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11th International Congress of the Brazilian Geophysical Society
- Conference date: 24 Aug 2009 - 28 Aug 2009
- Location: Salvador, Brazil
- Published: 24 August 2009
1 - 100 of 418 results
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Effect Of Net To Gross On Time-Lapse Seismic Response In Campos Basin, Brazil
Authors Marcos Grochau and Boris GurevichQuantitative time-lapse studies require precise knowledge of the pressure response of rocks sampled by a seismic wave. Usually this knowledge is obtained from measurements of ultrasonic velocities as a function of pressure. These measurements are typically made on reservoir sandstone samples. However, if the reservoir is composed of sand and shale layers, the response of shales as well as sands has to be taken into account. The pressure response of shales is quite different from that in sand: since shales have very low permeability, an increase of pore pressure in the sand will cause an increase of confining pressure in the intra-reservoir shale. To estimate the effect of intra-reservoir shale on the time-lapse response to depletion or injection, we compute the combined seismic response as a function of net to gross (NTG – sand-shale proportion). This is done by applying Backus average using typical shale and sandstone stress sensitivity for an oil field located in Campos Basin, Brazil. For a typical NTG of 0.6, there is an error of approximately 35% in reflection coefficient estimation if these shales are neglected. Consequently, not considering the small shales intra-reservoir may mislead quantitative 4D studies. We suggest expanding this approach to 3D models in order to incorporate other geomechanical effects.
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Lithological Differentiation Through Wavelet Transform And Zonation Process Using Geophysical Well Logs Of Namorado Oilfield
Authors Abel Carrasquilla and Jamilson DelesposteOn the geophysical well logging there is a great interest in improving the vertical resolution, with the aim to differentiate the lithology of geological formations through the well. This is of extreme importance in the petroleum industry, therefore, through this process is possible to separate the reservoirs from the seals, but also to determine the geometry and physical properties of each unit, with a view to the future tasks of commercial production. To achieve these goals, several techniques have been tested, such as log deconvolution, time-series analysis, multivariate statistical techniques, artificial intelligence techniques, etc. In this study, it was conducted a comparative study between two techniques to achieve this differentiation, such as Zonation Process (ZP) and Wavelet Transform (WLT). The used data come from the Namorado Oilfield, in Campos Basin, which is known to have a reservoir composed of a clayeysandstone,
especially difficult to be characterized by well logs. The results show that the differentiation derived from the WLT was superior to those found with the ZP, in both, the visual aspect of the layers and the improvement of the values of correlation between logs.
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Fuzzy Logic In The Simulation Of Sonic Log Using As Input Combinations Of Gamma Ray, Resistivity, Porosity And Density Well Logs From Namorado Oilfield
Authors Abel Carrasquilla and Marcos Vinicius LeiteThe main premise of this work is to consider that any geophysical well log may be derived from combinations of two other logs measured at the same depth, even if its physical principles are very different. Thus, our proposal is to simulate the sonic log (DT), because it is not always present on the set of logs, it may present problems in its measurement and it is very useful in the oil industry activities. To achieve these objectives, the basic suite of well logs from Namorado Oilfield was analyzed: DT, gamma ray (GR), resistivity (RT), porosity (NPHI) and density (RHOB). The results show a high correlation between DT-GR, DT-NPHI, DT-RHOB, GR-NPHI, RT-RHOB and NPHI-RHOB pairs, meanwhile, low correlations between DT-RT, GR–RT, GR-RHOB and RT-NPHI couples. The couples DT-NPHI and DT-RHOB reveal linear relationships, potential relationship for DT-GR, GR-NPHI, GR-RHOB and NPHI–RHOB pairs, and logarithmic ones for the couples RT – RHOB, RT – NPHI, GR – RT and DT- RT. In the simulation, it was found low fit errors regarding real data ranging between 5% to 7% for all the pairs, showing this that the utilized approach functioned very well, even in the presence of low correlations and non linear relationships between logs, caused by a clayey sandstone reservoirs present in Namorado Oilfield.
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Calculating The Mud Drilling Invasion Through Geophysical Well Logs In Theoretical Reservoirs Models
Authors Abel Carrasquilla and Mariléa RibeiroDuring drilling process, muds of different compositions are used, aiming to support the wall and to remove the debris originated by the action of the bit. These muds invade the geological formations and modify the well surrounding zones, mainly, in terms of porosity and permeability. In the present work, we used the approach developed by Ribeiro (2007) to determine the invasion diameter, which is similar to Tornado Charts methodology utilized by SCHLUMBERGER, inclusive, using the same ILD and LLD well logs. We tested this approach with
different kind of theoretical reservoirs, with the presence of oil, water and gas in different proportions. This procedure shows fast and accuracy, because it considers better the characteristics of the invasion process.
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A Study On The Solar Cycle And Annual Distribution Of Geomagnetic Storms
More LessA list of geomagnetic storms for the period 1957-2008 was compiled using the geomagnetic Dst index from World Data Center for Geomagnetism – Kyoto. Geomagnetic storms with peak Dst -50 (moderate and intense) have been selected. A total of 1377 geomagnetic storms were identified. An exponential fit is derived to give the probability of occurrence of a geomagnetic storm of a specific strength. An updated analysis for the solar cycle and yearly distributions of storms is shown. The well known distributions with solar cycle and along the year are confirmed: dual
peak variation with solar cycle, with one peak near solar maximum and other in the declining phase; semiannual variation with maximum intensity around equinoxes. It is also confirmed the increase in July in the number of storms, for more intense events. The solar cycle variation also shows change in the storm occurrence with the level of intensity, with less intense storms occurring predominantly in the declining phase, while more intense storms close to solar maximum or immediately afterwards.
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Modelo Gamaespectrométrico Análogo Da Formação Ponta Grossa (Bacia Do Paraná)
More LessIn analogue modelling, ground gamma-ray spectrometric data of the Devonian Ponta Grossa Formation (Paraná Basin) allowed for a better understanding of the spatial distribution of lithotypes. Correlations based on gammaray values obtained from deep well logging could be improved. Ground values, spaced 50 cm in sandstones and 100 cm in shales, were taken along four sections. The sections were 30, 250, 12, and 16 meters thikness, respectively. The results of the first section showed that both ground and deep values reflect the gradual clay
enrichment trend noticed along the transition beds between Furnas and Ponta Grossa formations. Along the second section total organic carbon values are in direct relation to ground and deep gamma-ray data. In the third section a clear decrease of intensity was observed in sandy layers. In the last section, which is characterized by higher sand-fraction content, showed a gamma-ray signature compatible with the coarsening upward observed in well data. In this context, a massive clayey interval was defined by high gamma-ray values in both
investigation levels. Ground gamma-ray spectrometry combined with detailed outcrop descriptions and deep source data proved to be useful in the establishment of analogue models for the Ponta Grossa Formation in the Paraná Basin.
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Aplicação De Sondagens Elétricas Verticais No Estudo Da Contaminação Na Lixeira De Porto Velho (Ro)
Authors Adeilton Fernandes Da Costa and Walter Malagutti FilhoThis paper presents the results of the application of the electric resistivity geophysical method, by mean of vertical electrical sounding (Schlumberger configuration), were done at the waste
disposal area, in city of Porto Velho, State of Rondônia, Brazil with the objective to identify the contamination of underground at the waste disposal area. The local geology is constituted by
pleistocenic sediments (clay-sandy litology with lateritic concretionary) overlies granitic rocks of Santo Antônio Formation.
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Modeling Of A Synthetic Presalt 2D Seismic Dataset Representative Of Offshore East Margin Basins (Brazil) – Preliminary Results
Authors Alexandre De Souza Oliveira and Carlos A.S. FerreiraThe offshore East margin basins, especially Campos, Santos and Espírito Santo, are the main oil producers in siliciclastics reservoirs in Brazil. However, in recent times large volumes of light oil in carbonate reservoirs in the Aptian presalt section in Santos (BM-S-11, Tupi prospect) have also called the attention of the oil industry due to its potential hydrocarbon content. To the geophysical community, imaging this kind of reservoir represents a new exploration frontier in its characterization and its seismic signature. The main challenge here is the
imaging under salt followed by the mapping of amplitude anomalies (e.g., AVO) related to carbonate reservoirs, which are extremely anisotropic in nature. This paper then presents the results of a simple modeling of a representative offshore presalt prospect considering its main geological characteristics.
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Double Diffraction Stack For An Alternative Strategy For Crs-Based Limited-Aperture Kirchhoff Depth Migration
Authors Ines Veile and Jürgen MannIn Kirchhoff migration, the proper choice of the aperture is essential: the optimum aperture is the limited aperture defined by the first projected Fresnel zone. This is the smallest aperture providing interpretable amplitudes along with the highest possible S/N ratio and the minimum number of required summations. In addition, limited-aperture migration naturally prevents operator aliasing. The commonreflection-surface (CRS) stack provides kinematic wavefield attributes which allow to estimate the optimum aperture size for zero-offset and its dislocation with varying offset. The aperture is centered around the stationary point, but this point has to be associated with the corresponding point in the migrated domain in an additional process. Kirchhoff migration itself implicitly connects the stationary point and the image point in depth by collecting the energy in the vicinity of the former and assigning it to the latter. In principle, any smoothly varying property can be migrated “on top” of the seismic data themselves by applying multiple weighted diffraction stacks. The most generic property to be migrated in this way is the source/receiver midpoint which yields the lateral position of the stationary point mapped to the image location in depth. We investigate the validity and accuracy of this approach for simple
synthetic data and apply it to a real land data set. A straightforward extension is introduced to solve some of the numerical problems inherent to this approach and CRSbased strategies are transferred from the time domain to the depth domain to identify the reflector images and to attenuate migration noise. Finally, the approach is compared to another CRS-based approach which directly evaluates the tangency criterion.
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The Bgr Aerogravity System: Results From A Survey Of The German Bight (North Sea)
By Ingo HeydeThe Federal Institute of Geosciences and Natural Resources (BGR) has carried out a multitude of gravity surveys onboard marine research vessels since the 1960s. Since 1984 these measurements are performed with the KSS31 gravity meter system. This system has been modified and complemented during the last years for use in aerogravity surveys as well. In May 2007 the first aerogravity campaign was carried out with this updated system. Gravity data of the main part of the German exclusive economic zone in the North Sea were obtained. During 17 flights 32 northwest-southeast running profiles with a spacing of 5 km and 11 tie profiles with a spacing of 20 and 30 km respectively were surveyed. The total profile length added up to 10500 km. The standard survey altitude was 1000 ft above sea level. Depending on the wind speed and direction the survey ground velocity ranged between 170 and 230 km/h.
