- Home
- Conferences
- Conference Proceedings
- Conferences
11th International Congress of the Brazilian Geophysical Society
- Conference date: 24 Aug 2009 - 28 Aug 2009
- Location: Salvador, Brazil
- Published: 24 August 2009
401 - 418 of 418 results
-
-
On-Going Uplift Rate Of The Saint Peter Saint Paul Peridotite Ridge, Equatorial Atlantic Ocean, Base On Geomorphologic Analyses Of Wave-Cut Bench And 14C Dating For Coral Fossils
The Saint Peter Saint Paul Islets is situated at
the Equatorial Atlantic Ocean on the top of the
morphologic elevation of 90km in length, 25km
in width, and 3800m in height constituted by
abyssal mantle peridotite. The submarine
morphology around the islets is highly
accidental characterised by steep slopes and
subvertical cliffs. The morphological features
and the absence of large coral reef suggest
that the islets are formed by recent tectonism
that may continue up to the present. It is
considered that the peridotite ridge top was
present at the ocean bottom and it has just
reached to the present sea level. The summit
level map shows a wave-cut bench of 7~9 m
above sea level. Based on the correlation of
this bench to the Flandrian Transgression, the
uplift rate in recent 6000 years is calculated as
1.5 mm/year. The 14C datings for the coral
fossils also indicate the same uplift rate. If the
peridotite ridge corresponds to a tectonically
deformed megamullion, total uplift is 1500 to
3000m and the tectonism started at 1 to 2Ma.
On the other hand, if the ridge is originated
directly from subcrustal mantle, the total uplift
becomes about 9000m and tectonism is active
in recent 6 million years.
-
-
-
Practical Issues In The Wave Field Extrapolation Analysis From An Observation Surface
In this work it will be presented an analysis about the reliability of wave field extrapolation on the multiple reflection prediction based on the Kirchhoff-Helmholtz Integral approach. At a first moment, there is a brief review about the Kirchhoff-Helmholtz Integral theory. After that, it is performed a comparison between the direct wave field extrapolation and the Kirchhoff-Helmholtz
approach in order to evaluate this methodology. The 2-D synthetic acoustic seismic modeling will be done by means of the Finite Difference Method and analizing the possible issues of these processes for a homogeneous medium.
-
-
-
Estimativa Da Orientação Do Eixo De Simetria De Um Meio Ti A Partir De Dados De Onda P Em Experimentos De Vsp Walkaway
More LessA reliable description of seismic anisotropy in
the overburden is necessary for accurate seismic
imaging, reflection amplitude analysis, and the
correction of borehole sonic logs. A walkaway
VSP provides an opportunity of local determination
of anisotropy parameters in the overburden from
recorded polarization vectors and vertical components
of slowness vectors. On synthetic examples, we study
quality of the estimates of the local transverse isotropy
(TI) and of the orientation of its symmetry axis, from Pwave
data recorded along a single line of the walkaway
VSP. We study sensitivity of the estimates to the
used type of the wave (direct, reflected or both), to
the varying level of noise applied separately to each
component of recorded direct and reflected waves and
sensitivity to other parameters.
-
-
-
Caracterização Estrutural E Hidrológica Do Aqüífero Urucuia Nas Sub-Bacias Dos Rios Das Fêmeas E Do Cachorro
Authors Kátia Rejane F. Do Nascimento and Olivar A.L. De LimaThe physical characterization of the Urucuia aquifer
in the western portion of Rio Grande basin were
performed based on the inversion of 128 Schlumberger
geoeletrical soundings measuring both resistivity and
time domain induced polarization. Geophysical logs
and well data were used to control the interpretation.
The results allowed to define the aquifer structure
up to 500 m depth and to outline several fault zone
displaying the aquifer substratum from 20 to more
150 m.
-
-
-
Paraná Basin As Basement In The Northern Region Of The Pelotas Basin: Evidence From Seismic And Magnetic Data Analysis
Authors Michael Holz and Silvia Beatriz Alves RolimSeismic and magnetic data analysis of the northern
region of the Pelotas Basin were developed in order to
understand the relationship to Paraná Basin, which in that
region seems to extend towards the ocean. The studied
geologic indicators suggest that in pre-rift times in fact the
Parana Basin extended further eastwards, now lying
deeply buried below the sedimentary succession of the
Pelotas Basin. The present paper deals with the
evaluation of this issue, discussing seismic and magnetic
data which support that assumption.
