On the role of diffractions in velocity model building: a full-waveform inversion example

Dell, Sergius; Abakumov, I.; Znak, Pavel; Gajewski, D.; Kashtan, Boris; Ponomarenko, Andrey

doi:10.1007/s11200-019-0733-6

Cited by 6 publications

(1 citation statement)

References 24 publications

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“…This issue can be important for target not very close to the well and in presence of lateral variations of velocity. As a comparison, the diffractions are considered as a noise for a classical processing approach whereas it carries useful information for FWI (e.g., [9], helping to accurately build an edge or discontinuous surface. In other words, the classical VSP data processing approach reduces the complexity of the recorded complex wavefield by separating the wave field to up and downgoing waves and often removes part of the information contained in the data.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity Analysis of FWI Applied to OVSP Synthetic Data for Fault Detection and Characterization in Crystalline Rocks

Abdelfettah¹,

Barnes

2021

Geosciences

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We have performed several sensitivity studies to assess the ability of the Full Wave Inversion method to detect, delineate and characterize faults in a crystalline geothermal reservoir from OVSP data. The distant goal is to apply the method to the Soultz-sous-Forêts site (France). Our approach consists of performing synthetic Full Wave 2D Inversion experiments using offset vertical seismic and comparing the estimated fields provided by the inversion, i.e., the estimated underground images, to the initial reference model including the fault target. We first tuned the inversion algorithmic parameters in order to adapt the FWI software, originally dedicated to a sedimentary context, to a crystalline context. In a second step, we studied the sensitivity of the FWI fault imaging results as a function of the acquisition geometry parameters, namely, the number of shots, the intershot distance, the maximum offset and also the antenna length and well deviation. From this study, we suggest rules to design the acquisition geometry in order to improve the fault detection, delineation and characterization. In a third step, we studied the sensitivity of the FWI fault imaging results as a function of the fault or the fault zone characteristics, namely, the fault dip, thickness and the contrast of physical parameters between the fault materials and the surrounding fresh rocks. We have shown that a fault with high dip, between 60 and 90° as thin as 10 m (i.e. lower than a tenth of the seismic wavelength of 120 m for Vp and 70 m for Vs) can be imaged by FWI, even in the presence of additive gaussian noise. In summary, for a crystalline geological context, and dealing with acceptable S/N ratio data, the FWI show a high potential for accurately detecting, delineating and characterizing the fault zones.

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Section: Introductionmentioning

confidence: 99%