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Comparação Entre As Amplitudes E Fases Das Marés Nos Ventos Medidos Com Radar Meteórico Na Mesosfera E Alta Atmosfera Acima De Cachoeira Paulista E O Modelo Gswm
Authors Lenine M. Aguiar, Paulo P. Batista and Barclay R. ClemeshaWinds over Cachoeira Paulista have been measured with meteor radar in order to determine the amplitudes and phases of the diurnal and semidiurnal tidal components and compare them with the GSWM model. This comparison has shown that the values given by the meteor radar and the GSWM are in accordance under some aspects, but, inconsistencies exist in others. These inconsistencies are discussed along this work
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Some Lapses Of Time-Lapse Feasibility And Interpretation Studies
There are numerous successful applications of seismic monitoring of hydrocarbon production in different types of reservoirs. Even quantitative evaluations of saturation and pressure evolution due to reservoir production can be observed in some case histories. Every 4D study, however, involves some restrictive assumptions related to rock and fluid behavior. This paper discusses some shortcomings of time-lapse feasibility and interpretation studies as well as yields an insight on the possible errors involved.
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A 3D Gravimetric Model Of Las Salinas Basin, San Juan, Argentina
Authors Edgardo A. Azeglio, Mario E. Gimenez and Antonio IntrocasoFrom a gravimetric study done in the Las Salinas basin, situated in the province of San Juan, Argentina, the geometry of the geologic structures that form this sedimentary trough could be determined. The average depth to the basement was found to be about 5 km, and it increases to the north of the basin. The depth values were obtained by applying spectral analysis and Euler deconvolution to the Bouguer anomaly chart. The alineations of the Euler solutions resulted highly consistent with the seismic interpretations and thereby permitted to confirm the existence of a wrench fault system mainly oriented north-south, which flank the sedimentary trough and cuts it off in the middle part. This information, plus densities obtained from logs of two hydrocarbon exploration wells drilled in the basin, permitted the elaboration of a gravity inversion model with variable density, which justifies the Bouguer residual anomaly. The results show that the basin extends over about 5750 km2. The sedimentary depths, reachs 5 km, is 1.5 km larger than those obtained with seismic. This leads to the assumption that our results show the depth of the crystalline basement, whereas the seismic ones indicate a shallower presence of a technical basement.
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Parameters Estimation Of Vti Media, Using Hybrid Genetic Algorithms
Authors Samuel G. Huamán Bustamante and Marco Aurélio C. PachecoAt this work is proposed a sequential method based on hybrid genetic algorithms (HGA) composed by the genetic algorithm and the Nelder mead simplex algorithm to estimate parameters of a model from seismic reflexion. The model represents layers into underground. In this way, the parameters of a layer form a chromosome of the HGA and the set of layers forms a seismic model. In the inversion process of multiple layers, the representative velocities are the main problem to get the layer velocities. Consequently, the proposed method estimates sequentially the seismic parameters for solving this problem. The experiments use seismic models with horizontal layers with isotropy and vertical transverse isotropy (VTI). The proposed method is compared to the method of Medeiros (2005); that considers a chromosome for all seismic models. The results, when is applied the proposed method, are better than refereed method. The data with the travel times are synthetic and without noise. Other advantage is the reduction of the runtime of estimation algorithms; that allows processing of more quantity of data.
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Multi-Point Observation Of The Shock Front Longitudinal Extent In The Inner Heliosphere
The two Helios probes traveled at variable longitudinal and radial separations through the inner heliosphere. They collected most valuable high resolution plasma data for an entire solar cycle. The mission is still so successful that no other missions will collect the same kind of data in the next 20 years. One of the subjects studied after the success of the Helios mission was the identification of more than 390 shock waves driven by Interplanetary Coronal Mass Ejections (ICMEs). Combining the data from both probes, we make a statistical study for the extension of shock waves in the interplanetary medium. For longitudinal separations of 90 degrees we found a cutoff value at this angular separation. A shock has 50% of chance to be observed by both probes and the same probability for not being observed by two spacecrafts at the same time, when the angle between them is around 90 degrees. We describe how with decreasing separation the chance for shocks to be observed by both probes grows. Including plasma data from the ISEE-3 and IMP-8 spacecrafts, improves our statistical evaluation substantially.
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Aplicação Da Decomposição Espectral De Dados Sísmicos No Estudo Das Acumulações De Hidratos De Gás Da Bacia De Pelotas
More LessIn the last years, seismic researches are producing more detailed and precise information for characterization and reservoir management. The spectral decomposition have been recently applied in seismic data as a powerful tool to interpret the properties of reservoirs, to determine the thickness of layers, to detect accumulations of hydrocarbon and to show stratigraphic details not visible in their original form. There are a lot of spectral decomposition methods that can be used but in this work we will apply the Continuous Wavelet Transform (CWT) in
seismic data of the Pelotas Basin to check how this technique responds to accumulations of gas hydrates in Brazilian coast.
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Power-Gradient Velocity Model
More LessI propose a power-gradient velocity model which incorporates several well-known velocity models as special cases. The proposed velocity model covers wide range of possible velocity distributions and has four parameters, which gives more flexibility in velocity-model manipulation. For the proposed non-linear velocity model, I compute the kinematical characteristics: offset-traveltime parameteric equations, traveltime parameters, relative geometrical spreading and the phase of the propagator. The kinematical characteristics are investigated with respect to a parameter responsible for non-linearity of velocity distribution. The inversion of traveltime parameters is discussed in three- and four-parameter framework.
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Análise Climática Da Cidade De Manaus (Am), Usando Dados Geotérmicos E Meteorológicos
The focus of this paper is on the detect microclimate
changes in Manaus City (AM), Brazil in attempting to
indicate the possible causes for the fluctuations and
trends observed. The analysis is based in
Meteorological and shallow geothermal records. The
meteorological data indicated an increment of 0.27 ±
0.04 ºC in the mean surface air temperature during
the last 80 years with reference to the 1950-1979
climatological mean and this increment has not been
continuous, but seem to be modulated by frequency
of El Niño, La Niña e Neutral events over the tropical
Pacific Ocean. Though, an quasi-instantaneous
increment of 3.17 ± 0.53 ºC was determined from
geothermal data, which is likely associated with the
land-use changes. From shallow geothermic data
under sites with vegetation cover we verified that
transient perturbations are good indicators of recent
annual climate variability, while analysis of
temperature profiles data under sites without
vegetation cover seem to indicate microclimate
changes related to the anthropogenic actions like
deforest and urbanization action.
Keywords: Microclimate Changes; Anthropogenic
Actions; Natural Variability
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Controlled Beam Migration – Application In Gulf Of Mexico
Authors Chu-Ong Ting and Daoliu WangIn this paper we review the subsalt challenges and present a specialized beam migration to address the issues of steep dip imaging, multi-arrival capability, and S/N ratio enhancement. We show its applications in the Gulf of Mexico area, for both narrow azimuth and wide azimuth data.
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Solar Activity Signatures In The Brazilian Climate
Authors Anatoly Gusev, Inacio Martin and Mauro AlvesComparison of long-term components of variation of the sunspot number with those of liquid precipitation in Fortaleza, CE is performed. The result of the analysis points to a possibility of existence of a resonant mechanism of interaction of solar activity with eigen atmospheric oscillation.
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Ss-Traveltime Parameters From Pp- And Ps-Reflections
Authors Bjørn Ursin, Martin Tygel and Einar IversenSS-wave traveltimes can be derived from PP- and PS-wave data with the previously derived “PP + PS=SS” method. We extend this method as follows: 1) The previous requirement that sources and receivers need to be located on a common acquisition surface is removed, which makes the method directly applicable to PS-waves recorded on the ocean bottom and PP-waves recorded at the ocean surface. 2) By using the concept and properties of surface-tosurface propagator matrices, the second-order traveltimes of the SS-waves are obtained. In the same way as for the original “PP+PS=SS” method, the proposed extension is valid for arbitrary anisotropic media. The propagator matrix and geometric spreading of an SS-wave reflected at a
given point on a target reflector are explicitly obtained from the propagators of the PP- and PS-waves reflected at the same point. These additional parameters provided by the extended ”PP+PS=SS” method can be used for a partial reconstruction of the SS-wave amplitude as well as for tomographic estimation of the elastic velocity model. A full simulation of the SS-wave, which includes reflection and transmission coefficients, cannot be directly obtained from the knowledge of PP- and PS-amplitudes.
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Multiple Attenuation With A Modified Parabolic Radon Transform
Authors B. Ursin, B. Abbad and M.J. PorsaniWe present a fast and efficient frequency-domain implementation of a modified parabolic Radon transform (modified PRT) based on a singular value decomposition with applications to multiple removal. With a change of variable, the problem is transformed into a complex linear system involving a single operator after merging the curvature-frequency parameters into a new variable. A complex singular value decomposition (SVD) can be applied to this operator and the forward modified parabolic Radon transform is computed for all frequency components within the signal bandwidth by means of complex back-substitution only.
The standard PRT can be obtained by interpolation in the modified transform domain. The method is also able to resolve the multiple energy from the primaries when they interfere in a small time interval and resists well to AVO effects in the data. The proposed modified PRT was successfully applied to a deep-water seismic line at the Gulf of Mexico to attenuate water-bottom multiples and subsequent peg-legs originating from multiple paths in the water column.
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Estimativa De Litofácies Através De Perfis De Poços Do Campo De Namorado (Bacia De Campos, Rj)
More LessThe recognition of several patterns has been used broadly in the interpretation of geophysical data. These data are specific physical answers of geological formations. The data, usually, it contains important physical information of the geology of the which those they result and reveals significant patterns of these geological structures. Among the methods of geophysical exploration, the well logging has great application in the location and evaluation of mineral resources, as the petroleum. A great challenge that it presents is the segmentation of these profiles in zones capable to identify some standards found in the reservoirs of petroleum. For the identification of some litologies, Gama Ray profiles were used (GR), Density (RHOB) and Neutron Porosity (NPHI). This work has for objective to identify the litologies patterns through the data of well log of Namorado Field in Campos Basin (RJ). The data were given up by Agência Nacional do Petróleo (ANP). For this work was utilized Interactive PetrophysicsTM software, which is commercialized by Schlumberger.
