areas with low resistivity, presented in the geoelectrics sections, demonstrated that the contamination has connection with the depth of the water table and with the time of burial. The applied methods in this work demonstrated as an important instrument for evaluation of the environmental quality in cemeteries.
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Geoelectrical investigation to select an area to install a sanitary landfill over the Guarani aquifer
Authors José Domingos Faraco Gallas, Fabio Taioli and Flávio Luiz VieiraLocated mainly in Brazil, the Guarani Aquifer covers around 1.2 million square kilometers (463,323 square miles) and is characterized by sandstones (named, in Brazil, the Pirambóia and Botucatu Sandstones) covered by lava flows of the Serra Geral Formation of the Paraná Basin. It is considered one of the most important fresh water supplies in the world. The municipality of Timburi is located in the São Paulo State, Brazil, on the border of the basin where there are outcrops of basaltic rocks of the Serra Geral Formation and of the Botucatu Sandstone. The municipality has a population of about 3000 inhabitants and plans to become an important tourist attraction mainly due to its beautiful landscapes and the occurrence of several freshwater springs. One of the problems to be faced is that the domestic waste is taken to a landfill located over the Botucatu Sandstone, in the recharge zone of the aquifer. A geophysical survey was carried out to select an area over basaltic rocks for the installation of a new sanitary landfill. Several vertical electrical soundings were carried out to measure the thickness of the basaltic rock and the weathered basalt soil, which is relatively impermeable and considered an appropriate material for the foundation of the landfill. Profiles of resistivity imaging were carried out to verify the presence of vertical fractures in the basaltic rocks which could provide a hydraulic connection, allowing the percolation of the leachate in the event of leakage in the landfill. In addition, self potential measurements were taken to evaluate the groundwater flow direction. The results facilitated the rejection of areas with thin basalt and weathering thickness and areas where the basaltic rock contained vertical fractures and enabled the selection of an appropriate area to install a new sanitary landfill.
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Mapeamento tridimensional de pluma de contaminação através de resistividade elétrica
This work aims at the detection of the contamination caused by a waste disposal area, by the electrical geophysic method of resistivity. Field measurements had been carried out in Mococa, São Paulo, Brazil, in a deactivated waste disposal area. The obtained data had been dealt with appropriate softwares that enabled the distinction of the anomalies which help the characterization of the environmental pollution problem.
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Desenvolvimento de mini sonda para avaliações ambientais a pequenas profundidades
The evaluation of soil and groundwater contamination has been an important task in the geosciences field and pushing on the methodological improvement. The contamination extension is normally investigated using geophysical methods or boreholes and chemical analysis. Otherwise, several contamination problems are at low depths (less than 0.5m) allowing the easy access to the contaminated region. Therefore, a low-cost and simple system (mini-probe Wenner) was developed and tested and it is aimed at low depth resistivity measurements. The system is formed by a current source (AC) and a PVC probe which contains a Wenner array with a electrode spacing of 1 cm. Laboratory tests show that the current source works adequately in the resistance range normally associated with contaminated materials while the system tests (including the current source and probe) indicated apparent resistivity values very similar to the resistivity values calculated using the equation proposed by Archie, in the 1.5 to 57 Ω.m interval. Preliminary field tests showed that the mini-probe is easily applicable in sandy and sand-silty soils while in clayey or hard soils is difficult its introduction. Therefore, interesting applications to the proposed system are the study of agricultural areas or the study of contamination in predominantly sandy litologies.
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Estudos geofísicos para mapeamento de contaminaçãoe utilização como instrumento de conscientização sócio-ambiental
Authors Juliano das Flores Bahia and Roberto ElisThe high populational density in urban areas, had caused environmental problems related to the genesis and, mainly, the deposal of residuals generated by these inhabitants, which in many situations, the final destiny is the ground.
The present work has the propose of evaluating the contamination caused by the “in situ” deposition of domestic residuals and sewerage, using geophysics methods to build an efficient methodology on evaluation and characterization of environmental problems with these characteristics. Subsequently the research is applied in environmental education in schools near the investigated area and the guests that comes to the park.
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Avaliação da representatividade isotópica da bacia Experimental do rio do Cedro para estudos da evaporação na bacia do rio Jacuípe – região semi-árida baiana
The Jacuípe river is the greater tributary of the Paraguaçu river and its basin has great importance for the State of Bahia, involving a extensive area in the semi-arid region. Experimental Basin of the Cedro river (BHEC), monitored by the Federal University of
Bahia, is inserted in this basin. In order to evaluate the representation of the BHEC, related to the isotopic behavior, isotopic analyzes were carried out in superficial waters of these basins in samples developed among of June and December of 2006. The
local lines of the studied regions showed lesser inclination than global meteoric water line (GMWL), with similar inclination for BHEC and Jacuípe basin, with slope 5.2 0.2 and 5.0 0.1, respectively. This result corroborates with high evaporations rates from
semi-arid region. It was verified that BHEC can be used as laboratory for study of the evaporation effect in reservoirs in the Jacuípe river basin, applying isotopic franctionation methodology, in order to subsidize management action to minimize losses in water amount and quality at semi-arid region due to this phenomenon.
