Full-waveform inversion with reflected waves for 2D VTI media

Pattnaik, Sonali; Tsvankin, Ilya; Wang, Hui; Alkhalifah, Tariq

doi:10.1190/segam2016-13967833.1

Cited by 5 publications

(9 citation statements)

References 26 publications

(17 reference statements)

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“…Besides, a long‐offset acquisition geometry is needed to retrieve η from the surface recorded data (Pattnaik et al . ). Since far‐offset data only recover the low‐wavenumber part of the model, the inverted η has lower resolution (Alkhalifah ).…”

Section: Introductionmentioning

confidence: 97%

“…To be more specific, δ in VTI media cannot be inverted without prior geology information (Feng and Schuster 2016;Xia 2016;Wu and Alkhalifah 2016). Besides, a long-offset acquisition geometry is needed to retrieve η from the surface recorded data (Pattnaik et al 2016). Since far-offset data only recover the low-wavenumber part of the model, the inverted η has lower resolution (Alkhalifah 2016).…”

Section: Introductionmentioning

confidence: 99%

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Full waveform inversion using oriented time‐domain imaging method for vertical transverse isotropic media

Zhang

Alkhalifah

2017

Geophysical Prospecting

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Full waveform inversion for reflection events is limited by its linearised update requirements given by a process equivalent to migration. Unless the background velocity model is reasonably accurate, the resulting gradient can have an inaccurate update direction leading the inversion to converge what we refer to as local minima of the objective function. In our approach, we consider mild lateral variation in the model and, thus, use a gradient given by the oriented time‐domain imaging method. Specifically, we apply the oriented time‐domain imaging on the data residual to obtain the geometrical features of the velocity perturbation. After updating the model in the time domain, we convert the perturbation from the time domain to depth using the average velocity. Considering density is constant, we can expand the conventional 1D impedance inversion method to two‐dimensional or three‐dimensional velocity inversion within the process of full waveform inversion. This method is not only capable of inverting for velocity, but it is also capable of retrieving anisotropic parameters relying on linearised representations of the reflection response. To eliminate the crosstalk artifacts between different parameters, we utilise what we consider being an optimal parametrisation for this step. To do so, we extend the prestack time‐domain migration image in incident angle dimension to incorporate angular dependence needed by the multiparameter inversion. For simple models, this approach provides an efficient and stable way to do full waveform inversion or modified seismic inversion and makes the anisotropic inversion more practicable. The proposed method still needs kinematically accurate initial models since it only recovers the high‐wavenumber part as conventional full waveform inversion method does. Results on synthetic data of isotropic and anisotropic cases illustrate the benefits and limitations of this method.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Full waveform inversion using oriented time‐domain imaging method for vertical transverse isotropic media

Zhang

Alkhalifah

2017

Geophysical Prospecting

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“…This sequence (see also Wang and Tsvankin ; Pattnaik et al . ) is repeated until further iterations no longer reduce the objective function.…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, parameter estimation can be performed sequentially by first fitting conventional-spread moveout (via updates in V nmo and δ) and then non-hyperbolic moveout (via updates in η). This sequence (see also Wang and Tsvankin 2013b;Pattnaik et al 2016) is repeated until further iterations no longer reduce the objective function.…”

Section: E T H O D O L O G Ymentioning

confidence: 99%

Image‐domain wavefield tomography for tilted transversely isotropic media

Tsvankin

Guitton

et al. 2019

Geophysical Prospecting

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Transversely isotropic models with a tilted symmetry axis have become standard for imaging beneath dipping shale formations and in active tectonic areas. Here, we develop a methodology of wave‐equation‐based image‐domain tomography for acoustic tilted transversely isotropic media. We obtain the gradients of the objective function using an integral wave‐equation operator based on a separable dispersion relation that takes the symmetry‐axis tilt into account. In contrast to the more conventional differential solutions, the integral operator produces only the P‐wavefield without shear‐wave artefacts, which facilitates both imaging and velocity analysis. The model is parameterized by the P‐wave zero‐dip normal‐moveout velocity, the Thomsen parameter δ, anellipticity coefficient η and the symmetry‐axis tilt θ. Assuming that the symmetry axis is orthogonal to reflectors, we study the influence of parameter errors on energy focusing in extended (space‐lag) common‐image gathers. Distortions in the anellipticity coefficient η introduce weak linear defocusing regardless of reflector dip, whereas δ influences both the energy focusing and depth scale of the migrated section. These results, which are consistent with the properties of the P‐wave time‐domain reflection moveout in tilted transversely isotropic media, provide important insights for implementation of velocity model‐building in the image‐domain. Then the algorithm is tested on a modified anticline section of the BP 2007 benchmark model.

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“…Based on the analysis of the radiation patterns, the parameterization in terms of v n , η and δ has limited trade-off (Alkhalifah and Plessix, 2014). and Pattnaik et al (2016) also employed the parameterization given by v n , η and δ to represent the VTI model in their inversion algorithm. For VTI FWI, a combination of the horizontal velocity v h and the parameters η and ε can generate the optimal inversion results especially when the diving waves are available (Alkhalifah and Plessix, 2014;Alkhalifah, 2016).…”

Section: Introductionmentioning

confidence: 99%

Reflection waveform inversion in acoustic VTI media

Alkhalifah

2019

SEG Technical Program Expanded Abstracts 2019

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Full waveform inversion (FWI) in transversely isotropic media with vertical symmetry axis (VTI) provides the opportunity to better match the data at the near and far offsets. However, multi-parameter FWI in general suffers from a serious cycle-skipping and trade-off problem. Reflection waveform inversion (RWI) can help us build a background model by minimizing the reflection data residuals. Thus, we apply RWI to acoustic VTI media. According to the radiation patterns analysis, the acoustic VTI media should be described by a combination of the normal-moveout (NMO) velocity v n and the anisotropic parameters η and δ in the RWI applications. To reduce the trade-off, we first invert for the background v n , and then update the background v n and η, simultaneously to fit the far-offset reflections. We apply Born modeling to produce the reflections for the two stages of the RWI method. For a follow up FWI applications, we use the background v n and η to calculate the horizontal velocity v h and the parameters η and ε. The acoustic VTI FWI will utilize the diving waves to improve the background, as well as utilize the reflections for high resolution information. We test the inversion algorithm on the modified VTI Sigsbee 2A model (a salt free part). The results show that the approach can converge to a reasonable result starting from an isotropic model with a linearly increasing v n , even in absence of low frequencies.

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Full-waveform inversion with reflected waves for 2D VTI media

Cited by 5 publications

References 26 publications

Full waveform inversion using oriented time‐domain imaging method for vertical transverse isotropic media

Full waveform inversion using oriented time‐domain imaging method for vertical transverse isotropic media

Image‐domain wavefield tomography for tilted transversely isotropic media

Reflection waveform inversion in acoustic VTI media

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