Multiple Weights in Diffraction Stack Migration

Tygel, Martin; Schleicher, Jörg; Hubral, Peter; Hanitzsch, C.

doi:10.3997/2214-4609-pdb.324.253

Cited by 7 publications

(10 citation statements)

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“…We have revisited the double diffraction stack approach proposed by Tygel et al (1993). In this paper, our intention is to use it as a simple and efficient method to calculate the relation between the stationary point in the unmigrated domain and the corresponding image point in the depthmigrated domain.…”

Section: Discussionmentioning

confidence: 99%

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Double diffraction stack for an alternative strategy for CRS-based limited-aperture Kirchhoff depth migration

Veile¹

2009

11th International Congress of the Brazilian Geophysical Society &Amp; EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009

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In Kirchhoff migration, the proper choice of the aperture is essential: the optimum aperture is the limited aperture defined by the first projected Fresnel zone. This is the smallest aperture providing interpretable amplitudes along with the highest possible S/N ratio and the minimum number of required summations. In addition, limited-aperture migration naturally prevents operator aliasing. The commonreflection-surface (CRS) stack provides kinematic wavefield attributes which allow to estimate the optimum aperture size for zero-offset and its dislocation with varying offset. The aperture is centered around the stationary point, but this point has to be associated with the corresponding point in the migrated domain in an additional process. Kirchhoff migration itself implicitly connects the stationary point and the image point in depth by collecting the energy in the vicinity of the former and assigning it to the latter. In principle, any smoothly varying property can be migrated "on top" of the seismic data themselves by applying multiple weighted diffraction stacks. The most generic property to be migrated in this way is the source/receiver midpoint which yields the lateral position of the stationary point mapped to the image location in depth. We investigate the validity and accuracy of this approach for simple synthetic data and apply it to a real land data set. A straightforward extension is introduced to solve some of the numerical problems inherent to this approach and CRSbased strategies are transferred from the time domain to the depth domain to identify the reflector images and to attenuate migration noise. Finally, the approach is compared to another CRS-based approach which directly evaluates the tangency criterion.

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Section: Discussionmentioning

confidence: 99%

“…Based on this observations, we introduce an extended workflow which overcomes most of the encountered problems and apply it to a real land data set. Tygel et al (1993) established the so-called double diffraction stack. Originally, it was intended to economize trueamplitude migration.…”

Section: Introductionmentioning

confidence: 99%

Double diffraction stack for an alternative strategy for CRS-based limited-aperture Kirchhoff depth migration

Veile¹

2009

11th International Congress of the Brazilian Geophysical Society &Amp; EXPOGEF 2009, Salvador, Bahia, Brazil, 24-28 August 2009

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“…These two approaches do not necessarily require an accurate velocity model, but they are computationally more intensive. The diffraction stack has been used previously to perform amplitude-preserving migrations (Schleicher et al, 1993;Tygel et al, 1993;Hubral et al, 1996). The slowness weighting presented in this paper may help reduce migration smiles, but the SWDS does not preserve reflection amplitude because of the scaling of stack weights with data semblance.…”

Section: Discussionmentioning

confidence: 99%

Slowness‐weighted diffraction stack for migrating wide‐angle seismic data in laterally varying media

Avendonk

2004

GEOPHYSICS

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Wide-angle prestack depth migration is an important tool for studying the nature of reflecting boundaries in the earth's crust. The slowness-weighted diffraction stack (SWDS) method has been used to incorporate both two-way traveltime constraints and slowness information in the migration. For this purpose, traveltimes and apparent slownesses of reflected arrivals must be calculated in the image space. Earlier applications of SWDS required a 1D or gently varying seismic velocity structure to obtain these quantities by ray tracing in the image space. I show that the apparent slownesses can also be derived directly from one-way traveltime maps using Fermat's principle. The SDWS is applied to an existing onshore-offshore wide-angle data set, and the example shows that the method can be used to image detailed reflectivity structure at great depths.

