Wave equation processing using finite-difference propagators, Part 1: Wavefield dissection and imaging of marine multicomponent seismic data

Geophysics ◽  
2014 ◽  
Vol 79 (6) ◽  
pp. T287-T300 ◽  
Author(s):  
Lasse Amundsen ◽  
Johan O. A. Robertsson
Keyword(s):  
Finite Difference ◽  
Seismic Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Time Migration ◽  
Time Space ◽  
Recorded Data ◽  
Electromagnetic Models ◽  
Marine Seismic ◽  
Multicomponent Data

Methods for wavefield injection are used in, for instance, reverse time extrapolation of shot gathers in reverse time migration. For correct injection of recorded data without any ambiguity of the propagation direction, the wavefield-injection methodology requires pressure and particle velocity data such as multicomponent towed marine or seabed seismic recordings. We discovered that by carefully considering the models (medium parameters and boundary conditions) for injection, wavefield injection of multicomponent data can also be used to solve several long-standing challenges in marine seismic data processing by means of conventional time-space-domain finite-difference propagators. We outlined and demonstrated several of these important applications including up-down separation of wavefields (deghosting), direct-wave removal, source-signature estimation, multiple removal, and imaging using primaries and multiples. Only acoustic models are considered, but the concepts are straightforward to generalize to elastodynamic and electromagnetic models.

Near-Borehole Imaging Using Full-Waveform Sonic Data

2021 ◽  
Author(s):  
Hala Alqatari ◽  
Thierry-Laurent Tonellot ◽  
Mohammed Mubarak
Keyword(s):  
Seismic Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Full Waveform ◽  
Time Migration ◽  
Imaging Results ◽  
High Resolution Images ◽  
Recorded Data ◽  
The Impact ◽  
Processing Steps

Abstract This work presents a full waveform sonic (FWS) dataset processing to generate high-resolution images of the near-borehole area. The dataset was acquired in a nearly horizontal well over a distance of 5400 feet. Multiple formation boundaries can be identified on the final image and tracked at up to 200 feet deep, along the wellbore's trajectory. We first present a new preprocessing sequence to prepare the sonic data for imaging. This sequence leverages denoising algorithms used in conventional surface seismic data processing to remove unwanted components of the recorded data that could harm the imaging results. We then apply a reverse time migration algorithm to the data at different processing stages to assess the impact of the main processing steps on the final image.

Implicit interpolation in reverse‐time migration

Geophysics ◽  
1997 ◽  
Vol 62 (3) ◽  
pp. 906-917 ◽  
Author(s):  
Jinming Zhu ◽  
Larry R. Lines
Keyword(s):  
Wave Equation ◽  
Finite Difference ◽  
Real Data ◽  
Seismic Sources ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Difference Wave ◽  
Time Migration ◽  
Seismic Acquisition ◽  
Recorded Data

Reverse‐time migration applies finite‐difference wave equation solutions by using unaliased time‐reversed recorded traces as seismic sources. Recorded data can be sparsely or irregularly sampled relative to a finely spaced finite‐difference mesh because of the nature of seismic acquisition. Fortunately, reliable interpolation of missing traces is implicitly included in the reverse‐time wave equation computations. This implicit interpolation is essentially based on the ability of the wavefield to “heal itself” during propagation. Both synthetic and real data examples demonstrate that reverse‐time migration can often be performed effectively without the need for explicit interpolation of missing traces.

Data- and model-domain up/down wave separation for reverse-time migration with free-surface multiples

2020 ◽  
Vol 223 (1) ◽  
pp. 77-93
Author(s):  
Peng Guo ◽  
Huimin Guan ◽  
George A McMechan
Keyword(s):  
Wave Equation ◽  
Free Surface ◽  
Seismic Data ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Wave Separation ◽  
Time Migration ◽  
Model Domain ◽  
Image Artefacts ◽  
Recorded Data

SUMMARY Seismic data recorded using a marine acquisition geometry contain both upgoing reflections from subsurface structures and downgoing ghost waves reflected back from the free surface. In addition to the ambiguity of propagation directions in the data, using the two-way wave equation for wavefield extrapolation of seismic imaging generates backscattered/turned waves when there are strong velocity contrasts/gradients in the model, which further increases the wavefield complexity. For reverse-time migration (RTM) of free-surface multiples, apart from unwanted crosstalk between inconsistent orders of reflections, image artefacts can also be formed along with the true reflector images from the overlapping of up/downgoing waves in the data and in the extrapolated wavefield. We present a wave-equation-based, hybrid (data- and model-domain) wave separation workflow, with vector seismic data containing pressure- and vertical-component particle velocity from dual-sensor seismic acquisition, for removing image artefacts produced by the mixture of up/downgoing waves. For imaging with free-surface multiples, the wavefield extrapolated from downgoing ghost events (reflected from the free surface) in the recorded data act as an effective source wavefield for one-order-higher free-surface multiples. Therefore, only the downgoing waves in the data should be used as the source wavefield for RTM with multiples; the recorded upgoing waves in the seismograms will be used for extrapolation of the time-reversed receiver wavefield. We use finite-difference (FD) injection for up/down separation in the data domain, to extrapolate the down- and upgoing waves of the common-source gathers for source and receiver wavefield propagation, respectively. The model-domain separation decomposes the extrapolated wavefield into upgoing (backscattered) and downgoing (transmitted) components at each subsurface grid location, to remove false images produced by cross-correlating backscattered waves along unphysical paths. We combine FD injection with the model-domain wavefield separation, for separating the wavefield into up- and downgoing components for the recorded data and for the extrapolated wavefields. Numerical examples using a simple model, and the Sigsbee 2B model, demonstrate that the hybrid up/down separation approach can effectively produce seismic images of free-surface multiples with better resolution and fewer artefacts.

Adjoint-state reverse time migration of 4C data: Finite-frequency map migration for marine seismic imaging

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. WA159-WA172 ◽  
Author(s):  
Clement Fleury ◽  
Ivan Vasconcelos
Keyword(s):  
Seismic Data ◽  
Finite Frequency ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Directional Information ◽  
Time Migration ◽  
Adjoint State ◽  
Dual Source ◽  
Map Migration ◽  
Marine Seismic

Recent advances in marine seismic acquisition allow for the recording of vector-acoustic ([VA] pressure and particle velocity) seismic data from dual-source configurations, i.e., using monopole as well as dipole sources. VA reverse time migration (RTM) can be custom designed to accurately handle amplitude and directivity information from 4C seismic data. We present a method for multicomponent RTM that is based on an adjoint-state formulation using the full VA wave equations for pressure and corresponding displacement fields. This method takes advantage of the directional finite-frequency information contained in the 4C acoustic fields by using source and receiver weighting operators in the adjoint-state imaging scheme. With this adjoint-state method, the source and receiver radiation properties are tailored by choosing specific weighting operators. Weighting operators were chosen so that source- and receiver-side ghost arrivals are jointly migrated with primary energy. Because the dipole field components (e.g., components of particle displacement or acceleration) are proportional to the spatial gradient components of the pressure field, our method is in fact a formulation for reverse-time map migration that images pressure fields while jointly using the directional information contained in its full 3C gradients. As a result, our reverse time 4C map migration method yields less aperture- and sampling-related artifacts when compared to imaging of the pressure-only or 2C seismic data. In addition, our method sets a framework for full-waveform inversion using dual-source 4C seismic data. We demonstrated our findings with synthetic data, including a subsalt imaging example.

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