Programa de Pós-Graduação em Geofísica - CPGF/IG

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2355

O Programa de Pós-Graduação em Geofísica da UFPA (CPGF) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA). Foi o segundo no Brasil a formar recursos humanos em Geofísica em nível de pós-graduação stricto sensu. Criado em 1972, funcionou até 1992 junto com os Cursos de Pós-Graduação em Geoquímica e Geologia.

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Agora exibindo 1 - 20 de 31

Acesso aberto (Open Access)
Uma análise de métodos de supressão de múltiplas de superfície livre aplicados a um dado real
(Universidade Federal do Pará, 2011-10-14) OLIVEIRA, Andrei Gomes de; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
The seismic record in 2D linear events are common features in the seismograms. These events are overlap with interesting reflections (early reflections) complicating the stages of seismic processing and identification of possible subsurface geological horizons. It possible highlight multiple surface that distinguished from others by a low frequency, high amplitude and low velocity of propagation. The identification and removal of multiple reflflections in seismic data is a real step of great importance in seismic processing, because the attenuation can prevent many of these errors in the interpretation of geological images seismic. This study is the determination of a processing flow for multiple attenuation free surface. Methods of elimination of multiple surface (SRME, Radon filtering, predictive deconvolution domain τ - p and fk filltering) applied to a real data 2D were used in different combinations. These are analyzed and presented the results are the best combinations.
Acesso aberto (Open Access)
Análise de um esquema de inversão para estimativa de anisotropia local a partir de dados de VSP
(Universidade Federal do Pará, 2012-05-18) BARRETO, Adriano César Rodrigues; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
Inversion scheme for the determination of arbitrary in a vicinity of a receiver situated inside a borehole from the data obtained during a multi-offset multi-azimuthal VSP experiment is studied. The data consist of vertical components of the slowness vector and all components of the polarization vector of P waves direct and reected. The inversion is made from a first order approximation around an reference arbitrary isotropic medium, that does the relation between the data of slowness and polarization of P waves parameters and the weakly anisotropic medium (WA parameters). This inversion scheme applies to arbitrary anisotropy medium, provided that the anisotropy is weak and independent of downhole type (vertical, horizontal or inclined). The results show that reversing is sensitive to the number and orientation of the proles of sources that are distributed on the surface. An analysis of the design of an experiment and discussion about the choice of parameters of the reference isotropic medium are presented. Within the realistic assumptions about the level of noise is possible to estimate the phase velocity for a limited angular aperture around the well.
Acesso aberto (Open Access)
Aplicação de modelos de substituição de fluido em rochas sedimentares oriundas do nordeste brasileiro
(Universidade Federal do Pará, 2015-06-06) TROVÃO, Ana Alzira Fayal; FIGUEIREDO, José Jadsom Sampaio de; http://lattes.cnpq.br/1610827269025210
Carbonates reservoirs corresponds on about 50% of the hydrocarbon reservoir in the planet . This type of lithology presents different forms of heterogeneity, which are the main causes of errors in its characterization. This misunderstanding, can induces erroneous estimative elastic modules of rocks in saturated state. The main goal of this work is to perform a comparative analysis of fluid substitution models in unconventional carbonate reservoir. Specifically, fluid substitution processes analyzed in outcrops from Brazilian Northeast, under controlled laboratory conditions (temperature, pressure and degree of saturation) and under perspectives of the petrophysical and ultrasonic features by conventional theories (Gassmann, Biot) and unconventional (Brown and Korringa, Muller and Sahay). In this research, we analyzed six samples of carbonate rock and one sample of sandstone rock. The input data our analysis were: permeability, porosity, rock and grain density, elastic measures of compressional (Vp) and shear (Vs1 and Vs2) velocities. The measure of velocities was performed in cases of 100% gas (dry rock) and then replaced by water (100 % saturated by water). Our results show, that predictions performed by conventional fluid substitution models best fit in experimental measurements of sample considered homogenous. However, predictions performed by unconventional models (e. g., Muller and Sahay) shown best fit with most carbonates types, including tufa and limestanes.