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Evapotranspiração da cana-de-açúcar na região do Recôncavo Bahiano
Authors A.T. Vidal, A.B. Novaes and L.C. PereiraRadiation fluxes over a surface close to a farm in Jaguaripe-BA were measured on clear day. The Bowen ratio method for calculating latent heat e sensible heat fluxes density was used by measuring temperature and water vapour at two heights. Each of energy fluxes density was computed from the Bowen ratio and net radiation minus soil heat fluxes density. The site of interest, under drought conditions, the Bowen ratio was in the range 0 – 1, and the latent heat flux accounted the range 70 – 80% of the net radiation.
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Evolução Isotópica de Oxigênio-18 e Deutério das águas meteóricas da cidade de Salvador no período 2003-2005
Meteoric water samples collected between 2003, october and 2005, july in the Applied Nuclear Physics Laboratory from UFBA. The obtained results indicated that, the δ18O and δD values follow the same trend. These values show also that exist a inverse relationship between precipitation intensity and δ18O and δD values in the majority of the studied moths. The seasonal dependence was observed with deuterium excess parameter d. These values are higher in the cold months and low in the hot months. The
equation parameters values without 2004/jan rain, shows a good agreement with global line of meteoric precipitation and send us to conclusion that this value is out of normal precipitation from this region. The weighted average of δ18O, δD and d values in this work, shows a good agreement with International Atomic Energy Agency values when calculated without anomalous value. This value is probably due to quantity effect united to clouds from intertropical convergence zone.
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Análise da sensibilidade na determinação da porosidade e grau de saturação em DNAPL a partir da inversão das velocidades das ondas P, S e de Radar
More LessThis paper aims to analyze the sensibility of the simultaneous inversion of seismic and electromagnetic wave velocities in saturated porous media to estimate porosity and DNAPL concentration (dense nonaqueous phase liquids). We used numerical simulations. The solution of the inversion problem came from minimizing an objective function. The results pointed out that this approach is satisfactory for media with high porosity and DNAPL concentration. On the other hand, for sediments with low porosity and DNAPL concentration only the porosity value was possible to be estimated.
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Detecção de Contaminação de Solo e Água Subterrânea por Vinhaça através de Eletroresistividade e Polarização Induzida
Given the recent demand on ethanol manufacturing based on sugar cane, there has been a relative increase of the amount of the byproduct known as vinasse.It wellknow that, although its adequate use could improve the production of sugar cane, its overuse not only can decrease the production but also acts as a soil and groundwater contaminant. In this paper we present the results of geophysical investigations on soil fields and groundwater at the Sepé Tiarajú Camp located at the cities of Serrana and Serra Azul, SE Brazil, in order to verify a potential contamination caused by vinasse application. There were made three surveys where were applied the methods of eletroresistivity and induced polarization (IP) using the dipole-dipole array. The obtained results indicate a contamination focus on a site placed nine meters deep around a deactivated vinasse buried tank.
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Processamento e interpretação de dados aerogamaespectrométricos da bacia hidrográfica do rio São Domingos, noroeste do estado do Rio de Janeiro
In the present work we show the results of an airborne gamma-ray data processing and interpretation in the Northwestern portion of Rio de Janeiro State. The studied area is characterized by small private lands with a low-level technological agriculture soil handling techniques. Our results show that weathering processes may control the isotopes distribution in the region.
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Comparação de resultados de modelagens diretas e investigações elétricas 2D em área de depósito de resíduos urbanos
Authors S.J.S. Fachin, V.R. Elis, W.R. Borges, A.L. Lago, A.T. Ustra, I.M. Carlos, E.C. Santos and J. HigarashiThe use of direct and inverse modeling to planning geophysical investigations to provide the best field parameters. This work compares synthetic and real data electric resistivity 2D results obtained in the area of the antique landfill of Ribeirao Preto, Sao Paulo state. The results confirm the efficiency of the polo-dipole array in the identification of the limits and the ditches base of residues disposition and the find the zone of leachate flow.
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The Meteorology contribution to the Brazilian Energy Sector
This paper aims at presenting the main products of Solar and Wind Energy Resource Assessment (SWERA) project for Brazil and how this information on solar and wind energy resources can be used to spread out the energy production matrix improving the energy security and reducing the dependency on fossil fuels. The SWERA project were developed in Brazil under the coordination of Climate and Environmental Division of CPTEC/INPE and illustrates how the scientific research in meteorology and climatology can contribute to the energy planning and policies developed in Brazil. The products of SWERA project include information that will be extremely useful to foster capital investments providing private sector and government institutions with reliable database of energy resources. The paper presents the main results in solar and wind energy mapping and discusses some renewable energy scenarios taking in account the technologies in use currently.