-
-
-
Crs-Beam Psdm : Migração Pré-Empilhamento Em Profundidade Usando O Operador Crs
Authors German C. Garabito and Carlos A.S. FerreiraThe Common-Reflection-Surface (CRS) stack method produces from multi-coverage seismic data a zero-offset (ZO) stacked section with high signal-to-noise ratio and improved resolution. Besides the ZO section, the CRS method produces three useful kinematic attributes, which can be applied to determine the projected Fresnel zone and geometrical spreading factor required for Kirchhoff true-amplitude limited-aperture migration. In this work, we present a new depth migration procedure combining the Kirchhoff depth migration and the CRS stacking method. This new Kirchhoff type prestack depth migration called CRS-beam PreSDM is based on beam stack using the CRS operator to do the imaging from time-domain to depth-domain. To demonstrate the efficiency and robustness of the proposed migration procedure, it was applied to very noise synthetic dataset of a model with steeper dip reflectors.
-
-
-
Evaluation Of Time To Depth Conversion Algorithms For Depth Velocity Model Building
Authors Leandro Da S. Sadala Valente, Jessé C. Costa and Jörg SchleicherTime-to-depth conversion of a velocity model is
highly desirable to provide alternative initial depth
velocity models for tomographic methods. Unfortunately,
the problem is intrinsically unstable and thus
requires regularization. Recently, a number of similar
techniques using image-rays have been proposed
to achieve this aim. We review three time-to-depth
conversion techniques, discuss their algorithmic procedures
and show their differences by applying them
to a 2D synthetic data set. In particular, we demonstrate
that the different procedures react differently to
different kinds of regularization. Although the imageray
trajectories and the resulting depth velocity models
depend on the regularization employed, the final
depth images corresponding to these different models
are very similar.
-
-
-
First Magnetic/Gamma-Spectrometry Survey For Hydrocarbon Exploration In Brazil Identifies Micro-Seepage Anomalies
We performed the first high-resolution land magnetic
and gamma-spectrometry survey with the objective of
identifying micro-seepage anomalies for the
exploration of oil and gas in Brazil. A total of 120 km
along 26 profiles of High Resolution Ground
Magnetics (HRGM) and gamma-spectrometry data
were acquired. The data were jointly interpreted and
five anomalies were preliminarily interpreted and
related to the location of hydrocarbon microseepages.
These anomalies were also related to fault
structures as observed in the residual magnetic
anomaly map. These anomalies will be tested by
drilling later this year.
-
-
-
Gerenciamento Empresarial De Conteúdo De Informações De Exploração E Produção Da Petrobras Com O Apoio De Um Sig Especializado
Authors Vinicius Botelho, Carina Lopes, Adriano Simões and Leonardo MatricianoEnterprise Content Management (ECM) has been a challenging subject for the industry for the past decade because it comprises many subject areas such as Eletronic Document Management (EDM), Information Resource Management (IRM) and so on. For the petroleum industry it has been even more challenging, since the nature of the exploration and production data is extremely peculiar in terms of volume and heterogeneity. In this paper, we show the collection of software tools developed by Petrobras, a brazillian oil company, which addresses those problems. We show how an integrated GIS can be used in conjunction to those tools to visualize, recover and support the management of this information.
-
-
-
The Influence Of Velocity Field On Wave Equation Migration
Authors Mitchel Xavier, Leo Nascimento and Shengwen JinHOW DENSE IS DENSE ENOUGH FOR A VELOCITY FIELD?
Because of the recent discoveries of giant fields in provinces located beneath the salt layer (subsalt leads), exploratory interpreters are increasingly requesting geophysical techniques to enable better definition, higher resolution, and better imaging of the oil field. The most advanced geophysical method is the PreStack Depth Migration (PDSM) technique, which uses the wave equation. It enables an improved confidence level in the geological model and better delineation of the reservoir.
Velocity and tomography analyses are labor-intensive processes. This study provides an analysis of how a dense velocity field affects the wave equation migration results. We will decimate the velocity field and migrate the same data on a similar image grid. This will help the people who process the data to determine how many velocity interpretations are needed to obtain the expected seismic image.
The primary challenge of technique has been the cost of the PSDM by wave equation; however, this challenge has been overcome as a result of the availability of powerful hardware and smart algorithms. The availability of the PSDM technique will enable more reliable geological models, which will result in more discoveries.
