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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
61 - 80 of 418 results
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O Uso Integrado Dos Métodos De Sísmica De Refração E De Ondas Superficiais Visando À Caracterização Da Subsuperfície Rasa
Authors Fabio Bordotti Schumann and Renato Luiz PradoThis paper presents the data analysis from two shallow seismic methods carried out in a sedimentary area. We used a combination of seismic refraction tomography and multi-channel analysis of surface waves – MASW techniques aiming to characterize the shallow subsurface. The seismic refraction tomography and MASW data were acquired simultaneously using the same hardware and field geometry, i.e., a Geode seismograph coupled with ninety six 14 Hz geophones spaced 2 meters apart and seventeen shot points spaced 12 meters apart along
the entire spread.Two 2D sections, P wave velocity image (from refraction data) and S wave velocity image (from surface waves data) were analyzed and compared. Joining the data we derived a Poisson's ratio section aiming to infer strength characteristics of soils and sediments.This approach showed to be complemental to map geologic interfaces and suitable to infer mechanical
properties of soils and sediments.
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Bandwidth Extension Using Harmonics
More LessWe show a new method of seismic resolution improvement using the Continuous Wavelet Transform (CWT). Using the CWT and the available bandwidth in the seismic, the phase and amplitude spectra of harmonics and sub-harmonics can be computed. These harmonic and sub-harmonic frequencies are then convolved onto the input data. Only frequencies for reflectivity that is above the ambient noise level in the CWT domain is added to the seismic wavelet. This process broadens the bandwidth of the signal which increases the resolution of the seismic data.
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Effects Of Compression On Attributes
In this work we calculate a series of attributes on seismic data with different degrees of compression and compare with the attributes calculated from the original data. We find that, although primary attributes are nearly unaffected by compression, secondary attributes, as Instantaneous Frequency, can be affected by a relatively low compression, say 90% of nominal fidelity, what can be a source of pitfalls on interpretation of the data.
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O Alto De Vitória E Seu Papel Na Evolução Sedimentar Da Margem; Porção Norte Da Bacia De Campos E Sul Da Bacia Do Espírito Santo
More LessThis study focus on the role of the Vitória Structural High on the deep-water tectono-stratigraphic evolution of the adjacent Campos and Espírito Santos basins , based on 2D seismic analysis. The Vitoria High has been currently reffered to in the literature as the structural limit between the Campos and Espírito Santo marginal basins. However, our seismic analysis shows that on the lower slope and continental rise, the Vitoria High has a rather limited geographical and morphological expression and does not act as barrier that influences the stratigraphic
records of both basins. On the other hand, our seismic analysis reveals that the morphology of the Vitoria High is characterized by fault scarps and ramps inherited from the extensional rift tectonics. Fault scarps and ramps in such a context acted as residual morphologies at the base of the Aptian mobile salt layer, affecting the structural evolution of salt-related extensional faults that were conditioned to sole out in the residual morphology at the salt base. As a consequence, the morphology of the Vitória High had an indirect impact on the sedimentary
architecture of overlying marine sequences, determining the location and development of local depocenters (minibasins) along rollover structures in the extensionsal domain of salt tectonics.
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Influence Of The Discrete Laplace And Fourier–Bessel Transforms On The Solution To Direct Seismic Problems Within The Frequency Domain
Authors Georgy Mitrofanov and Viatcheslav PriimenkoTheoretical solution to the direct seismic problem for a thin layer elastic model of medium in the spectral domain can be constructed effectively using the Laplace and Fourier-Bessel transforms. However, for practical use, as a tool of modeling and the solution of inverse problems, it is important to analyze properties of the corresponding discrete transforms and their influence on the solution obtained. This research presents some of the results of our investigation of the properties of the transforms using functions giving analytically, which allows the possibility to analyze the most important features of the transforms. Such investigations permitted to determine the conditions for application of these transforms to the solution of considered problems in more details.
