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12th International Congress of the Brazilian Geophysical Society
- Conference date: 15 Aug 2011 - 18 Aug 2011
- Location: Rio de Janeiro, Brazil
- Published: 15 August 2011
61 - 80 of 465 results
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Parametrização de Campo Bidimensional de Velocidades Sísmicas Usando Ondaletas
Authors Helcio Moreira Perin and Wilson Mouzer FigueiróThe aim of this work is the representation (parameterization) of compressional seismic velocity field model of two dimensional geological structure by means of orthogonal functions known as wavelets more specifically, those so-called Haar wavelet. Some
comparative numerical experiments are performed among wavelet series with and without the use of scale function. The velocity field approximation, obtained by such technique, depends on the indices values used in the series, these have influence on the quality of the model representation. It is observed that the proposed parameterization offers a good accuracy for representation of the used field, however it is just advantageous the use of the scale function in the wavelet series with lower indices values.
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Pillargrid Conversion for Seismic Modeling
Authors Charles Cote and Michael Prange and Hugues DjikpessePillargrid and unstructured mesh models describe geometry and properties in different ways that are optimized for distinct types of simulation. For instance, finite-element simulators typically require unstructured, watertight and piecewise-polynomial descriptions of geometry and properties, while industry-standard fluid-flow simulators often use a pillargrid description of "connected bricks" in which the hexahedral cells may have voids between them when converted into a piecewise-linear description of the surface geometries, and the properties within each cell are constant. A conversion method is described to extract the geometry and properties from a pillargrid to build a watertight, piecewise linear model. The algorithm comprises partitioning the pillargrid into subvolumes within which properties are smoothly varying, building triangulated bounding surfaces for each of the subvolumes, and generating a mesh of property nodes for each of the subvolumes. Such conversion is useful for instance to simulate geophysical and geomechanical wave fields inside high-resolution reservoir models that are consistent with fluid-flow simulation models. The proposed algorithm has been validated on both synthetic and field examples.
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Eagle Ford Shale Prospecting with 3D Seismic and Microseismic Data
Authors Galen Treadgold and Bill McLain and Steven SinclairThe Eagle Ford Shale in South Texas (Figure 1) is one of the more exciting shale plays in the United States at the current time. Recently published reports of well tests describe gas well rates exceeding 17 mmcf/d and oil well rates commonly in excess of 1500 bopd with numerous 2000+ bopd tests. Acreage lease rates continue to climb as more positive results come from drilling within the trend. A key issue for the exploration companies is finding where to focus acreage acquisition and optimize drilling plans for optimal gas and oil recovery. Our paper will first consider the geologic context of the Eagle Ford and then look at the geologic drivers for locating a productive well. With improved understanding of local rock properties, focus shifts to geophysical techniques, in particular, comparing and contrasting the value of seismic and microseismic data in building a successful exploration plan.
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Regional and Local Anomaly Separation in the Almada Basin (Bahia State), Using Gravity Data from the Grace Satellite
Authors A.C. Gordon and C.F. Valeria and U. WebsterWe have detected in the Almada Basin, northeast Brasil, a high correlation between the regional gravity effects produced by the crust-mantle interface obtained from 2D forward modeling and the gravity data from the GRACE satellite. The altitude of the satellite mission of about 500 km works naturally as an upward continuation filter, allowing the use of this kind of data as an independent estimator of the regional component of the gravity field in the Almada Basin.
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Wave Form Inversion Migration (WFIM) Method
We represent a 3D time variant of the Wave Form Inversion Migration (WFIM) method. The method is based on the exact solution of an inverse problem for the wave equation considered in the Born approximation. The formulae obtained are tested on the synthetic and real field data.
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4D Monitoring: Example of 4D Interpretation in Lower Flanks Systems, Dália - Angola
More LessSome field of Lower Congo Basin deep offshore are composed of heterogeneous turbidites channels of Miocene age located in Angola at water depth that range between 700 – 1500 meters. The Dalia field, located in Block 17, is characterized by four main sedimentary complexes, called Upper Main Channel, Lower Main Channel, Lower Flanks and Camelia. This area is characterized by high resolution seismic data (10 m) that is used for fine reservoir characterization and monitoring.
After one year and half of production, a first 4D seismic survey was acquired. This 4D seismic monitor bring more accurately interpretation on facies distribution and a better understanding of reservoir communications. The 4D effects seen on Dalia are large since time shifts associated to production were used to interpret 4D signals and upscale them inside the reservoir model.