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Variação Climática Secular e Mapeamento do ‘Efeito Estufa’ no Território Brasileiro
More LessBorehole temperature data from the eastern parts of Brazil has been examined in an attempt to extract information on surface thermal perturbations of the recent past at low latitudes. Forward models were employed in the analysis of temperature logs from 29 localities and, in addition, inverse modeling was carried out for data from 10 selected sites. The model results have allowed determination of the magnitude as well as the duration of ground surface temperature (GST) changes in five major geographic zones of Brazil. Prominent among such events are the warming episodes that occurred over much of the subtropical highland regions in the southeastern parts of Brazil. The present magnitude of GST changes in this region are in the range of 2 to 3.5oC but have had their beginning during the early decades of the 20th century. Nearly similar trends are also seen in temperature-depth profiles of bore holes in the subtropical humid zones of the interior parts of southern Brazil. In the coastal areas however, the magnitudes of surface warming are relatively smaller (falling in the range of 1.7 to 2.2oC) while its beginning appears to have shifted to the mid decades of the 20th century. The data from semi arid zones of northeast Brazil also indicate occurrence of surface warming events but the magnitudes are in the range of 1.4 to 2.2oC while the duration of the warming event is larger, extending back into the last decades of the 19th century. The present work also includes preliminary inferences on GST variations in the northern tropical regions of Brazil, based on analysis of borehole data in shallow wells at two localities: Belém (state of Pará) and Manaus (state of Amazon). Surface temperature changes inferred for these localities are relatively small, being less than 1oC in areas where the
vegetation cover has been removed. In areas of tropical rain forest GST changes are found to be less than 0.5oC. There are indications that changes in both climate and vegetation cover contribute to variations in GST. Another important result emerging from model studies is that the climate was relatively cooler during the 17th and 18th centuries. The climate histories, deduced from geothermal data, are found to be consistent with results of available meteorological records in southern Brazil. Comparative studies also indicate that the magnitudes and duration of recent climate changes in southern and eastern Brazil are similar to those found in other continental areas such as North America, Asia and Europe.
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Caracterização da pluma de Contaminação de Al e Pb através do método da eletroresitividade no Município do Rio de Janeiro –RJ
More LessThis paper presents a characterization of plume of contamination of “ Al “ and “ Pb” in soil study, carried out with the Resistivity Method. This study was made before of the construction of a building in the District Colégio at County of Rio de Janeiro. The site there was a Industry of the Galvanoplastic. In principle was investigated by conventional borings , and detected Al (Aluminium) and Pb (lead) in analysis of soil, the electral method were evaluated for the capacity to detect the interfaces between different layers, in particular the plume soil-contamination. The data obtained with the configuration Wenner, the data obtained with the electrica were satisfatory. The resistivity method produced other interesting data and corroborated with the interpretation of the subsoil.
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Preliminary results of Electrical Resistivity Tomography applied to a feedlot to detect conductivity anomalies
Authors Claudia Sanato, Beatriz Losinno and Horacio MallevilleThe intensive animal production is considered highly risky for groundwater and soil.
The aim of this work was to obtain an electrical conductivity image of unsaturated and saturated zone at a feedlot (cattle feeding field) at the surroundings of Buenos Aires city (Argentina) in order to detect the most critical sectors of the field, respecting contamination by animal wastes. Dipole-dipole electrical soundings (electrical resistivity tomography) were performed at the corral zone and the surroundings. 2D models of conductivity were obtained with the UBCGIF software.
Even if there is a calcareous plate bellow the corral soils, vertical infiltration or subsurface runoff may have occurred since these sites show conductivities three times higher than the surroundings (greater than 1600 μS/cm) up to a depth of 10 m, particularly near a small channel of effluents. The models showed higher conductivities in the direction of groundwater flow and decreasing topography, allowing further designs of soil sampling and infiltration experiments.
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Geoelectrical observations at the mining dumps of the Peña de Hierro copper mine in the Rio Tinto mining district / Spain
Detailed geoelectrical measurements reveal a 3D-resistivity model of the internal structures of a heap of mining residuals dumped at the abandoned copper mine Peña de Hierro which is located at the headwaters of the Rio Tinto in Spain. The model reveals also the relief of the bedrock underlying the heap. Aspects of water movement at the surface are investigated by an artificial precipitation experiment with monitoring the subsequent changes of resistivities. The investigation is part of a research project dedicated to the role of hard pan formation with respect to natural reduction of acid mine drainage, funded by the German Federal Ministry for Education and Research.
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Geophysical characterisation of an abandoned waste disposal site near an area of environmental interest
Authors G.P. Deidda, F. Loddo, C. Piga and G. RanieriSolid waste disposal represents an urgent problem for public administrations worldwide. Today in Italy more than 58% is deposited in landfill sites. The examination of possibly appropriate landfill sites together with the discovering of the abandoned waste disposal of those already employed for this purpose and their reclamation is therefore a primary issue. In the present paper a geophysical characterisation of an abandoned waste disposal situated in the Central-Eastern part of Sardinia, near the town of Tortolì, is presented. The geophysical survey allowed to delineate the different parts of the landfill and to calculate their volumes and individuate the plume of leachate.
