Jandyr Travassos | Universidade Federal do Rio de Janeiro (UFRJ) (original) (raw)
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Sandy and/or conglomeratic turbidites and shales of Urucutuca Formation outcrops occur in onshore... more Sandy and/or conglomeratic turbidites and shales of Urucutuca Formation outcrops occur in onshore Almada Basin, northeast Brazil. These rocks are part of an exhumed portion of the filling-section of the Almada Canyon, which is well mapped by seismic studies in offshore part. Such outcrops can be considered as analogues to some important turbidite reservoirs of Campos Basin, the main Brazilian petroleum basin. Ground Penetrating Radar (GPR) is an electromagnetic method that can obtain subsurface images with a sub-meter vertical resolution, which is appropriated to study such thin structures usually found in turbidite outcrops. This work shows the results from a set of georadar (GPR) profiles obtained at one outcrop in Almada Basin. Those data yielded high-resolution images of the outcrop, which aided by a geological interpretation of the exposed section and radar 2D forward modeling, could assist on the delineation of channels and layering patterns. That information may prove to be u...
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Ninth International Conference on Ground Penetrating Radar, 2002
ABSTRACT Turbidite outcrops of the on shore portion of Almada Basin are made of conglomeratic san... more ABSTRACT Turbidite outcrops of the on shore portion of Almada Basin are made of conglomeratic sandstones and shales of the Urucutuca Formation. Those rocks are the unique Turbidite examples of the marine transgression mega-sequence in the Brazilian passive margin, which were sedimented during late Cretaceous. They are analogues to important Campos Basin reservoirs, offshore of Rio de Janeiro State, which is the largest Brazilian oil producer basin. A combined GPR, resistivity and well log survey was planned in the region to provide information regarding rock properties, such as lithology, geometry and permeability. The survey's goal was to predict the variability on the characteristics normally encountered in this kind of deposits. The GPR survey was done in order to provide a stratigraphic interpretation.
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Brazilian Journal of Geophysics, 2018
Para solicitação de resumo, entrar em contato com editor-chefe (editor@sbgf.org.br).
Bookmarks Related papers MentionsView impact
Geophysical Prospecting, 1993
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Journal of Applied Geophysics, Mar 1, 2004
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Anais Da Academia Brasileira De Ciencias, 2022
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DOAJ (DOAJ: Directory of Open Access Journals), Sep 1, 2000
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The International journal of radiation applications and instrumentation. Part E. Nuclear geophysics, Oct 1, 1994
This work estimates the screening effect of a tropical rain forest on airborne γ-ray measurements... more This work estimates the screening effect of a tropical rain forest on airborne γ-ray measurements. The screening effect is expressed as a multiplicative coefficient. The results were obtained using cylindrical sources on the ground. A layered approximation was used to obtain a first approximation for the screening coefficient for the biomass of the forest. However, the layered approach, neglects the strong anisotropy of the absorber. This is particularly conspicuous for the trunks of trees that contribute up to 80% to the total value of the screening coefficient. Due to the anisotropy of the absorbers layered calculations may produce upward biased screening coefficient values. A Monte Carlo simulation was used to calculate the effect of anisotropy on the screening coefficient of the biomass
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Traditionally, first-arrival travel-time tomographic problems are treated as nonlinear inverse pr... more Traditionally, first-arrival travel-time tomographic problems are treated as nonlinear inverse problems solved by deterministic optimization methods. These methods minimize the objective function by taking its derivatives. In some problems these derivatives are slow to compute and the method becomes inefficient. Another limitation inherent to deterministic methods is the strong relation between the starting model and local minima entrapment. To deal with these drawbacks, we apply a genetic algorithm with elitism (EGA) to cross-hole tomography of Ground Penetrating Radar (GPR) data. Regardless the starting model, this heuristic method ideally finds the region of the solution space containing global minima without calculating derivatives. We obtain good results in applying our method in two noise-corrupted synthetic cross-hole data sets. The first simulates horizontal strata and the second consists of a homogeneous background medium with single low-slowness anomaly. The methodology is also applied to field data where a cross-strata pattern is achieved. This pattern is in accordance with the geological feature of the region. Heuristic methods applied to highdimensional geophysical problems yield good results but are computationally expensive. Coupling heuristic and deterministic methods is recommended to exploit the full power of each optimization technique.
