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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 - 50 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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