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“…onde t = τ MZO (ξ,ξ 0 ,t 0 ) é a curva de empilhamento para o MZO, ξ é a coordenada do ponto médio variando ao longo da abertura A, D 1/2 representa o operador de meia derivada em tempo negativo e K MZO (ξ,,ξ 0 ,t 0 ) é a função peso. Conforme Schleicher et al (1993), â integral (1) pode ser avaliada assintoticamente pelo método da fase estacionária (BLEISTEIN, 1984) para as altas freqüências, no ponto estacionário.…”

Section: Método Unificado De Imageamento Sísmico Em Meios 25dunclassified

“…Observando-se a equação para o fator de estiramento no MZO (5) percebe-se que a aplicação da migração para afastamento nulo aos dados sísmicos em afastamento comum fornece uma medida independente do ângulo de incidência Θ, desde que seja possível estimar a assinatura da fonte antes e depois do MZO. Como a estimativa da assinatura da fonte é problemática, um método de obter os ângulos de reflexão para cada afastamento comum que compõem o experimento sísmico, mais especificamente, em estudos de AVO é executar um segundo MZO com uma função peso modificada de forma conveniente (BLEISTEIN, 1987), TYGEL et al, 1993;BLEISTEIN et al, 1999). Este procedimento apresenta um pequeno esforço computacional, uma vez que os pesos envolvidos são multiplicadores que dependem das quantidades já calculadas pelo operador do MZO.…”

Section: Método Unificado De Imageamento Sísmico Em Meios 25dunclassified

Recuperação de atributos sísmicos utilizando a migração para afastamento nulo

et al. 2002

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A conventional processing, without a reliable adjustment in order to preserve the seismic amplitudes, could damage the mapping of the petrophysical properties, jeopardizing the correlation between the seismic data and the well profile. A manner to estimate correctly the amplitudes and, therefore, the reflection coefficients is to perform a pre-stack migration in true amplitude, where an amplitude distortion caused by the geometrical spreading throughout the ray path is compensated by the migration calculation. Nevertheless, this process has an expensive cost as well as is dependent from the velocity model. A routine less expensive than the other one and also more stable taking into account the velocity model, is to transform the seismic section obtained from the acquisition in common offsets in simulated section in zero offset with true amplitudes. This transformation is called true amplitude Zero Offset migration (TA MZO). In a media with constant velocity, the stack curve for the MZO and the weight function are reduced in analytic formulas, mitigating the computational effort. This work has two main objects: the first is to verify the TA MZO algorithm efficiency for a constant velocity in a synthetic model to a complex geology based on a Neo-Albian turbidity reservoir, where the assumption of constant velocity is not respected. The second one is to perform quantitative studies as results of the technique described above. Likewise, the study tries to analyze how useful is the methodology to compute the graphics for AVO and AVA analyses, helping the reservoir characterization.Keywords: spreading; seismic; migration; coefficient. RESUMOO processamento convencional, sem um tratamento adequado de preservação de amplitude, mascara ou até inviabiliza o mapeamento de propriedades petrofísicas, prejudicando a correlação entre o dado sísmico e a informação de perfil. Uma forma de estimar corretamente as amplitudes e, por conseqüência, os coeficientes de reflexão nas interfaces sísmicas, é efetuar uma migração pré-empilhamento em verdadeira amplitude, onde a distorção das amplitudes devido ao espalhamento geométrico ao longo do raio de reflexão é compensado pela operação de migração. Entretanto, esse processo tem um custo elevado, sendo também dependente do modelo de velocidades utilizado. Uma rotina menos dispendiosa e mais estável em relação a erros no modelo de velocidade, consiste na transformação da seção sísmica obtida com a geometria de aquisição no afastamento comum em seções simuladas de afastamento nulo em amplitude verdadeira. A operação de transformação de uma seção sísmica de afastamento constante para a sua correspondente em afastamento nulo recebe o nome de migração para afastamento nulo em verdadeira amplitude (TA MZO). No caso de um meio com velocidade constante, a curva de empilhamento do MZO e a função peso se reduzem a fórmulas analíticas, minimizando o esforço computacional. O trabalho em questão tem dois objetivos principais: o primeiro é verificar a eficácia do algoritmo de TA MZO para velo...

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Multiple Weights in Diffraction Stack Migration

Cited by 7 publications

References 0 publications

Double diffraction stack for an alternative strategy for CRS-based limited-aperture Kirchhoff depth migration

Double diffraction stack for an alternative strategy for CRS-based limited-aperture Kirchhoff depth migration

Slowness‐weighted diffraction stack for migrating wide‐angle seismic data in laterally varying media

Recuperação de atributos sísmicos utilizando a migração para afastamento nulo

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