Reconstruction of the Near-Surface Velocities with Trap Bodies by the Full Waveform Inversion

Mapping Intimacies ◽

10.2118/206594-ms ◽

2021 ◽

Author(s):

Kirill Gennadievich Gadylshin ◽

Vladimir Albertovich Cheverda ◽

Danila Nikolaevich Tverdokhlebov

Keyword(s):

Free Surface ◽

Surface Area ◽

Waveform Inversion ◽

Full Waveform Inversion ◽

Near Surface ◽

Velocity Models ◽

Full Waveform ◽

Seismic Image ◽

Geological Conditions ◽

Velocity Anomalies

Abstract Seismic surveys in the vast territory of Eastern Siberia are carried out in seismic and geological conditions of varying complexity. Obtaining a high-quality dynamic seismic image for the work area is a priority task in the states of contrasting heterogeneities of the near-surface. For this, it is necessary to restore an effective depth-velocity model that provides compensation for velocity anomalies and calculates static corrections. However, for the most complex near-surface structure, for example, the presence of trap intrusions and tuffaceous formations, the information content of the velocity models of the near-surface area obtained based on tomographic refinement turns out to be insufficient, and a search for another solution is required. The paper considers an approach based on Full Waveform Inversion (FWI). As the authors showed earlier, multiples associated with the free surface reduce the resolution of this approach. But their use increases the stability of the solution in the presence of uncorrelated noise. Therefore, at the first stage of FWI, the full wavefield is used, including free surface-related multiples, but they are suppressed in the next steps of the data processing. The results obtained demonstrate the ability of the FWI to restore complex geological structures of the near-surface area, even in the presence of high-velocity anomalies (trap intrusions).

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Optimal coding of blended seismic sources for 2D full waveform inversion in time

CT&F - Ciencia Tecnología y Futuro ◽

10.29047/01225383.78 ◽

2018 ◽

Vol 8 (2) ◽

Author(s):

Katherine Flórez ◽

Sergio Alberto Abreo Carrillo ◽

Ana Beatriz Ramírez Silva

Keyword(s):

Waveform Inversion ◽

Velocity Model ◽

Computational Time ◽

Inversion Method ◽

Single Shot ◽

Full Waveform Inversion ◽

Velocity Models ◽

Full Waveform ◽

Seismic Image ◽

Blended Data

Full Waveform Inversion (FWI) schemes are gradually becoming more common in the oil and gas industry, as a new tool for studying complex geological zones, based on their reliability for estimating velocity models. FWI is a non-linear inversion method that iteratively estimates subsurface characteristics such as seismic velocity, starting from an initial velocity model and the preconditioned data acquired. Blended sources have been used in marine seismic acquisitions to reduce acquisition costs, reducing the number of times that the vessel needs to cross the exploration delineation trajectory. When blended or simultaneous without previous de-blending or separation, stage data are used in the reconstruction of the velocity model with the FWI method, and the computational time is reduced. However, blended data implies overlapping single shot-gathers, producing interference that affects the result of seismic approaches, such as FWI or seismic image migration. In this document, an encoding strategy is developed, which reduces the overlap areas within the blended data to improve the final velocity model with the FWI method.

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Full Waveform Inversion in generalized coordinates for zones of curved topography

CT&F - Ciencia Tecnología y Futuro ◽

10.29047/01225383.84 ◽

2018 ◽

Vol 8 (2) ◽

Author(s):

César Augusto Arias- Chica ◽

David Abreo ◽

Sergio Abreo ◽

Luis Fernando Duque- Gómez ◽

Ana Beatríz Ramírez- Silva

Keyword(s):

Computing Time ◽

Waveform Inversion ◽

Surface Velocity ◽

Full Waveform Inversion ◽

Near Surface ◽

Velocity Models ◽

Full Waveform ◽

Wide Range ◽

Rugged Topography ◽

Uniform Rectangular Grid

Full waveform inversion (FWI) has been recently used to estimate subsurface parameters, such as velocity models. This method, however, has a number of drawbacks when applied to zones with rugged topography due to the forced application of a Cartesian mesh on a curved surface. In this work, we present a simple coordinate transformation that enables the construction of a curved mesh. The proposed transformation is more suitable for rugged surfaces and it allows mapping a physical curved domain into a uniform rectangular grid, where acoustic FWI can be applied in the traditional way by introducing a modified Laplacian. We prove that the proposed approximation can have a wide range of applications, producing precise near-surface velocity models without increasing the computing time of the FWI.

