Navegando por Assunto "Empilhamento CRS"

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Acesso aberto (Open Access)
2-D ZO CRS stack by considering an acquisition line with smooth topography
(2005-03) OLIVA, Pedro Andrés Chira; CRUZ, João Carlos Ribeiro; CALLAPINO, German Garabito; HUBRAL, Peter; TYGEL, Martin
The land seismic data suffers from effects due to the near surface irregularities and the existence of topography. For obtaining a high resolution seismic image, these effects should be corrected by using seismic processing techniques, e.g. field and residual static corrections. The Common-Reflection-Surface (CRS) stack method is a new processing technique to simulate zero-offset (ZO) seismic sections from multi-coverage seismic data. It is based on a second-order hyperbolic paraxial traveltime approximation referred to a central normal ray. By considering a planar measurement surface, the CRS stacking operator is defined by means of three parameters, namely the emergence angle of the normal ray, the curvature of the normal incidence point (NIP) wave, and the curvature of the normal (N) wave. In this paper the 2-D ZO CRS stack method is modified in order to consider effects due to the smooth topography. By means of this new CRS formalism, we obtain a high resolution ZO seismic section, without applying static corrections. As by-products the 2-D ZO CRS stack method we estimate at each point of the ZO seismic section the three relevant parameters associated to the CRS stack process.
Acesso aberto (Open Access)
Aproximações hiperbólicas dos tempos de trânsito com topografia
(Universidade Federal do Pará, 2005-05-23) COSTA, Manuel de Jesus dos Santos; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
The simulation of a zero-offset seismic section (ZO) from multicoverage data can be carried through the seismic stacking, which is a very used method of seismic reflection imaging in the oil industry. Seismic stacking process allows to reduce the amount of data and is aimed to improve the signal/noise ratio. Based in the hyperbolic approach of the traveltime, dependent on three parameters or kinematic attributes of wavefronts, recently it was developed a new method to simulate zero-offset sections (ZO), called seismic stack for Common Reflection Surface method (or SRC stack). This new formalism can be extended to construct ZO sections from multicoverage data, using the approach of the paraxial traveltimes in the neighborhood of a central ray with zero offset, for the case of a line of measurement with soft and rugged topography. These two approaches of traveltime also depend on three kinematic attributes of wavefronts. In this work, a theoretical revision of the paraxial theory of the ray for the attainment of the approaches of the paraxial traveltimes is presented, considering a line of measurement with rugged and soft topography. From the approaches of the paraxial traveltimes with relation to a central ray with zero-offset (ZO), two new approaches had been derived from traveltimes using the condition of a diffraction point in depth, reducing the original equations for two parameters. For the approaches of reflection and diffraction, using the same synthetic model, a graphical representation of their respective stacking surfaces were compared, using the traveltime approaches for the soft and rugged topography. After that, we analyze the behavior of the operators associated with the reflection and the diffraction surfaces when these are disturbed, where we investigate the sensibilities in relation to each one of the three parameters (β0, KNIP, KM). This sensibility analysis was perfomed in two ways: Sensibility through the disturbance of each parameter visualized in the stacking surfaces SRC-TR and SDC-TR, and the first derivative of the traveltimes SRC-TR and SDC-TR. Finally, using these hyperbolic approaches as a function of three and two parameters, and based on the results of the sensibility analysis, were considered an algorithm to simulate ZO sections from data of multi coverage.