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Aplicação de Gpr Para Avaliação de Via Permanente em Estrada Férrea no Brasil
Authors Debora S. Carvalho and Roberto OkabeThis paper presents the application of GPR on a Brazilian railway mapping, for evaluation and management of the railroad. GPR antennas were installed in a vehicle used in daily inspections of the track. The qualitative parameters mapped were moisture, contamination and thickness of ballast and intermediate layers and the results were validated with the excavation of a trench at a selected spot on the road, categorized as a priority number one for maintenance. The use of GPR is presented as a tool for decision making in the management process of railway maintenance, through the fast and continuous detection and identification of formations of endemic degradation’s processes on the track railway, even incipient and not visible from the surface, with no traffic interruption, and ranking and prioritization in a rational manner and using a systematic way for the problems according to the seriousness of its occurrences.
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Preliminary Study of Atmospheric Methane Emissions in a Lentic Systems
More LessThe decaying organic matter releases, among other gases, methane (CH4), composed of semi-opaque to infrared radiation has an important role in the greenhouse. The knowledge of how the lentic systems emit gases from the anaerobic decomposition of non
lignified material, primarily composed of herbaceous plants and areas of peeling macrophytes has been highlighted in several studies. This paper presents the results of a preliminary test to work on the emission of greenhouse gases in reservoirs on the methane produced in one of the ponds for water supply INPE - National Institute for Space Research, Cachoeira Paulista / SP. To determine the flow of methane was carried out a campaign in December 2010 and the gas flow determined using the static chamber technique. The environmental parameters measured were the temperature of air and water, pH, redox potential, conductivity, dissolved oxygen and total dissolved solids. The overall average of valid flows was 59.1 ± 91.98 mgCH4/m2/dia and analysis of
the environmental parameters indicates that the methane concentration was high in environments with a pH lower than 4 and lower levels of dissolved oxygen in water.
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Ocean Bottom Node Processing in Deep Offshore Environment for Reservoir Monitoring
More LessTo complement a 3D High Resolution streamer survey, Total E&P operated in 2008-2009 a large 3D Ocean Bottom Node (OBN) acquisition to monitor a hydrocarbon reservoir in deep offshore Angola (Ceragioli et al, 2010). Mirror node imaging has already proved to be more appropriate for 4D imaging and reconciliation with streamer data. However positioning and timing issues as well as azimuthal coherent stacking of data need to be precisely tackled for better preserving their high frequency content. In this paper we show the importance of estimating accurate time statics for nodes deployed in a deep offshore environment. Secondly we demonstrate that the concept of Offset Vector Binning using hexagonal tiles is applicable to this node data acquisition. Mirrored data migration in Common Offset Vector domain provides Common Image Gathers with preserved offset and azimuthal information, which enables azimuthal residual velocity analysis for a better stacking of information at all offsets and azimuths.
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Monitoramento Temporal De Contaminação Por Chorume Usando Métodos Geoelétricos
Authors José Ricardo Melges Bortolin and Walter Malagutti FilhoThis work describes a temporal monitoring of the contamination plume from the controlled landfill of Rio Claro (SP), through the resistivity method, comparing 2D Electrical Profiling dipole - dipole results, carried out in 1999 and 2008. The leachates produced on the landfill diminish the electrical resistivity of the natural ambient, characterizing the contamination. Thus, zones of low resistivity, with values smaller or same a 50 ohm.m, had been associates to the contamination for landfill wastewater. The joint interpretation of the sections of apparent resistivity allowed to identify alterations of the dimensions of the contamination plume in elapsing of the years. Governed by the main and secondary flows, the contamination plume advanced in direction to the limits west and soul of controlled landfill. Complementarily, Vertical Electrical Soundings had allowed verifying the depth and the direction of the underground water flow, and to characterize geo-electrically the lithology on which is seated the controlled landfill: predominantly sandy and silty sediments.
