Unlocking seismic monitoring of stiff reservoirs with 4D OBN: A case study from Brazil pre-salt

Kiyashchenko, Denis; Wong, Wai-Fan; Cherief, Dalila; Clarke, Dan; Duan, Yuting; Hatchell, Paul

doi:10.1190/segam2020-3426740.1

Cited by 8 publications

(3 citation statements)

References 11 publications

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“…Lula Pilot surveys were planned to investigate the 4D signal of the PreSalt reservoirs in the Lula field, Santos Basin, in response to a two-year WAG (water alternate gas) injection scheme (Kiyashchenko et al, 2020). Each survey comprises 970 nodes 325 x 375 m apart in a hexagonal pattern and a shot carpet of approximately 150,000 shots 50 m apart.…”

Section: Resultsmentioning

confidence: 99%

Interbed multiples modeling for OBN data

Guerra¹,

Hargreaves²

2021

Proceeding of the 17th International Congress of the Brazilian Geophysical

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Section: Resultsmentioning

confidence: 99%

Interbed multiples modeling for OBN data

Guerra¹,

Hargreaves²

2021

Proceeding of the 17th International Congress of the Brazilian Geophysical

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“…Lecerf et al ( 2011) described a processing-based technique to take care of the many factors influencing time-shifts simultaneously. Kiyashchenko et al (2020) presented two approaches for deep water 4D OBN applications in which seawater variations and bulk timing errors are decoupled using the travel-time information from the primaries and water bottom multiples (assuming the node depth and tidal factors are fixed by other non-seismic data).…”

Section: Navigation and Timing Differencesmentioning

confidence: 99%

“…Finally, Kiyaschchenko et al. (2020) described the importance of corrections for node timing errors, tidal variations and shot coordinate errors for deep water Brazilian 4D OBN applications.…”

Section: Acquisition and Processing‐related Errorsmentioning

confidence: 99%

A review and analysis of errors in post‐stack time‐shift interpretation

MacBeth

Izadian

2023

Geophysical Prospecting

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This study complements two earlier papers on the interpretation and estimation of post‐stack time‐shifts that detail the most popular measurement methods to date. In this current work, the focus is on describing the magnitude and identifying the origin of the uncertainty present in these time‐shift values. We also consider how the underlying assumptions behind conventional time‐shift estimation methods can contribute to the inadequate resolution of the subsurface time‐lapse changes. The various errors fall into three broad categories: (1) those related to intrinsic data limits that cannot be avoided; (2) those associated with seismic measurement methods that can be corrected with some effort; and finally (3) those that arise due to approximations to the wave physics made during the design or implementation of the methods. In the first category are limitations due to sampling rate and signal‐to‐noise ratio, and wavelet interferences resulting from the narrow band nature of the seismic data and the heterogeneous nature of the geology itself. The effects produce errors of typically a fraction of a millisecond, but exceptionally in 4D data with poor repeatability up to 1 ms. In the second category are acquisition and processing errors. These are usually of the order of a few milliseconds but can reach up to 10s of milliseconds and are, therefore, essential to correct. It is possible to correct the effects of tides and seawater variations in marine acquisition if these changes are monitored and measured. Navigation and timing are identified as issues to consider carefully. For land data, daily and seasonal near‐surface variations are still problematic, and source and sensors must be buried to deliver interpretable time‐shifts. The impact of choices made during processing can be significant but is specific to the workflow and dataset and thus cannot be generically assessed. However, the effects from residual multiples can be identified and treated. Of moderate importance is the third category of errors, which consists of four items. Of these, the effect of lateral image shifts and amplitude effects are judged to play a minor role. Deviation from the assumption of vertical ray‐paths during post‐stack analysis appears to be of concern only for reservoirs with noticeably dipping structures and strong contrasts. The effect of pre‐stack variations on the post‐stack measurements remains a topic to be more thoroughly examined, and the conclusion is unclear. Finally, it is apparent that uncertainties in all categories are strongly dependent on the field setting and geographical location.

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Nonrepeatability effects on time-lapse 4D seismic full-waveform inversion for ocean-bottom node data

Zhou

Lumley

2021

GEOPHYSICS

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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.

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Unlocking seismic monitoring of stiff reservoirs with 4D OBN: A case study from Brazil pre-salt

Cited by 8 publications

References 11 publications

Interbed multiples modeling for OBN data

Interbed multiples modeling for OBN data

A review and analysis of errors in post‐stack time‐shift interpretation

Nonrepeatability effects on time-lapse 4D seismic full-waveform inversion for ocean-bottom node data

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