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Caracterização preliminar da área da lixeira de Porto Velho – RO empregando o método eletroresistividade
Geophysical experiments using eletroresistivity method, by means of vertical electrical sounding and electric profiling (Shulumberger and dipole-dipole configurations), were done at the municipal “landfills” of the cities of Porto Velho, Rondônia. These studies were done in order to identify the anomalies of the local underground. The regional geology, which crop out at the Porto Velho sites, is caracterized by immature laterites, pleitocenic age, seated on rocks granities of the formation Santo Antônio, that surfaces in the area of the embankment of Porto Velho. The integration of eletroresistivity and local geology, allowed starting from interpreted geoelectric models and permits the determination of the leachate percolation zones, identify the different lithotypes of the underground, analyze the behavior of the feather of chorume contamination and direction of the groundwater.
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Uso Do SBP (Sub Bottom Profiler) 3,5kHz No Mapeamento Do Substrato De Uma Lagoa De Descarte De Efuentes Industriais
This paper presents the results of an SBP (Sub Bottom Profiler) application for sedimentary and environmental evaluation in a hydrocarbon industrial saline lake.
The SBP allows the bathymetry mapping, making images of the sedimentary geometry as well as identifying the acoustic anomalous zones related to the hydrocarbon contamination. A case history in a new 3D approach presented here, indicates this methodology as a strong tool for geophysical and geological evaluation in a saline water and clay environment.
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Tomografia Elétrica Entre Poços na Investigação Ambiental de Sítios Contaminados por Hidrocarbonetos e Água Salinizada
The usual electrical multielectrode methods can be replaced by the cross-hole multielectrode one (borehole electrical tomography), with advantages in terms of apparent resistivity measurement precision, depth of investigation and space restriction areas with a large amount of surface interferences. This paper shows the applications of the electrical borehole tomography considering three different sites: the first one representing a free phase hydrocarbon resistive contamination, the second one representing a dissolved hydrocarbon phase conductive contamination and the third one presenting a salt water conductive contamination. The geophysical result was correlated with well logging, geochemistry and hydrochemistry analysis and can confirm this methodology as a powerful tool when applied to the environmental evaluation.
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Uses, abuses, and examples of seismic-derived acoustic impedance data: What does the interpreter need to know?
More LessThroughout the years there has been a concerted effort to integrate the geoscience disciplines to become more adept at understanding the hydrocarbon potential of a given area. In the 1980s, geophysicists interpreted 2D seismic data by overlaying well log data on paper seismic sections and using generalized depth-to-time curves to determine which events represented markers on the logs. Geologists interpreted cross-sections by drawing straight lines between wells to represent their correlations. Because technology advances have changed the process, many people today have become “interpreters” of 2D or 3D data on workstations where the log data, seismic data, and many derivations of the seismic data (attributes, coherence, P impedance, inversions, elastic impedance, lambda rho, etc.) are available to fine-tune the analysis process. The question, however, still remains: Are we integrating the data yet?
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Seismic Stratigraphy of Pre-Salt in the Southernmost of Santos Basin
Authors Márcia Kuhn Karam, Roberto Porto and Makoto SaitoThe evaluation of Pre-Salt in the Southernmost of Santos Basin using 2D and 3D seismic data reveals that there are three seismic stratigraphic sequences compounded by (1) a lower volcanic rocks sequence, (2) an intermediate sequence where half grabens predominate, related to an intense period of tectonic activity and (3) the upper sequence characterized by tectonic quiescence identified as Sag Phase. It is suggested that the two first sequences would be related to rifting events (Rift Sequence) and the third would belong to Transitional Sequence including the upper part of Guaratiba Formation. In this last sequence began the thermal subsidence.
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Detailed seismic exploration of the Orelka monocline, Ukraine – a case study
Authors Viktor Mershchiy, Olga Mershchiy and Myroslav DmitrovskyIn spite of the fact that Ukraine is one of the oldest oil producing regions, the oil and gas production in Ukraine provides a national industry only partially and for the most part depends on the import. Practically all traditional traps of oil and gas in Ukraine are already striked and are in exploitation. Therefore the main task of seismic survey on oil and gas fields are the exploration of non-conventional traps, situated, in particular, on the vast monoclines of large-scale basins. In the given report we consider the successful seismic survey on a monoclinal slope of Dnieper-Donetsk basin (DDB), Ukraine, as an example.
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Building Time-Depth Curves: The Shift/Drift Methodology
More LessThe Checkshot is a well acquisition technique whose data are used to try to establish a correlation among depth of geological layers in well to the time of seismic events in a seismic section. In a petroleum company, it is a routine to discuss about bad quality in seismic to well correlation, regardless the commercial tool in use. This correlation may be done by using synthetic seismograms. The first perception trying to do this correlation is that there is a time shift that must be solved. In general this time shift may be observed correlating good geological markers that are also good seismic events: the time of events in seismic section doesn’t agree with the time of checkshot readings. By the time the initial correlation is assumed good enough, the technician involved in the task may note also that there is an increasing uncoupling among geological markers and seismic events, starting from the initial point of correlation. Also it is easy to observe that amplitude, frequency and phase of seismic events doesn’t match the same properties in the synthetic seismogram. The scope of this paper is to investigate and establish an acceptable solution to the correlation between geological markers in well and the correlative seismic events in seismic section.