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Multibeam Echosounders Capability to Detect Fluid-Mud Layers in the Water Column
More LessDuring extreme rain events occurred in Itajaí, SC, Brazil in November 2008, the high water flow in the Itajaí-Açú River caused intense sediment transportation, which destroyed harbor facilities. Several objects, as ship containers, were carried through the channel, forcing maritime authorities to close the harbor in order to guarantee the navigation security. An expeditionary bathymetric survey has been requested, with the main purpose to quickly map hazards and depth variations within the main navigation channel. The Brazilian Navy Directorate of Hydrography and Navigation (DHN) provided a small team, which has been moved from Laguna-SC to Itajaí-SC, to perform a bathymetric survey using an EM3000 multibeam echosounder. Also, a small boat, termed LB Betelgeuse, had to be moved from Florianópolis-SC to Itajaí-SC. In 2 days, a total of 19 Km distance of channel has been surveyed, from its entrance at seashore until inside the Itajaí-Açú River. A full-coverage seafloor map was built enabling the harbor authorities to safely proceed with further operations in the area. During this survey, some intriguing echo-character features were detected close to the channel entrance, which has been investigated by divers, proving to be correlated with the presence of fluid-mud sediments. This echosounder has no water column imagery available, so original depth telegram was used. Water column low-density features were unexpected to be detected by the survey team, as they should be filtered out by the bottom tracking algorithms used to calculate the depths. But, this echosounder model demonstrated to be very useful to reliably detect the fluid-mud layers in the water column. This work presents the fluid-mud echo-character features detected by a multibeam echosounder, so it can be better recognized in the future surveys.
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Fibre Optic Permanent Reservoir Monitoring Breakthrough
Authors Hilde Nakstad and Jan Langhammer and Morten EriksrudThe largest ever offshore fibre optic permanent reservoir monitoring installation was successfully finished in October 2010 at a producing oil field in the North Sea. All the channels are working and recording seismic traces (i.e. channel status is 100%), which is a great achievement for such large seismic spread in the marine environment. The decision to install an optical sensing system was mainly due to the design life expectancy of the fibre optic system. The installation of the seismic system is expected to contribute to enhancing the remaining production, which will extend the life of the field and ensure optimal location of future production wells.
We advocate optical sensing technology as an important part of the toolbox for maximizing field production in a cost efficient way. The “optical oil field” may represent the next significant step in technology for reservoir monitoring and improved hydrocarbon recovery.
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4D Gravity Modeling: Integrating Seismic Data With Highly Constrained Gravity Inversions for Effective Reservoir Monitoring
Authors Richard A. Krahenbuhl and Yaoguo LiWe demonstrate a robust workflow for time-lapse gravity modeling in reservoir sequestration/production monitoring applications. This systematic approach outlines a reliable methodology to understanding the value and limitations of 4D gravity at a particular site, for both pre-acquisition decision making, and as a guide for post-data acquisition interpretation. To demonstrate, we present a multifaceted feasibility study for monitoring CO2 injection into a reservoir at various injection times using 4D micro-gravity method. The simulations are performed for a currently active CO2-EOR site, the Louisiana Delhi Field in the United State. We construct an accurate representation of the field directly from current seismic data, followed by application of binary inversion technology adapted to the time-lapse gravity problem and tailored to the specific site. Finally, we illustrate a method of resolution analysis to demonstrate the decreased recoverability of fluid movement at the site in the presence of varying data noise.
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Observações de Ondas de Gravidade de Méedia Escala na Região Equatorial do Brasil
Authors I. Paulino, H. Takahashi, A. F. Medeiros, R. A. Buriti, C. M. Wrasse and D. GobbiUsing images of the OHNIR airglow emission over S˜ao Jo˜ao do Cariri (7:4oS; 36:5oW) during the second Spread-F Experiment (SpreadFEx), from September to November 2009, 26 medium-scale gravity waves (MSGW) were observed, and their observed parameters were estimated. Simultaneous measurements of the mesospheric winds and temperature [obtained by a meteor radar and an OH(6,2) photometer, respectively] were used to calculate the intrinsic parameters of these waves. The characteristics of these waves, in general, are similar to it was observed during the first campaign. Most waves presented wavelengths between 50 and 150 km, periods from 20 to 100 min, and phase between 20 m/s and 80 m/s, propagating eastward. The intrinsic parameters revel that the wind may reduce the phase speeds. Most waves had vertical wavelength smaller than 20 km. Furthermore, two MSGWs presented an unusual intrinsic phase speed, i.e, they were faster than 85 m/s. These two waves have a potential to reach altitudes higher than 150 km, and, consequently, they may be more powerful in seeding equatorial spread F.
