Stacking velocity inversion in anisotropic media

Williamson, Paul; Sexton, Paul; Robein, E.; Bertuet, P.

doi:10.3997/2214-4609.201408934

Cited by 2 publications

(2 citation statements)

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“…When the structure is not too complex we typically obtain the background velocity models for the migration using the stacking velocity inversion method described in Williamson et al (1996Williamson et al ( , 1997. This builds a layered model from interpreted interfaces by map demigration and migration, and seeks interval parameters which optimise the fit between modeled and observed data.…”

Section: Methodsmentioning

confidence: 99%

“…We illustrate the impact of anisotropy on PSDM by considering various isotropic migrations of a synthetic reflection profile from a model containing a TIV layer with a range of dips. Next we apply our 2D PSDM to a real data case study from offshore Africa, using isotropic and anisotropic background models, built with a method based on inversion of stacking velocities described in Williamson et al (1996). Finally we discuss our results and attempt to draw some conclusions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ray-Based 2d Anisotropic Pre-Stack Depth Migration on Synthetic and Real Data

Berthet

Mispel²,

Williamson³

1998

Rev. Inst. Fr. Pét.

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La migration profondeur avant sommation (PSDM), bien que cožteuse, est un outil puissant dÕimagerie et dÕanalyse de vitesse. On pense maintenant que lÕanisotropie de la vitesse sismique est largement rŽpandue dans les roches sŽdimentaires, et plus particuli•rement dans les argiles. Nous avons Žcrit un code de migration profondeur avant sommation en 2D ˆ des fins dÕutilisation dans les milieux ˆ isotropie plane avec un axe de symŽtrie vertical (TIV). Nous lÕutilisons afin dÕŽtudier les effets de lÕanisotropie sur la migration isotrope avant sommation au moyen dÕun exemple synthŽtique simple. Les rŽsultats sugg•rent quÕil est difficile de trouver des mod•les isotropes plausibles qui donnent des images correctes des rŽflecteurs sur tous les pendages. Nous appliquons en plus notre code PSDM ˆ un profil en 2D de donnŽes rŽelles provenant dÕun champ offshore dÕAfrique occidentale, o• il y a une Žpaisse sŽrie argileuse, en utilisant des mod•les de vitesse anisotropes et isotropes. Un plan de faille inclinŽ est mis en images plus clairement avec le mod•le anisotrope, mais certains miroirs presque horizontaux sont moins bien reprŽsentŽs, suggŽrant par lˆ que ce mod•le pourrait •tre amŽliorŽ et confirmant la sensibilitŽ de la migration profondeur avant sommation ˆ tous les aspects du mod•le de vitesse. RAY-BASED 2D ANISOTROPIC PRE-STACK DEPTH MIGRATION ON SYNTHETIC AND REAL DATAPre-stack depth migration (PSDM), while costly, is a powerful tool for imaging and velocity analysis. Seismic velocity anisotropy is now thought to be widespread in sedimentary rocks, particularly shales. We have written a 2D pre-stack depth migration code for use in transversely isotropic media with a vertical symmetry axis (TIV). We use it to investigate the effects of anisotropy on isotropic pre-stack migration by means of a simple synthetic example. Results suggest that it is difficult to find plausible isotropic models which give good images of reflectors at all dips. We further apply our PSDM code to a 2D line of real data from offshore West Africa, where there is a thick shale sequence, using isotropic and anisotropic velocity models. A dipping fault plane is imaged more clearly with the anisotropic model, but some of the near horizontal reflectors are less well imaged suggesting that this model could be improved and confirming the sensitivity of pre-stack depth migration to all aspects of the velocity model. La migraci-n en profundidad pre-acumulativa (PSDM), a pesar de su costo, constituye una poderosa herramienta para la obtenci-n de im ‡genes y para el an ‡lisis de velocidad. La anisotrop'a de velocidad s'smica es considerada actualmente muy frecuente en rocas sedimentarias, y en particular en esquistos. Hemos escrito un c-digo de desplazamiento en profundidad pre-acumulativo bidimensional para utilizarlo en medios transversalmente isotr-picos con un eje de simetr'a vertical (TIV). Habitualmente, investig ‡bamos los efectos de la anisotrop'a sobre la migraci-n isotr-pica pre-acumulativa mediante un ejemplo sintŽtico simple. Los resultado...

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%