Analysis of radiation patterns for optimized full waveform inversion in fluid-saturated porous media

Parameterization lies at the center of anisotropic full-waveform inversion (FWI) with multiparameter updates. This is because FWI aims to update the long and short wavelengths of the perturbations. Thus, it is important that the parameterization accommodates this. Recently, there has been an intensive effort to determine the optimal parameterization, centering the fundamental discussion mainly on the analysis of radiation patterns for each one of these parameterizations, and aiming to determine which is best suited for multiparameter inversion. We have developed a new parameterization in the scope of FWI, based on the concept of kinematically equivalent media, as originally proposed in other areas of seismic data analysis. Our analysis is also based on radiation patterns, as well as the relation between the perturbation of this set of parameters and perturbation in traveltime. The radiation pattern reveals that this parameterization combines some of the characteristics of parameterizations with one velocity and two Thomsen’s parameters and parameterizations using two velocities and one Thomsen’s parameter. The study of perturbation of traveltime with perturbation of model parameters shows that the new parameterization is less ambiguous when relating these quantities in comparison with other more commonly used parameterizations. We have concluded that our new parameterization is well-suited for inverting diving waves, which are of paramount importance to carry out practical FWI successfully. We have demonstrated that the new parameterization produces good inversion results with synthetic and real data examples. In the latter case of the real data example from the Central North Sea, the inverted models show good agreement with the geologic structures, leading to an improvement of the seismic image and flatness of the common image gathers.

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Parameter crosstalk and leakage between spatially separated unknowns in viscoelastic full-waveform inversion

Geophysics ◽

10.1190/geo2019-0370.1 ◽

2020 ◽

Vol 85 (4) ◽

pp. R397-R408 ◽

Cited By ~ 2

Author(s):

Scott Keating ◽

Kristopher A. Innanen

Keyword(s):

Waveform Inversion ◽

Numerical Approach ◽

Full Waveform Inversion ◽

Optimization Strategy ◽

Radiation Patterns ◽

Point Scatterer ◽

Phase Dependence ◽

Full Waveform ◽

Seismic Sensors

Elastic and attenuative effects play a major role in the determination of wave amplitudes and phases observed at seismic sensors. Viscoelastic full-waveform inversion (FWI) has the potential to recover much of the information content of measured seismic data by simultaneously accounting for these effects. However, the frequency variations and phase information present in viscoelastic FWI introduce new challenges to the inversion, especially through their impact on interparameter crosstalk. Crosstalk is typically characterized through analysis of the radiation patterns of point scatterers; however, the point scatterer model is not well suited to viscoelastic FWI because (1) attenuation introduces a significant potential for crosstalk between variables distant from one another in space and (2) interpreting the effect of frequency and phase dependence on the radiation patterns of point scatterers is not straightforward. We have introduced and examined a numerical approach for assessing the viscoelastic crosstalk modes expected for a given parameterization, optimization strategy, and acquisition geometry based on differencing various synthetic inversion results. With this approach, we have characterized the viscoelastic crosstalk for a typical parameterization for several possible acquisition geometries. Of particular note is the strong tendency for [Formula: see text] variables to leak into elastic variables from which they are spatially separated.

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Frequency domain full-waveform inversion in a fluid-saturated poroelastic medium

Geophysical Journal International ◽

10.1093/gji/ggaa579 ◽

2020 ◽

Author(s):

Qingjie Yang ◽

Alison Malcolm

Keyword(s):

Frequency Domain ◽

Seismic Data ◽

Waveform Inversion ◽

Full Waveform Inversion ◽

Saturated Porous Media ◽

Poroelastic Medium ◽

Full Waveform ◽

Trade Offs ◽

Poroelasticity Theory ◽

Two Parameter

Summary Determining subsurface properties is of fundamental importance in exploration seismic imaging. Poroelasticity theory provides an opportunity to extract quantitative fluid- and attenuation-dependent properties from seismic data. Following Pratt’s frequency-domain full-waveform-inversion (FWI) procedure and extending the basic FWI equations from the elastic case to the poroelastic case, we implement poroelastic FWI (PFWI) of fluid-saturated porous media. By analyzing the sensitivity kernels of poroelastic parameters, we explain the reason why some parameters are more difficult to recover than others. We also show the analytical and numerical radiation patterns based on which we predict the trade-offs among parameters. In numerical experiments, we invert two models to demonstrate the feasibility and effectiveness of the proposed PFWI and to verify our predictions about trade-offs for two-parameter PFWI. Finally, we discuss the various factors that influence the inversion results.

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Optimal full-waveform inversion strategy for marine data in azimuthally rotated elastic orthorhombic media

Geophysics ◽

10.1190/geo2017-0762.1 ◽

2018 ◽

Vol 83 (4) ◽

pp. R307-R320 ◽

Cited By ~ 9

Author(s):

Ju-Won Oh ◽

Tariq Alkhalifah

Keyword(s):

High Resolution ◽

Reservoir Characterization ◽

Waveform Inversion ◽

Horizontal Layer ◽

Full Waveform Inversion ◽

Radiation Patterns ◽

Trade Off ◽

Full Waveform ◽

Gradient Direction ◽

Marine Data

The orthorhombic (ORT) anisotropic description of earth layers can allow the capture of much of the earth’s anisotropic complexity. The inversion for high-resolution azimuthal variation of anisotropy is important for reservoir characterization, among other applications. A high-resolution description of the azimuth of fractures can help us to predict flow preferences. To verify the feasibility of multiparameter full-waveform inversion (FWI) for marine data assuming azimuthally rotated elastic ORT media, we have analyzed the radiation patterns and gradient directions of ORT parameters to the reflection data. First, we express the gradient direction of the ORT parameters considering the azimuthal rotation of the symmetric planes. Then, to support our observations in the gradient direction, the radiation patterns of the partial derivative wavefields from each parameter perturbation are also derived under the rotated elastic ORT assumption. To find an optimal parameterization, we compare three different parameterizations: monoclinic, velocity-based, and hierarchical parameterizations. Then, we suggest an optimal multistage update strategy by analyzing the behavior of the rotation angle as a FWI target. To analyze the trade-off among parameters in different parameterizations, we calculate the gradient direction from a hockey-puck model, in which each parameter is perturbed at the different location on a horizontal layer. The trade-off analysis supports that the hierarchical parameterization provides us with more opportunities to build up subsurface models with less trade-off between parameters and less influence of the azimuthal rotation of ORT anisotropy. The feasibility of the proposed FWI strategy is examined using synthetic marine streamer data from a simple 3D reservoir model with a fractured layer.

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