Acesso aberto (Open Access)
Aproximações hiperbólicas dos tempos de trânsito de raios paraxiais a um raio central refletido e difratado
(Universidade Federal do Pará, 2005-05-23) COSTA, Marcos Benedito Caldas; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
The simulation of a zero-offset seismic (ZO) section from multicoverage, through of stack, is a very used method of seismic reflection imaging, that reduce the amount of data and is aimed to improve the signal/noise ratio. Based on hyperbolic traveltime approximation depending on three kinematic attributes, recently, it was developed a new method to simulate zero-offset (ZO) sections called common reflection surface stack (CRS) method. Also, following this new concept of seismic imaging it was introduzed a method to simulate common-offset (CO) sections from multicoverage data by using a paraxial traveltime approximation for paraxial rays in the vicinity of the finite-offset centra ray. This new traveltime approximation depend on five kinematic attributes. In this work, from the hyperbolic paraxial traveltime approximation with finite-offset central ray, we derive a new formula of traveltime approximation by using the diffraction point condition, reducing the original formula to four parameters. For both approximations, that´s for reflection and diffractions, we show the finite-offset FO-CRS stack operators. We, also obtain these formulas to the four seismic configurations (common-shot (CS), common-receiver (CR), common-midpoint (CMP) and common-offset (CO)). To analise behaviour FO-CRS stack, when this is perturbed, we debatable the sensibility with respect to each one the five parameters (K1, K2, K3, βS and βG). This sensibility analysis was perfomed in two ways: Sensibility through the disturbance of each parameter visualized in the stacking surfaces FO-CRS- and FO-CDS, and the first derivative of the traveltimes FO-CRS and FO-CDS. After realize the sensibility analysis, we utility a new condition, K2 = 0 and therefore, we obtained a new approximation, now depend on three parameters. Using that hyperbolic traveltime approximations (in function of five, four and three parameters), we propose an algorithm multicoverage seismic reflection data. Finally, is presented a studed of Fresnel zone, to delimit the aperture of FO-CRS stacking surface.
Acesso aberto (Open Access)
Comparação dos filtros de velocidade e do operador WHLP-CRS na atenuação de múltiplas
(Universidade Federal do Pará, 2004-04-20) CRUZ, Edson Costa; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
The geological motivation of this work is the imaging of sedimentary basin structures of the Amazon region, where the generation and accumulation of hydrocarbons is related to the existence of diabase sills. The seismic motivation is the fact that these intrusive rocks present a great impedance contrast with respect to the host rock, what gives rise to external and internal multiples, with primary-like amplitudes. The seismic signal of the multiples can predominate over the primary reflection signals from deeper interfaces, making difficult the processing, interpretation and imaging of seismic sections. In this work we study the attenuation of multiples in common shot (CS) sections by the comparison of two methods. The first one is the combination of the Wiener-Hopf-Levinson (WHLP) and the common reflection surface (CRS) stacking techniques, here called WHLPCRS, where the operator is exclusively designed in the space-time domain. The second method is a velocity filter (ω-k), applied after the CRS stacking, where the operator is exclusively designed in the frequency-wavenumber domain. The identification of the multiples is performed on the zero-offset (ZO) section simulated by the CRS stacking, using the periodicity between primaries and its multiples. The wavefront attributes, obtained through CRS stacking, are inserted on movable space-time windows, used to calculate the WHLP-CRS operator. The ω-k filter calculations are performed in the frequency-wavenumber domain, where the events of interest are selected for cutting or passage. The ω-k filter is classified as a cut-off filter, with amplitude alteration and preservation of phase, the limits of it are imposed by a space-time sampling. In practical aspects we conclude that for the case of multiples, separated events on the x-t domain are not necessarily separated on the ω-k domain, which raise difficulties in the designing of a ω-k operator with a similar performance when compared to the x-t operator.
Acesso aberto (Open Access)
CRS seismic data imaging system: a case study for basib reevaluation
(2007-09) LEITE, Lourenildo Williame Barbosa; HEILMANN, Björn Zeno; GOMES, Anderson Batista
This paper summarizes practical results of a consistent attention to the seismic processing and interpretation of some land data lines from a set of the Tacutu graben (Brazil), where was applied the fundamental steps of the WIT imaging system grounded on the data-driven CRS (Common Reflection Surface) stack.As a major result, we expect to establish a work-flow for seismic reevaluation of sedimentary basins. Founded on the recovered wave front attributes of the CRS stack, a smooth macro-velocity model was obtained via tomographic inversion. Using this macro-model, pre- and post-stack depth migration was carried out. Besides that, other CRS-stack based processing techniques were performed in parallel as residual static correction and limited-aperture migration based on estimated projected Fresnel zone. A geological interpretation was attempted on the stacked and migrated sections. From visual details of the panels, we could interpret discontinuities, thinning, a principal faulted anticline where plays of horsts, grabens and rollovers are present. Also, part of the selected line needs more detailed processing to make better evident any present structures in the subsurface.