Acesso aberto (Open Access)
Aplicação de Well-Tie no imageamento de uma área da bacia Tumbes-progresso
(Universidade Federal do Pará, 2014-08-29) CHAGAS, Tiago Paulo Câncio das; SILVA, Carolina Barros da; http://lattes.cnpq.br/5306784916926352; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
Geological areas with large lateral velocity variations, such as in areas with faults and salt domes are complex areas, in general, seismic imaging time is limited. In these cases, the seismic imaging depth can provide better results. However, a velocity model is needed in depth with precision, which is not an easy task. An alternative to estimate the depth velocity model is provided by Well-tie technique. With the calibration of the synthetic trace data obtained from wells, seismic section with the depth map of velocity can be obtained through the time-depth curve. In this study, we used the Well-Tie to improve the model of RMS velocity obtained from the processing of seismic data. The updated velocity model was converted to depth and used to generate an in depth migrated seismic image of a region of Tumbes Basin-Progress.
Acesso aberto (Open Access)
Aproximações não-hiperbólicas do tempo de trânsito utilizando aproximantes de Padé
(Universidade Federal do Pará, 2017-07-03) NEVES, Rodolfo André Cardoso; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
Traveltime approximation is a fundamental tool of the stack and migration steps in seismic data processing. To increase the accuracy of these approximations, we propose new traveltime approximations based on Padé approximants, to CMP and CRS gathers. Hyperbolic approximations such as normal moveout (NMO) and comom reflection surface (CRS) are taylor series approximations of second order of the reflection traveltime. Padé approximants appear as an alternative to Taylor series, because they converge quickly to the desired function, and they have a major radius of convergence improving approximations acuracy. They can be obtained through the proper Taylor serie of the approximated function. This new approximation is obtained from the [2/2] Padé approximation of the generalized moveout equation; and from [2/2] Padé approximation of the Taylor series expansions of fourth order of the CRS surface. The acuracy of Padé approximation is superior when compared with other convencional approximations: normal moveout, shifted hyperbola and Transversal isotropic medium with vertical symetry axis (VTI). CMP gather Padé approximations depend just only one more parameter than normal moveout approximation and they keep the acuracy for long offsets. CRS gather non hyperbolic approximations, non hyperbolic CRS, fourth order CRS and Padé CRS, have major acuracy than hyperbolic CRS, increasing the convergence of the approximation for offset and CMP domain. The quadratic approximation of fourth order CRS is superior than non hyperbolic CRS approximation, producing less error in least square CRS parameter inversion.
Acesso aberto (Open Access)
Caracterização de hidratos de gás a partir de dados geofísicos da região da Bacia Tumbes-Progresso (Peru)
(Universidade Federal do Pará, 2014-02-25) TEJADA SOTO, Zoraida Roxana; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
Gas hydrate is known as a potential source of hydrocarbon energy. However, the detection of exploitation of this resource is still inexpressive. This is due to two factors: the diculty of detecting pro table areas of gas hydrates and due to the high risk involved in exploration. In this study, an analysis is presented to detect possible areas of gas hydrate ocurrence in a region of Tumbes-Progresso Basin, using geophysical data: magnetic, gravity, seismic and borehole (well data). It presents three approaches to demarcate the possible zones of hydrate: First, magnetic and gravity anomalies analyzed with respect to the geology and the study area that was chosen. It was subsequently made a seismic imaging the region of interest and the gas hydrates has been identied based on the presence identication of BSR (Bottom Simulating Refletor), This reflector correspond to a limit between gas hydrate and free gas zone. BSR potential was applied the AVO analysis (Amplitude Versus Oset). Finally, in the third approach, well data are evaluated, calculating the porosity and saturation of the rock in the gas hydrate stability zone. According to the analysis presented, It was veried the occurrence of gas hydrate in the study area.