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A General Framework for 3D Interpretation of Magnetic Data Affected by Remanence and Self-Demagnetization
Authors Yaoguo Li and Richard A. Krahenbuhl3D inversion of magnetic data has been successfully used in many aspects of geophysical exploration over the last decade. In a majority of cases, one can assume that the direction of magnetization is the same as the current inducing field direction, and generalized magnetic inversions requiring this information typically perform well in recovering susceptibility distributions. However, the sometimes unknown direction of total magnetization, caused either by the presence of high magnetic susceptibility or remanent magnetization, has limited the use of this technique. We present a general framework for solving these problems by examining the three classes of magnetization and formulate a suite of methods of practical utility in any magnetic environment. The first class performs inversion for the case of induced magnetization with weak magnetic susceptibility, where the magnetization direction is the same as the Earth’s inducing field. The second class focuses on the estimation of total magnetization direction when the field is not purely induced, and then incorporates the resultant direction into an inversion algorithm that assumes a known direction. The final class focuses on the direct inversion of the amplitude of magnetic anomaly vector, a quantity that depends weakly upon magnetization direction. With these new developments, we show that it is now feasible to invert any magnetic exploration data set, regardless of whether it is purely induced, or affected by strong remanence or self-demagnetization.
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Prospecção de Água Subterrânea no Município de Piçarra–Pa Usando Vlf e Resistividade
Authors Gilvana Bezerra de Sousa and José Gouvêa LuizThis research was carried through in the city of Piçarra, Located in the southwest of the state of Pará. The study was done to map lineaments associated to fractures in basement rocks and to investigate the nature of the subsoil through geophysics, using the electromagnetic VLF and resistivity methods . The integrated analysis of the geophysical data allowed to recognize in the area two hydrogeologic dominions: Fractures zones in basement and sediments. The results guided the location of wells for ground-water exploitation.
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Reducing Exploration Cycle Time in the Campos Basin: Integrating Seismic Data Acquisition and Processing
Authors Kerly Sanchez and Alex Cooke and Franck LeDiagonThis paper presents the integrated approach to seismic data acquisition and processing currently being used in the Campos basin. An advanced onboard data processing workflow is described that was designed to provide high-quality data directly from the seismic vessel, enabling earlier reservoir and exploration decisions.
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Large-Scale TTI Imaging in Areas of Limited to No Well Control
Authors Olga Zdraveva, Michael Cogan, Saeeda Hydal and Rafik DerbalaDepth imaging with anisotropic models has been shown to deliver more geologically plausible and accurate images. Derivation of accurate parameters describing anisotropic properties of the medium requires incorporating well information. However, there are vast exploration areas around the world with very limited to no well control that do require high-quality anisotropic imaging to allow adequate interpretation of deeper targets. We use a simple workflow that allows building of tilted transversely isotropic (TTI) models in areas of very limited well control. We present a case study from the Kwanza basin offshore Angola where we built a detailed TTI model over an area of more than 8000 km2. We incorporate general knowledge of the area and analysis of data anellepticity in the process, derive Thomsen’s δ in wells from a neighboring area, and use spatially variable ε and δ fields, honoring the variation of the anellipticity and the geometry of the provided horizon interpretation. The results are compared against images produced with both an isotropic model and a much simpler regional TTI model. The results illustrate that accounting for TTI in complex media is a prerequisite for producing geologically plausible and interpretable images, and that adding interpretation driven complexity in the TTI models could further improve the interpretability of pre-salt targets.
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High Resolution Imaging for Subtle Geological Features in the Llanos Basin
Authors Michael Smith and Paul Cunningham and David BehrmanWe demonstrate in a seismic processing project from the Llanos basin in Colombia that increasing bandwidth prior to migration can improve the spatial (lateral and vertical) resolution and the subsequent velocity analysis can produce a more detailed velocity profile which in turn improves image quality. The increase in bandwidth prior to migration reduces both vertical and lateral wavelet widths and, thus, increases spatial resolution. The improved spatial resolution in turn permits a more detailed velocity field to be defined both laterally and vertically. This approach, bandwidth expansion prior to migration, can be applied to both time and depth migration flows.
We apply the high resolution imaging technique to the relatively thin Oligocene to Early Miocene Carbonera sandstones from the Llanos basin. Traps are typically three-way structural closures bounded by faults with relatively small throws. Using the high-resolution imaging, the thin sands, their lateral pinchouts and the fault locations can be more accurately mapped reducing exploration risk.
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Estimativas da Umidade de Solos Com Gpr: Revisão e Resultados
Authors Marcelo Jorge Luz Mesquita and José Gouvêa LuizA summary on the application of GPR as a tool to estimate soil humidity is presented. Several relations that allow estimating humidity from dielectric constant obtained from the GPR wave velocity are discussed, as well as the methodology for the GPR data acquisition. Results from experiments are also presented to show the viability and limitations of this GPR application.
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