Acesso aberto (Open Access)
Empilhamento pelo método superfície de reflexão comum 2-D com topografia e introdução ao caso 3-D
(Universidade Federal do Pará, 2003-01-27) OLIVA, Pedro Andrés Chira; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023; HUBRAL, Peter; http://lattes.cnpq.br/7703430139551941
The CRS stacking method simulates ZO seismic sections from multi-coverage data and does not dependente on a macro-velocity model. For 2-D medium the stacking traveltime depends on three parameters: the emergence angle of the normal ray (with respect to the measurement surface normal) and the wavefront curvatures of two hypothetical waves, called Normal-Incidence-Point (NIP) wave and Normal (N) wave. The CRS method consists of summing the amplitudes of the seismic traces in the multicoverage data along the surface defined by CRS stacking traveltime which that fits best the data set. The result of the CRS stack is assigned to points of a grid pre-defined in the ZO section. As the result obtain a simulated ZO section. This means that for each point of the ZO section must be estimated the three optimal parameters that yield the maximum coherence between the events of seismic reflection. In this Thesis I present formulae for the 2-D CRS method and for the NMO velocity that consider the topography of the measurement surface. The algorithm is based on the optimization strategy divided into three steps: 1) To search for the emergence angle and the curvature of the NIP wave, by applying a global optimization, 2) to search for the curvature of the N wave, by applying global optimization, and 3) to refine the initial parameters estimated in first two steps by applying local optimization. In the first two steps is used the Simulated Annealing (SA) algorithm and in the third step the Variable Metric (VM) algorithm. For the case of a measurement surface with smooth topography the curvature of this surface is included in the 2-D CRS stack formalism. This CRS algorithm implemented was applied to synthetic data set. The result is a simulated ZO section of high quality, with a high signal-to-noise ratio, and the estimative of the parameter triplet. It is performed a sensibility analysis for the new CRS stacking traveltime with respect to the curvature in several points of the curved measurement surface. This study showed that the CRS traveltime is more sensitive for fast midpoints of the central points and larger offsets. The expressions for the NMO velocities presented here is applied to estimate the interval velocities and the depth of the reflectors for 2-D model with a smooth topography. For the inversion of the velocities and the depth of the reflectors is considered the Dix-type inversion algorithm. The NMO velocity for a curved measurement surface deserves to best estimate the velocities and the depths of the reflectors than NMO velocities referred to planar surfaces. Also, I present an introduction to 3-D stack. In this case, the stacking traveltime depends on eight parameters. These parameters can be obtained by using some parameter-search strategies that I have showed in this Thesis. The combination of the strategy of the Traveltime Approximations and the strategy of Arbitrary Curvatures is used to apply 3-D CRS stack successful in synthetic and real data sets, respectively.
Acesso aberto (Open Access)
Empilhamento sísmico por superfície de reflexão comum: um novo algoritmo usando otimização global e local
(Universidade Federal do Pará, 2001-10-25) GARABITO CALLAPINO, German; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023; HUBRAL, Peter; http://lattes.cnpq.br/7703430139551941
By using an arbitrary source-receiver configuration and without knowledge of the velocity model the recently introduced seismic data stacking method called Common Reflection Surface (CRS) simulates a zero-offset (ZO) section from multi-coverage seismic reflection data. For 2-D acquisition, as by-products provides three normal ray parameters: 1) the emergence angle (β0); 2) the radius of curvature of the Normal Incidence Point Wave (RNIP); and 3) the radius of curvature of the Normal Wave (RN). The CRS stack is based on the hyperbolic traveltime paraxial approximation depending on β0, RNIP and RN. In this thesis is presented a new algorithm of the CRS stack based on two-parameters and one-parameter search strategy combining global and local optimization methods for determine the three parameters that define the stacking surface (or operator). This is performed in three steps: 1) two-parameters search by applying global optimization to determine β0 and RNIP; 2) one-parameter search by applying global optimization to determine RN; and 3) three-parameters search by applying local optimization to determine three parameters, using as initial approximations the parameter triple of the earlier two steps. In the first two steps is used the Simulated Annealing (SA) algorithm and the Variable Metric algorithm is used in the third step. To simulate the conflicting dip events, for each ZO sample where there are interference of intersecting events is determined an additional parameter triple corresponding to a local minimum. The stacking along the respective operator for each particular event allows to simulate their interference in the simulated ZO section by means of their superposition. This new CRS stack algoritm was applied to synthetic data sets providing high-quality simulated ZO sections and high precision determination of the stack parameters in comparison with the forward modeling. Using the hyperbolic traveltime approximation for identical radii of curvature RNIP = RN, an algorithm called Common Diffraction Surface (CDS) stack was developed to simulate ZO sections for diffracted waves. In a similar way to the CRS stack procedure, this new algorithm also uses the SA and VM optimization methods to determine the optimal parameter couple (β0, RNIP) that define the best CDS operator. The main features of the algorithm are the data normalization, common-offset data, large aperture of the CDS operator and positive search space for RNIP. The application of the CDS stack algorithm in a synthetic dataset containing reflected and diffracted wavefields provides as main result a simulated ZO section containing diffracted events clearly defined. The post-stack depth migration of the ZO section locates correctly the discontinuities of the second interface.