-
-
-
Two Decades Of 4D Geophysical Developments – Experiences, Value Creation And Future Trends
Authors Ivar A. Sandø, Ola-Petter Munkvold and Rigmor EldeSince the introduction of the marine seismic 4D technology in the early 90’s, StatoilHydro has been piloting a large spectrum of novel technology developments, and applied these to solve a variety of reservoir challenges. In addition, we have successfully developed and implemented high resolution 4D marine gravimetric. Geophysical reservoir monitoring helps maximizing recovery from producing reservoirs using seismic, gravity and electromagnetic based methods for reservoir imaging, characterization and monitoring. Building on our ongoing IOR research efforts, StatoilHydro aims to be a leading company in quantitative integration of 4D data in reservoir modelling, and lead in tailor-made data acquisition and processing for seismic imaging and reservoir characterisation so that we can meet the challenges of the most complex reservoirs. This presentation summarizes our experience and value creation from a large number of time-lapse projects and offers our view on the future trends for 4D in reservoir management projects.
-
-
-
Fiber Optic Permanent Seismic System For Increased Hydrocarbon Recovery
Authors Jan Langhammer, Morten Eriksrud, Carl Berg and Hilde NakstadPermanent seismic installations at the sea-floor have emerged as a potential tool for oil companies in their work to actively monitor oil/gas flows and injection processes in order to increase hydrocarbon recovery and optimize production. The advantage of fiber optic over electric sensors is that the fiber optic sensor technology is completely passive at the wet-end, i.e. no short circuits will happen, longer life-time of components, high sensitivity, high dynamic range, less intrinsic noise, no corrosion of sensing components, fewer parts and potentially cheaper complete receiver systems. Large fiber optical ocean-bottom receiver systems for 4D-applications, can now be produced and installed at locations where the oil companies would like to exploit the life-of-field seismic concept. We are advocating optical sensing technology to be an important part of the tool box for the oil companies in their work to implement the instrumented oil field in a cost efficient way.
-
-
-
Detecção De Erros Grosseiros Em Banco De Dados Gravimétrico Terrestre Do Estado Do Rio Grande Do Sul
Since 1950, terrestrial gravity data of the State of Rio
Grande do Sul has been systematically collected by the
Department of Geodesy of the Federal University of Rio
Grande do Sul (UFRGS). This paper proposes three
methods for detection of gross errors in this database,
based on: 10) the digital elevation model of Shuttle Radar
Topography Mission (SRTM), 20) the Gravity Recovery
and Climate Experiment (GRACE) and 30
) the
interpolated terrestrial gravity observations. The first
method identified 217 points of altimetry, representing
3.00% of the database. The second identified 645 points
of gravity observations, representing 8.93% of the
database. The third method identified 60 points of
terrestrial gravity observations, representing 0.83% of the
database. The criterion for elimination of observations
was based on identifying coincident outliers in, at least, 2
methods. The matching points of coarse errors between
altimetry, gravity and bouguer anomaly were grouped in
177 points, representing 2.45% of total database. These
points were considered and disposed of coarse errors
database. This approach is accepted as a preliminary
correction of the RS gravity database and we suggest
field checking. Statistics is a tool and, as such, does not
replace the lack of geological or geophysical knowledge.
-
-
-
Using Potential Field Data For Petroleum Exploration Targeting, Amadeus Basin, Australia
Authors Mike Dentith and Duncan CowanThe Amadeus Basin, a large Proterozoic basin located in
central Australia, is the least explored onshore petroleumbearing
basin with proven reserves in Australia. The size and
remoteness of the Amadeus Basin makes ground exploration
expensive, but airborne gravity and magnetic surveys have
been shown to be capable of resolving intra-basin structures
in sufficient detail to allow prospective areas to be identified.
In the western part of the basin the Gillen Petroleum System
is considered most significant: This system has the important
characteristic that the source is stratigraphically higher than
the reservoir. Thin skinned deformation is expected at the
source level and above, with detachments at evaporitic
horizons, but deformation of the reservoir is expected to be
thick-skinned. This model can form the basis for predicting
potential field responses. The most prospective areas are
where (i) gravity suggests basement (and reservoir) is
shallow, (ii) magnetics maps fold-thrust complexes (structural
trap), (iii) these features occur adjacent to gravity lows,
indicative of significant thicknesses of basin fill (source at
depth and below reservoir). Faults at the margins of the
depocentre (mapped using magnetic data) provide a possible
migration path for the hydrocarbons.