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Challenges in shallow targets reconstruction by 3D elastic full-waveform inversion — Which initial model?

Geophysics ◽

10.1190/geo2019-0523.1 ◽

2021 ◽

pp. 1-91

Author(s):

Daniela Teodor ◽

Cesare Cesare ◽

Farbod Khosro Anjom ◽

Romain Brossier ◽

Valentina Socco Laura ◽

...

Keyword(s):

Field Data ◽

Weighting Function ◽

Waveform Inversion ◽

P Wave ◽

Full Waveform Inversion ◽

Initial Model ◽

Near Surface ◽

Velocity Models ◽

Full Waveform ◽

3D Acquisition

Elastic full-waveform inversion (FWI) is a powerful tool for high-resolution subsurface multi-parameter characterization. However, 3D FWI applied to land data for near-surface applications is particularly challenging, since the seismograms are dominated by highly energetic, dispersive, and complex-scattered surface waves (SWs). In these conditions, a successful deterministic FWI scheme requires an accurate initial model. This study, primarily focused on field data analysis for 3D applications, aims at enhancing the resolution in the imaging of complex shallow targets, by integrating devoted SW analysis techniques with a 3D spectral-element-based elastic FWI. From dispersion curves (DCs), extracted from seismic data recorded over a sharp-interface shallow target, we built different initial S-wave (VS) and P-wave (VP) velocity models (laterally homogeneous and laterally variable), using a specific data-transform. Starting from these models, we carry out 3D FWI tests on synthetic and field data, using a relatively straightforward inversion scheme. The field data processing before FWI consists of bandpass filtering and muting of noisy traces. During FWI, a weighting function is applied to the far-offset traces. We test both 2D and 3D acquisition layouts, with different positions of the sources and variable offsets. The 3D FWI workflow enriched the overall content of the initial models, allowing a reliable reconstruction of the shallow target, especially when using laterally variable initial models. Moreover, a 3D acquisition layout guaranteed a better reconstruction of the target’s shape and lateral extension. In addition, the integration of model-oriented (preliminary monoparametric FWI) and data-oriented (time-windowing) strategies into the main optimization scheme has granted further improvement of the FWI results.

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Seismic imaging of complex onshore structures by 2D elastic frequency-domain full-waveform inversion

Geophysics ◽

10.1190/1.3215771 ◽

2009 ◽

Vol 74 (6) ◽

pp. WCC105-WCC118 ◽

Cited By ~ 339

Author(s):

Romain Brossier ◽

Stéphane Operto ◽

Jean Virieux

Keyword(s):

Free Surface ◽

Surface Waves ◽

Frequency Domain ◽

Wave Velocity ◽

Waveform Inversion ◽

Surface Effects ◽

Full Waveform Inversion ◽

S Wave ◽

Velocity Models ◽

Full Waveform

Quantitative imaging of the elastic properties of the subsurface at depth is essential for civil engineering applications and oil- and gas-reservoir characterization. A realistic synthetic example provides for an assessment of the potential and limits of 2D elastic full-waveform inversion (FWI) of wide-aperture seismic data for recovering high-resolution P- and S-wave velocity models of complex onshore structures. FWI of land data is challenging because of the increased nonlinearity introduced by free-surface effects such as the propagation of surface waves in the heterogeneous near-surface. Moreover, the short wavelengths of the shear wavefield require an accurate S-wave velocity starting model if low frequencies are unavailable in the data. We evaluated different multiscale strategies with the aim of mitigating the nonlinearities. Massively parallel full-waveform inversion was implemented in the frequency domain. The numerical optimization relies on a limited-memory quasi-Newton algorithm thatoutperforms the more classic preconditioned conjugate-gradient algorithm. The forward problem is based upon a discontinuous Galerkin (DG) method on triangular mesh, which allows accurate modeling of free-surface effects. Sequential inversions of increasing frequencies define the most natural level of hierarchy in multiscale imaging. In the case of land data involving surface waves, the regularization introduced by hierarchical frequency inversions is not enough for adequate convergence of the inversion. A second level of hierarchy implemented with complex-valued frequencies is necessary and provides convergence of the inversion toward acceptable P- and S-wave velocity models. Among the possible strategies for sampling frequencies in the inversion, successive inversions of slightly overlapping frequency groups is the most reliable when compared to the more standard sequential inversion of single frequencies. This suggests that simultaneous inversion of multiple frequencies is critical when considering complex wave phenomena.