Acesso aberto (Open Access)
Conversão tempo-profundidade de seções sísmicas empilhadas por raio imagem e raio normal
(Universidade Federal do Pará, 2014-06-24) REZENDE, Diogo Pena; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
In general, the oil industry makes the time-to-depth conversion of seismic data by the image ray tracing method. This method takes time into the depth, point to point, the amplitudes of the time migrated seismic section. For each point of the migrated time section, it is necessary to trace a ray perpendicular to the surface. After this, the amplitude of the migrated point of the section takes place in depth. The seismic migration method pre- or post-stack consists of placing seismic events in the correct positions in time or depth sections. Seismic depth sections provide an image near of the subsurface, in order to facilitate the identification of possible oil accumulating geological structures. The conversion of sections from the time to the depth domain is an intermediate step in the construction of seismic images in depth. This work developed and tested a method of converting time to depth the zero-offset seismic sections. In this case, the construction of sections in depth uses normal ray tracing method. The proposed method makes use of the (slowness versus time of intersection) transformation on the zero-offset section. Each point in the domain provides initial conditions for the normal ray tracing: a start position of the initial rays and initial angles formed with the normal to the surface, i.e., the slowness initial parameter. Unlike ray image method, several rays use the same travel time and the same initial position, defining an isochronous curve. The amplitude of each point in the zero-offset section takes place to depth from the distribution of values along each isochronous curve in depth. The image ray based time-to-depth conversion has good recovery of the depths of reflectors as well as low computational cost, since it is necessary only one ray to convert each point of the section in time. However, the reflector continuity may be damaged in case of sharpened curvature. In turn, by normal ray the time-to-depth conversion correctly approximate the depth of the reflectors, since the same point in time assigns several times in depth. However, it has a higher computational cost, because it is necessary many rays to convert one point in time.
Acesso aberto (Open Access)
Determinação de modelo de velocidades para a migração em profundidade de dados sísmicos 2-D da Bacia do Jequitinhonha
(Universidade Federal do Pará, 2013-12-13) OLIVEIRA, Lelis Araújo de; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
The migration time domain is quite employed by the oil industry for its low computational requirements, however in areas where the velocity field has great lateral variation as result of the environment is complex subsurface structures, such as faults, salt domes, etc.., this technique becomes inefficient in the characterization of geological features. Although the computational cost is high, migration in the field of depth, proves more effective than time migration to deal with these structures. However for a section in depth there is a need for a velocity model in depth with some degree of precision. In this paper, two methodologies for time to depth conversion for obtaining the velocity model in depth to two real 2-D marine lines Jequitinhonha Basin are applied. The accuracy of the models generated were analyzed from migrated seismic sections obtained by means of these velocityes.
Acesso aberto (Open Access)
Estimativa de parâmetros em meios VTI usando aproximações de sobretempo não hiperbólicas
(Universidade Federal do Pará, 2015-09-30) PEREIRA, Rubenvaldo Monteiro; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
Transversely isotropic (TI) media is a more realistic model for processing seismic data, for example, fractured media with preferred fracture direction, or composite by periodic thin layers. In particular, TI media with vertical symmetry axis (VTI) are widely used as models for P-wave propagation in shales, abundant rock in hydrocarbon reservoirs. However, the P-wave propagation in homogeneous media VTI have as their main characteristics, depend on four parameters of rigidity and also to possess: complicated algebraically phase velocity equation, difficult group velocity equation to explain and moveout equation nonhyperbolic. Therefore, several authors have presented parameterization and obtained approximations to these equations depending on three parameters only. Among these, the moveout approximations have been widely used in inverse methods to estimate lithological parameters in homogeneous media VTI. Such methods have generally been successful in estimated stacking velocity vn and the anellipticity parameter η, since these are the only ones required for generating initial models for the steps of seismic processing in the time domain. One of the most used methods for estimating parameters is the basedsemblance velocity analysis, though, because this method is limited to sections with small offset-depth ratio, adaptations for anisotropic media, considering nonhyperbolic moveout approximatios are required. In this paper, based on anelliptical approximation shifted hyperbola, anelliptical rational approximations are presented for: phase velocity, group velocity and moveout nonhyperbolic in homogeneous VTI horizontally layered media. The validity of these approximations is made by calculating their relative errors by comparing with other known approximations in the literature. To semblance-based velocity analysis is performed to measure the accuracy of the rational moveout approximations to estimate parameters in VTI media. The results demonstrate the great potential of rational approximations in inverse problems. In order to adapt to VTI media, we modify two coherence measurements by semblance which are sensitive to amplitude and phase variations. The accuracy and robustness of the adapted coherence measurements are validated by estimation of in anisotropic parameters in VTI media.