Acesso aberto (Open Access)
Estudo do método de empilhamento SRC e aplicação em dados sintéticos e reais
(Universidade Federal do Pará, 2005-04-08) PASCHOAL JUNIOR, Waldomiro Gomes; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
Seismic stacking is a method designed to simulate zero-offset (ZO) seismic sections from multi-coverage seismic data. The resulting simulated ZO section gives rise to a significant increase of the signal to noise ratio. This method is done by means of seismic processing socalled the common mid point (CMP) method, through makes use of the so-called normal moveout and dip moveout (NMO/DMO) corrections. In this work, a new seismic stacking method called common reflection surface (CRS) is used to simulate ZO seismic sections. The main characteristic of the CRS method is: 1) the use of a more general, multi-parametric stacking operator that approximates the traveltimes of the primary reflections for sources and receiver pairs arbitrarily located on the vicinity of the normal ray. The parameters or attributes of the stacking operator are the radii of curvatures of two hypothetical waves called normal incidence point (NIP) wave and normal (N) wave; as well as the emergency angle of the normal ray. The CRS method assumes that the near-surface velocity is a priori known. To determine the abovementioned parameters appropriately, main for the CRS imaging method, is necessary search strategies that use cases special of the approach of second hyperbolic order of the traveltimes. The presented search strategies are: extended-pragmatic CRS and global-local CRS. To show the efficiency of these strategies they are applied in the synthetic Marmousi and real land datasets of the Amazon palaeozoic basin. As result sections ZO simulated by three different stacking methods (CMP, CRS extended- pragmatic and global-local CRS), to compare the efficiency of these, with relationship I cost her computational and the resolution of the seismic image.
Acesso aberto (Open Access)
Estudo do método de inversão tomográfica 2D baseada nos atributos cinemáticos da onda NIP e construção de interface gráfica para o processo de picking
(Universidade Federal do Pará, 2007) OLIVEIRA, Iran Gadelha de; CALLAPINO, German Garabito; http://lattes.cnpq.br/6064981270181319
In this work, a new tomographic reflection inversion method is studied, with the objective of determining smooth and isotropic velocity models for real and synthetic seismic data. The velocity model is obtained by the program NIPTOMO, which is an implementation of a tomographic inversion method of the kinematic attributes of the hypothetical waves NIP (normal incidence point). The input data for the tomographic inversion, e. g., traveltime tables and NIP attributes (wavefront curvature radius and emergence angle) are obtained through a set of picked points on a simulated zero-offset (ZO) section, previously obtained by the common-reflection surface (CRS) method. The choice of picked points in a ZO section is normally made using automatic picking programs that identify locally coherent events in a seismic section, based in user-defined parameters. The picking process is one of the most critical steps in this new method, since the choice of non primary reflection events, such as diffractions and multiples, may lead to errors in the velocity model obtained by the tomographic inversion. This work has as main objective develop an interative picking program to give to the user the control of the choice of primary reflection points that are used as input for the tomographic inversion. The present picking program was tested on the synthetic Marmousi dataset and on a real data from the Tacutu Basin, Brazil (seismic line 50-RL-90). The results obtained show that the interative picking process for the choice of primary reflection events points favors the determination of a precise velocity model.