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Towards A Method For Ghost-Free Marine Acquisition
Authors Eivind Fromyr and Guillaume CamboisA dual sensor streamer effectively removes the receiver ghost from seismic data through dual sensor summation. The source ghost can be attenuated by spreading out the ghost contribution in time by towing the gun arrays in a multilevel arrangement. The combination of the two dramatically increases the bandwidth of marine seismic data. In particular, the low frequencies are significantly enhanced, which provides better penetration and improved Q estimation. The multi-level source will be biased towards low frequencies and have an anisotropic radiation pattern.
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Estudos Geofísicos Para Avaliação Ambiental De Uma Estação De Esgoto
Authors Eduardo Fernandes Henriques and Vagner Roberto ElisEstudos geofísicos para avaliação ambiental de uma estação de esgoto
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Título: Variações No Fluxo Geotermal Raso Em Locais Com Diferentes Graus De Proteção Vegetal Na Cidade De Humaitá (Am)
More LessA realização de monitoramento geotérmico na cidade de Humaitá-Am, no período de outubro/2007 a setembro/2008, às profundidades de 0,02 m, 0,5 m e 1,0 m, em locais com (c/c) e sem (s/c) cobertura vegetal, permitiu avaliações do fluxo geotérmico raso em escala local. Também foram utilizados os dados de condutividade térmica de amostras obtidas no local
estudado. Os resultados obtidos indicam variações do valor médio do fluxo geotermal raso de até 0,60 W/m2 , à profundidade de 0,5 m e de 0,15 W/m2, à profundidade de 1,0 m. Tais variações foram da ordem de 103 acima do valor do fluxo terrestre profundo na região. Constatouse a influência da proteção vegetal nos valores do fluxo geotermal raso, às profundidades estudadas. A existência de variações mensuráveis do fluxo a 1,0 m de profundidade indica que tais valores não podem ser negligenciáveis, nem associadas somente ao fluxo geotermal proveniente do interior da Terra, deve-se considerar também a intensidade da radiação solar incidente na superfície terrestre local.
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Survey Design Considerations For Full Azimuth Acquisition Using A Single Recording Vessel
Authors David Hill, Gordon Brown, Rob Campbell and Ed HagerAzimuth-rich towed-streamer acquisition is established as a successful method for exploration in the Gulf of Mexico. The azimuth-rich data acquired to date has delivered better illumination and imaging, a higher signal-to-noise ratio, and improved seismic resolution. However, the azimuth-rich towed-streamer acquisition configurations used in the Gulf of Mexico are all multi-vessel. Moldoveanu (2008) introduced a method of acquiring azimuth-rich data with a single vessel. This paper describes a survey design and field test for a single-vessel azimuth-rich technique, which has the same acquisition effort as a 3-survey narrow-azimuth survey.
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Modelagem De Eletrofácies Em Minério De Ferro Por Classificador Knn
In this work are showed results for a logfacies procedure applied to a Brazilian iron ore deposit. The procedure has in its central core a KNN classifier, which is a multivariate statistical approach. Some auxiliary tools as step-by-step discriminant analysis, data standardization, and measurement of an n-dimensional Euclidian distance are also used. The well logs used for logfacies modeling are Gamma Ray (GR), Short Normal resistivity (SN), Self Potential (SP) and Sonic (DT). Five facies types are recognized. Due to the high number of available data, it
was possible to adopt K = 3, in a KNN procedure, providing a facies prediction with low error rate and without an excessive smoothed solution. Results show, at the majority of wells, a very good correspondence between lithofacies and logfacies columns, but in two wells the logfacies column show, in their upper part, a higher resolution than that of lithofacies column. The
general average index for correct prediction was 91.1%, thus indicating the applied procedure as suitable for iron ore facies recognition, at least for this ore deposit.
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Modelo Gravimétrico 2D Y Su Comparación Con Espesores Corticales Sísmicos En Una Sección A Los 30 ° De Latitud Sur
Authors Mario E. Gimenez, Myriam P. Martinez and Francisco RuizWe made a gravimetric model, on a section which crossed through the Andean Cordillera, Pampean Ranges and Precordillera in an west to east direction, at -30° latitude south and 71° at 65° longitude west. The response of gravimetric model of the crust, fixed to the curve of the Bouguer anomaly upward continuation at 40km in height, which would correspond to the moho ondulations. This result was compared with the crustal thickness obtained by means of: (1) the Moho depths given by the apparent phase velocities Pn (Fromm et al., 2004)and (2) receiver function of wave S (Heit et al., 2008). In This study evaluated the gravimetric effect of the three cortical models compared with the regional Bouguer anomaly. The conclusions reveal that the major discrepancy between the models is produced in the Cuyania terrane, principally in the Precordillera zone. This includes the "PACH" and "HEDI" seismological stations and on minor measurement to the "RINC" station, located in the Famatina terrane. In accordance with the existing geological information, the Precordillera is a thin-skin structure, whith a décollement horizon at 18km of depth.
From the isostatic viewpoint, based on the Airy concept, the region is an unbalanced, manifesting a scarcity of root. This evidence would be the contrast-position to the seismological models which indicate that below the Precordillera, the Moho excedes depths of 70 km, that being the deepest of the Andean Cordillera.
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Análise E Comparação Da Contaminação Por Hidrocarbonetos Em Postos De Combustíveis Utilizando O Método Gpr
Authors Fabíola Magalhães De Almeida and José Gouvêa LuizThe 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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Features Of Lightning That Result On Fires In Some Regions Of Brazil
Authors Ana Paula Dos Santos Zepka and Osmar Pinto Jr.Fires caused by lightning are long studied worldwide. In Brazil, however, little is known about this issue and the characteristics of lightning that cause these fires. In order to study the characteristics of these natural fires a climatology of lightning that hit two important parks in Southeast and Center regions of Brazil, the National parks “Serra da Canastra” (PNSCa) in Minas Gerais and “Emas” (PNE) in Goiás, was made for the period from 2002 to 2007. The analysis was carried out using lightning data obtained from BrasilDat (Brazilian Lightning Detection Network) considering multiplicity, positive and negative peak current, number of flashes, percentage of positive flashes, complemented by temperature and relative humidity data. It was observed that the PNSCa has annually around 40% more lightning than PNE, although they are located in very close latitudes, but in the three months more critical for the occurrence of fires (August, September and October), the number of lightning is larger in the PNE.
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Behavior Of The Atmospheric Sulphur Dioxide (So2) At Cachoeira Paulista – Sp, Through The Data Obtained By The Brewer Spectrophotometer
More LessFor a better comprehension of the atmospheric chemistry, it is necessary to understand the behavior of the trace gases and aerosols, since the atmospheric chemical and radiative properties depend upon them. But the behavior of some of these species is not well studied and characterized. An example is sulphur, that both in the gaseous as in the aerosol phase have great
environmental impact. With this purpose, a study to evaluate the behavior of the sulphur dioxide, an acid rain and sulfate aerosol precursor, and whose the main natural source are the volcanic eruptions will be shown. The ground-based observations presented in this study were made in the city of Cachoeira Paulista (22.6ºS, 45ºW), in the countryside of the State of São Paulo,
through the acquisition of the gas total column measured by the Brewer Spectrophotometer of the National Institute for Space Research – INPE, as part of a doctorate thesis that will focus the data along South America.
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Complex Imaging
Authors Jerry Kapoor, Denes Vigh, Nick Moldoveanu, Bill Dragoset, Hongyan Li and Pete WattersonThe past couple of years have seen a tremendous increase in the acquisition of wide azimuth (WAZ) surveys that provide improved subsalt imaging. We have seen a step change improvement in image quality compared to conventional narrow azimuth (NAZ) surveys, even when using minimal processing and existing, conventional-survey velocity models. The improvement in image quality is taken to the next level when the wide azimuth data are combined with other seismic and non-seismic measurements to build ever more highly constrained models, and then more accurately migrated with two-way wave-equation methods. In this presentation we will show examples of WAZ data processed with the latest technology such as true azimuth 3D multiple attenuation using the general surface multiple prediction (GSMP), wave equation based multiple attenuation (WEM MOD) and reverse time migration (RTM). We will also discuss development of our next generation of velocity model building tools and techniques such as full waveform inversion (FWI).
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Predição De Perfis Geofísicos De Poços Por Classificador Knn
More LessThere is a large diversity of well log curves but, in practice, its availability is always limited. Thus, sometimes a desired log curve is not available for a given application. However, well logs are in some level interdependent, so, it is possible to use some well logs to estimate another missing curve. In this work the multivariate statistical method KNN (K-nearest neighbors) is used to estimate a basic suite of well logs (GR, RHOB, NPHI, DT and ILD) from Namorado Field, offshore Brazil. KNN is adopted due to its simple implementation, low computer cost and
high resolution. A training data set was composed by random choice of 30% of standardized well log curves from 12 vertical wells. The remaining data was used for well log prediction. All wells have the complete suite of logs, but in order to check the performance of prediction, each time one log curve was removed from data base, a synthetic one was estimated and compared to the original curve, furnishing an average prediction error. KNN was a suitable method for synthetic curve estimation of the majority of well logs, with estimated curves well correlated
to real curves in terms of curve shape, well log values and resolution level. Nevertheless, the same prediction performance was not achieved for all log curves. For ILD curve the general prediction error was 186.9%, an unacceptable high value, meanwhile the prediction error was clearly satisfactory for GR (13.2%), NPHI (12.6%), DT (4.1%) and RHOB (1.5%).
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Comparison Of Measurements Of Diffusive Methane Fluxes And Stagnant Film Model Flux Estimate On The Manso Reservoir, Mato Grosso, Brazil
Authors Marcelo Gomes Da Silva, Luciano Marani and Plínio C. AlvaláThis work presents the methane fluxes and the used methodology in the reservoir hydroelectric power plant of Manso (Matogrosso, Brazil) were presented. Measurements of water dissolved methane (DM) in three different depths (subsuperficial, middle and near the sediments) were also made. These measurements show that the primary production of methane occurs mainly on
the sediments, and the consumption on water column is important to the emission balance. The diffusive methane flux was also estimated with the stagnant film model from the DM measured on the sub superficial water. The results were compared with the measured diffusive fluxes and shows that this model gives a good first estimative and that the water turbulence and wind have an important role on the methane emission from water bodies.