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Integration of surface and subsurface data to optimize G&G interpretation workflow
More LessGeologic and Geophysics (G&G) interpretations typically use only seismic data in planning for the development of oil and gas prospects. However, the integration of seismic data with aerial photography and satellite images, for example, in the same workflow can reduce the time needed to obtain environmental approvals for proposed onshore well locations. Due the short time required to fulfill exploratory concession contracts, a shorter overall approval cycle is crucial. The integration of these two major sources of pertinent data — seismic and aerial — is capable of reducing the overall cycle time by at least 50 percent, besides being able to reduce costs and safety risks.
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Estudos geofísicos integrados na região da Bacia de Lajeado na Faixa Apiaí, sudoeste de São Paulo, Brasil
Authors Mario Jesus Tomas Rosales and Wladimir ShukowskyTerrestrial gravity and airborne magnetic data covering an area of approximately 4000 km2 were used to refine the existing geological mapping of the Apiaí Belt, as a contribution to the detailed geological knowledge of the differents litologies that constitute the Lajeado basin, as well as of its tectonic setting. The terrestrial gravity and aeromagnetic data were interpreted qualitatively, using techniques of filtering and transformation of the potential, and quantitatively, by 2.5 D modeling along regional geophysical profiles.
The main result is the structural characterization for the presence of thick packages of metasedimentary and volcano-sedimentary rocks and, with intercalations of metabasites to the Lajeado sub-group (VL) that amounts an estimated thickness of approximately 3 km.
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Geophysical properties associated to Juá District geology, Ceará, Brazil
Airborne magnetic and electromagnetic highresolution data were processed to unveil physical properties of Pre-Cambrian high-grade terrains in Northeast Brazil. The method followed the common data correction plus, map and profile interpretation, ending with spatial analysis by probability ratio technique. Local geologic map and, lineament interpretation complete the data set. Results show a geophysical differentiation exclusive for some rock units and, boundaries were redefined improving the geologic map. Also, shallow and deep structures were distinguished
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Pre-drill pore pressure study for a high temperature well in the Gulf of Mexico using reprocessed fit-for-purpose seismic velocities
Predrill formation pressure predictions are essential forwell planning and for optimizing drilling decisions. In this case study, a predrill model for an exploration well in the Gulf of Mexico is described. The interval velocities obtained from the available stacking velocities were reprocessed based on a method that maximizes the stacking power of spatially continuous events in prestack gathers. The reprocessing resulted in a fit-for-purpose velocity model appropriate for pore pressure prediction. Calibration of the velocity-to-pore pressure transform was performed with existing well log data from offset wells. Because of large-scale major faulting and possible pressure compartments, only offset wells in geologically comparable locations, e.g., same major fault block, were
used for transform calibration. Also the influence of overpressure on flow focusing (centroid-effect) was estimated for three sand horizons in the area.
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3D opacity in volume rendering of seismic data
It is presented a technique called 3D opacity for the volume rendering of seismic data. The technique employs a transfer function composed of three attributes. It not only improves the image quality, but also takes advantage of the Graphics Processor Unit and thus speeds up the rendering process. Two applications are considered in order to validate the proposed technique.
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Sondagens TDEM no Sítio Controlado de Geofísica Rasa do IAG-USP: Resultados Preliminares
Authors Thiago Gomes dos Santos and Jorge Luís PorsaniIn this Work are presented preliminary results of electromagnetic soundings in the time-domain - TDEM acquired in the area where the Controlled Site of Shallow Geophysics of the IAG/USP is installed. The objective is to map the geoelectrical stratigraphy of the sediments of the sedimentary basin of São Paulo with emphasis in the studies of groundwater. Although preliminary, the results of TDEM soundings are satisfactory and show a good agreement with the stratigraphy of the sedimentary basin of São Paulo. Other soundings will be acquired aiming to obtain the geoelectrical stratigraphy of some places inside the campus of USP. With the resulted futures of this research, one expects to show the applicabilities of TDEM method in the urban environment emphasizing the groundwater studies in sedimentary basins.
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Interpretación volumétrica de ambientes sedimentarios en al Campo Socororo - Venezuela
More LessUtilizando datos sísmicos 3D experimentales del Campo Socororo, se pretende determinar si es posible la visualización de paleo-ambientes sedimentarios utilizando técnicas de opacidad y transparencia, en conjunto con el software Earthcube de Landmark Graphics, donado a través del Grant Program al Laboratorio de Integración de datos sísmicos y geológicos (Lisg) en la Universidad Estadual Paulista en Rio Claro – São Paulo-Brasil. El objetivo de conocer los paleoambientes, es determinar indirectamente la distribución de cuerpos de arena con capacidad de almacenar hidrocarburo. El estudio se concentra sobre los niveles tradicionalmente productores como son las formaciones Oficina y Merecure, en el Área Mayor Socororo. Con el conocimiento de la distribución espacial de las áreas potencialmente productoras será disminuido de una forma eficiente el riesgo exploratorio.
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Detecting of unstructured traps using the Prony technology
Authors Georgy Mitrofanov and Viatcheslav PriimenkoWe discuss some current results concerned to the processing and interpretation of surface seismic data using the Prony filtration method. It is the new method in the characterization of oil/gas fields. In particular the Prony filtration method can be applied to detecting of fracture zones and zones with high permeability, which can be connected with fluids reservoirs and traps of unstructured forms. Possibilities of this approach are demonstrated on real seismic data and results of monitor wells, drilled using the information obtained by the Prony method only.