Acesso aberto (Open Access)
Experimental verification of Hudson and Eshelby-Chen’s effective crack theory
(Universidade Federal do Pará, 2015-12-04) HENRIQUES, Jéssica Pena; FIGUEIREDO, José Jadsom Sampaio de; http://lattes.cnpq.br/1610827269025210
Physical modeling of cracked / fractured media in downscaled laboratory experiments has served as a great alternative for understanding the anisotropic media behavior. In this work, it was performed ultrasonic measurements on samples with low crack densities and different aspect ratios. The main goal was to investigate the experimental behavior of elastic parameters, such as: waves velocities and Thomsen parameters ε and 𝛾 and elastic stiffness coefficients for transverse isotropic media. Comparison of the results with the predictions made by the effective models of Hudson (1981) and Eshelby-Cheng (1993), it was also investigated in this work. Twelve samples were prepared with two types of cracks density, 5 and 8%. The cracks that have three different aspect ratios (0.133, 0.1778 and 0.2667) were formed by rubber inclusions in a homogeneous isotropic matrix resin. Moreover, an isotropic matrix sample was constructed by only epoxy resin. Among all samples, six (three for each density) have only one aspect ratio type (samples with single crack), while another six (three for each density) have three types of different aspect ratio (mixed samples). Among the predictions of the models, the Eshelby-Cheng (1993) shows a better fit in relation to the experimental results for samples with single crack (for the two densities of inclusions). However, none of the models predicts accurately with minimal tendency for the mixed samples.
Acesso aberto (Open Access)
Implementações alternativas de tomografia do tempo de trânsito utilizando a equação da onda
(Universidade Federal do Pará, 2014-04-23) CARDOSO FILHO, Josafat Lopes; COSTA, Jessé Carvalho; http://lattes.cnpq.br/7294174204296739
Wave equation tomography is a robust methodology for velocity analysis when strong velocity variations occurs. This approach has been successfully applied for reservoir monitoring and characterization using crosswell data. The choice of the objective functions, preconditioners and regularizing functionals controls the robustness, eciency and the quality of the velocity reconstruction. This dissertation investigates each of these design parameters and its consequences for the performance of the wave equation tomography using synthetic crosswell data generated from smoothly and strongly heterogeneous velocity models. Two proposals for the objective functions are used in this work; the first is sensitive to phase dierences and the other is proposal to be less sensitive to the source pulse. Both do not require velocity picking performed well in the numerical experiments. A preconditioning strategy adapted from the imaging processing literature produced a noticiable improvement the convergence rate of the algorithm by eliminating artifacts caused by limited aperture, random noise and artifacts produced by sources and receivers. A regularizing functional penalizing deviations from velocity information available near the wells additionally contributes to recover a velocity tomogram with higher resolution and consistent with the synthetic model. Wave equation tomography is a robust methodology for velocity analysis when strong velocity variations occurs.
Acesso aberto (Open Access)
Interpolação de eventos de reflexão em traços sísmicos de dados pré-empilhamento usando aproximação de tempo de trânsito SRC-AF
(Universidade Federal do Pará, 2014-06-24) FERNANDES, Alexandre Sodré; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
The seismic method is a well known technique for revealing details of the geological subsurface structures because the seismic data are processed and produce seismic sections, which are images of subsurface structures. The quality of the recorded seismic data depends on factors such as the complexity of the subsurface, level of noise, surface topography of acquisition, heterogeneities in the mantle of weathering, among others. Irregular acquisition, short offsets, low coverage in common points in depth lead to a low quality imaging in subsurface and low resolution in seismic sections. In common reflection surface imaging, the hyperbolic approximation of traveltimes for paraxial rays in the vicinity of a central ray reflected with finite source-receiver offset, function of five kinematic attributes of the wave field, represent better the time field reflection compared to conventional methods. The Common Reflection Surface for Common Offset (CRS-CO) approaches reflection events within the vicinity of the trace with a fixed offset that we want to interpolate, adding correlated events, where the output is defined as the weighted average of the amplitudes along the traveltime approximation SRC-AF, assigning the result to its trace to all points of an common offset section. The specific objective of this work is to model the regularization of temporal sections filling areas lacking seismic data, increasing the signal to noise ratio by interpolation of reflection events in seismic traces based on the approximation of traveltime for Common Reflection Surface for Common Offset (CRS-CO). The algorithm was applied to the seismic acquisition settings Common Source, Common Offset and Common Mid Point for a set of 2D synthetic data, modeled by ray tracing.