-
-
-
Tectonic Framework And Basement Configuration Delineation Through The Integration Of Airborne Gravity Gradiometer, Magnetic And Seismic Data Over Chirete Area, Argentina
The tectonic framework and basement configuration are
delineated through the integrated interpretation of newly
acquired airborne gravity gradient and magnetic data with
the existing seismic data from the Chirete Block, onshore
northern Argentina. The study area is comprised of
approximately 3675 square km and covers approximately
35 km in an east-west direction and 105 km in north-south
direction. The main project objective was to map the
basement and associated major structural elements for
the oil-and-gas prospect selection. The basement related
faults/lineament maps were generated using several
enhancements of gravity gradient and magnetic data. 2D
seismic depth sections were used as initial constraints for
2.5D and 3D gravity and magnetic modeling. Well log
densities and velocities are also constrained in this
modeling process. The basement depth estimates are
computed from the total magnetic intensity profile data.
The Werner, Euler, and Peters half slope techniques are
used in basement depth computations as well as the
depths to the magnetic sources within the sedimentary
section. This interpretation was then refined by utilizing
the gravity gradient data and seismic data using 2.5 D
and 3D modeling. Several of these depths are related to
volcanic sources and were identified as igneous
provinces and probably related to the rift and post rift
periods. The basement depths show significant variation
from south to north and ranging approximately 4-13.5 km
below sea level. The enhanced potential field data
yielded basement faults and structural framework of the
area. The general basement faults trends are striking
mostly in ENE-WSW direction. Two major East-West
faults were identified as being the major bounding faults
of the Lomas de Olmedo rift. There exists a remarkable
correlation between these faults derived independently
from seismic reflection data and enhanced Airborne
Gravity Gradiometry data. A number of positive structural
features were identified with the associated faulting may
provide leads for oil & gas exploration.
-
-
-
A 2D Ray-Based Maximum Field Green’S Function Simulator
More LessGoing against last decade’s hegemonic trend to propagate
the field through the wave front reconstruction (Lambar ´e et
al., 1996), this method is based on the full tracing of each
ray at a time and the immediate application of information
available in Hamilton’s differential equations (1) and the first
variation (2) thereof. After that, all information of the ray is
discarded avoiding to spend great amount of RAM memory.
The algorithm is even capable to capture the maximum
field times and amplitudes aiming to increment the seismic
imaging quality.
Thus, like all others, it does not represent any structural
reformulation in the ray theory (Popov, 1977), (Popov and
P˘sen˘cik, 1978b), (Popov and P˘sen˘cik, 1978a), but rather the
details in the form of its implementation to obtain a higher
effectiveness for industrial purposes.
It is different from other similar methods also based on
the full ray tracing by and efficient precision control, by having
a criterion consistent with geometric optics and asymptotic
series.
The heart of the algorithm is the way to extrapolate amplitudes
from an ray point to an grid point.
It is robust and can be employed both in seismic imaging
and in velocity field inversion by travel time tomography.
The proposed algorithm involves the numerical asymptotic
solution of the extended (include the second derivative
of slowness respect to the ray parameter) differential equations
system, in rectangular coordinates, followed by the determination
Taylor’s series coefficients and the expansion
around one region close to each ray point.
Despite the need to solve a system of ODEs the algorithm
allows to avoid to propagate field in shadow zone, in
this case it can achieve a orders of magnitude faster than
Eikonal solvers like Schneider’s.
-
-
-
Seismic Data Quality Considerations - Seafloor Versus Towed Streamer Recording
Authors Chris Walker and Tony MathiesonSeabed data acquisition methods offer a number of inherent
advantages over towed streamer data. These advantages can
lead to improvements in shallow resolution, deep data
imaging, signal-to-noise ratio and spectral content, as well as
more effective 3D illumination and undershooting through
efficient wide-azimuth data acquisition.
-
-
-
Design, Acquisition And Processing Of Wide Azimuth 3D Land Seismic Data Utilizing Offset Vector Tiles
Authors Michael Fry, Eloy Martinez, Gastón Espinoza, Gonzalo Romero, Sissy Theisen and Mark WallaceIn 2008, a wide azimuth 3D land seismic survey was
acquired in the Percheles area south of Santa Cruz,
Bolivia. The survey was designed to properly populate
offset vector tiles (OVT), which are composed of common
mid points (CMP) with similar source-receiver offsets and
azimuths. An acquisition design program was used to
analyze OVT offset and azimuth distributions for the
proposed acquisition plan. The seismic acquisition
contractor successfully acquired the data with a minimal
difference between pre and post acquisition plots. The
data was then processed using an OVT pre-stack time
migration (PreSTM) followed by correction for azimuthal
velocity anisotropy using a proprietary surface-fitting
technique. The final results showed a significant
improvement in the seismic image quality when compared
to the conventional processing results.
-