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First Break, Sep 1, 1992
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Proceedings of the 4 Simpósio Brasileiro de Geofísica, 2010
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Proceedings of the 2 Simpósio Brasileiro de Geofísica, 2006
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Proceedings of the 2 Simpósio Brasileiro de Geofísica, 2006
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Proceedings of the 2 Simpósio Brasileiro de Geofísica, 2006
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11th International Congress of the Brazilian Geophysical Society & EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009, Apr 28, 2009
Instantaneous spectral analysis applied on 7 CMP profiles is used to detect some of the few phase... more Instantaneous spectral analysis applied on 7 CMP profiles is used to detect some of the few phases developed from a young controlled spill of 100 l of LNAPL. The presence of the LNAPL affects the traces differently at earlier and later times and introduces important spectral changes. The LNAPL concentrates the spectral energy within a window in the time-frequency spectrum, bounded in frequency and in TWT. Below the TWT range amplitudes are attenuated producing a low frequency shadow zone below it. The late TWT bound not only limits the useful time information in the trace but also is very sensitive to the vapor phase of the LNAPL. We use this bound as a useful instantaneous attribute of the GPR trace. The LNAPL also narrows and attenuates the amplitudes inside the spectral window, acting as a filter for the scattered field from a volume limited in depth by the late TWT bound. We suggest the construction of a spectral pseudosection, which is able to show clearly the limits of the influence of the LNAPL.
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In general, data collected by GPR systems are acquired via a fixed-offset strategy. The latter im... more In general, data collected by GPR systems are acquired via a fixed-offset strategy. The latter impinges on our ability to perform velocity analysis and to apply modern signal enhancement methodologies. The solution is to use multi offset GPR measurements with varying receiver-source distances. However, the deployment of antennas makes it difficult to gather data that are amenable to form high fold Common Mid Point (CMP) gathers for velocity analysis and restock imaging. This paper proposes applying interpolation to ground-penetrating radar (GPR) data; the method applied here is called Singular Spectrum Analysis (SSA), and it’s anti-alias modification to reconstruct multi-offset GPR gathers. We did tow tests, in a modeled and real data. The test was done by applying an heavy alias on data and trying to recover them back. The result presented in the paper shows that the interpolation method had success on data reconstruction.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Sandy and/or conglomeratic turbidites and shales of Urucutuca Formation outcrops occur in onshore... more Sandy and/or conglomeratic turbidites and shales of Urucutuca Formation outcrops occur in onshore Almada Basin, northeast Brazil. These rocks are part of an exhumed portion of the filling-section of the Almada Canyon, which is well mapped by seismic studies in offshore part. Such outcrops can be considered as analogues to some important turbidite reservoirs of Campos Basin, the main Brazilian petroleum basin. Ground Penetrating Radar (GPR) is an electromagnetic method that can obtain subsurface images with a sub-meter vertical resolution, which is appropriated to study such thin structures usually found in turbidite outcrops. This work shows the results from a set of georadar (GPR) profiles obtained at one outcrop in Almada Basin. Those data yielded high-resolution images of the outcrop, which aided by a geological interpretation of the exposed section and radar 2D forward modeling, could assist on the delineation of channels and layering patterns. That information may prove to be u...
Bookmarks Related papers MentionsView impact
Ninth International Conference on Ground Penetrating Radar, 2002
ABSTRACT Turbidite outcrops of the on shore portion of Almada Basin are made of conglomeratic san... more ABSTRACT Turbidite outcrops of the on shore portion of Almada Basin are made of conglomeratic sandstones and shales of the Urucutuca Formation. Those rocks are the unique Turbidite examples of the marine transgression mega-sequence in the Brazilian passive margin, which were sedimented during late Cretaceous. They are analogues to important Campos Basin reservoirs, offshore of Rio de Janeiro State, which is the largest Brazilian oil producer basin. A combined GPR, resistivity and well log survey was planned in the region to provide information regarding rock properties, such as lithology, geometry and permeability. The survey's goal was to predict the variability on the characteristics normally encountered in this kind of deposits. The GPR survey was done in order to provide a stratigraphic interpretation.
Bookmarks Related papers MentionsView impact
Brazilian Journal of Geophysics, 2018
Para solicitação de resumo, entrar em contato com editor-chefe (editor@sbgf.org.br).