Acesso aberto (Open Access)
Joining diffraction filter and residual diffraction moveout to constructo a velocity model in the depth and time domains: application to a Viking Graben data set
(Universidade Federal do Pará, 2014-08-14) COLLAZOS GONZALEZ, Jaime Andres; FIGUEIREDO, José Jadsom Sampaio de; http://lattes.cnpq.br/1610827269025210
Diffracted seismic waves are generated by unsmooth structures in the subsurface with a size on the order of seismic wavelengths. Because the incident wave field can be significantly affected by these discontinuities, many important properties of the seismic events can be used to improve the velocity model building. In this thesis, we propose a practical approach to construct velocity models in the time and depth domains using diffractions. This methodology applies the plane wave destruction (PWD) filter jointly with the residual diffraction moveout (RDM) method to construct velocity models in time and depth domains. Our method does not depend on any requirements except for identifiable diffractions filtered from reflection events and an arbitrary initial velocity model as input. The post-stack migrated images (in the time and depth domains) are compared with the mi- grated images derived from conventional seismic processing steps. In both cases, we used post-stack Kirchhoff Migration. Beyond the to the need to identify and select the diffraction events in the post-stack migrated sections in the depth domain, the method has a very low computational cost of processing time. To reach an acceptable velocity model was less compared with conventional processing. The applicability of our methodology was verified using a real Viking Graben seismic dataset.
Acesso aberto (Open Access)
Migração Kirchhoff paraxial pré-empilhamento em profundidade com amplitudes verdadeiras
(Universidade Federal do Pará, 2015-08-31) MOREIRA, Marcio Fernando de Andrade; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
The seismic depth migration is one of the most important steps in the exploration of geologically complex process areas of the oil industry interest. To obtain a more realistic image of the structure, it needs is a great settings recovery process of the reflectors in the subsurface and efficient determination of reflection coefficients to characterize the oil and gas reservoirs. One of the techniques used to obtain the seismic image is the Kirchhoff migration method which can be greatly enhanced by appropriate weights, which when applied to amplitudes during the stacking diffraction provides an estimate of the reflection coefficients. In this work, we used the 2-D paraxial ray prestack Kirchhoff depth migration method. In the calculation step traveltimes makes use of second-order paraxial approximation, by which one can get a good approximation of the traveltimes in the mesh migration. The weights used during migration were calculated using the equations of dynamic radius and the extrapolation to the points of the mesh migration. Compared with the conventional Kirchhoff method, the results were quite satisfactory as regards the increase in image resolution of the reflectors as well as in obtaining the reflection coefficients. The efficiency of the proposed technique was tested on synthetic data type anticlinal geological structure and seismic data Marmousi.
