Non-repeatability Effects on Time-Lapse 4D Seismic Full Waveform Inversion for Ocean-Bottom Node Data

Geophysics ◽  
2021 ◽  
pp. 1-60
Author(s):  
Wei Zhou ◽  
David Lumley
Keyword(s):  
Waveform Inversion ◽  
Time Lapse ◽  
Seismic Survey ◽  
Double Difference ◽  
Full Waveform Inversion ◽  
Ocean Bottom ◽  
Central Difference ◽  
Change Models ◽  
Full Waveform ◽  
4D Seismic

Full waveform inversion (FWI) can be applied to time-lapse (4D) seismic data for subsurface reservoir monitoring. However, non-repeatability (NR) issues can contaminate the data and cause artifacts in the estimation of 4D rock and fluid property changes. Therefore, evaluating and studying the NR effects on the 4D data and FWI results can help, for instance, discriminate inversion artifacts from true changes, guide seismic survey design and processing workflow. Using realistic reservoir models, data and field measurements of NR, we show the effects of NR source-receiver position and seawater velocity changes on the data and the 4D FWI results. We find that ignoring these NR effects in the inversion can cause strong artifacts in the estimated velocity change models, and thus should be addressed before or during inversion. The NR source-receiver positioning issue can be addressed by 4D FWI successfully, whereas the NR water velocity issue requires measurements or estimations of water velocities. Furthermore, we compare the accuracy and robustness of the parallel, double-difference and central-difference 4D FWI methods to realistic NR ocean-bottom node data in a quantitative way. Parallel 4D FWI fails to capture geomechanical changes and also overestimates the aquifer layer changes with NR data. Double-difference 4D FWI is capable of recovering the geomechanical changes, but is also sensitive to NR noises, generating more artifacts in the overburden. By averaging the forward and reverse bootstrap 4D estimates, central-difference 4D FWI is more robust to NR noises, and also produces the most accurate 4D estimates.

scholarly journals Time-lapse full-waveform inversion with ocean-bottom-cable data: Application on Valhall field

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. R225-R235 ◽  
Author(s):  
Di Yang ◽  
Faqi Liu ◽  
Scott Morton ◽  
Alison Malcolm ◽  
Michael Fehler
Keyword(s):  
Seismic Data ◽  
Waveform Inversion ◽  
Time Lapse ◽  
Double Difference ◽  
Baseline Survey ◽  
Data Sets ◽  
Full Waveform Inversion ◽  
Ocean Bottom ◽  
Full Waveform ◽  
Future Production

Knowledge of changes in reservoir properties resulting from extracting hydrocarbons or injecting fluid is critical to future production planning. Full-waveform inversion (FWI) of time-lapse seismic data provides a quantitative approach to characterize the changes by taking the difference of the inverted baseline and monitor models. The baseline and monitor data sets can be inverted either independently or jointly. Time-lapse seismic data collected by ocean-bottom cables (OBCs) in the Valhall field in the North Sea are suitable for such time-lapse FWI practice because the acquisitions are of a long offset, and the surveys are well-repeated. We have applied independent and joint FWI schemes to two time-lapse Valhall OBC data sets, which were acquired 28 months apart. The joint FWI scheme is double-difference waveform inversion (DDWI), which inverts differenced data (the monitor survey subtracted by the baseline survey) for model changes. We have found that DDWI gave a cleaner and more easily interpreted image of the reservoir changes compared with that obtained with the independent FWI schemes. A synthetic example is used to demonstrate the advantage of DDWI in mitigating spurious estimates of property changes and to provide cross validations for the Valhall data results.

Central-difference time-lapse 4D seismic full waveform inversion

Geophysics ◽  
2020 ◽  
pp. 1-42
Author(s):  
Wei Zhou ◽  
David Lumley
Keyword(s):  
High Resolution ◽  
Seismic Velocity ◽  
Waveform Inversion ◽  
Computational Cost ◽  
Time Lapse ◽  
Full Waveform Inversion ◽  
Central Difference ◽  
Data Set ◽  
Velocity Inversion ◽  
Full Waveform

Repeated seismic surveys contain valuable information regarding time-lapse (4D) changes in the subsurface. Full waveform inversion (FWI) of seismic data can provide high-resolution estimates of 4D change. We propose a new time-domain 2D acoustic time-lapse FWI method based on the central-difference scheme with higher-order mathematical accuracy and reasonable computational cost. The method is rigorously tested on the SEAM 4D time-lapse model and OBN data set. High-resolution 4D velocity estimates are obtained, which show strong ~25% velocity increases in a 75 m-thick gas layer, as well as weaker (5%) changes due to geomechanical effects, the latter of which are poorly recovered by the conventional parallel 4D FWI method. We also perform the bootstrap 4D FWI method and the result is contaminated by strong artifacts in the underburden, whereas the proposed central-difference method has fewer underburden artifacts allowing more reliable interpretations. In this realistic case study, acoustic FWI erroneously overfits the elastic scattered waves, and cannot fit the strong elastic 4D coda waves at all. The results show that the proposed central-difference 4D FWI method within the acoustic approximation may be a practical solution for time-lapse seismic velocity inversion.

Source-independent time-lapse full-waveform inversion for VTI media

Geophysics ◽  
2021 ◽  
pp. 1-51
Author(s):  
Yanhua Liu ◽  
Ilya Tsvankin
Keyword(s):  
Waveform Inversion ◽  
Transversely Isotropic ◽  
Time Lapse ◽  
Model Complexity ◽  
Double Difference ◽  
Full Waveform Inversion ◽  
Reservoir Properties ◽  
Hydrocarbon Production ◽  
Full Waveform ◽  
Adjoint State

Time-lapse full-waveform inversion can provide high-resolution information about changes in the reservoir properties during hydrocarbon production and CO2 injection. However, the accuracy of the estimated source wavelet, which is critically important for time-lapse FWI, is often insufficient for field-data applications. The so-called “source-independent” FWI is designed to reduce the influence of the source wavelet on the inversion results. We incorporate the convolution-based source-independent technique into a time-lapse FWI algorithm for VTI (transversely isotropic with a vertical symmetry axis) media. The gradient of the modified FWI objective function is obtained from the adjoint-state method. The algorithm is tested on a model with a graben structure and the modified VTI Marmousi model using three time-lapse strategies (the parallel-difference, sequential-difference, and double-difference methods). The results confirm the ability of the developed methodology to reconstruct the localized time-lapse parameter variations even for a strongly distorted source wavelet. The algorithm remains robust in the presence of moderate noise in the input data but the accuracy of the estimated time-lapse changes depends on the model complexity.

Time-lapse full waveform inversion based on curvelet transform: Case study of CO2 storage monitoring

2021 ◽  
Vol 110 ◽  
pp. 103417
Author(s):  
Dong Li ◽  
Suping Peng ◽  
Xingguo Huang ◽  
Yinling Guo ◽  
Yongxu Lu ◽  
...  
Keyword(s):  
Co2 Storage ◽  
Waveform Inversion ◽  
Curvelet Transform ◽  
Time Lapse ◽  
Full Waveform Inversion ◽  
Full Waveform
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