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Redes neurais artificiais para mapeamento do potencial mineral de Cu-Au na Província Mineral de Carajás, norte do Brasil
Authors Emilson Pereira Leite and Carlos Roberto de Souza FilhoThis work presents an application of a Radial Basis Function Neural Network (RBFNN) and a Probabilistic Neural Network (PNN) to map the potential for Cu-Au mineralizations in the Carajás Mineral Province, northern Brazil. Geophysical gamma-spectrometric and magnetic data and proximity to faults/lithological contacts values were used as evidential maps to derive input feature vectors. A set of feature vectors representing known mineralized locations was used as a training data set. The networks were created based on the training data set and the whole data set was classified using these networks. Ternary maps showing high, moderate and low favorability sectors were generated for the study area. Results from the RBFNN method shows that 10% of the study area has a great potential to contain some type of Cu-Au mineralization, whereas the high favorability area mapped by the PNN method represents 15,3% of the study area. Although the RBFNN method was more efficient in narrowing the search area for Cu-Au
mineralizations, the classification values obtained from the PNN method showed a well defined threshold that delimitates non-favorable areas.
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Análise exploratória integrada da porção noroeste da Bacia do Espírito Santo Mar
Baseado no sucesso exploratório das descobertas dos campos de Peroá e Cangoá, o presente estudo visa a caracterização do potencial petrolífero da região centro-oeste da Bacia do Espírito Santo Mar. O objetivo foi alcançado utilizando-se a interpretação de dados sísmicos integrados com mapas de atributos sísmicos, técnicas de balanceamento de seção geológica e modelagem do sistema petrolífero. Verificou-se a presença de um sistema compressivo formado provavelmente pelo levantamento dos Abrolhos, configurando armadilhas no Cretáceo, as quais seriam capazes de conter hidrocarbonetos. Como resultado da análise dos sucessos e insucessos dos poços perfurados na região, interpretou-se que o sucesso exploratório está associado à presença de armadilhas estruturais em associação com fácies favoráveis à ocorrência de hidrocarbonetos. Os mapas de atributos sísmicos integrados com informações de poços permitiram a correlação das anomalias de amplitude com as características das rochas.
O balanceamento e a retrodeformação da seção geológica indicaram que a rocha geradora começou a gerar hidrocarbonetos a partir de uma espessura de soterramento superior a 4.000 metros, espessura esta atingida no Oligoceno com a associação de sedimentação e encurtamento da seção de aproximadamente 19 km nesta época. O encurtamento total da seção atingiu 29,48 km, ou 26,2%. Finalmente, com a modelagem do sistema petrolífero concluiu-se que nos atuais horizontes portadores de hidrocarbonetos (Oligoceno e Eoceno Superior), o volume de reservas na área estudada poderia ser dobrado, em relação ao volume de gás contido nos campos de Peroá e Cangoá, alcançando entre os dois níveis estratigráficos volumes de até 33,6 bilhões de metros cúbicos de gás. Por sua vez, para outros horizontes estratigráficos foram calculados volumes adicionais de 12,7 bilhões de metros cúbicos de gás no Cretáceo Superior e 35,5 bilhões de metros cúbicos de gás no Albiano-Cenomaniano.
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Geophysical and geological evidence of Precambrian evaporites within western São Francisco basin – A working hypothesis for gas and oil exploration to unveil an Earth´s secret of central Brazil
Authors E.M. Meister, M.C. Lobianco and J.M. TravassosGeological and geophysical evidence is presented for the highly probable local presence of evaporites within the Precambrian São Francisco basin of Brazil. This working hypothesis has obvious implications both for the exploration of gas and oil, and for more general scientific and macroeconomic questions.
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Application of 3D Reverse Time Migration
Authors P.A. Farmer and I.F. JonesFollowing completion of model building, amplitude preserving 3D depth migration is usually performed using a Kirchhoff scheme for modest structural problems with steep dips. For structures where multi-valued ray-paths exist (e.g. complex salt bodies), we generally use a oneway Wavefield Extrapolation (WE) algorithm instead. However, more recently, full two-way solutions of the wave equation, such as Reverse Time Migration (RTM) have become commercially available:- these are suited for highly complex environments, where both steep dips and multi-pathing are an issue. Standard shot-based one-way WE preSDM techniques image the subsurface by extrapolating the source and receiver wave-fields for each shot. The imaging condition is invoked by cross correlating these two wave-fields at each depth level, and then summing the contributions from all shots in the aperture to form the image. One of the assumptions made in using this technique is that the wave-fields travel along the direction of extrapolation only
in one direction: downwards for the source wave-field, and upwards for the receiver or scattered wave-field. In practice, each of these wave-fields will generally travel both up and down when the velocity model is complex, when turning (diving) raypaths are involved, or when multiples are being generated. In addition, approximations in the extrapolation techniques usually limit the dips present in the final image to less than seventy degrees. Steeper dips, and turning rays are usually imaged using Kirchhoff techniques, but these fail to deliver acceptable images once we have a multi-pathing problem. One technique which can address all these issues is migration using the two-way wave equation. Here we have used an RTM algorithm to achieve this. RTM properly propagatesthe wave-field through velocity structures of arbitrary complexity, correctly imaging dips greater than 90 degrees. It even has the potential to image with internal multiples when the boundaries responsible for the multiple are present in the model. We will show examples of RTM from the North Sea andthe Gulf of Mexico to demonstrate the the potential benefit of migrating with the full acoustic two-way wave equation
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Neo-morfotectônica e diapirismo de lama na região de Cartagena, Colômbia
More LessExpõem-se as feições morfo-estruturais na sísmica e no campo, que revelam atividade tectônica recente e atual na região costeira norte da Colômbia. O diapirismo de lama e os recifes de coral quaternários soerguidos até 200 msnm são as mais chamativas
evidências. A partir de informações geofísicas geradas nos últimos 25 anos e indicadores cinemáticos coletados recentemente, discute-se sobre o arcabouço estrutural que relaciona os domos com o tectonismo local e regional.