Acesso aberto (Open Access)
Migração Kirchhoff pré-empilhamento em profundidade usando aproximação paraxial do tempo de trânsito
(Universidade Federal do Pará, 2014-08-28) CUNHA, Antonio Rizimar de Andrade; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
In order to get an accurate image of the subsurface we need efficient techniques for evaluating the wave field. In literature we find several geophysical methods based on the numerical solution of the seismic wave equation. Among the various techniques of seismic imaging, Kirchhoff prestack depth migration remains widely used because of its flexibility in processing data through several geometries of acquisition, and its practicality in solving problems related to imaging. Assuming this view, we seek to create more efficient alternatives for the accurate calculation of the parameters involved in migration processes. We consider the efficient calculation of the traveltimes as a critical factor, focusing on the fundamental amplitude in their respective points in depth using the Paraxial Ray Theory through the Runge-Kutta method of fourth order. The paraxial extrapolation of the traveltimes belongs to the class of dynamic ray tracing, where it is possible to determine information in complex geological environment on regions influenced by shadow zones. The application of this technical demands amounts previously arranged in a central reference beam that is obtained from the kinematic ray tracing, furthermore a macro velocity model of the medium is necessary for the traveltimes calculation. For comparison, we consider two different ways to calculate the traveltimes tables: The first was performed by routine RAYT2D from SEISMIC UNIX (SU) package, which is considered a robust method of evaluation; the second is based on Paraxial05 method. The depth migration required the seismic data input and the traveltimes. The images were obtained from an algorithm written in SHELL and a third image is obtained through the difference between the two initial results.
Acesso aberto (Open Access)
Modelagem sísmica acústica e elástica por diferenças finitas e imageamento do depósito de minério de ferro N4WS no estado do Pará
(Universidade Federal do Pará, 2017-07-03) HOLANDA, Rafael Mansano; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
The finite difference method consists in the numerical resolution of differential equations and one of its applications is a solution of the wave equations or elastodynamics, by replacing the partial derivatives in space and time by their approximations of finite differences. The present work consisted in the accomplishment of the seismic modeling using the method of the finite differences, to acoustic and elastic case. Then, we performed the seismic imaging, to acoustic case, in a model that simulates an iron ore deposit area of N4WS, located in the mineral province of Carajás, in the state of Pará. We found a heterogeneous, isotropic and bidimensional velocity model to acoustic and elastic cases. In order to generate the synthetic seismogram, we executed the program FDSKALAR, to acoustic case, and SOFI2D, to elastic case, using fourth-order approximation of the equation of acoustic and elastic wave in space and time. For a validation of the programs of finite differences and aid in the interpretation of the events, we compared the results with the travel times obtained by the ray theory. After the seismic modeling, we accomplished the processing of the data generate, using the open-source software package Seismic Unix, to obtain an image of the reflector contained in the mineral model. In this way, we searched a better understanding and control on the problems of seismic modeling and imaging, contributing to an interpretation of seismic data and understanding about a seismic wave propagation in environments where there are significant heterogeneities. In addition, we sought to demonstrate the application of seismic methods in the study and delimitation of mineral bodies.
Acesso aberto (Open Access)
NIP-tomografia usando método CRS e dados sísmicos marinhos
(Universidade Federal do Pará, 2013) AFONSO, João Batista Rodrigues; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This work consisted on the application of techniques for processing, inversion and imaging of the Marmousoft synthetic data, and of the Jequitinhonha real data obtained on the eastern Atlantic continental shelf of the State of Bahia. The convencional NMO and CRS stack methods, and NIP-tomographic inversion were applied to the mentioned data. The NMO stack served to produce RMS and interval velocity distribution maps on the semblance domain. The CRS stack of both data we used for picking of re ection events to obtain the wave eld parameters that served to constrain the model as input for the NIP-tomographic inversion. The inversion characterizes as resulting in a smooth velocity model. Kirchhoff depth migration was used for verifying the obtained velocity models. We critically analyzed the applied techniques, and compared the CRS and the NMO stacks. The evolution of the visual quality of the obtained CRS and NMO sections were analyzed as measured by event continuity trace-by-trace and the signal/noise ratio. The di erences and improvements on the velocity model obtained by NIP-tomographic were also analyzed. The Kirchhoff prestack depth migration was applied aiming at geological interpretations, and to point out for better conditions of processing and imaging.