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Unlocking the potential of conventional narrow azimuth data by full-waveform inversion: a deep carbonate imaging case study, offshore Indonesia

10.29118/ipa21-g-163 ◽

2021 ◽

Author(s):

J. Wang

Keyword(s):

Complex Structure ◽

Time Lag ◽

Waveform Inversion ◽

Low Frequency ◽

Time Shift ◽

Full Waveform Inversion ◽

Velocity Models ◽

Full Waveform ◽

Seismic Image ◽

Refraction Tomography

Full-waveform inversion (FWI) has evolved to be the contemporary solution to resolve velocity models in areas of complex structure. Further, wide azimuth, long offset and rich low-frequency seismic data, resulting from broadband seismic acquisition, helps FWI update deeper with better convergence and stability. In this study from the South Mahakam area in offshore Indonesia, multiple layers of carbonate exist from shallow to deep with sharp velocity contrast. The target reservoir is down to 3.5 kilometers. However, for the acquired data with narrow azimuths (NAZ), short offsets (3 kilometers) and low signal to noise in the low frequencies, FWI encounters challenges of cycle skipping and unstable updates in the deeper targets that are beyond the diving-wave penetration depth. Time-lag FWI (TLFWI) (Zhang et al., 2018) uses time-shift differences between observed and modeled data as the cost function, and also makes better use of the low-frequency refraction and reflection energy. TLFWI gave good velocity updates in both the shallow and deep regions and, hence, gave an improved deep carbonate image. The anisotropic model is an important factor for the success of any FWI due to the coupling between velocity and anisotropy. In this paper, joint reflection and refraction tomography (Allemand et al., 2017) were applied in order to obtain stable anisotropy models for TLFWI. Following that, TLFWI with both refraction and reflection energy gives sensible velocity updates down to 3.5 kilometers. These updates to the model improve the seismic image and, importantly, reduce the depth uncertainties in this complex geological setting. The cumulative improvements increase interpretation confidence and can reduce future drilling risks. For the seismic processing community, the reprocessing of narrow azimuth, short-offset data with TLFWI, and associated technologies, offers great potential for generating improved and more reliable images from legacy, conventional, acquisition scenarios.

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A new parameter set for anisotropic multiparameter full-waveform inversion and application to a North Sea data set

Geophysics ◽

10.1190/geo2015-0349.1 ◽

2016 ◽

Vol 81 (4) ◽

pp. U25-U38 ◽

Cited By ~ 32

Author(s):

Nuno V. da Silva ◽

Andrew Ratcliffe ◽

Vetle Vinje ◽

Graham Conroy

Keyword(s):

North Sea ◽

Waveform Inversion ◽

Real Data ◽

Model Parameters ◽

Full Waveform Inversion ◽

Radiation Patterns ◽

Data Set ◽

Full Waveform ◽

Seismic Image ◽

Central North Sea

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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Velocity model building by 3D frequency-domain, full-waveform inversion of wide-aperture seismic data

Geophysics ◽

10.1190/1.2957948 ◽

2008 ◽

Vol 73 (5) ◽

pp. VE101-VE117 ◽

Cited By ~ 93

Author(s):

Hafedh Ben-Hadj-Ali ◽

Stéphane Operto ◽

Jean Virieux

Keyword(s):