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Inverse Crs
Authors Hervé Perroud, Martin Tygel and Lucas FreitasThe CRS method is a powerful tool to produce highquality stacked images of multi-coverage seismic data. As a result of the application of CRS, not only a stacked section, but also a number of attributes defined at each point of that section, is produced. In this way, one can think of the CRS application as a transformation from data space to attribute space. However, as the CRS method is purely kinematic, it should be completed by amplitude information, that we propose to obtain from the zero-offset (ZO) section and common midpoint (CMP) gather. In this
paper, we propose an algorithm for an (approximate) inverse CRS transformation, namely one that (approximately) transforms the CRS attributes back to data space. The CRS transform pair established in this way may find a number of applications in seismic imaging and data processing, in the same way as other wellknown transformations, e.g., Fourier, Radon, tau-p, etc.
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Tectonic Framework Of The Rio Do Peixe Basin (Northeast Brazil)
The “Interior Basins” of Northeast Brazil represent
erosional remnants of a series of basins located south of
the Potiguar Basin, overlying the pre-Cambrian crystalline
basement of the Borborema Province. These basins were
originated during the early Cretaceous rifting that shaped
the present continental margin of northeastern Brazil.
Besides their own hydrocarbon exploration potential, the
Interior Basins provide terrain analogues for better
understanding the continental margin basins, this being
one of the objectives of the Interior Basins Project
(agreement PETROBRAS / UFRN / PPGG), which
supported the seismic survey in the Rio do Peixe Basin,
subject of this paper. Combined with gravity and field
data, the seismic sections allowed an improved view of
the three-dimensional architecture of the Rio do Peixe
Basin. In this basin, the combination of the current
erosion level with the geometry of the main faults
highlights the existence of different half-grabens (Pombal,
Sousa, Brejo das Freiras), whose sedimentary filling
(apart from Cenozoic deposits) defines the Rio do Peixe
Group, comprising the Antenor Navarro (alluvial fans /
braided channels), Sousa (shallow lacustrine / floodplain)
and Rio Piranhas (alluvial fans / braided channels)
formations. Structural data integration characterizes a
NW-extension kinematics for the rifting event, responsible
for fault nucleation controlled by basement structures,
particularly the location and foliation dip of the late
Neoproterozoic, Brasiliano strike-slip shear zones. Based
on the structural style and petrographic-diagenetic
features, one can infer larger original dimensions for this
basin and similar counterparts in the region, which were
reduced (with exposure of the crystalline highs) by the
significant erosion that occurred in late to post-rift and
subsequent evolutionary stages of this region.
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Extração De Atributos De Atenuação De Ondas Elásticas Em Rochas Sedimentares
Authors Zigma M. Moreira, José Agnelo Soares and Luiz LandauThis work presents practical results for extraction of Pand
S-wave attenuation attributes in samples of badly
selected sandstone and mature and immature shales.
Laboratorial measurements in dry rock samples, under
several levels of confining pressure, were done through
ultrasonic transmission of pulses. The attenuation
attributes had been extracted by the spectral ratio
method. Results indicate that the procedure adopted for
extraction of attenuation attributes was efficient in
supplying compatible values with those presented in
literature. For all samples, the factor Q, both for P and S
waves, grows with the increase of the confining pressure.
Samples of immature shale present low speeds and high
values of factor Q. While QP is greater than QS for
samples of immature shale, inverse relationship is
observed for mature shales, suggesting a potential new
method for distinction between oil generating and sealing
shales.
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Seismic Modeling As A Tool For Designing 3D Seismic Surveys
It is well known to the geophysical community that
the use of seismic modeling is an important tool for
survey design. However, operational restrictions and
cost together with a tight time schedule for the
design of 3D projects restricts the amount of different
parameters and geometries that can be tested for a
particular area. Ray tracing over 3D geologic models
has been applied by the oil industry for some time to
decide what parameters should be applied to a given
survey. These parameters include, for example, sail
line direction, streamer separation and length. These
studies are also important for the development of
new techniques, in which is possible to evaluate the
contribution of long offsets and azimuths. In this
work, the area under study is characterized by the
presence of a thick allochthonous salt body, and our
aim was to assess different survey parameters and
geometries so the subsalt layers of interest can be
well illuminated. Two software’s running in different
platforms were used to assess the appropriate survey
design and it will be shown that they could effectively
contribute for parameter evaluation.
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Requirements For Resolution
Authors Mark S. Egan, Antoun Salama, George El-Kaseeh and Joe SeissigerEvery seismic survey has resolution objectives for the final 3D migrated image. Temporal resolution cannot be considered separately from spatial resolution. This would be true even for the case of continuous functions. But in the world of sampled data, the interrelationship is even stronger. A result is that in order to achieve a desired temporal resolution, the most key parameter can sometimes be the spatial sampling interval. If that interval does indeed need to be small, one immediate implication is that very accurate coordinate information is needed for the source and receiver positions. Theoretically this is not a problem in onshore surveys, but it is a little more challenging offshore. Another immediate implication is that a dramatic increase in the number of shots and/or the use of high channel-count systems can be required for the data acquisition. Assessing the resolution obtainable from such candidate survey designs can be accomplished by modeling. Examples are provided.
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3D General Surface Multiple Prediction: An Algorithm For All Surveys
Authors Bill Dragoset, Ian Moore, Margaret Yu, Wei Zhao and Alex Cooke3D general surface multiple prediction (GSMP) is a datadriven
3D SRME algorithm that solves the problem of
trace sparseness. Rather than overcoming the
sparseness problem by changing the data to fit the
algorithm – for example, by means of regularization and
interpolation – GSMP changes the SRME algorithm to fit
the data. This not only makes GSMP a universal compute
engine for the 3D prediction of multiples, but also makes it
quite versatile. We illustrate this versatility by showing
successful applications of GSMP to narrow-azimuth,
wide-azimuth, and rich-azimuth seismic surveys.
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Interpreter Driven, Interactive 3D Multi-Attribute Classification
Authors J. Henderson, James Lowell, Steve Purves, Gaynor Fisher and David WalravenThis paper presents a novel 3D seismic attribute classification technique based on a framework in which the interpreter defines the data partitioning required to generate the classified data volume by directly interacting with a multi-attribute visualisation system. The classification process utilises the latest advances in graphics processing unit (GPU) parallel computation technology, enabling the classification to be achieved in real time on standard (non-cluster) desktop workstations.
The ability to deliver classification results in real time enables interpreter driven feature definition and introduces a new paradigm in multi-attribute analysis techniques, that can be applied so quickly and easily that they can be incorporated simply into any standard 3D seismic interpretation workflow.
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Three-Component Geoacoustic Logging In Investigation Of Fluid-Gas Dynamic Processes In Gas Boreholes
In was shown that three-component geoacoustic logging allows to solve the problems of control over gas deposit mining. The examples of the method, applied to distinguish gas -saturated seams, detect overflows outside the column and study a profile of inflow in the intervals of seam perforation, were adduced.
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Orientação Do Topo Estratigráfico De Um Testemunho Horizontal Através Da Análise De Anisotropia Sísmica
Neste trabalho estimamos a orientação estratigráfica de um intervalo de testemunho horizontal de rocha através da análise de anisotropia de velocidades sísmica (VelAn). Análises de tomografia computadorizada foram importantes para o controle de qualidade dos resultados. Os resultados obtidos concordam satisfatoriamente com a direção de orientação recuperada nos registros da sonda.
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Geoacoustic Emission In Deep Boreholes As An Indicator Of Geodynamic Processes In Crystalline Rocks Massifs
The results of experimental investigations of geoacoustic emission (GAE) in deep boreholes were considered. Temporal changes of geoacoustic signal amplitude level, signal envelope spectra and dominating in them periodicities were analysed. GAE potential as an indicator of geodynamic processes in crystalline rock massifs was shown.
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Sedimentary Thickness In The Paraná Basin Using High-Frequency Receiver Function: Estimated Depth Of A Buried Graben In The Ms/Go Border
Authors Marcelo Assumpção, José Roberto Barbosa, Renato Prado, Fábio Bordotti and Fábio DiasReceiver Functions (RF) in the frequency range 0.1 to 1 Hz have been extensively used to estimate crustal thicknesses. Here we show that high frequency RF (1 to 5 Hz) can be used to determine the thickness of sedimentary basins. However, the non-uniqueness of the RF inversion requires other information to be added in the inversion scheme. For example, different velocity profiles of the shallow (<100m) layers have a large effect in the inversion results for the deeper layers. We used a shallow seismic refraction survey to constrain the seismic velocities in the first 30m. Surface-wave group-velocity dispersion was used to constrain the average crustal S-wave velocity. Long-period RF was jointly inverted with high-frequency RF to estimate both the deep crustal and the sedimentary structure. Station CDSB is located in the northern part of the Paraná Basin, in the middle of a low-gravity anomaly, which has been attributed to a buried graben. Our inversion of the RFs suggests the graben could be about 7-8 km deep, consistent with gravity modeling, but has a thick basalt flood layer, perhaps related to the graben evolution.
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Caracterização Sedimentar E Estratigrafica Da Planície Costeira De Itaipuaçú, Durante O Quaternário, Utilizando Dados De Gpr E De Sondagens
Sea level variations during the Quaternary directly influenced the sedimentation of Itaipuaçú Coastal Plain. The paleomorphology of the basement in the area strongly controlled deposits that correspond to the Itaipuaçú Coastal Sedimentation Sequence. The integration of GPR data with the results of well data revealed five stages that represent different positions on
the line coast through the coastal plain (regressions and transgressions), showing a active sedimentation during the last thousands of years.
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Separation Of Pressure And Saturation Effects Using Avo 4D In Marlim Field
Using the method introduced by Landro (2001), it has been possible to study the pressure and saturation changes induced by production in the Marlim field, figure 1. This methodology does not make any assumption about production, requiring only petrophysical and seismic data covering the field of interest. Maps representing pressure and saturation changes are presented and also a section over one well, showing how these anomalies can be compared with flow simulator prediction. The main result obtained is a better understanding of the mechanism by which water saturation and effective pressure changes are created during field production.
