3D PP/PS prestack depth migration on the Volve field

Szydlik, Teresa; Smith, Patrick J.; Way, S.; Aamodt, Lars; Friedrich, Christina

doi:10.3997/1365-2397.25.1106.27412

Cited by 57 publications

(4 citation statements)

References 4 publications

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“…We finally apply the proposed method to a 2D line extracted from the 3D Volve OBC field data set, which was acquired in the Norwegian North Sea. The survey area is characterized by a small dome-shaped structure (Szydlik et al, 2007). Twelve parallel cables with a sampling interval of 400 m were used to record the data.…”

Section: Volve Obc Datamentioning

confidence: 99%

A reflection-based efficient wavefield inversion

Song

Alkhalifah

2021

GEOPHYSICS

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Full-waveform inversion (FWI) is popularly used to obtain a high-resolution subsurface velocity model. However, it requires either a good initial velocity model or low-frequency data to mitigate the cycle-skipping issue. Reflection-waveform inversion (RWI) uses a migration/demigration process to retrieve a background model that can be used as a good initial velocity in FWI. The drawback of the conventional RWI is that it requires the use of a least-squares migration, which is often computationally expensive, and is still prone to cycle skipping at far offsets. To improve the computational efficiency and overcome the cycle skipping in the original RWI, we incorporate it into a recently introduced method called efficient wavefield inversion (EWI) by inverting for the Born scattered wavefield instead of the wavefield itself. In this case, we use perturbation-related secondary sources in the modified source function. Unlike conventional RWI, the perturbations are calculated naturally as part of the calculation of the scattered wavefield in an efficient way. As the sources in the reflection-based EWI (REWI) are located in the subsurface, we are able to update the background model along the reflection wave path. In the background velocity inversion, we calculate the background perturbation by a deconvolution process at each frequency. After obtaining the REWI inverted velocity model, a sequential FWI or EWI is needed to obtain a high-resolution model. We demonstrate the validity of the proposed approach using synthetic data generated from a section of the Sigsbee2A model. To further demonstrate the effectiveness of the proposed approach, we test it on an ocean bottom cable (OBC) dataset from the North Sea. We find that the proposed methodology leads to improved velocity models as evidenced by flatter angle gathers.

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Section: Volve Obc Datamentioning

confidence: 99%

A reflection-based efficient wavefield inversion

Song

Alkhalifah

2021

GEOPHYSICS

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“…The sail line is 12 km long with a shot interval of 25 m (50 m between the flips). The data are recorded using a cable (at a depth of about 92 m) containing 240 receivers separated by 25 m. Equinor (then Statoil) pre-processed the vertical and horizontal particle-velocity components by applying noise suppression, multiple attenuation and other standard steps described in Szydlik et al (2007). Only the shots with (absolute) offsets less than 5000 m were kept for further processing.…”

Section: Acquisition Designmentioning

confidence: 99%

“…The parameter-estimation procedure was constrained by well data, such as compressional and shear sonic logs and check shots. The P-and S-wave vertical velocities V P0 and V S0 and the anisotropy parameters and δ in each layer were updated by flattening common-image gathers, minimizing the misties between seismic and well data, co-depthing the key horizons on PP and PS migrated sections, and incorporating compressional sonic logs (Szydlik et al, 2007). Wang and Tsvankin (2013) apply reflection tomography to the vertical particle-velocity component from the twodimensional line (inline 5089 from the survey) recorded along y = 2.8 km (white vertical lines in Fig.…”

Section: Acquisition Designmentioning

confidence: 99%

“…The inverted models contain more information about the subsurface velocity fields than the initial parameter distributions. In particular, there is a low-velocity (V P0 ) layer at a depth of 3.1 km that likely represents the reservoir (Szydlik et al, 2007). The radiation-pattern analysis for the velocity-based parameterization demonstrates that the vertical displacement component may not be sufficiently sensitive to some TI parameters (in particular, to V hor,P and V S0 ; see Singh et al, 2021).…”

Section: Unconstrained Fwimentioning

confidence: 99%

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Facies‐based full‐waveform inversion for anisotropic media: a North Sea case study

Singh

Tsvankin

Naeini³

2021

Geophysical Prospecting

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Elastic full-waveform inversion can increase the resolution of reservoir characterization using seismic data. However, full-waveform inversion for realistic anisotropic media suffers from the trade-offs between the medium parameters and strongly relies on the accuracy of the initial model. Here, we employ a regularization methodology that utilizes geologically consistent information to reduce the inversion non-linearity and crosstalk between the parameters. The geologic constraints are obtained from well logs and interpolated along major horizons in the migrated image. The algorithm, designed for transversely isotropic media with a tilted symmetry axis, is applied to ocean-bottom data acquired at Volve field in the North Sea. The facies-based constraints help build high-resolution velocity fields and accurately image the reservoir region. In particular, the developed algorithm increases the resolution of the Pand S-wave symmetry-direction velocities and other parameters at the reservoir level. The facies-based inversion also provides robust estimates of density, which is inverted simultaneously with the velocity fields. Overall, even relatively sparse prior information proves to be sufficient for the proposed methodology to achieve a much higher spatial resolution than the unconstrained full-waveform inversion.

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