High Resolution ◽

Frequency Domain ◽

Distributed Memory ◽

Waveform Inversion ◽

Steepest Descent Method ◽

Frequency Domain Method ◽

Full Waveform Inversion ◽

Direct Solver ◽

Velocity Models ◽

Full Waveform

We assessed 3D frequency-domain (FD) acoustic full-waveform inversion (FWI) data as a tool to develop high-resolution velocity models from low-frequency global-offset data. The inverse problem was posed as a classic least-squares optimization problem solved with a steepest-descent method. Inversion was applied to a few discrete frequencies, allowing management of a limited subset of the 3D data volume. The forward problem was solved with a finite-difference frequency-domain method based on a massively parallel direct solver, allowing efficient multiple-shot simulations. The inversion code was fully parallelized for distributed-memory platforms, taking advantage of a domain decomposition of the modeled wavefields performed by the direct solver. After validation on simple synthetic tests, FWI was applied to two targets (channel and thrust system) of the 3D SEG/EAGE overthrust model, corresponding to 3D domains of [Formula: see text] and [Formula: see text], respectively. The maximum inverted frequencies are 15 and [Formula: see text] for the two applications. A maximum of 30 dual-core biprocessor nodes with [Formula: see text] of shared memory per node were used for the second target. The main structures were imaged successfully at a resolution scale consistent with the inverted frequencies. Our study confirms the feasibility of 3D frequency-domain FWI of global-offset data on large distributed-memory platforms to develop high-resolution velocity models. These high-velocity models may provide accurate macromodels for wave-equation prestack depth migration.

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FULL-WAVEFORM INVERSION WITH SOURCE AND RECEIVER COUPLING EFFECTS CORRECTION

Geophysics ◽

10.1190/geo2020-0331.1 ◽

2021 ◽

pp. 1-37

Author(s):

Xinhai Hu ◽

Wei Guoqi ◽

Jianyong Song ◽

Zhifang Yang ◽

Minghui Lu ◽

...

Keyword(s):

Waveform Inversion ◽

Nonlinear Least Squares ◽

Real Data ◽

Model Parameters ◽

Full Waveform Inversion ◽

Linear Inversion ◽

Near Surface ◽

Model Parameter ◽

Full Waveform ◽

Coupling Factors

Coupling factors of sources and receivers vary dramatically due to the strong heterogeneity of near surface, which are as important as the model parameters for the inversion success. We propose a full waveform inversion (FWI) scheme that corrects for variable coupling factors while updating the model parameter. A linear inversion is embedded into the scheme to estimate the source and receiver factors and compute the amplitude weights according to the acquisition geometry. After the weights are introduced in the objective function, the inversion falls into the category of separable nonlinear least-squares problems. Hence, we could use the variable projection technique widely used in source estimation problem to invert the model parameter without the knowledge of source and receiver factors. The efficacy of the inversion scheme is demonstrated with two synthetic examples and one real data test.

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Tunnel detection at Yuma Proving Ground, Arizona, USA — Part 1: 2D full-waveform inversion experiment

Geophysics ◽

10.1190/geo2018-0598.1 ◽

2019 ◽

Vol 84 (1) ◽

pp. B95-B105 ◽

Cited By ~ 5

Author(s):

Yao Wang ◽

Richard D. Miller ◽

Shelby L. Peterie ◽

Steven D. Sloan ◽

Mark L. Moran ◽

...

Keyword(s):

Surface Wave ◽

Waveform Inversion ◽

Velocity Profiles ◽

Infinite Length ◽

Full Waveform Inversion ◽

S Wave ◽

Near Surface ◽

Tunnel Detection ◽

Full Waveform ◽

Wave Methods

We have applied time domain 2D full-waveform inversion (FWI) to detect a known 10 m deep wood-framed tunnel at Yuma Proving Ground, Arizona. The acquired seismic data consist of a series of 2D survey lines that are perpendicular to the long axis of the tunnel. With the use of an initial model estimated from surface wave methods, a void-detection-oriented FWI workflow was applied. A straightforward [Formula: see text] quotient masking method was used to reduce the inversion artifacts and improve confidence in identifying anomalies that possess a high [Formula: see text] ratio. Using near-surface FWI, [Formula: see text] and [Formula: see text] velocity profiles were obtained with void anomalies that are easily interpreted. The inverted velocity profiles depict the tunnel as a low-velocity anomaly at the correct location and depth. A comparison of the observed and simulated waveforms demonstrates the reliability of inverted models. Because the known tunnel has a uniform shape and for our purposes an infinite length, we apply 1D interpolation to the inverted [Formula: see text] profiles to generate a pseudo 3D (2.5D) volume. Based on this research, we conclude the following: (1) FWI is effective in near-surface tunnel detection when high resolution is necessary. (2) Surface-wave methods can provide accurate initial S-wave velocity [Formula: see text] models for near-surface 2D FWI.

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