Bookmarks Related papers MentionsView impact
Geophysical Prospecting, 1993
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Journal of Applied Geophysics, Mar 1, 2004
Bookmarks Related papers MentionsView impact
Anais Da Academia Brasileira De Ciencias, 2022
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
DOAJ (DOAJ: Directory of Open Access Journals), Sep 1, 2000
Bookmarks Related papers MentionsView impact
The International journal of radiation applications and instrumentation. Part E. Nuclear geophysics, Oct 1, 1994
This work estimates the screening effect of a tropical rain forest on airborne γ-ray measurements... more This work estimates the screening effect of a tropical rain forest on airborne γ-ray measurements. The screening effect is expressed as a multiplicative coefficient. The results were obtained using cylindrical sources on the ground. A layered approximation was used to obtain a first approximation for the screening coefficient for the biomass of the forest. However, the layered approach, neglects the strong anisotropy of the absorber. This is particularly conspicuous for the trunks of trees that contribute up to 80% to the total value of the screening coefficient. Due to the anisotropy of the absorbers layered calculations may produce upward biased screening coefficient values. A Monte Carlo simulation was used to calculate the effect of anisotropy on the screening coefficient of the biomass
Bookmarks Related papers MentionsView impact
Traditionally, first-arrival travel-time tomographic problems are treated as nonlinear inverse pr... more Traditionally, first-arrival travel-time tomographic problems are treated as nonlinear inverse problems solved by deterministic optimization methods. These methods minimize the objective function by taking its derivatives. In some problems these derivatives are slow to compute and the method becomes inefficient. Another limitation inherent to deterministic methods is the strong relation between the starting model and local minima entrapment. To deal with these drawbacks, we apply a genetic algorithm with elitism (EGA) to cross-hole tomography of Ground Penetrating Radar (GPR) data. Regardless the starting model, this heuristic method ideally finds the region of the solution space containing global minima without calculating derivatives. We obtain good results in applying our method in two noise-corrupted synthetic cross-hole data sets. The first simulates horizontal strata and the second consists of a homogeneous background medium with single low-slowness anomaly. The methodology is also applied to field data where a cross-strata pattern is achieved. This pattern is in accordance with the geological feature of the region. Heuristic methods applied to highdimensional geophysical problems yield good results but are computationally expensive. Coupling heuristic and deterministic methods is recommended to exploit the full power of each optimization technique.
Bookmarks Related papers MentionsView impact
First Break, Sep 1, 1992
Bookmarks Related papers MentionsView impact
Proceedings of the 4 Simpósio Brasileiro de Geofísica, 2010
Bookmarks Related papers MentionsView impact
Proceedings of the 2 Simpósio Brasileiro de Geofísica, 2006
Bookmarks Related papers MentionsView impact
Proceedings of the 2 Simpósio Brasileiro de Geofísica, 2006
Bookmarks Related papers MentionsView impact
Proceedings of the 2 Simpósio Brasileiro de Geofísica, 2006
Bookmarks Related papers MentionsView impact
11th International Congress of the Brazilian Geophysical Society & EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009, Apr 28, 2009
Instantaneous spectral analysis applied on 7 CMP profiles is used to detect some of the few phase... more Instantaneous spectral analysis applied on 7 CMP profiles is used to detect some of the few phases developed from a young controlled spill of 100 l of LNAPL. The presence of the LNAPL affects the traces differently at earlier and later times and introduces important spectral changes. The LNAPL concentrates the spectral energy within a window in the time-frequency spectrum, bounded in frequency and in TWT. Below the TWT range amplitudes are attenuated producing a low frequency shadow zone below it. The late TWT bound not only limits the useful time information in the trace but also is very sensitive to the vapor phase of the LNAPL. We use this bound as a useful instantaneous attribute of the GPR trace. The LNAPL also narrows and attenuates the amplitudes inside the spectral window, acting as a filter for the scattered field from a volume limited in depth by the late TWT bound. We suggest the construction of a spectral pseudosection, which is able to show clearly the limits of the influence of the LNAPL.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
In general, data collected by GPR systems are acquired via a fixed-offset strategy. The latter im... more In general, data collected by GPR systems are acquired via a fixed-offset strategy. The latter impinges on our ability to perform velocity analysis and to apply modern signal enhancement methodologies. The solution is to use multi offset GPR measurements with varying receiver-source distances. However, the deployment of antennas makes it difficult to gather data that are amenable to form high fold Common Mid Point (CMP) gathers for velocity analysis and restock imaging. This paper proposes applying interpolation to ground-penetrating radar (GPR) data; the method applied here is called Singular Spectrum Analysis (SSA), and it’s anti-alias modification to reconstruct multi-offset GPR gathers. We did tow tests, in a modeled and real data. The test was done by applying an heavy alias on data and trying to recover them back. The result presented in the paper shows that the interpolation method had success on data reconstruction.
Bookmarks Related papers MentionsView impact