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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 - 20 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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