Global Visco-Acoustic Full Waveform Inversion

Silva, N.V. da; Yao, Gang; Warner, Mike; Umpleby, A.; Debens, H.

doi:10.3997/2214-4609.201700504

“…With this aim, several authors have implemented viscoacoustic FWI in the frequency domain, in which viscous effects are incorporated in seismic modeling by introducing intrinsic attenuation as the imaginary component of P-wave velocity (Pratt, 1990(Pratt, , 1999Pratt and Worthington, 1990;Song et al, 1995;Plessix et al, 2012;Prieux et al, 2013;Operto et al, 2015), whereas others have implemented FWI in the time domain (Cheng et al, 2015;Plessix et al, 2016;Bai et al, 2017). A variety of approaches have been used to recover the intrinsic attenuation, including compensating the gradient for viscous effects (Xue et al, 2016(Xue et al, , 2017, running tomography for Q after having performed tomography and FWI for velocity only (Zhou et al, 2013), and using a semiglobal inversion algorithm (da Silva et al, 2017). Kurzmann et al (2013) recently apply a passive viscoacoustic FWI strategy in which intrinsic attenuation was incorporated into the modeling as a fixed parameter in a time-domain inversion.…”

Section: Introductionmentioning

confidence: 99%

Addressing Viscous Effects in Acoustic Full-waveform Inversion

Agudo¹,

Silva²,

Warner³

et al. 2017

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In conventional full-waveform inversion (FWI), viscous effects are typically neglected, and this is likely to adversely affect the recovery of P-wave velocity. We have developed a strategy to mitigate viscous effects based on the use of matching filters with the aim of improving the performance of acoustic FWI. The approach requires an approximate estimate of the intrinsic attenuation model, and it is one to three times more expensive than conventional acoustic FWI. First, we perform 2D synthetic tests to study the impact of viscoacoustic effects on the recorded wavefield and analyze how that affects the recovered velocity models after acoustic FWI. Then, we apply the current method on the generated data and determine that it mitigates viscous effects successfully even in the presence of noise. We find that having an approximate estimate for intrinsic attenuation, even when these effects are strong, leads to improvements in resolution and a more accurate recovery of the P-wave velocity. Then, we implement and develop our method on a 2D field data set using Gabor transforms to obtain an approximate intrinsic attenuation model and inversion frequencies of up to 24 Hz. The analysis of the results indicates that there is an improvement in terms of resolution and continuity of the layers on the recovered P-wave velocity model, leading to an improved flattening of gathers and a closer match of the inverted velocity model with the migrated seismic data.

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Q-factor inversion using reconstructed source spectral consistency

Shustak

¹

,

Lellouch

²

2018

GEOPHYSICS

5

0

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Seismic waves propagating in an anelastic medium undergo phase and amplitude distortions. Although these effects may be compensated for during imaging processes, a background [Formula: see text]-model is generally required for their successful application. We have developed a new approach to the [Formula: see text]-estimation problem, which is fundamentally related to the basic physical principle of time reversal. It is based on back-propagating recorded traces to their known source location using the reverse tomographic equation. This equation is a ray approximation of viscoelastic wave propagation. It is applied assuming a known and correct velocity model. We subsequently measure consistency between spectral shapes of traces that were back-propagated using the tomographic equation. We formulate an inverse problem using this consistency as an objective function. In conventional inversion, on the contrary, the discrepancy between modeled and recorded data, or some data characteristics, is minimized. The inverse problem is solved by ant-colony optimization, a global optimization approach, to avoid local minima present in the objective function. This method does not require knowledge of the source function and uses the full spectrum rather than its parametric reduction. Through synthetic and field cross-hole examples, we illustrate its accuracy and sensitivity in inverting for complex attenuation models. In the synthetic case, we also compare reconstructed source consistency with the conventional centroid frequency shift objective function. The latter displays poor resolution when recovering complex [Formula: see text] structures. We determine that the reconstructed source-consistency approach should be used as a part of an iterative workflow, possibly yielding initial models for a joint velocity and [Formula: see text] inversion.

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Addressing viscous effects in acoustic full-waveform inversion

Agudo

¹

,

Silva

²

,

Warner

³

et al. 2018

GEOPHYSICS

8

0

View full text Add to dashboard Cite

In conventional full-waveform inversion (FWI), viscous effects are typically neglected, and this is likely to adversely affect the recovery of P-wave velocity. We have developed a strategy to mitigate viscous effects based on the use of matching filters with the aim of improving the performance of acoustic FWI. The approach requires an approximate estimate of the intrinsic attenuation model, and it is one to three times more expensive than conventional acoustic FWI. First, we perform 2D synthetic tests to study the impact of viscoacoustic effects on the recorded wavefield and analyze how that affects the recovered velocity models after acoustic FWI. Then, we apply the current method on the generated data and determine that it mitigates viscous effects successfully even in the presence of noise. We find that having an approximate estimate for intrinsic attenuation, even when these effects are strong, leads to improvements in resolution and a more accurate recovery of the P-wave velocity. Then, we implement and develop our method on a 2D field data set using Gabor transforms to obtain an approximate intrinsic attenuation model and inversion frequencies of up to 24 Hz. The analysis of the results indicates that there is an improvement in terms of resolution and continuity of the layers on the recovered P-wave velocity model, leading to an improved flattening of gathers and a closer match of the inverted velocity model with the migrated seismic data.

show abstract

Global Visco-Acoustic Full Waveform Inversion

Cited by 4 publications

References 0 publications

Addressing Viscous Effects in Acoustic Full-waveform Inversion

Addressing Viscous Effects in Acoustic Full-waveform Inversion

Q-factor inversion using reconstructed source spectral consistency

Addressing viscous effects in acoustic full-waveform inversion

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