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3D Csem Inversion Strategy: An Example Offshore West Of Greenland
Authors A. Lovatini, M.D. Watts, K. Umbach and A. FersterAlthough there have been many publications on theoretical aspects of marine CSEM, covering most elements from data processing through to inversion, there have been few on interpretation and practical use of these data. Amongst these, significant contributions have been made by: Carazzone et al. for subsalt exploration in Brazil (2008) and in Angola (2005), Buonora et al. (2008) in Brazil, Price et al. (2008) in Nigeria, and Darnet et al. (2007) in Malaysia. In this paper, we show how multidimensional inversion and interpretation contribute to the ranking of prospects in two blocks west of Greenland. In both, the geological targets are Cretaceous sandstones in elongate structures; known complicating factors include the presence of shallow resistive volcanics and the intermittent presence of crystalline basement at relatively shallow depths below some of the targets.
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Effects Of Geomagnetically Induced Currents-Gic On Electric Power Technology In Brazil
Geoelectric fields induced in the Earth during geomagnetic storms drive electric currents through the windings of power transformers and the transmission lines carrying electric power. These currents, known as GIC (Geomagnetically Induced Currents), flow in the entire electric power systems and cause deleterious effects. The well-known and documented GIC events of
13-14 March 1989 and 29-30 October 2003 inflicted considerable damages and power failures in the northern auroral regions. In Brazil, there is an on-going project to study GIC in a collaborative effort between the National Institute for Space Research-INPE and Furnas Centrais Elétricas S.A. We present here the already published results on calculated intensity of GIC flowing in the transmission lines near Itumbiara in central Brazil during the event of 7-11 November 2004 and the recent progress of the work. We established a linear relationship
between the rate of variation of the horizontal geomagnetic dH/dt and the calculated GIC flowing in the transmission lines near Itumbiara (Goiás). Although no significant geomagnetic storms have occurred after November 2004 we present here results from direct measurements of GIC on the neutral phase of the power transformer at the electric power substation at Itumbiara
and compare the measured GIC values to the deduced GIC values flowing in the transmission lines.
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Fitting Nmr Spectra For Retrieving Fluid Distributions
By Pedro RomeroThe de-convolution of low field NMR spectra, especially those obtained from borehole logging tools, is a very important procedure that can unveil information hidden in the T1, T2 or Diffusion. This information is associated with the determination of the spectral components present in the distributions that can be used to identify reservoir rock quality and fluid types. The fitting method presented in this paper uses as input only spectral data already available after inverting the NMR echo trains; it identifies the bins where the spectral components are located and quantifies them in terms of height, mean and variance corresponding to the selected fitting curves. The method has been tested with simulated T2 distribution data, considering combination of different amounts of heavy oil, clay-bound water, capillary-bound water, movable water and oil-based mud filtrate. The versatility of the method relies on its applicability to any kind of spectral distribution whether coming from lab measurements or from the borehole. The results shown in this paper reveal that individual components could be detected down to a two-percent porosity units and the spectral resolution is about one unit more than the standard deviation when fitting with a Standard Gaussian curve.
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Including Lateral Velocity Variations Into True-Amplitude Wave-Equation Migration
Authors D. Amazonas, R. Aleixo, J. Schleicher, J. Costa, A. Novais and G. MeloIn heterogeneous media, standard one-way wave equations only describe the kinematic parts of oneway wave propagation correctly. For a correct description of amplitudes, the one-way wave equations must be modified. In vertically inhomogeneous media, the resulting true-amplitude one-way wave equations can be solved analytically. The corresponding amplitude modifications can be taken into account in split-step and Fourier finite difference migrations in such a way that they use these true amplitude oneway wave equations instead of the standard ones in order to implement a true amplitude wave equation migration for zero-offset data. Synthetic data examples demonstrate that the technique improves amplitude recovery in the migrated images.
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Aplicabilidade Do Método Magnetotelúrico Em Área De Cobertura Carbonática – Estudo De Caso Na Serra Do Mel, Bacia Potiguar
Authors Paulo T.L. Menezes, Andrea Zerilli and Tiziano LabruzzoIn the present paper we present the results of a MT field campaign at Potiguar basin. The main objectives of this survey were to test the MT signal to noise ratio and the feasibility of the MT data to define the base of Jandaíra Formation (shallow carbonates) and the structural framework of the basement.
To that end, MT data of 17 remote reference sites were processed and investigated through tensor analysis decomposition followed by 1D inversion. Three main geoeletrical units were identified: an outcropping strong resistor associated to Barreiras sandstones, followed by the carbonates of Jandaíra Fm and a strong conductor at depth, associated to siliciclastic sediments. The top of the basement was also properly imaged as a strong resistor underlying the sedimentary sequence.
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Anisotropic Complex-Pad´e Hybrid Finite-Difference Depth Migration
Authors D. Amazonas, R. Aleixo, J. Schleicher and J. CostaStandard real-valued finite-difference (FD) and Fourier finite-difference (FFD) migrations cannot handle evanescent waves correctly, which can lead to numerical instabilities in the presence of strong velocity variations. A possible solution to these problems is the complex Pad´e approximation, which avoids problems with evanescent waves by a rotation of the branch cut of the complex square root. In this paper, we apply this approximation to the acoustic wave equation for vertical transversely anisotropic (VTI) media to derive more stable FD and hybrid FD/FFD migrations for such media. Our analysis of the dispersion relation of the new method indicates that it should provide more stable migration results with less artifacts and higher accuracy at steep dips. These studies lead to the conclusion that the rotation angle of the branch cut that should yield the most stable image is 60◦. This result is confirmed by the numerical
impulse responses and synthetic data examples.
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Identifying Diapiric Bodies With Potential Field Methods
More LessThis paper shows some aspects about the gravimetric and magnetic response of diapiric bodies, and it intends to elucidate the way to recognize and modeling these geologic features by using potential field methods. Theoretical 2D models have been used to represent some geologic scenarios and evaluate the response of the structures in terms of amplitude and frequency of the calculated anomalies. Using 2D models, it is possible to evidence how changes in depth, morphology, density and volume respond in terms of the gravimetric and magnetic
anomalies. All these observations help to characterize the signature variations of the diapiric bodies.
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Levantamentos Geofísicos (Ecobatimetria E Gpr) No Estudo De Uma Área Assoreada No Município De Brotas-Sp
This paper presents de results of a geophysical survey carried through to assist the studies of erosive processes and silting in area located at the city of Brotas-SP, Brazil. Surveys had been carried through in water-covered area (lake in silting process) using bathymetry and on land (area where there was an ancient lake that is entirely silted nowadays) by using GPR method.
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Efeito Do Fluxo Solar (F10.7) Na Deriva Vertical Pré-Reversão Da Ionosfera Equatorial No Setor Brasileiro
Authors A.M. Santos, M.A. Abdu and P.A.B. NogueiraThis study presents an analysis of the evening F-region prereversal vertical drift variation over Brazil as a function of the solar flux (F10.7). The vertical drift is determined using true heights data obtained from ionograms recorded by digisondes operated at in São Luis and Fortaleza. Data collected from October to December in the solar minimum years of 2006 and 2007 were used in the analysis. The results show that for both São Luis and Fortaleza the evening vertical drift presents significant dependence on solar flux variation, i.e., the vertical drift increases with the increase in solar flux.
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Applying Dual-Sensor Streamer Technology To A Guyana 2-D Survey
Authors Jack Kinkead, Lorin Friedberg Cramer, Quoi Truong and Dave CarlsonDual-sensor technology allows one to separate the upgoing and down-going wave fields, and ultimately remove the receiver ghost. This increases the spectral bandwidth of the recorded data and results in a final image that is improved for all depths. Application of this technology in offshore Guyana has resulted in an improved image of the subsurface as compared to what could be achieved with more conventional streamer technology.
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The Super Giant Discoveries In The Pre-Salt Hydrocarbon Province Located In The Deep And Ultra Deep Water In The Greater Campos Basin, Brazil
In most areas of the deep and ultra deep waters from the Brazilian South Margin Basins, exploration has just begun with the discovery, in the last two years, of six of the biggest oil fields found in the whole world. The oil fields encompassing more than 20 billion bbls of oils of reserves are the Tupi, Jupiter, Guará, Iará, Carioca, and Parati (Figure 01). This article presents the results of petroleum system modeling that was run on a detailed 3D geological framework built on PSDM seismic data and on geological data of HRT & Petroleum (Figure 01). We present the
temperature and pressure conditions that allowed the formation and preservation of supergiant accumulations of light oil and condensates trapped below the salt layer.
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Petrobras Management Of National Geophysical Data
In this paper we present the state of the art of Petrobras data management in national area. We start with a short historical retrospective of Petrobras experience with data management. We then present the main features of geological and geophysical data in Brazil and the implications of the production of a large amount of data in the huge territory that comprises Petrobras exploration area. Finally, we discuss the recent Petrobras data management approaches in order to organize legacy and incoming data.
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O Uso Integrado Dos Métodos De Sísmica De Refração E De Ondas Superficiais Visando À Caracterização Da Subsuperfície Rasa
Authors Fabio Bordotti Schumann and Renato Luiz PradoThis paper presents the data analysis from two shallow seismic methods carried out in a sedimentary area. We used a combination of seismic refraction tomography and multi-channel analysis of surface waves – MASW techniques aiming to characterize the shallow subsurface. The seismic refraction tomography and MASW data were acquired simultaneously using the same hardware and field geometry, i.e., a Geode seismograph coupled with ninety six 14 Hz geophones spaced 2 meters apart and seventeen shot points spaced 12 meters apart along
the entire spread.Two 2D sections, P wave velocity image (from refraction data) and S wave velocity image (from surface waves data) were analyzed and compared. Joining the data we derived a Poisson's ratio section aiming to infer strength characteristics of soils and sediments.This approach showed to be complemental to map geologic interfaces and suitable to infer mechanical
properties of soils and sediments.
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Bandwidth Extension Using Harmonics
More LessWe show a new method of seismic resolution improvement using the Continuous Wavelet Transform (CWT). Using the CWT and the available bandwidth in the seismic, the phase and amplitude spectra of harmonics and sub-harmonics can be computed. These harmonic and sub-harmonic frequencies are then convolved onto the input data. Only frequencies for reflectivity that is above the ambient noise level in the CWT domain is added to the seismic wavelet. This process broadens the bandwidth of the signal which increases the resolution of the seismic data.
