An example of wavefield depth migration and Monte Carlo imaging in West Africa deep waters

Cazzola, Luca; Pizzaferri, Luigi; Ratti, Luigi; Cardone, Giovanni; Bonomi, Ernesto

doi:10.1190/1.1851066

Cited by 6 publications

(4 citation statements)

References 7 publications

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“…We conclude that Monte‐Carlo imaging is a migration method that has the potential to become a new standard for 3D prestack wavefield depth migration. The main advantage of the stochastic approach is that it enables shot‐profile wave‐equation migration to be performed at sustainable computing costs, even with large production data sets (Cazzola et al 2004).…”

Section: Resultsmentioning

confidence: 99%

Wavefield Migration plus Monte Carlo Imaging of 3D Prestack Seismic Data

Bonomi¹,

Brieger

Cazzola

et al. 2006

Geophysical Prospecting

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A B S T R A C TPrestack wave-equation migration has proved to be a very accurate shot-by-shot imaging tool. However, 3D imaging with this technique of a large field acquisition, especially one with hundreds of thousands of shots, is prohibitively costly. Simply adapting the technique to migrate many superposed shot-gathers simultaneously would render 3D wavefield prestack migration cost-effective but it introduces uncontrolled nonphysical interference among the shot-gathers, making the final image useless. However, it has been observed that multishot signal interference can be kept under some control by averaging over many such images, if each multishot migration is modified by a random phase encoding of the frequency spectra of the seismic traces.In this article, we analyse this technique, giving a theoretical basis for its observed behaviour: that the error of the image produced by averaging over M phase encoded migrations decreases as M −1 . Furthermore, we expand the technique and define a general class of Monte-Carlo encoding methods for which the noise variance of the average imaging condition decreases as M −1 ; these methods thus all converge asymptotically to the correct reflectivity map, without generating prohibitive costs.The theoretical asymptotic behaviour is illustrated for three such methods on a 2D test case. Numerical verification in 3D is then presented for one such method implemented with a 3D PSPI extrapolation kernel for two test cases: the SEG-EAGE salt model and a real test constructed from field data.

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Section: Resultsmentioning

confidence: 99%

Wavefield Migration plus Monte Carlo Imaging of 3D Prestack Seismic Data

Bonomi¹,

Brieger

Cazzola

et al. 2006

Geophysical Prospecting

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“…Random shot‐encoding migration (Morton and Ober 1998; Romero et al 2000; Cazzola et al 2004) is used to image data by simultaneously migrating a number of shots, which are linearly combined after the application of random delays. The main goal is to reduce the computational cost of wave‐equation migration.…”

Section: Introductionmentioning

confidence: 99%

Wave‐equation migration with dithered plane waves

Perrone

Sava

2011

Geophysical Prospecting

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A B S T R A C TWave-equation based shot-record migration provides accurate images but is computationally expensive because every shot must be migrated separately. Shot-encoding migration, such as random shot-encoding or plane-wave migration, aims to reduce the computational cost of the imaging process by combining the original data into synthesized common-source gathers. Random shot-encoding migration and planewave migration have different and complementary features: the first recovers the full spatial bandwidth of the image but introduces strong artefacts, which are due to the interference between the different shot wavefields; the second provides an image with limited spatial detail but is free of crosstalk noise. We design a hybrid scheme that combines linear and random shot-encoding in order to limit the drawbacks and merge the advantages of these two techniques. We advocate mixed shot-encoding migration through dithering of plane waves. This approach reduces the crosstalk noise relative to random shot-encoding migration and increases the spatial bandwidth relative to conventional plane-wave migration when the take-off angle is limited to reduce the duration of the plane-wave gather. In turn, this decreases the migration cost. Migration with dithered plane waves operates as a hybrid encoding scheme in-between the end members represented by plane-wave migration and random shot-encoding. Migration with dithered plane waves has several advantages: every synthesized common-source gather images in a larger aperture, the crosstalk noise is limited and higher spatial resolution is achievable compared to shot-record migration, random shot-encoding and linear shot-encoding, respectively. Computational cost is also reduced relative to both random and linear shot-encoding migration since fewer synthesized commonsource gathers are necessary to obtain a high signal-to-noise ratio and high spatial resolution in the final image.

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“…Random shot-encoding migration (Morton and Ober 1998;Romero et al 2000;Cazzola et al 2004) is used to image data by simultaneously migrating a number of shots, which are linearly combined after the application of random delays. The main goal is to reduce the computational cost of waveequation migration.…”

Section: Introductionmentioning

confidence: 99%

Wave-equation Migration with Dithered Plane Waves

Perrone

Sava

2010

72nd EAGE Conference and Exhibition Incorporating SPE EUROPEC 2010

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Wave-equation based shot-record migration provides accurate images but is computationally expensive because every shot must be migrated separately. Shot-encoding migration, such as random shot-encoding or plane-wave migration, aims to reduce the computational cost of the imaging process by combining the original data into synthesized common-source gathers. Random shot-encoding migration and planewave migration have different and complementary features: the first recovers the full spatial bandwidth of the image but introduces strong artefacts, which are due to the interference between the different shot wavefields; the second provides an image with limited spatial detail but is free of crosstalk noise. We design a hybrid scheme that combines linear and random shot-encoding in order to limit the drawbacks and merge the advantages of these two techniques. We advocate mixed shot-encoding migration through dithering of plane waves. This approach reduces the crosstalk noise relative to random shot-encoding migration and increases the spatial bandwidth relative to conventional plane-wave migration when the takeoff angle is limited to reduce the duration of the plane-wave gather. In turn, this decreases the migration cost. Migration with dithered plane waves operates as a hybrid encoding scheme in-between the end members represented by plane-wave migration and random shot-encoding. Migration with dithered plane waves has several advantages: every synthesized common-source gather images in a larger aperture, the crosstalk noise is limited and higher spatial resolution is achievable compared to shot-record migration, random shot-encoding and linear shot-encoding, respectively. Computational cost is also reduced relative to both random and linear shot-encoding migration since fewer synthesized commonsource gathers are necessary to obtain a high signal-to-noise ratio and high spatial resolution in the final image.

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An example of wavefield depth migration and Monte Carlo imaging in West Africa deep waters

Cited by 6 publications

References 7 publications

Wavefield Migration plus Monte Carlo Imaging of 3D Prestack Seismic Data

Wavefield Migration plus Monte Carlo Imaging of 3D Prestack Seismic Data

Wave‐equation migration with dithered plane waves

Wave-equation Migration with Dithered Plane Waves

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