Acesso aberto (Open Access)
Métodos de otimização global aplicados na busca dos parâmetros SRC
(Universidade Federal do Pará, 2004-06-21) CARMO, Klaus Mairan Laurido do; GARABITO CALLAPINO, German; http://lattes.cnpq.br/6064981270181319
The Common Reflection Surface Stack (CRS) method provides the simulation of zerooffset (ZO) sections by means of the summing seismic events of the multicoverage data contained in the stacking surface. This method does not depend on the velocity macro-model of medium; it only requires a priori knowledge of the near-surface velocity. The simulation of ZO sections for this stacking method uses a hyperbolic second-order traveltime approximation of the paraxial rays to define the CRS stacking surface or CRS stack operator. For 2D media, this operator depends on three kinematic attributes of two hypothetical waves (NIP and N waves), observed in the point of emergency of the central ray with normal incidence, namely, the angle of emergency of the central ZO ray (β0), the radius of curvature of the Normal Incidence Point Wave (RNIP) and the radius of curvature of the Normal Wave (RN). Therefore, the optimization problem in the CRS method consists in the determination, from the seismic data, of the three optimal parameters (β0, RNIP, RN) associated to each sample point of ZO section to be simulated. The simultaneous determination of these parameters can be made by means of multidimensional global search process (or global optimization), using as objective function some coherence criterion. The optimization problem in CRS method is very important for the good performance with respect to quality of the results and mainly to computational cost, compared with the methods traditionally used in the seismic industry. There are several search strategies to determine these parameters, based on systematic searches and using optimization algorithms, where only one parameter at each time can be estimated, or the two or three parameters simultaneously. Taking in to account the search strategy by means of the application of global optimization, these three parameters can be estimated through of procedures: in the first case the three parameters can be simultaneously estimated and in second case initially two parameters can be determined simultaneously (β0, RNIP), and subsequently the third parameter (RN), using the values of the two parameters already known. In this work it is presented the application and comparison of four algorithms of global optimization to find the CRS optimal parameters: Simulated Annealing (SA), Very Fast Simulated Annealing (VFSA), Differential Evolution (DE) and Controlled Random Search – 2 (CRS2). As importants results of the application of each optimization method, as well as between the methods regarding the effectiveness, efficiency and reliability to determine the best CRS parameters are presented. Subsequently, applying the global search strategies for the determination of these parameters, by means of the optimization method VFSA that presented the best performance, the CRS stacking was applied to the Marmousi dataset, one stacking using two parameters (β0, RNIP), estimated by global search, and another CRS stacking using the three parameters (β0, RNIP, RN), also estimated by global search.
Acesso aberto (Open Access)
Migração em profundidade pré-empilhamento utilizando os atributos cinemáticos do empilhamento por superfície de reflexão comum
(Universidade Federal do Pará, 2007-11-12) LUZ, Samuel Levi Freitas da; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
The Common-Reflection-Surface (CRS) stack is a new seismic processing method for simulating zero-offset (ZO) and common-offset (CO) sections. It is based on a second-order hyperbolic paraxial approximation of reflection traveltimes in the vicinity of a central ray. For ZO section simulation the central ray is a normal ray, while for CO section simulation the central ray is a finite-offset ray. In addition to the ZO section, the CRS stack method also provides estimates of wavefield kinematic attributes useful for solving interval velocity inversion, geometrical spreading calculation, Fresnel zone estimate, and also diffraction events simulation. In this work, Its proposed a new strategy to do a pre-stack depth migration by using the CRS derived wavefield kinematic attributes, so-called CRS based pre-stack depth migration (CRS-PSDM) method. The CRS-PSDM method uses the CRS results (ZO section and kinematic attributes) to construct an optimized stack traveltime surface along which the amplitudes of the multi-coverage seismic data are to be summed and the result is put in a point of the migration target zone in depth. In the same sense as in Kirchhoff type pre-stack depth migration (K-PSDM), the CRSPSDM method needs a migration velocity model. Unlike the K-PSDM method, the CRS-PSDM needs only to calculate the zero-offset traveltimes, i.e, along only ray conecting the considered point in depth to a given coincident position of source-receptor at surface. The final result is a zero-offset time-to-depth converted seismic image of reflectors from pre-stack seismic data.
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)
Processamento e imageamento NMO/CRS de dados sísmicos marinhos
(Universidade Federal do Pará, 2010) NUNES, Fernando Sales Martins; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This work is devoted to processing and imaging of marine seismic reflection data selected from the Jequitinhonha Basin, Bahia, where two stack methods were used, the NMO-based and the CRS-based. It was also applied the CRS-partial prestack data enhancement for the densification of CMPs. Several tests were performed with these methods to optimize parameters of the stacking operators, and to improve the processing strategies. One of the efforts during processing was the attenuation of the surface-related multiple, what was attacked by applying the Radon and SRME techniques. It was also applied the densification of the data to improve the signal/noise ratio. As a conclusion, a strategy was chosen based on the comparative results of better visual and higher coherence values, having the CRS method presented superior results to the results with the NMO method, based on the visualization of reflection events that were not noticed in other sections.