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Effects Of Compression On Attributes
In this work we calculate a series of attributes on seismic data with different degrees of compression and compare with the attributes calculated from the original data. We find that, although primary attributes are nearly unaffected by compression, secondary attributes, as Instantaneous Frequency, can be affected by a relatively low compression, say 90% of nominal fidelity, what can be a source of pitfalls on interpretation of the data.
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O Alto De Vitória E Seu Papel Na Evolução Sedimentar Da Margem; Porção Norte Da Bacia De Campos E Sul Da Bacia Do Espírito Santo
More LessThis study focus on the role of the Vitória Structural High on the deep-water tectono-stratigraphic evolution of the adjacent Campos and Espírito Santos basins , based on 2D seismic analysis. The Vitoria High has been currently reffered to in the literature as the structural limit between the Campos and Espírito Santo marginal basins. However, our seismic analysis shows that on the lower slope and continental rise, the Vitoria High has a rather limited geographical and morphological expression and does not act as barrier that influences the stratigraphic
records of both basins. On the other hand, our seismic analysis reveals that the morphology of the Vitoria High is characterized by fault scarps and ramps inherited from the extensional rift tectonics. Fault scarps and ramps in such a context acted as residual morphologies at the base of the Aptian mobile salt layer, affecting the structural evolution of salt-related extensional faults that were conditioned to sole out in the residual morphology at the salt base. As a consequence, the morphology of the Vitória High had an indirect impact on the sedimentary
architecture of overlying marine sequences, determining the location and development of local depocenters (minibasins) along rollover structures in the extensionsal domain of salt tectonics.
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Influence Of The Discrete Laplace And Fourier–Bessel Transforms On The Solution To Direct Seismic Problems Within The Frequency Domain
Authors Georgy Mitrofanov and Viatcheslav PriimenkoTheoretical solution to the direct seismic problem for a thin layer elastic model of medium in the spectral domain can be constructed effectively using the Laplace and Fourier-Bessel transforms. However, for practical use, as a tool of modeling and the solution of inverse problems, it is important to analyze properties of the corresponding discrete transforms and their influence on the solution obtained. This research presents some of the results of our investigation of the properties of the transforms using functions giving analytically, which allows the possibility to analyze the most important features of the transforms. Such investigations permitted to determine the conditions for application of these transforms to the solution of considered problems in more details.
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Ground Roll Attenuation With Singular Value Decomposition
Authors Peter W. Cary and Changjun ZhangGround roll attenuation is an important step in seismic data processing. We implement a procedure to eliminate ground roll from seismic data that is based on eigen-images. We use singular-value decomposition (SVD) to distinguish between signal and noise within narrow frequency bands of the ground-roll cone at near offsets in the data. The estimate of the energy of the signal comes from an uncontaminated portion of the seismic records. The method is able to adapt to the changing character of the noise and signal about the seismic survey. The modeled noise is then subtracted from the data while preserving the reflections.
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Borda Centro-Leste Da Bacia Do Recôncavo (Estado Da Bahia): Uma Nova Fronteira Exploratória Na Mais Profícua Bacia Petrolífera Terrestre Do Brasil
Authors Ademilson Fagundes De Brito and João Ítalo GhignoneBased on 3D seismic data and wells were identified
structural features here called Eastern’s Steps Border of
Recôncavo Basin, located east of the Lower Miranga,
over which could to be lay the excellents fluvio-aeolians
reservoirs of the Sergi and Agua Grande formations in
lateral direct contacts with the layers of source rocks of
the Gomo Member (Candeias Formation), located in
adjacent blocks, setting a high potential oil to be proven in
the basin.
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Effects Of Long-Lasting Interplanetary Magnetic Field Perturbations On The Equatorial Ionosphere
During 3 – 7 July, 2003, long-lasting and large-amplitude
interplanetary magnetic field perturbation event occurred.
This event is classified as high-intensity long-duration
continuous AE activity (HILDCAA) which occurs outside
the main phase of magnetic storms. The responses of the
equatorial ionosphere to HILDCAA events have been
poorly known so far. In this work, we investigate the
effects of HILDCAA events on the equatorial ionosphere
using ionosonde data (hmF2) observed at São Luís,
Brazil and the ACE satellite data. The results indicate
presence of short-time prompt penetration electric field
disturbances and long-lived positive charge accumulation
at the magnetic equator around the midnight sector due to
the disturbance dynamo effect.
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The Impact Of Verifiable Data Quality In Today’S Exploration Cycle
Authors Richard Johnston and Dwight SmithIn today’s exhausting search for oil and gas the targets are getting tougher to locate and more difficult to commercially produce. There are far fewer drilling opportunities and areas available for drilling – and the competition is fierce. Today’s advances in data quality and information management can help the time strapped geoscientist increase the quality of their interpretation/prospect generation and reduce the decision time that may be required to identify and commit to a prospect. There are tools and processes now available to the industry that can be used to create a quality environment through automation and best practices, such as the environment created in the Gulf of Mexico operations at Chevron.
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Use Of Full Tensor Gravity Invariants In Detection Of Intrusion-Hosted Sulphide Mineralization: Implications For Emplacement Mechanisms
Authors James Mataragio and John KieleyGeological and geophysical characteristics of
the Budgell’s Harbour prospect in Newfoundland, Canada
were investigated over known geochemical and magnetic
anomalies using Airborne Full Tensor Gradiometry (Air-
FTG®). A total of 407 line-km were flown at a line spacing
of 200m x 2000m. Several cylindrical, plug-like anomalies
were generated that are interpreted to be associated with
steeply dipping ultramafic intrusions.
An integrated interpretation focusing on
geological models and gravity tensor invariants suggests
a mechanism in which ultramafic magma was rapidly and
forcefully emplaced. Radial fracturing caused by forceful
eruption of these magmas is evident in horizontal tensor
invariants. Particularly, the invariants of the gravity tensor
provide a means in which individual and sub-vertical
plugs, dikes, or diatremes associated with alkaline
intrusions can be outlined and clearly distinguished from
larger porphyry-like anomalies.
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Drilling Directly From A Magnetic Airborne Fixed Wing Survey: Is It Possible? A Proposed Criterion And A Real Example
More LessOne of the main issues in modern mineral exploration is
whether you can drill directly from an airborne survey or
not, since ground surveys can be very high cost in both
money and environmental points of view.
Modern helicopter systems with very tight line spacings
are usually used for direct drilling (Witherly 2004), but in
general airborne fixed wing surveys are not expressly
recommended for direct drilling.
The aim of the present paper is to run forward models
and to present a real example in order to discuss this
issue, trying to supply an orientation guide that can be
used to consider drilling directly from the airborne
magnetic fixed wing surveys.
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Hca Methodology Applied To Model The Interaction Of Faulting And Salt Movement In Campos Basin, Brazilian Atlantic Margin
More LessThe kinematic evolution along an offshore regional crosssection
was studied by using the forward modelling HCA
approach implemented in the software FORC3 (ÓSalvini -
Roma Tre University). This approach consisted in the
comparative analysis of the time evolution of the tectonic
elements present in the sections (namely salt domes
activity and faulting) with the thickness and architecture of
the syntectonic sediments. The link between
sedimentation and tectonics was carefully replicated
during the evolution of the sections from late Cretaceous
to recent, and allowed to set the time constraints of the
tectonic evolution of the region, together with its velocity
and the interaction between salt doming and faulting.
The FORC3 modeling tool allowed to compute along the
cross-section a distribution of the expected brittle
deformation intensity.
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Aplicação De Ensaios Elétricos E Eletromagnéticos Em Uma Área Industrial Contaminada Em São Paulo – Brasil – Resultados Preliminares
Authors Marina Minozzo, Vagner Roberto Elis, Andréa Teixeira Ustra and Fábio MissakiThis work presents the results of Electromagnetic and
Resistivity methods applied to an industrial facilitie
polluted with benzene, toluene, xylene (BTX) and
organochlorine compounds, in São Paulo city, Brazil. The
results suggest that high resistivity anomalies are due to
contaminated compounds in the soil, typically resistive;
and low resistivity anomalies are consequences of
electrical properties changes of the polluted environment,
caused by biodegradation. The acquisition techniques
showed to be efficient for contamination mapping in
industrial sites studies and should be considered in this
type of study.
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4D Petrophysical Seismic Inversion On The Troll West Field
Inversions of seismic surveys often give quite low-resolution results that are difficult to compare with well data and geological models. We are therefore developing a multi-vintage seismic inversion based on a Petro-Elastic Model (PEM), called PetroSI-4D. This involves input from the geological model and good control on the petrophysical correlation between porosity and PEM-based seismic velocities. All vintages and input angle stacks are combined to jointly invert for layer thickness, rock properties and saturations. Perturbations of selected properties of the geological model are introduced using a simulated annealing algorithm to optimise the degree of match between the synthetic and the real angle stacks. There are no restrictions on number of input angles or number of monitor surveys, but new monitor surveys require new input to 4-D PEM. The base inversion result is delivered in porosity cubes instead of ordinary acoustic impedance and Vp/Vs results. The 4-D inversion result is planned to deliver saturation cubes instead of cubes of acoustic impedance or Vp/Vs changes. These parameters should be easier to compare and use in update of geological and reservoir models to validate the results. The Troll West Field shows that the Petrophysical seismic inversion with rock physics PEM connected to the inversion, gives good results and comparison with the porosity input model is shown. The purpose of 4-D petrophysical inversion is to make use of all available seismic data simultaneously, multi-vintage and pre-stack, to constrain the evolution of the saturation field.
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Eiagrid: In-Field Optimization Of Seismic Data Acquisition By Real-Time Subsurface Imaging Using A Remote Grid Computing Environment
Authors Björn Z. Heilmann, Ana M. Vallenilla Ferrara, Guido Satta and Ernesto BonomiThe constant growth of contaminated sites, the unsustainable
use of natural resources, and, last but not least, the
hydrological risk related to extreme meteorological events
and increased climate variability are major environmental
issues today. Finding solutions for these complex problems
requires an integrated cross-disciplinary approach, providing
a unified basis for environmental science and engineering.
In computer science, grid computing is emerging
worldwide as a formidable tool allowing distributed computation
and data management with administratively-distant
resources. Utilizing these modern high performance computing
technologies, the GRIDA3 project bundles several
applications from different fields of geoscience aiming
to support decision making for reasonable and responsible
land use and resource management. In this abstract we
present the geophysical application of the GRIDA3 project
named EIAGRID. As illustarted in Figure 1, it aims at supporting
environmental research by enabling the use of grid
computing facilities to provide real-time subsurface imaging
directly during data acquisition. Furthermore, shared
data storage using georeferencing tools and data grid technology
facilitates acquisition design, workflow construction
and the interpretation of results.
