Traditionally, reservoir elastic parameters inversion suffers from the overburden multiple scattering and transmission imprint in the local input data used for the target-oriented inversion. In this paper, we present a full-wavefield approach, called reservoir-oriented joint migration inversion (JMI-res), to estimate the high-resolution reservoir elastic parameters from surface seismic data.As a first step in JMI-res, we reconstruct the fully redatumed data (local impulse responses) at a suitable depth above the reservoir from the surface seismic data, while correctly accounting for the overburden interal multiples and transmission losses. Next, we apply a localized elastic full waveform inversion on the estimated impulse responses to get the elastic parameters. We show that JMI-res thus provides much more reliable local target impulse responses, thus yielding high-resolution elastic parameters, compared to a standard redatuming procedure based on time reversal of data. Moreover, by using this kind of approach we avoid the need to apply a full elastic full waveform inversion-type process for the whole subsurface, as within JMI-res elastic full waveform inversion is only restricted to the reservoir target domain.

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The different processing steps used to create the target-oriented data for the local elastic parameters inversion introduces algorithm-related amplitude bias and artifacts, especially in the low S/N ratio data, and thus can lead to the variability in the inverted elastic parameters. However, given the shear amount of time and effort required, we seldom generate the target-oriented data using different processing steps to show this bias. In this paper, we redatum the surface data to create the target-oriented data for a field dataset using the wavefields and the angle gathers estimated via joint migration inversion that ensures to account for internal multiples and transmission losses. We show the intermediate steps taken to generate the local impulse responses in both the approaches results in a certain amplitude bias and artifacts that ultimately results in the variation of estimated elastic parameters.

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We address the estimation of the impulse response at a reflector by deconvolving the up- and downgoing waves. Deconvolution in the time domain can be written as a linear system with multiple right-hand sides in the frequency domain. A straightforward way of solving these systems is by applying an iterative method like LSQR. However, these solvers are dependent on the right-hand side and for every right-hand side we have to use LSQR again. This can be a costly process. We propose to solve the linear systems using block Krylov methods. We show that these methods give comparable accuracy compared to standard Krylov methods, but at a much lower computational cost. This is due to the fact that block methods are able to exploit similarities in the data and are able to constructs solutions in a much richer subspace. We also show that it is hard to solve the MDD problem in the frequency domain alone, and that additional optimization in the time domain is most likely required.

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We present the first field data application of the full reservoir-oriented joint migration inversion (JMI-res) workflow to estimate the reservoir elastic parameters. JMI-res first reconstructs the fully redatumed data (local impulse responses) at the target reservoir level, while correctly accounting for interbed multiples and transmission losses from the overburden and then applies a localised FWI on the estimated impulse responses to get the reservoir elastic parameters. With this approach, we avoid the need to apply a full elastic process for the whole subsurface. In this paper, we show that JMI-res provides reliable local target impulse responses, thus yielding high-resolution elastic parameters, compared to a standard redatuming process based on time reversal, courtesy of proper handling of interbed multiples and transmission losses in the redatuming step. Even for cases where there are no clear interbed multiples cross-cutting the reservoir, the improvement can be substantial due to recovered transmission losses in the overburden.

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Nowadays, there is a strong emphasis on explaining the full seismic wavefield for obtaining detailed subsurface information, which is indeed the way forward to improve the final resolution of images and – after that – reservoir properties. Within the full waveform inversion (FWI) community there is a strong bias towards one type of modelling, which is the finite-difference based solutions of the wave equation. However, one issue associated with FWI is that it does not yet provide a full strategy towards a broadband elastic reservoir inversion process. Traditionally, FWI is used for estimating the velocity model that is used as input for standard migration-inversion approaches, thereby losing the advantages of the full waveform approach, such as including the effect of multiples. As an alternative, the Joint Migration Inversion process, with an operator-based modelling engine, provides an open framework that can include many physical features (such as anisotropy, elastic angle-dependent reflectivity), without having to re-implement a certain wave equation. By using one-way propagators in combination with reflectivity operators, a full two-way response can be built. It provides consistent full wavefield outputs that can lead to accurate elastic parameters in the reservoir, while fully removing the overburden imprint.@en

Any target-oriented localised inversion scheme for reservoir elastic parameters is as good as the input dataset. Thus, the accuracy of the input dataset i.e. local reflection response or impulse response (virtual source-receiver response) is of utmost importance, especially when the target area is below a complex overburden. In these subsurface settings, the overburden internal multiples and associated transmission imprint obscure the local response, which in turn affects the estimated elastic parameters resolution. Here, we demonstrate a novel process called JMI-res, based on Joint Migration Inversion (JMI), to estimate the reservoir elastic parameters from the surface seismic elastic data for a complex subsurface scenario. In JMI-res, we first obtain the accurate local impulse
responses at the target depth level, while correctly accounting for overburden internal multiples and then we apply a localized inversion scheme on the estimated impulse responses to get the reservoir elastic parameters. Moreover,
the propagation velocity estimation is an integral part of JMI-res. In this paper, we show that JMI-res provides much more reliable local target impulse responses, thus yielding high-resolution elastic parameters, compared to
standard redatuming based on time reversal of recorded data, courtesy of proper handling of internal multiples in the redatuming step.@en

The Joint migration inversion (JMI) is a data-driven and effective approach to simulateously estimate the reflectivity (seismic image) and the propagation velocity. As it is a full waveform method, it explains all the multiple scattering and transmission effects present in the data and can also be extended to full-wavefield redatuming process. Here, we demonstrate the impact of JMI in correctly explaining the internal multiples present both in the overburden and the reservoir, using a field dataset from the North Sea. By comparing the JMI and JMI-based redatuming results with the least-squares migration and standard redatuming results, we also show, even though the internal multiples may not be that strong in these settings, that their effects is clearly visible in the prestack image domain and in the local reservoir impulse responses that may finally blur the elastic inversion process.