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Ground Roll Attenuation With Singular Value Decomposition
Authors Peter W. Cary and Changjun ZhangGround roll attenuation is an important step in seismic data processing. We implement a procedure to eliminate ground roll from seismic data that is based on eigen-images. We use singular-value decomposition (SVD) to distinguish between signal and noise within narrow frequency bands of the ground-roll cone at near offsets in the data. The estimate of the energy of the signal comes from an uncontaminated portion of the seismic records. The method is able to adapt to the changing character of the noise and signal about the seismic survey. The modeled noise is then subtracted from the data while preserving the reflections.
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Borda Centro-Leste Da Bacia Do Recôncavo (Estado Da Bahia): Uma Nova Fronteira Exploratória Na Mais Profícua Bacia Petrolífera Terrestre Do Brasil
Authors Ademilson Fagundes De Brito and João Ítalo GhignoneBased on 3D seismic data and wells were identified
structural features here called Eastern’s Steps Border of
Recôncavo Basin, located east of the Lower Miranga,
over which could to be lay the excellents fluvio-aeolians
reservoirs of the Sergi and Agua Grande formations in
lateral direct contacts with the layers of source rocks of
the Gomo Member (Candeias Formation), located in
adjacent blocks, setting a high potential oil to be proven in
the basin.
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Effects Of Long-Lasting Interplanetary Magnetic Field Perturbations On The Equatorial Ionosphere
During 3 – 7 July, 2003, long-lasting and large-amplitude
interplanetary magnetic field perturbation event occurred.
This event is classified as high-intensity long-duration
continuous AE activity (HILDCAA) which occurs outside
the main phase of magnetic storms. The responses of the
equatorial ionosphere to HILDCAA events have been
poorly known so far. In this work, we investigate the
effects of HILDCAA events on the equatorial ionosphere
using ionosonde data (hmF2) observed at São Luís,
Brazil and the ACE satellite data. The results indicate
presence of short-time prompt penetration electric field
disturbances and long-lived positive charge accumulation
at the magnetic equator around the midnight sector due to
the disturbance dynamo effect.
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The Impact Of Verifiable Data Quality In Today’S Exploration Cycle
Authors Richard Johnston and Dwight SmithIn today’s exhausting search for oil and gas the targets are getting tougher to locate and more difficult to commercially produce. There are far fewer drilling opportunities and areas available for drilling – and the competition is fierce. Today’s advances in data quality and information management can help the time strapped geoscientist increase the quality of their interpretation/prospect generation and reduce the decision time that may be required to identify and commit to a prospect. There are tools and processes now available to the industry that can be used to create a quality environment through automation and best practices, such as the environment created in the Gulf of Mexico operations at Chevron.
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Use Of Full Tensor Gravity Invariants In Detection Of Intrusion-Hosted Sulphide Mineralization: Implications For Emplacement Mechanisms
Authors James Mataragio and John KieleyGeological and geophysical characteristics of
the Budgell’s Harbour prospect in Newfoundland, Canada
were investigated over known geochemical and magnetic
anomalies using Airborne Full Tensor Gradiometry (Air-
FTG®). A total of 407 line-km were flown at a line spacing
of 200m x 2000m. Several cylindrical, plug-like anomalies
were generated that are interpreted to be associated with
steeply dipping ultramafic intrusions.
An integrated interpretation focusing on
geological models and gravity tensor invariants suggests
a mechanism in which ultramafic magma was rapidly and
forcefully emplaced. Radial fracturing caused by forceful
eruption of these magmas is evident in horizontal tensor
invariants. Particularly, the invariants of the gravity tensor
provide a means in which individual and sub-vertical
plugs, dikes, or diatremes associated with alkaline
intrusions can be outlined and clearly distinguished from
larger porphyry-like anomalies.
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Drilling Directly From A Magnetic Airborne Fixed Wing Survey: Is It Possible? A Proposed Criterion And A Real Example
More LessOne of the main issues in modern mineral exploration is
whether you can drill directly from an airborne survey or
not, since ground surveys can be very high cost in both
money and environmental points of view.
Modern helicopter systems with very tight line spacings
are usually used for direct drilling (Witherly 2004), but in
general airborne fixed wing surveys are not expressly
recommended for direct drilling.