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Insights About St. Peter Peridotitic Ridge In The Equatorial Atlantic Tectonic Setting: Deep Upper-Mantle Structure With Ductile And Brittle Deformation
Authors Jennifer Angel-Amaya and Susanna E. SichelThe St Peter peridotitic ridge (SPPR) is a large structure in the Equatorial Atlantic Ocean, located at southern side of the intersection of the Mid Atlantic Ridge (MAR) with the St. Paul´s Transform Fault (SPTF); It is composed for upper-mantle derivate lherzolitic and harzburgitic rocks with serpentinitic and mylonitic processes superimposed. Basaltic rocks and sediments are presents in less proportion. The sigmoid structure of the SPPR is elevated 4000 m above the ocean bottom and it´s northern side protrudes above the sea level forming the St. Peter and St. Paul´s Archipelago (SPSPA) in the geographical coordinates 0° 55’.1 N and 29° 20’.7 W. This segment ridge corresponds to the wall of the active SPTF, for this reason is the more intensity deformed and mylonitized, that constitute a excellent outcrop of the mantle related rocks with accessible structural elements of the ductile and brittle deformation.
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Coda Wave Attenuation For Center North Of Parecis Basin In The Amazon Craton – Brazil
More LessSmall local earthquakes from two aftershocks
sequences in Porto dos Gaúchos, Amazon craton -
Brazil were used to estimate the coda wave
attenuation in the frequency band of 1 to 20 Hz. The
time-domain coda-decay method of a single
backscattering model is employed to estimate
frequency dependence of quality factor (Qc) of coda
waves. Qc values have been computed at central
frequencies and (band) of 1.5 (1-2), 3.0 (2-4), 6.0 (4-8),
9.0 (6-12), 12 (8-16) and 18 (12-24) Hz in the lapse time
ranging from 25 to 60 sec for five different datasets,
selected according to the geotectonic environments
of the stations locations as well as the ability to
sample crustal structures at depths.
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Acoustic Noises In Boreholes: Aspects Of Practical Use
More LessA distribution of acoustic noises in massifs of sedimental
and crystalline rocks was considered. It was shown, that
the level of acoustic noises is higher in crystalline rocks.
Three-component geoacoustic logging allow to distinguish
zones of an elliptical cross-section of a borehole shaft.
Opportunities of geoacoustic noises to distinguish oil and
water saturated stratums were shown.
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A Importância Da Modelagem Na Distribuição Espacial De Variáveis Ambientais Utilizando Procedimentos Geoestatísticos
This article evaluates the quality of groundwater
potentially impacted by nitrate (NO3), using a geostatistical
analysis. It was found that in 67% of the samples were identified
levels greater than 3 mg/L, and 33% of wells tested, nitrate levels
were found above or very close to 10 mg/L, maximum allowed in
Brazil, which indicates chemical water quality and commitment of
its drinking.
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A Comparison Of Two True-Amplitude Gaussian Beam Migration/Inversion Operators
Authors Carlos A.S. Ferreira and João Carlos Ribeiro CruzThe use of the concept of Gaussian beams in seismic
migration has been highly considered in recent times and
it is not a new issue. With the advent of non-conventional
and mandatory new exploration targets in Brazil (such as
the presalt), the imaging task has been highly demanded
in order to bypass common (known ones) and new
features of the wavefield propagation, such as anisotropy
and some other factors. Since migration algorithms today
are not anymore imaging-only process, comes into play
the task of inversion, alongside with interpretation,
prospecting and drilling. This paper then compares the
theoretical results of two true-amplitude migration
algorithms and their abilities as attributes estimators.
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Geometric Theory Of Seismic Imaging
More LessIn this paper I provide an overview of main concepts and results by S.V.Goldin in the field of geometric theory of seismic imaging. Then I present some recent results on velocity continuation of seismic images developing his ideas.
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Inversão Sísmica Em Três Dimensões A Partir De Dados De Reflexão Sísmica Por Algoritmos Genéticos Híbridos
Authors Samuel G. Huamán Bustamante and Marco Aurélio C. PachecoThe objective of the present work is to investigate a
method to help in the quantification of seismic
characteristics underground. The two-dimensional
seismic model of reflection employs the equation Normal
Move Out (NMO) to calculate the travel times of P waves
reflected on inclined and isotropic layers. This equation
uses the root mean square velocity as a representative
value of the joined layers velocities. At the inversion
process, for multiple layers, the root mean square
velocities are the main problem to estimate the layer
velocities. Consequently, to solve that problem, the
proposed method estimates sequentially the parameters
of the seismic model using travel times and the Hybrid
Genetic Algorithms (Genetic algorithm and the Nelder
Mead Simplex algorithm). The travel times are synthetic
and the estimation of parameters is treated as a
minimization problem. With proposed method was
obtained high grade of accurate, and the reduction of
85.23% of computing time when the method uses only
Genetic Algorithms. For decreasing the complexity and
the delay to generate the models in three dimensions is
proposed the construction of a three-dimensional seismic
model formed with two-dimensional models, under every
rectangular cell of the mesh of receptors of the seismic
survey, for curved isotropic layers with soft variations in
the gradient and without discontinuities. The twodimensional
models form polygons that represent the
surfaces of interfaces that are designed under the
rectangles of the surface or soil. Two sets of polygonal
surfaces are generated to help at the geometric
localization of layers.
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Adaptive Method For Swell Noise Attenuation In The Time-Frequency Domain
Authors Julio Valença Tavares and Luiz Geraldo LouresCoherent noises are those that appear through a systematic way and swell noise is a kind of coherent seismic noise. This happens during the marine seismic acquisition and is generated basically by the motion of the ship, cable depth controllers, or sea surface waves. For the swell noise analysis and attenuation we used a one dimensional wavelet transform, in the sense that it operates on single traces, to apply a time-frequency domain filter. The shifting (time) and level (frequency) dependent soft-threshold is estimated using a method based on Bayes’ Rules. Using this proposed methodology for synthetic data analysis the results were satisfactory. When real seismic data is used the results show good agreement due to the algorithm adaptive structure. The noise is removed considerably and the signal doesn't loose the interesting information, validating the proposed model. As the algorithm makes the threshold estimation in function of the scale and for each trace time interval, nine threshold values are calculated for each trace. Therefore, it is possible to reduce the noise for different signal-to-noise ratios (SNR) along each trace. The noise free traces don't change, because in those cases the threshold tends to be zero making possible the perfect signal reconstruction. However, when the SNR tends to be one or the noise and signal amplitude and frequency are similar their coefficient variances tend to be close causing a threshold estimation enough to mute the signal. In agreement with the increasing demand for offshore exploration, also driven by 4D seismic acquisitions, the swell noise will be a frequent problem, because in order to achieve a good geologic model all the distortions generated by the data acquisition should be attenuated.
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Anomalias Magnéticas Da Província Alcalina Rio Verde - Iporá, Sudoeste De Goiás
Authors Alanna C. Dutra and Yára R. MarangoniThe Rio Verde - Iporá Province is a suite of alkaline rocks
predominantly mafic-ultramafic, in central Brazil. These
alkaline complexes are characterized by a series of small
bodies with strong aeromagnetic signal presenting
themselves as almost circular anomalies. The
aeromagnetic anomaly varies from +6000 to -3000 nT.
The anomaly magnetic field was used in the 3D inversion
to model the magnetic susceptibility distribution. The
model has a maximum value for magnetic susceptibility
0.1 (SI) in prisms that reaches up to 10 km depth under
the alkaline anomalies. The bodies resemble magmatic
chambers emplaced in the upper crust in a NW-SE
direction.
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Eletrorresistividade Aplicada No Sítio Arqueológico Ap-Ma-05, Macapá-Ap: Resultados Preliminares
In this article we present preliminary results of resistivity
measurements that were carried out at the archaeological
site AP-MA-05 to find remains buried by ancient people
that could have lived in the area. Archaeological
excavation on places indicated by resistivity anomalies
revealed concentration of lateritic rocks fragments and
fragmented pottery.
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Aplicação Das Técnicas De Medição De Gás Radônio E De Imageamento Elétrico 3D E 2D Em Áreas Sob Contaminação De Hidrocarboneto
Authors Sérgio Luiz Da Silva Quintão, Andresa Oliva, Ciências Exatas, Mathias Du Puits, Axel Schmidt, Holger Weiβ, Jorge Ibirajara Coelho, Marcus Paulus Martins Baessa, Fátima Do Rosário, José Ribamar Silveira Da Silva, Carlos Silva Rosa, Flávia Castro, Marco Aurélio Zequim Pede, Chang Hung Kiang and Márcio Costa AlbertoA contaminação do solo por NAPL (contaminantes não-voláteis) oriundo de vazamentos de combustíveis, óleo mineral e solventes orgânicos é considerada um problema mundial. Para a realização de uma remediação adequada em áreas impactadas é fundamental o conhecimento da distribuição do NAPL no subsolo. Para se estabelecer um plano de remediação adequado, geralmente são coletadas amostras de solo que posteriormente serão enviadas ao laboratório para as análises pertinentes. Entretanto, o número de amostras pode ser limitado, impedindo assim a delimitação adequada da pluma de contaminação. Além disso, a análise das amostras em laboratório pode levar algum tempo, causando atraso no trabalho de investigação. Dessa maneira, técnicas que permitam tanto um aumento no número de pontos de investigação, como rapidez na obtenção de dados, vêm sendo cada vez mais utilizadas com sucesso na identificação de áreas impactadas. Neste trabalho utilizou-se as técnicas de imageamento elétrico 3D e 2D e uma nova técnica envolvendo a medição de gás Radônio 222 em solos/sedimentos, para identificar e delimitar as áreas impactadas em subsuperfície.
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Diurnal Variation Of The Occurrence Of Plasma Irregularities In The Equatorial Electrojet Over Brazilian Sector
Authors L.M. Guizelli, C.M. Denardini, H.C. Aveiro, P.D.S.C. Almeida and L.C.A. ResendeEquatorial electrojet (EEJ) observations using VHF radars show backscattered echoes from two types of electron density irregularities, Type 1 and Type 2. In this paper, we present an statistics of occurrence irregularities in the ionospheric plasma at the e-region hight, observed by a 50 MHz coherent backscatter radar installed in Brazil. This radar detects small-scale irregularities (3 meters) between approximately 90 to 130 km heights in the equatorial ionosphere.