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Due to the non-linearity and high-computational costs associated with Elastic full-waveform inversion (FWI), it is still avoided at large and acoustic wave equation-based forward modeling algorithms are used in FWI to explain the elastic data, which in turn are not able to correctly explain the true elastic amplitudes. Thus, it’s output is then used in conventional migration methods to explain the elastic reflection amplitudes (Rpp). In this paper, we present a data-driven inversion algorithm (Full Wavefield Migration) based on Full Wave-field Modeling (FWMod), which can go one step ahead of its forward model, unlike FWI, to explain the correct elastic reflection amplitudes (Rpp) present in data without explilicty imposing the elastic wave equation. They inherently explain the true reflectivity corresponding to the type of input data (acoustic or elastic), which are comparable to the theoretical reflection coefficients. This elastic Rpp estimation can easily be coupled with automatic velocity update using another FWMod-based algorithm, called Joint Migration Inversion
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Estimating the reservoir properties from surface seismic data for a target below a complex overburden is a challenging problem. One of the approaches is to apply reservoir-oriented local inversion schemes on the redatumed local reflection response. In this paper, we propose a process to estimate the reservoir impulse responses (redatumed reflection response) in a complex overburden setting for realistic data with angledependent or angle vs ray parameter (AVP) characteristics. The impulse responses are estimated using Joint Migration Inversion (JMI) followed by sparsity constrained Proximity Transformation. It comprises a full wavefield approach in the sense that it correctly accounts for all internal multiples and transmission effects. As a result, the estimated impulse responses are free of interference related to internal multiples in the overburden. The process involves a noval procedure to estimate the propagation velocity model using the flexibility in the JMI parameterization. We finally show that this proposed JMI redatuming provides a much more reliable local reflection response, compared to standard redatuming based on time reversal of recorded data.

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For a high-resolution inversion of elastic parameters at the target, preferably local full wavefield impulse responses need to be constructed. Along the target area, typically, these impulse responses are considered in the local CMP-(τ/p) domain. The success of these inversion schemes is highly dependent on the quality of this input data. Therefore, the wavefields at target level, estimated by Joint Migration Inversion (JMI) are good candidates, as all overburden effects are correctly taken into acount. Next, the Proximity Transformation in the standard JMI-based redatuming approach estimates the impulse responses in the shot-domain, which are later transformed to CMP-(τ/p) domain to be used as input for local inversion schemes. Here, we propose the direct estimation of CMP-(τ/p) domain impulse responses from the target level down-and upgoing wavefields, using a redefined Proximity Transformation as part of a modified JMI-based redatuming approach. The modified approach helps us to estimate high-resolution impulse responses with reduced artifacts and improved angle vs. ray parameter (AVP) characteristices at large plane-wave angles, which can directly be used as input for local inversion schemes. Moreover, the modified approach will be very well suited to estimate CMP-(τ/p) domain impulse responses in a 3D accquisition scenario, where we do not have sufficient sampling to apply explicit τ/px/py transform on shot-domain estimated impulse responses.@en

In this abstract, we demonstrate a target-oriented imaging strategy to estimate the impulse responses from a local target in the subsurface from surface seismic data. The presented strategy is a two-step procedure. The first step is Joint Migration Inversion to estimate the upgoing and downgoing wavefields at a specific subsurface depth level in the vicinity of the local target. The second step is the Proximity Transformation, based on iterative sparse inversion approach, to estimate the impulse responses from a local target. The presented strategy makes use of internal multiples to enhance the illumination at the target level below a complex overburden and to reduce the dependency on source sampling. Here, we have made use of a synthetic data example to show both steps of the method and to demonstrate the importance of incorporating internal multiples.

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The reservoir-oriented local inversion schemes, where surface data is first transformed to local reflection data, are highly sensitive to the given input dataset and their success is directly linked to the accuracy and reliability of this data. In this paper, we demonstrate an optimized strategy to accurately estimate the down- and upgoing wavefields at the subsurface target depth level. The proposed optimized scheme is an extension to the standard Joint Migration Inversion implementation in which we propose to include the upgoing wavefield update at the target depth level at the later stages of the inversion algorithm. It is being embedded as a part of the first step, of a two-step procedure, i.e. Joint Migration Inversion followed by Proximity Transformation, to estimate the impulse response from the target area below a complex overburden. The paper also highlights the importance of correctly handling the internal multiples in the inversion scheme.

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