The aim of the present paper is to run forward models
and to present a real example in order to discuss this
issue, trying to supply an orientation guide that can be
used to consider drilling directly from the airborne
magnetic fixed wing surveys.
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Hca Methodology Applied To Model The Interaction Of Faulting And Salt Movement In Campos Basin, Brazilian Atlantic Margin
More LessThe kinematic evolution along an offshore regional crosssection
was studied by using the forward modelling HCA
approach implemented in the software FORC3 (ÓSalvini -
Roma Tre University). This approach consisted in the
comparative analysis of the time evolution of the tectonic
elements present in the sections (namely salt domes
activity and faulting) with the thickness and architecture of
the syntectonic sediments. The link between
sedimentation and tectonics was carefully replicated
during the evolution of the sections from late Cretaceous
to recent, and allowed to set the time constraints of the
tectonic evolution of the region, together with its velocity
and the interaction between salt doming and faulting.
The FORC3 modeling tool allowed to compute along the
cross-section a distribution of the expected brittle
deformation intensity.
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Aplicação De Ensaios Elétricos E Eletromagnéticos Em Uma Área Industrial Contaminada Em São Paulo – Brasil – Resultados Preliminares
Authors Marina Minozzo, Vagner Roberto Elis, Andréa Teixeira Ustra and Fábio MissakiThis work presents the results of Electromagnetic and
Resistivity methods applied to an industrial facilitie
polluted with benzene, toluene, xylene (BTX) and
organochlorine compounds, in São Paulo city, Brazil. The
results suggest that high resistivity anomalies are due to
contaminated compounds in the soil, typically resistive;
and low resistivity anomalies are consequences of
electrical properties changes of the polluted environment,
caused by biodegradation. The acquisition techniques
showed to be efficient for contamination mapping in
industrial sites studies and should be considered in this
type of study.
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4D Petrophysical Seismic Inversion On The Troll West Field
Inversions of seismic surveys often give quite low-resolution results that are difficult to compare with well data and geological models. We are therefore developing a multi-vintage seismic inversion based on a Petro-Elastic Model (PEM), called PetroSI-4D. This involves input from the geological model and good control on the petrophysical correlation between porosity and PEM-based seismic velocities. All vintages and input angle stacks are combined to jointly invert for layer thickness, rock properties and saturations. Perturbations of selected properties of the geological model are introduced using a simulated annealing algorithm to optimise the degree of match between the synthetic and the real angle stacks. There are no restrictions on number of input angles or number of monitor surveys, but new monitor surveys require new input to 4-D PEM. The base inversion result is delivered in porosity cubes instead of ordinary acoustic impedance and Vp/Vs results. The 4-D inversion result is planned to deliver saturation cubes instead of cubes of acoustic impedance or Vp/Vs changes. These parameters should be easier to compare and use in update of geological and reservoir models to validate the results. The Troll West Field shows that the Petrophysical seismic inversion with rock physics PEM connected to the inversion, gives good results and comparison with the porosity input model is shown. The purpose of 4-D petrophysical inversion is to make use of all available seismic data simultaneously, multi-vintage and pre-stack, to constrain the evolution of the saturation field.
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Eiagrid: In-Field Optimization Of Seismic Data Acquisition By Real-Time Subsurface Imaging Using A Remote Grid Computing Environment
Authors Björn Z. Heilmann, Ana M. Vallenilla Ferrara, Guido Satta and Ernesto BonomiThe constant growth of contaminated sites, the unsustainable
use of natural resources, and, last but not least, the
hydrological risk related to extreme meteorological events
and increased climate variability are major environmental
issues today. Finding solutions for these complex problems
requires an integrated cross-disciplinary approach, providing
a unified basis for environmental science and engineering.