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Global 4-D Seismic Inversion And Time-Lapse Fluid Prediction
Authors Y. Lafet, B. Roure, P.M. Doyen, R. Bornard and H. BuranIndependent inversion of base and monitor seismic surveys can yield estimates of elastic properties that are inconsistent with expected production effects. We therefore propose a global time-lapse inversion scheme, involving joint inversion of base and monitor data. All vintages and input angle stacks are combined in a single objective function, which is optimized using simulated annealing to estimate the time-variant distribution of elastic attributes that best matches all available data. The multi-vintage nature of the optimization allows us to incorporate flexible, user-defined rock physics constraints on the evolution of Vp, Vs and density between consecutive surveys. There are no restrictions on the number of input angle stacks or number of monitor surveys. The constrained, global inversion solution can therefore be easily updated as new data become available. We apply the global 4-D inversion with rock physics coupling to data from the Brage Field and compare results with a workflow involving separate inversion of base and monitor data. The global 4-D inversion results are combined with a time-lapse Bayesian fluid classification scheme to map production-induced fluid movement and quantify associated uncertainty.
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Relevo Do Embasamento E Da Moho Na Borda Norte Da Bacia Do Paraná Através De Dados Gravimétricos
Authors Vanderlei C. Oliveira Jr. and Yára R. MarangoniThis paper presents the results from an iterative inversion
that considers all Bouguer anomaly signal and different
mass sources at each step. Results are compared with
independent geophysical and geological information.
Relief from mantle-crust and basement interfaces are
provided. The study area shows Moho going deeper
towards E, with depths from 38 to 42 km. Basement has
two grabens of 4 and 3 km deep with a horst in between.
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Undershooting In The Recovery Of The Coverage Affected By Operational Obstacles In A 3D Seismic Survey
More LessThere is a great difference between the developed (preplot)
and the executed (post-plot) projects in seismic data
acquisition processes. There are many possible causes
for these differences: cities, buildings, roads, oil pipelines,
etc. One way to minimize the negative effects of the
impossibility to perform a recording at a shot point is to
use the Undershooting method. This method enables the
acquisition of information regarding the common midpoint
(CMP), and can be used depending on the relation
between the offset and the objective depth at that point.
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Estrutura Da Plataforma Continental Do Sudeste Com Ondas De Superfície Do Sismo De S. Vicente De 2008: Primeiros Resultados
Authors Paula Gomes De Carvalho and Marcelo AssumpçãoWe present the first results of a study about the structure
of the continental shelf in SE Brazil. We use records of
the earthquake occurred in 2008 near São Vicente, São
Paulo’s southern coast. The surface waves (Love and
Rayleigh) show variation of velocity with the period
(dispersion) that is being analyzed using five
seismographic stations located in Brazilian SE. The
preliminary results shown in this paper are compared with
velocities found by Feng et. al., 2007 et. al. (2007) for the
periods of 10, 20 and 30s. We also obtained the velocity
profile for the ESAR station (Angra dos Reis, RJ - Brazil)
using the velocity inversion (Herrmann & Ammon,
2002).The velocities in the continental crust are larger
than the oceanic crust velocities and also indicates that
the Santos Basin’s basement is about 12 kilometers
deep. The velocity inversion of the others stations will be
made in the future, as well as the study of the focal
mechanism of the earthquake.
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Soa Based Data And Application Integration An Enabler For Creative Interpretative Workflows
By Clay HarterVirtually all geologic and geophysical interpretation
upon the use of computer software to retrieve
data and provide analytic and interpretive tools to
the subsurface. Most companies use a diverse set of
software applications and data to perform these tasks.
This paper describes some of the technical challenges
faced when integrating these applications and data and
describes an integration solution based upon
oriented architecture (SOA). Several example workflows
are then described that leverage a SOA integration
framework.
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Shear-Wave Coupling In Inhomogeneous Weakly Anisotropic Media
Authors Ivan Pšençík and Véronique FarraWe present an approximate procedure for computing coupled
S waves in inhomogeneous weakly anisotropic media.
The procedure can be used to compute S waves propagating
in smooth inhomogeneous isotropic or anisotropic
media. In anisotropic media, it can describe behaviour
of coupled as well as decoupled S waves. Basic part of
the procedure is an approximate computation of the common
S-wave ray, a trajectory, along which properties of
both S waves propagating in anisotropic media are computed.
For computation of the common ray and of the
approximate geometrical spreading along it, we use the
first-order ray tracing and dynamic ray tracing concept, developed
for computations of P waves in inhomogeneous
weakly anisotropic media. The amplitude coefficients of the
coupled S waves are computed by solving a coupled system
of ordinary differential equations - the coupling equations
- along the common S-wave ray. The performance
of the procedure is illustrated on several models of varying
strength of anisotropy. Its accuracy is tested by comparing
its results with results of the standard ray theory.
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Geofísica Aplicada À Arqueologia No Estado Do Pará, Brasil
More LessThe first geophysical experiments applied to Archaeology
in Pará were performed in 1977. Since then, the
application of geophysical methodologies to Archaeology
has allowed to the indication of excavations where
archaeologists found mainly ceramic artifacts (pottery,
burial urns, cooking hearts, sherds, pipes, and ax heads).
Experiments were also made to map the archaeological
black earth layer (TPA). Examples that show the success
of the geophysical methodologies as applied to
Archaeology in Pará are presented.
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Psdm Applications In Albacora Field, Campos Basin
Albacora field has a seismic survey acquired in 2002 whose area is 720 square kilometers. This extension and the variety of reservoirs, which contains since Cretaceous until Tertiary turbidite sandstones along ring fence area, required a velocity model building for prestack depth migration (PSDM) using regional horizons: Sea bottom, gray marker, blue marker, seismic cretaceous and top salt. During interpretation of PSDM data some improvements have been observed: better lateral positioning of geologic events (e.g. faults, sloping beds, channels) and enhancement of image in the vicinity of regions with lateral velocity variations (canyons, fault slips) northern of ring fence area. Attribute analysis in PSDM data have confirmed these benefits, which have resulted in change of the spatial positioning anomalies in relation to time maps.
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Estudo Time-Lapse E Análise De Avo Para Reservatórios Carbonáticos
More LessThe use of time-lapse technique has been a challenge for
the seismic monitoring of carbonate reservoirs, despite
great success for use in siliciclastic reservoirs. The oil
carbonate reserves increasingly gaining importance due
to the discovery and recovery fields already in production.
Thus, studies are necessary to understand anomalies in
seismic data through application of analysis AVO / AVA
(amplitude versus offset and amplitude versus angle) for
various saturations of fluids such as brine, oil and gas,
and the establishment of methodologies that allow timelapse
studies in carbonates, and promotion of more
efficient tests for fluids detection.
This work proposed a methodology to the time-lapse
study in carbonates, based on data synthetic idealized
second references and use of rock physics models, such
Gassmann (1951) and Batzle & Wang (1992). The tests
in dolostones and limestones cases showed trends of
variation in their elastic and petrophysical parameters in a
similar way, but with limited sensitivity to the stages of
saturation. The density parameter of the rock has good
distinction of fluids in saturation, even when combined
with other petrophysical attributes. Parameters such as
shear modulus, S velocity and S impedance are used for
lithological distinction between the dolostones and
limestones carbonates for the examples studied. The
analysis AVO / AVA allowed lithological differentiation and
fluid phases differentiation.
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Análise Preliminar De Estruturas Geotectônicas No Amapá, Borda Oriental Do Escudo Das Guianas, Através De Métodos Geofísicos
Authors Saulo Siqueira Martins and José Gouvêa LuizSeveral structures are observed in Paleozoic, Mesozoic,
and Cenozoic of Guiana Shield. The structures have a
NW-SE trend, representing shear belts. Many of the
structures suffered reactivation during those periods. In
this study we applied two geophysical methods,
gravimetry and ground penetrating radar, in order to
understand the dynamic of the structures and how they
can influence the formation of local Tertiary sedimentary
basins.
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The Early January Coronal Mass Ejection And The Estimate Of Its Arrival To Venus
Authors Alisson Dal Lago, Bern Inhester and Luis Eduardo Antunes VieiraOn January 8th, 2007, at 14:54UT, a coronal mass ejection (CME) was observed by LASCO C2, onboard SOHO. Latter on the same day, LASCO C3 also observed this CME, which continued moving outward during most of January 9th. SOHO/EIT did not detect any activity on the solar disk during this period, suggesting that the CME was ejected behind the East limb, towards planet Venus. Thus, we expect the CME to reach Venus some few days after its launch. STEREO/SECCHI COR1 and COR2, A & B, coronagraphs also observed the same CME event. Because STEREO was in the early beginning of its mission, both spacecrafts A and B were near the Earth, and it was possible to combine observations from their instruments and SOHO/LASCO. We estimate the travel time of the Jan. 8th-9th (2007) CME from the Sun to Venus using 3 approaches. In the near-future, our estimates should be confirmed when data from Venus Express mission is available.
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Geoelectrical Behavior Of Miocene And Quaternary Strata In Eastern Marajó Island/Pa
More LessThe use of VES in E Marajó Island had discriminated the
presence of an interval with anomalous high resistivity,
attributed to the presence of the concretionary horizon,
this was crucial to define the top of the Barreiras
Formation. The lateral occurrence of the Barreiras Fm
and the Quaternary deposits and the abrupt passage
between these units are consistent with the presence of a
tectonic fault. This information supports previous studies
that have claimed reactivation along tectonic faults as the
responsible for renewing sediment deposition during the
Quaternary in island.
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Processamento E Interpretação De Dados Eletromagnéticos Aéreos Do Sistema Vtem No Brasil
More LessSince 2005, there have been several VTEM surveys in
the Brazilian territory. There is no doubt of the success
and popularity of this system in Brazil. However,
frequently, VTEM contractors still do not understand the
basic concepts of processing and interpretation of such
data. This paper reviews the important aspects of the
processing and interpretation of VTEM from a perspective
of a geophysicist that has been intensely working with
Brazilian VTEM datasets as an interpreter and as a data
processing manager.
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