Enhanced imaging with high-resolution full-waveform inversion and reverse time migration: A North Sea OBC case study

Abstract

In a case study from the Tommeliten Alpha area of the Norwegian North Sea, imaging problems were caused by the presence of gas in the overburden. In particular, a large part of the reservoir is in a seismically obscured area (SOA) caused by the gas. Full-waveform inversion (FWI) and reverse time migration (RTM) dramatically improve the imaging from ocean-bottom cable (OBC) acquisition over the region. The FWI algorithm is pushed to 22 Hz to generate an extremely high-resolution velocity model, and RTM then becomes required to honor the complexity in the resultant velocity model. Consequently, migration is done with the FWI model to generate a highfrequency RTM image to 80 Hz. This image is approximately double the maximum frequency commonly used for RTM in the North Sea and matches that of equivalent Kirchhoff products, but with all the benefits in imaging that RTM brings, providing a subsequent impact on interpretation of the area. Figure 8. Comparison of 80-Hz VTI RTM sections zoomed to top-reservoir horizon depth for (a) line L1 migrated with the starting velocity model, (b) line L1 migrated with the FWI velocity model, (c) line L2 migrated with the starting velocity model, and (d) line L2 migrated with the FWI velocity model. Labels L1 and L2 refer to the yellow lines in Figure 4.

Application of ground penetrating radar to detect tunnel lining defects based on improved full waveform inversion and reverse time migration

“…Therefore, FWI and RTM are highly complementary. The combination of these two methods is usually used in seismic data processing (Ratcliffe et al 2014;Sun et al 2015). We use the combined methods into the processing of tunnel lining detection to enhance the interpretation accuracy.…”

“…The combination of the two methods is usually used in seismic data processing (e.g., Ratcliffe et al . ; Sun et al . ).…”

“…Therefore, FWI and RTM are highly complementary. The combination of the two methods is usually used in seismic data processing (e.g., Ratcliffe et al 2014;Sun et al 2015). The effect of these two methods is remarkable in seismic data processing (Berkhout 2015) but their applicability in tunnel lining defect detection is largely untested.…”

Extracting geologic information directly from high-resolution full-waveform inversion velocity models — A case study from offshore Trinidad

“…This mismatch is then iteratively minimized through updates to the velocity model (Lailly, 1983;Tarantola, 1984). We use the time-domain, preconditioned, steepest-descent algorithm as described in Warner et al (2013) and updated by Ratcliffe et al (2014). FWI of reflected wave data was not considered for the deeper part of the velocity model due to the expected uncertainties in the deeper macromodel, making it potentially unreliable at present.…”

Orthorhombic full-waveform inversion for imaging the Luda field using wide-azimuth ocean-bottom-cable data

“…This mismatch then is minimized iteratively through updates to the velocity model (Lailly, 1983;Tarantola, 1984). We use the time domain, preconditioned, steepest-descent algorithm as described in Warner et al (2013) and updated by Ratcliffe et al (2014). FWI of reflected wave data was not considered for the deeper part of the velocity model due to the expected uncertainties in the deeper macromodel, making it potentially unreliable at present.…”