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Caracterização geofísica da estrutura de Piratiniga - SP (Brasil)
More LessThe Piratininga Structure, located within coordinates 22°30'S and 49°10'W, is a possible meteorite impact crater of complex nature and Cretaceous age. The structure is in advanced stage of erosion, show 12 km in diameter and topographical gradients of up to 130 m between the rim and its center. The available geophysical data for this structure comprise airborne magnetics and seismic profile data, which were processed and interpreted together with the SRTM-derived (Shuttle Radar Topographic Mission) digital elevation model (DEM). The results allowed the recognition of the structure in subsurface and unraveled geophysical features that are akin to those observed in proven impact craters worldwide. Among the features revealed by the magnetic products there is a peak of high intensity located in the center of the structure, enclosed by magnetic anomalies with lower values. In the seismic profile, the following features were distinguished: (i) distinct normal faults with fault plane plunging to the interior of the structure e forming terraces; (ii) interruption of key stratigraphic layers; and (iii) verticalization of the sedimentary bedding around the center of the structure, possibly as a result of central uplift. The structure of Piratininga, however, cannot be considered an impact crater based only in subsurface structures. This requires finding typical shock features such as impact breccias, shatter cones, planar deformation features (PDFs) in quartz and feldspars, etc. Quartz grains derived from samples collected in the center of the structure were investigated in this work and although planar features have been identified, will be still necessary to demonstrate its origin by shock (e.g., evidence of shock melts along these planes).
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Fault identification using competitive learning
Authors Marcos Machado and Marcelo GattassManual fault mapping from 3D seismic data is a timeconsuming task. A plethora of seismic attributes have been proposed to enhance the discontinuity measures associated with the faults. However, some features in the attribute data make extraction of the fault surfaces as separate objects difficult. This paper proposes the use of competitive learning algorithms to tackle this problem and analyzes two different approaches. In the first approach, the Growing Neural Gas algorithm is used to transform the fault attribute volume in a graph, reducing drastically the number of samples to be considered in a surface modeling stage. The graph so obtained is then submitted to a pruning strategy in order to identify the main fault surfaces. In the second approach, the Neural Mesh algorithm is used to generate a fault surface triangulation.
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Aeromagnetometria e Deconvolução De Euler Apilcada à Interpretação Estrutural Do Sistema De Cisalhamento Porangatu, Brasil Central
High resolution aeromagnetic airborne survey is used to determinate the tectonic framework from the Porangatu region, NW Goiás. We recognized different crustal blocks and large lineaments that are interpreted as a system of strike slip shear zones. Euler deconvolution method is a potencial tool to define the geometry of these structures in deep.
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Algumas Reflexões sobre a tecnologia da exploração de petróleo abaixo do sal – exemplo da Bacia de Santos
More LessÉ amplamente conhecido que as características físicas apresentadas por níveis evaporíticos - incluindo os domos de sal - nas bacias petrolíferas, são um complicador natural no processo exploratório. Desde os primeiros fracassos, na década de 80, quando os exploracionistas de petróleo procuravam plays adjacentes às camada de sal com base unicamente em dados sísmicos bidimensionais, estão sendo desenvolvidas novas tecnologias tanto na área de processamento do dado sísmico quanto na área de interpretação. Este artigo, além de apresentar a história que conduz ao sucesso no play exploratório subsal, apresenta um exercício de modelagem em duas dimensões do sistema petrolífero abaixo do sal na Bacia de Santos. Desde os primórdios do sucesso exploratório relacionado à descoberta de petróleo no Campo de Cascade, nos Estados Unidos, localizado em águas ultraprofundas, o risco exploratorio neste tipo de play tem diminuído de 64% para 40%, utilizando-se técnicas de migração em profundidade pré e pós-stack. A exploração de acumulações situadas abaixo do sal envolve alguns métodos tradicionais, entre eles a interpretação do dado sísmico em tempo, com o objetivo de controlar o modelo de velocidades utilizado no processo de migração em profundidade pré e pós- empilhamento da seção sísmica (pre and post- stack depth migration). Como resultado, aplicando um processo exploratório integrado com todas as fases do tratamento do dado (processamento, interpretação e modelagem do sistema petrolífero), especificamente orientado para a exploração associada com a presença de sal, o risco exploratório pode diminuir para níveis inferiores a 40%. Finalmente, deve-se esclarecer que os resultados obtidos na modelagem do sistema petrolífero destes níveis subsal são meramente indicativos das áreas com maior probabilidade de conter hidrocarbonetos, sendo que estes níveis não têm reservas reportadas que sirvam de calibração para nossos modelos.