In computer science, grid computing is emerging
worldwide as a formidable tool allowing distributed computation
and data management with administratively-distant
resources. Utilizing these modern high performance computing
technologies, the GRIDA3 project bundles several
applications from different fields of geoscience aiming
to support decision making for reasonable and responsible
land use and resource management. In this abstract we
present the geophysical application of the GRIDA3 project
named EIAGRID. As illustarted in Figure 1, it aims at supporting
environmental research by enabling the use of grid
computing facilities to provide real-time subsurface imaging
directly during data acquisition. Furthermore, shared
data storage using georeferencing tools and data grid technology
facilitates acquisition design, workflow construction
and the interpretation of results.
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Insights About St. Peter Peridotitic Ridge In The Equatorial Atlantic Tectonic Setting: Deep Upper-Mantle Structure With Ductile And Brittle Deformation
Authors Jennifer Angel-Amaya and Susanna E. SichelThe St Peter peridotitic ridge (SPPR) is a large structure in the Equatorial Atlantic Ocean, located at southern side of the intersection of the Mid Atlantic Ridge (MAR) with the St. Paul´s Transform Fault (SPTF); It is composed for upper-mantle derivate lherzolitic and harzburgitic rocks with serpentinitic and mylonitic processes superimposed. Basaltic rocks and sediments are presents in less proportion. The sigmoid structure of the SPPR is elevated 4000 m above the ocean bottom and it´s northern side protrudes above the sea level forming the St. Peter and St. Paul´s Archipelago (SPSPA) in the geographical coordinates 0° 55’.1 N and 29° 20’.7 W. This segment ridge corresponds to the wall of the active SPTF, for this reason is the more intensity deformed and mylonitized, that constitute a excellent outcrop of the mantle related rocks with accessible structural elements of the ductile and brittle deformation.
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Coda Wave Attenuation For Center North Of Parecis Basin In The Amazon Craton – Brazil
More LessSmall local earthquakes from two aftershocks
sequences in Porto dos Gaúchos, Amazon craton -
Brazil were used to estimate the coda wave
attenuation in the frequency band of 1 to 20 Hz. The
time-domain coda-decay method of a single
backscattering model is employed to estimate
frequency dependence of quality factor (Qc) of coda
waves. Qc values have been computed at central
frequencies and (band) of 1.5 (1-2), 3.0 (2-4), 6.0 (4-8),
9.0 (6-12), 12 (8-16) and 18 (12-24) Hz in the lapse time
ranging from 25 to 60 sec for five different datasets,
selected according to the geotectonic environments
of the stations locations as well as the ability to
sample crustal structures at depths.
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Acoustic Noises In Boreholes: Aspects Of Practical Use
More LessA distribution of acoustic noises in massifs of sedimental
and crystalline rocks was considered. It was shown, that
the level of acoustic noises is higher in crystalline rocks.
Three-component geoacoustic logging allow to distinguish
zones of an elliptical cross-section of a borehole shaft.
Opportunities of geoacoustic noises to distinguish oil and
water saturated stratums were shown.
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A Importância Da Modelagem Na Distribuição Espacial De Variáveis Ambientais Utilizando Procedimentos Geoestatísticos
This article evaluates the quality of groundwater
potentially impacted by nitrate (NO3), using a geostatistical
analysis. It was found that in 67% of the samples were identified
levels greater than 3 mg/L, and 33% of wells tested, nitrate levels
were found above or very close to 10 mg/L, maximum allowed in
Brazil, which indicates chemical water quality and commitment of
its drinking.
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A Comparison Of Two True-Amplitude Gaussian Beam Migration/Inversion Operators
Authors Carlos A.S. Ferreira and João Carlos Ribeiro CruzThe use of the concept of Gaussian beams in seismic
migration has been highly considered in recent times and
it is not a new issue. With the advent of non-conventional
and mandatory new exploration targets in Brazil (such as
the presalt), the imaging task has been highly demanded
in order to bypass common (known ones) and new
features of the wavefield propagation, such as anisotropy
and some other factors. Since migration algorithms today
are not anymore imaging-only process, comes into play
the task of inversion, alongside with interpretation,
prospecting and drilling. This paper then compares the
theoretical results of two true-amplitude migration
algorithms and their abilities as attributes estimators.
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