Abstract
Reconstructing the details of subsurface structures deep beneath complex overburden structures, such as subsalt, remains a challenge for seismic imaging. Over the past few years, the Marchenko redatuming approach has proven to reliably retrieve full-wavefield information in the presence of complex overburden effects. When used for redatuming, current practical Marchenko schemes cannot make use of a priori subsurface models with sharp contrasts because of their requirements regarding initial focusing functions, which for sufficiently complex media can result in redatumed fields with significant waveform inaccuracies. Using a scattering framework, we evaluate an alternative form of the Marchenko representation that aims at retrieving only the unknown perturbations to focusing functions and redatumed fields. From this framework, we have developed a two-step practical focusing-based redatuming scheme that first solves an inverse problem for the background focusing functions, which are then used to estimate the perturbations to focusing functions and redatumed fields. In our scheme, initial focusing functions are significantly different from previous approaches because they contain complex waveforms encoding the full transmission response of the a priori model. Our goal is the handling of not only highly complex media but also realistic data — band-limited, unevenly sampled, free-surface-multiple contaminated data. To that end, we combine the versatility of Rayleigh-Marchenko redatuming with our scattering-based scheme allowing an extended version of the method able to handle single-sided band-limited multicomponent data. This scattering-Rayleigh-Marchenko strategy accurately retrieves wavefields while requiring minimum preprocessing of the data. In support of the new methods, we evaluate a comprehensive set of numerical tests using a complex 2D subsalt model. Our numerical results indicate that the scattering approaches retrieve accurate redatumed fields that appropriately account for the complexity of the a priori model. We find that the improvements in wavefield retrieval translate into measurable improvements in our subsalt images.
Highlights
Accurate estimation of the stratigraphy and properties of complex subsurface geology has long represented a challenge for seismic imaging, especially in the presence of salt formations in the overburden (Leveille et al, 2011)
We present two novel redatuming scattering-based schemes for wavefield redatuming with the Marchenko framework whose objective is to account for highly complex overburden media such as subsalt or sub-basalt
While the recent rise of redatuming and imaging approaches based on the Marchenko framework showed great promise for tackling the challenges of imaging in highly complex
Summary
Accurate estimation of the stratigraphy and properties of complex subsurface geology has long represented a challenge for seismic imaging, especially in the presence of salt (or basalt) formations in the overburden (Leveille et al, 2011). This is largely due to uneven illumination of the target area arising from the complex propagation in the overburden as well as the 17 presence of strong reverberations in the recorded surface data (Jones and Davison, 2014). A variety of approaches, emerged under the pursuit of imaging with multiples, have shown their effectiveness in such settings; these methods turn multiple reverberations originating from high impedance contrasts around salt and basalt structures into useful signal that can complement the illumination of primaries (Malcolm et al, 2008; Liu et al, 2015)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call