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Deconvolução iterativa tipo Wiener-Levinson
Authors Paulo E. M. de Melo and Milton J. PorsaniThe importance of the seismic resolution, and of the quality of the seismic images to the industry of petroleum, has motivated the development of new filtering techniques for processing of the seismic reflection data. In this paper we present a new filtering method to improve the resolution of the seismic sections. Unlike the conventional Wiener-Levinson approach which uses causal filter and L2 norm, the proposed method is iterative and uses causal and anticausal filters, combined with variable norm. Numerical results using synthetic seismic data demonstrates its ability to overcome some limitations of the conventional Wiener-Levinson method, providing good results even when the wavelet is not minimum-phase or the reflectivity series is not a random process. Numerical examples using poststack marine seismic reflection data, demonstrates the efficacy of the new iterative wavelet deconvolution method.
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Caminhamento Elétrico Multieletrodo Aplicado ao Mapeamento de Áreas de Risco em Travessias de Dutos: Estudos de Casos
The results of electrical multielectrode WENNER array in geophysical survey are geoelectrical sections marked by resistivity contrasts in different geological units, as well as the mapping of the bedrock, rock blocks, boulders and fractured zones. Different resistivity values are associated to the inhomogeneous and anisotropic layers related to different geological domains, due to its own geoelectrical characteristics. This geophysical technique was used to reduce the drilling risk for pipeline location below crossing rivers, where geological information is important and difficult to obtain. This paper presents three case histories in which this electrical method was used successfully showing how it should be extended to similar applications.
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Interpretação de Dados de GPR com Base na Hierarquização de Superfícies Limitantes e na Adaptação de Critérios Sismoestratigráficos
More LessThe goal of this research is to propose an interpretation methodology of GPR data able to perform this task at least for siliciclastic deposits. In order to do so, the proposed GPR interpretation method is based both on seismostratigraphic concepts and on the bounding surface hierarchy tool from Miall (1988). As consequence of this joint use, the results of GPR interpretation can be associated to the sedimentary facies in a genetic context, so that it is possible to: (i) individualize radar facies and correlate them to the sedimentary facies by using depositional models; (ii) characterize a given depositional system, and (iii) determine its stratigraphic framework highligthing how it evolved through geologic time. To illustrate its use the proposed methodology was applied in a GPR data set from Galos area which is part of the Galinhos spit, located in Rio Grande do Norte state, Northeastern Brazil.
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Simulações Numéricas GPR 2D para Caracterizar Vazamentos de Óleo Provenientes de Cabos Elétricos de Alta Tensão Instalados no Subsolo
More LessThis work shows results about GPR numeric simulation to locate electric cables in the subsoil and to characterize the contamination plume from the oil used in high-voltage electric cables. The models simulate electric cables of low, mean and high-voltage installed in the subsoil of SãoPaulo city, Brazil. 200MHz GPR profile over targets installed in test site of the IAG/USP present good agreement with the numeric simulation results for the same targets. The results can be used in the viability studies of the GPR method in mapping interferences in the subsoil and in environment contamination characterization.
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Correção topográfica em dados de GPR 3D
Authors Fábio José Miranda and Guilherme Pena CastilhoAtalmente, aina não é comum a aplicação de correção topográfica em dados de GPR Tridimensional, o que dificulta a integração dos dados com outros em que foi realizada tal correção e a integração com informações de investigações diretas, não retratando as possíveis variações topográficas do terreno onde se realizou a investigação. Este trabalho traz algumas informações sobre a estrutura de um arquivo de GPR3D e GPR2D no formato seg-y e as modificações que são verificadas quando aplica-se a correção topográfica, demonstrando a importância dessa correção para que o trabalho do inérprete seja mais preciso.
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Investigações GPR no Sítio Arqueológico Lapa do Santo-MG: Resultados Preliminares
Authors Guilherme de Matos Jangelme, Jorge Luís Porsani and Renato KipnisIn this article we present preliminary results of 2D and 3D GPR survey carried out at the archaeological site Lapa do Santo. This cave is found within the Lagoa Santa karstic region, Matosinhos, Minas Gerais. 44 GPR profiles were acquired with 200 and 400 MHz antennas focusing on three mains objectives: (1) to characterize stratigraphic layer; (2) to identify geological and archaeological anomalies; and (3) to identify potential areas for archaeological excavations. Data obtained with the 400 MHz antenna indicate two anomalous hyperbolic reflections that suggest potential archaeological targets. These results are very encouraging and will be used to guide future excavations at the site. The results also indicate the importance of geophysical survey as a tool for assisting with the paleoanthropological project being coordinated by Prof. Walter Neves (IB-USP).
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