Acesso aberto (Open Access)
Um novo algorítimo para implementação do método de empilhamento SRC 3-D e modelagem sísmica da Bacia do Amazonas
(Universidade Federal do Pará, 2006-05-23) LIMA, Charles Cristiano de Assis; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
The Common Reflection Surface Stack (CRS) is a seismic reflection imaging technique that is independent of velocity model to simulate Zero-Offset (ZO) seismic section or volume. This technique have been used, alternatively, in seismic reflection processing and many works have been demonstrate that the CRS method shows results with better signal to noise rate and lateral resolution in comparison with conventional methods, e. g., NMO/DMO stack. The CRS stack provides some attributes or wavefield parameters that could be used in many applications, e.g., velocity models estimation, AVO and AVA analysis, geometric spread factor estimation, projected Fresnel zone, and others. The CRS technique has a second order hyperbolic traveltimes approximation in central ray vicinity. In the 3-D case, for a normal central ray or ZO, the CRS operator depends on eight parameters, estimating by coherency analysis from seismic data. In this work, the 3-D ZO CRS operator is analyzed for both reflection and diffraction events with respect the traveltimes obtained from straight modeling. I present a new CRS stack algorithm to simulate ZO sections or volume. I still present, in this work, a 3-D seismic modeling of the sedimentary Amazon Basin with SW3D consortium packages. The geologic model was based in true geologic and geophysics data.
Acesso aberto (Open Access)
Post-imaging analysis of pressure prediction in productive sedimentary basins for oil and gas exploration
(Universidade Federal do Pará, 2015-05-26) VIEIRA, Wildney Wallacy da Silva; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This thesis has several aspects related to the problem of basin modeling towards oil and gas exploration, and with two general divisions: parameter estimation, and pressure prediction. For the structure of this work, the first topic is related to velocity analysis and effective media, where estimated a distribution for the P wave velocity in time, the transformation to depth, and the use an effective model for the density and for the S wave velocity distributions. The reason for initially focusing on these estimations is because they represent one of the most basic information that one can have from the seismic domain, from where the other seismic parameters can be calculated, and from where the second part of this is totally based. The second topic is related to computing stress, strain and pressure distribution in the subsurface using the information from the P and S wave velocities and the density models, in order to localize areas of high and low pressures that act as natural suction pumps for the mechanics of oil and gas accumulation into productive zones and layers. We have highlighted this second part for the final work presentation, and call attention to the sensitivity of pressure mapping to the velocity and density variations. We also classify the first division as dedicated to the conventional seismic processing and imaging, and have clled the second division as post-imaging stressstrain-pressure prediction. As for the final aim of geophysics is to create images of the subsurface under different properties, the stress calculation only makes total sense for real data, and this makes mandatory the acquired seismic data be three component. As an important conclusion from the numerical experiments, we show that pressure does not have a trivial behavior, since it can decrease with depth and create natural pumps that are responsible for accumulating fluids. The theory of porous media is based on integral geometry, because this mathematical discipline deals with collective geometrical properties for real reservoirs. It was shown that such collective properties are namely for porosity, specific surface, average curvature and Gaussian curvature. For example, cracked media has, as a rule, small porosity, but very large specific surface area that creates anomalous high 𝛾 = 𝑣𝑆/𝑣𝑃 ratio, what means a negative 𝜎 Poisson coefficient. Another conclusion is related to calculating discontinuity in pressure between solid and fluid, what depends on the structure of pore space.
Acesso aberto (Open Access)
Processamento de dados sísmicos da bacia do Camamu
(Universidade Federal do Pará, 2009) MATOS, Ligia Naia de; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660
Seismic Imagining is one of the manners to visualize on subsurface. To get at a reliable seismic imagining, a long way must be covered. The first stage is the seismic acquisition, its the planned evil its carries serious troubles. After the seismic acquisition we need to processes the data. Seismic data processing is alteration of seismic data to suppress noise, enhance signal and migrate seismic events to the appropriate location in space. Processing steps typically include analysis of velocities and frequencies, static corrections, deconvolution, normal moveout, dip moveout, stacking, and migration, which can be performed before or after stacking. In this work, our objective is a seismic migration from a Camamu basin 2D acquisition line. In this line we have many the dificulties arise from the factors free surface multiples e peg-lags. We are going to use as seismic processing methodology the common median point stack and the pos-stack migration by ProMax (Landmark Inc) software. To attenuate multiples we have used predictive deconvolution, radon filter and f - k filter techniques . The results are satisfactory when we compare to results without theses techniques.